Brakes 101..

[Sean Roe]

What a great time for that article to come out in the Viper Magazine. I hope many of you read it and follow along with the series, it should be very educational.

Hopefully, as the article progresses, the engineers will write more about the delicate balance of master cylinder volume, brake booster assist ratio and reaction ratio for proper feel. They did prepare you for it some by making it clear that threshold braking control is the key. I'm sure the production engineers worked hard to achieve the braking feel the management told them they had to end up with.

On racecars, a standard brake tuning practice is to have several master cylinders (fronts and rears individually) on hand for the initial testing and setup of the brakes. In order to gain more braking force with lighter brake pressure, you put in a master cylinder with a smaller piston & bore diameter. In order to reduce braking force to make threshold and lockup control easier for the driver, you put on a larger piston & bore master cylinder. The smaller the bore of the master, the higher the line pressure the master cylinder produces with the same pedal force. The larger the bore of the master cylinder, the less line pressure it produces with the same pedal force.

Quite simply, you cannot change a brake system (the stock Viper in this case) from 8 pistons total front, 2 pistons total rear, to 12 pistons front, 4 or 8 pistons rear and achieve the proper threshold braking control without changing the master cylinder. Adding fluid volume and number of pistons to the calipers gives you the same effect as putting on too small of a master cylinder (higher line pressure with lighter pedal force). If you want to have the feel of mega-power assisted brakes, you'll get it. If you want to have excellent control over wheel lockup during threshold braking while you're heel and toe downshifting, forget it.

As I have been putting our booster and master cylinder combination on Vipers with other tuners brake packages lately to get the feel and control right for the customers, I thought this was a very timely article in Viper Magazine.

Remember, ANYBODY can buy larger calipers, take them to a machine shop and say "can you make brackets so I can bolt these on my Viper?". The difficult part is getting the master cylinder and booster mechanics right. After 15 years of professional racing, working on 3 factory road race teams and campaigning programs myself with factory support, I'm having a hard time watching people who have only been club racing a couple years telling you otherwise.

 

[dtittle]

Hi Everybody,

Great information Shawn! As usual, you are _VERY_ right about the things you mentioned in your post as the Brakes 101 article was too! When it comes to braking at the limit the pedal feel is paramount and your analogies about "Small Bore MCs" create more pressure where "Large Bore MCs" create less pressure is a concept that most people don't, but should, understand thoroughly. Obviously your years of expertise both on and off of the track have paid off and that's why your one of the most respected Viper owners/tuners around.

I was wondering however, what you meant by a few things that you wrote. Can you elaborate on what you meant about changing the number of pistons in a brake system? I thought that the number of pistons was technically irrelevant especially since pedal feel is purely a translation of volume and pressure. So, what if you had 20 pistons that displaced the same amount of fluid as the 10 pistons that you mentioned? Does the MC require changing in that case? What if those 20 pistons actually enhanced the bias to the rear and ultimately enhanced the pedal feel? Would that _REQUIRE_ changes? I’m confused! I thought that racers of old actually started putting more pistons in the calipers to combat the ever-present problem of pad taper and not to screw up the pedal. Can you help me understand this?

Next, you said you can simply take parts to a machine shop and have them make stuff and put them on for you? Can you give me their number? We had to make many changes to our systems before we got all of the quirks out and a machine shop like that would really help. Not to mention all of the money we could’ve saved on parts and I’ve got some other “Stuff” that I want to make. Maybe they could help you with your parking brake?

Finally, I think you’re on to something regarding the credibility of some people! At least if I understood your point about whoever has just been “Club Racing” for a “Couple of Years”. You know, the other day I was talking to Bob Woodhouse at the TWS and the Viper Days Finals, where we missed you by the way, about running some “Special Rear Brake Rotor” and you made me realize that HE JUST PUT THOSE BRAKES ON HIS CAR.! AND, he’s only been “Club Racing” a while now! Until now I thought Bob was cool but you’ve got me to thinkin’! I’m going to give him a call and make sure that he’s talked to somebody smarter that could tell him what to do! Knowing him, I bet he didn’t consult ANYBODY and probably just threw a bunch of junk that nobody has ever heard on his car! I guess that it’s just DUMB LUCK that he kicked tail down in Texas! I don’t know how he did it, but, some people! I swear, sometimes you just don’t know how people survive. You should give Bob a call!

As always, Thank You, for the valuable insight into the inner workings. I guess it’s like I said at the beginning of this note, I guess that’s why you’re one of the best tuners around!

Best Regards, Tittle

 

[Supercharged Vipermad]

We should start a "Smack 101" for you two. Is this some form of educated trash talk going on here? Being that I've got a PhD in Smack, I'll give you a few of the basics...

Feel free to dispense with the pre-smack A** kissing and just come out flinging insults. If you're looking for some free advertising or publicity for your brakes, believe me this is the way to get it. This post has been up for two days and nobody has responded! Spruce it up a bit.

Next...dumb it down. You could substitute all of that confusing mechanical engineering talk with phrases like "Your brakes ****, mine rule!!!!" or "Your brakes **** more than Ken Adelberg's sister".

Finally, since you guys are basically competitors--act like it! Words like Pinoche, loser, ******-bag and Adelberg will always conjure up thoughts of ill-will.

These are just a few basic smack talking tips. Keep in mind it takes practice to master the fine art of trash talking, so keep working on it. Someday you guys will get it. I hate to see amatuers disgrace the fine art of trash talking and am always prepared to help my fellow man. You know where to find me if you need help.

Dr. Mumford

WAR TRASH TALK!!!!!!!!!!!!!!!

 

[dtittle]

I got it Paul, Thanks!

 

[dtittle]

Oh, and I almost forgot!

WAR BRAKES!!!!

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[Sean Roe]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by dtittle:

....I thought that the number of pistons was technically irrelevant especially since pedal feel is purely a translation of volume and pressure. So, what if you had 20 pistons that displaced the same amount of fluid as the 10 pistons that you mentioned? Does the MC require changing in that case?.... I’m confused!... <HR></BLOCKQUOTE>

Dave, it is highly unlikely that the 20 pistons would have the same piston area per pad as the 10 piston setup. This should help clear things up for you.

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>I thought that racers of old actually started putting more pistons in the calipers to combat the ever-present problem of pad taper and not to screw up the pedal. Can you help me understand this?<HR></BLOCKQUOTE>

The number of pistons increased because of the need to more evenly distribute the piston area on the backing plate of larger pads. Caliper piston diameter is what is used to reduce taper. The leading edge pistons are smaller and trailing edge pistons are larger in order to keep pad wear the same across long brake pads with multiple pistons

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Next, you said you can simply take parts to a machine shop and have them make stuff and put them on for you? Can you give me their number? We had to make many changes to our systems before we got all of the quirks out and a machine shop like that would really help. Not to mention all of the money we could’ve saved on parts and I’ve got some other “Stuff” that I want to make. Maybe they could help you with your parking brake?<HR></BLOCKQUOTE>

Sure, give me a call at the shop sometime. We have many high quality CNC machine shops in our area that we do business with. You can send them a caliper, pads, rotor, steering knuckle and wheel hub assembly (new parts), slide the caliper on the rotor and ask them to make a bracket that bolts it to the existing caliper mounts. Or, you can draw up one yourself and have them make the prototype pieces out of plastic and test fit (better).
Large full time CNC machine shops are specifically set up to do these kinds of projects and have the money invested in equipment and personell to do it well. Once I take a the time to draw up the 1992 to 1995 RT/10 parking brake mount, I'll have one of the shops make a prototype. As you know, those cars have the rear toe link arm cast in a different location than the 1996 and newer cars.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Finally, I think you’re on to something regarding the credibility of some people! At least if I understood your point about whoever has just been “Club Racing” for a “Couple of Years”. You know, the other day I was talking to Bob Woodhouse at the TWS and the Viper Days Finals, where we missed you by the way, about running some “Special Rear Brake Rotor” and you made me realize that HE JUST PUT THOSE BRAKES ON HIS CAR.! AND, he’s only been “Club Racing” a while now! Until now I thought Bob was cool but you’ve got me to thinkin’! I’m going to give him a call and make sure that he’s talked to somebody smarter that could tell him what to do! Knowing him, I bet he didn’t consult ANYBODY and probably just threw a bunch of junk that nobody has ever heard on his car! I guess that it’s just DUMB LUCK that he kicked tail down in Texas! I don’t know how he did it, but, some people! I swear, sometimes you just don’t know how people survive. You should give Bob a call!<HR></BLOCKQUOTE>

I consider Bob Woodhouse to be a fine upstanding memeber of the Viper community and would not dismiss his driving ability to be dumb luck.

Regarding the Viper Days event in Texas, I would have liked to been there on a social basis. But between business, meetings at the SEMA and PRI shows, new product development, etc, I could not get away for it. Sounds like it was too cold for me anyway

If anybody else would like to learn more about braking systems and dynamics, read through Carroll Smith's book "Tune To Win" The art and science of race car tuning and development, chapter 10 specifically. If you have time, the entire book makes for a good read and will educate you more about vehicle dynamics, which will help you become a smarter consumer and racer.

Paul,
I'll leave the trash talking to the Pro's (you and Ken)

 

[K Adelberg]

Oh Mumford. These guys are competitiors and know brake systems. I'm not certain if the entire Viper board needs to condescend to your level of smack babble to understand. Just understand this! Your reign is over! You can take your 300 rear wheel HP new 2001 ACR and go autocross. Don't show up to Viper Days at Willow. YOu will leave with your tail between your legs and be humiliated in your own house, Pinouch!

 

[Supercharged Vipermad]

Dear Adelberg,

Shall I have the Sheriff waiting at Willow Springs Jan. 27-28? Because you are gonna get your punk-*** evicted from "my house" once again. Just because my 2001 ACR had about 30 horses sent to the glue factory doesn't mean that you won't get your monthly beating. Maybe I'll bring the '98 out and beat you up with one cylinder tied behind my back just for good measure.

How many times do I have to tell you to pick on somebody your own size? Why don't you start by insulting the East-Coast Pinoches? Maybe some of them will become so enraged that they'll actually come out to a real racetrack to take their whippin' like men rather than cry of cheating.

WAR CHEATERS!!!!!!!!!!!!

 

[BWoodbury]

Finally!!!

Tony, the new board has arrived. You can stop working on it now. It is fully functionaly. For months now I was sure that this one was broken and the old board was still out there somewhere because I had not seen Mumford and Adelberg getting into it here.

I feel much better now.

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[Sean Roe]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Jim Hodel:
Sean and Dave, I still don't quite understand the relationship between the number of pistons per caliper, the piston caliper bore, and the piston area per pad.

I understand that multiple pistons and differential piston sizes can reduce pad taper, but help me understand how moving from the stock (or other) 4 piston caliper to a 6 piston Willwood, AP, Alcon, or other caliper effects fluid volume, piston area, and pedal feel.<HR></BLOCKQUOTE>

Hi Jim,
Please reference the Force Variation information in my post above.
Regarding the calipers, you can see that as the piston area per disc increases, so does the force on the disc at a given line pressure. A higher number of pistons generally yields a higher force on the disc.
Regarding the master cylinder, as the cylinder bore / piston area decreases, line pressure at a given force on the piston increases. Along with it, pedal travel to move the pistons and the force applied to an individual disc also increase.
Ultimately, when adding to the piston area, the master cylinder should be increased to reduce travel and pressure. If not, you will end up with more pedal stroke and a far more sensitive pedal at the point of lockup (because the line pressure changes so much with little pedal pressure).


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>The stock Viper pads are about 4.25 inches long, and I think the 6 piston pads are around 6 inches long (pads for Alcon 4 piston calipers are around 5 inches) I do not know what the relative piston sizes and overall piston volumes are between 4 *** and 6 *** calipers. How much larger is the total piston caliper bore, piston area per pad, and resulting fluid volume between the stock caliper and the 6 pots?

At what point does an increase in total piston area and fluid volume require a change (I.E larger) master cylinder? Also, do larger pads stop better, or is it more that they wear longer?
Thx, Jim Hodel
<HR></BLOCKQUOTE>

The point at which the master cylinder must be changed is a judgement call based on experience. The big auto makers have teams of engineers and test drivers who specialize in brake system development and feel for public motor vehicles. For most drivers who brake lightly, but like the car to stop hard, the stock master cylinder and booster combination, when used with calipers that have a greater piston area per disc, will feel better initially. Later, in the rain, on the track or in panic brake situations, the operator of that vehicle will have a more difficult time controlling lock up of the brakes. This is a fact which cannot be disputed.

During the testing and development of our brakes, we had experienced Viper Club racers (Ron Adee and Larry Hampton) say that the brakes felt great. But, because of my background in professional racing, I was not satisfied and ultimately, with Delphi Prototype Engineering support, we were able to create a better master cylinder and booster combination which yielded superior threshold braking control.

Recently, we installed our specification booster and master cylinder on Mickey Craig's GTS. He had an "tuner" system with Wilwood calipers and rotors all around which he grew to realize did not have the proper feel and control of lockup. He asked me to see what I could do to help while his car was here for other modifications. We installed our booster and master cylinder combination, testing the brake feel and stopping G force before and after. Initially, the rear brakes were locking up (they put a proportioning valve on the front and the rear, an obvious clue that they knew what they had setup was not right) and the car could achieve .98 G before wheel lock (rear). I noted that the pedal travel to unlock the wheels was high, though the pressure on the pedal itself was not very high. With the booster and master cylinder from our system installed (larger bore master cylinder and a lower ratio booster), the car was able to brake at 1.15 G (same as mine)(stock street tire limited). The difference between the two setups was the pedal travel and the control over threshold braking. With the larger master cylinder, pedal travel was reduced greatly and the brakes were far more controllable in threshold braking and trail braking (braking while cornering). I'm sure Mickey would give his unbiased opinion if asked.

Regarding the pad size, larger pads can (if properly configured with the rest of the brake system and tires) stop a car better and last longer. Here is a picture of the pad sizes of our brake system (AP 6 piston front, PBR 2 piston rear) versus stock size Viper brake pad sizes.

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As you can see, they have a much larger area. But, as I now hope people are beginning to understand, that's not all that matters.

Soon, our brake package will be enhanced with the same pad and rotor combination that was on the ORECA car when they won the 24 hours of Daytona. At that point, we will have available the most complete and controllable brake system the Viper community has seen. The only one with a properly matched master cylinder and booster.
www.roeracingonline.com/portfolio.html

 

[Ernie J]

TO Dave Tittle

Following are a few highlights of Sean Roe's automotive career.

1986---------Technician on factory Porsche GTP Lights team

1987---------Technician on Pontiac GTO factory team

1988/89------Chief technician at Spenard David Racing School

1990---------Won the Marlboro Cup race in Mexico while there doing chassis developement for Formula 2000 team

1991---------Technician on Porsche 911 Turbo team

1992---------Started own racing team /Bridgestone Supercar series
"won rookie of the year honors"

1993/95------Competed in the Bridgestone Supercar series with
numerous wins and podium finishes. Won the prestigious Sebring and Long Beach races.

1994---------Was awarded the IMSA Technician of the year award.
The only driver to win in twenty years.

1996/00------Building turnkey race cars and developing innovative
performance products.

Now in my opinion if someone with Sean Roe's background and experience said my brake system was deficient, I'd try to develope a fix for my thirty eight brake customers instead of
ridiculing the man that identified the problem.
And Dave, we would all love hear about your automotive career(just a few dozen highlights would be fine).

 

[Jim Hodel]

Sean and Dave, I still don't quite understand the relationship between the number of pistons per caliper, the piston caliper bore, and the piston area per pad.

I understand that multiple pistons and differential piston sizes can reduce pad taper, but help me understand how moving from the stock (or other) 4 piston caliper to a 6 piston Willwood, AP, Alcon, or other caliper effects fluid volume, piston area, and pedal feel.

The stock Viper pads are about 4.25 inches long, and I think the 6 piston pads are around 6 inches long (pads for Alcon 4 piston calipers are around 5 inches) I do not know what the relative piston sizes and overall piston volumes are between 4 *** and 6 *** calipers. How much larger is the total piston caliper bore, piston area per pad, and resulting fluid volume between the stock caliper and the 6 pots?

At what point does an increase in total piston area and fluid volume require a change (I.E larger) master cylinder? Also, do larger pads stop better, or is it more that they wear longer?

Thx, Jim Hodel

 

[dtittle]

Hi Guys,

First, for all of you Roe loyalist and possible flamers, remember that I’ve been a Roe patron for a long time so don’t take this too seriously. But, if you feel the need to “Spank” me for the subsequent “SMACK BACK”, please administer the whippin’ after the show. Ooopps, I may have to “Spank” myself since I’ve been a Roe’bee too.

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My take on this entire thing is Shawn is simply PO’d that I’m playin’ in what he considers his bathtub! Over the years I’ve talked to Shawn about his brakes and personally didn’t buy them because in my opinion, he obligates you to make too many changes to the car. Nothing personal, I just wanted more flexibility so I built my own brakes and I would’ve never expected him to get so worked up over it.

Lately, in various different posts, Sean has been very out of character as he’s been posting very superior and condescending articles and it’s clear that he feels like he’s the Obewan’ of brakes. No problem for me, except that he’s been using my name in his posts and has on more than one occasion inferred that simply because I haven’t spent as much time at the track or in a pit crew as he has, that I don’t know what I’m doing and that people shouldn’t listen to me. In these articles he insists that the Master Cylinder is king and he makes it sounds like it’s the final factor to the brake equation. The funny thing is that regarding the very specific point about how pedal feel can be tuned by the MC, Shawn is totally correct and I don’t think anyone disagrees. He’s so correct in fact, that it doesn’t warrant this kind of discussions and in my book should just be looked at as a WELL DUH! What Shawn has shown lately is that he’s not as creative and forward thinking as I gave him credit for. Look at it like this, if IBM (with ALL of their experience) hadn’t been so obtuse and set in their ways, young and inexperienced Bill Gates might not have smeared their a&&es all over the computer business. Do you see my point? I’m not sayin’ that I’m Bill but I am starting to feel a little nerdy!

Shawn and I are different and we take different approaches to the way we do business. Shawn is 100% race car and for his the sake of business he tries to hide this trait. His mentors and everyone that knows him will know this to be true. I, on the other hand, am about 70% race car and the rest street car. I simply love cars and I build my products with that philosophy.

For example: Rather that spend $12,000 bucks on 6 Piston Front and 4 Piston Rear brakes that required me to modify the he!! out of my car, replace the 4 sets of wheels and tires with 18” (that were expensive at the time), or buy some other mixed and matched kit that required you to have a bastardized tool box and tons of different pads, and THEN give up my parking brake. I made my own brakes. Contrary to Shawn’s method, I STARTED WITH THE MASTER cylinder and built from there. And I consulted with ALCON, BREMBO, WILWOOD, BRAKE MAN, blah, blah, blah Motorsports on how to properly do this. The result has been a complete brake package that works awesome, fits under stock wheels (fits under 15” rear drag wheels too), has a universal parking brake and doesn’t require any changes to the MC or to the proportioning valve. OF COURSE you could fine tune the FEEL our brakes with MC and prop changes but the IMPORTANT part is that you don’t HAVE TO. Myself, and all of our customers can drive their car from the street to the track, drive like crazy, then go home on the same set of pads and without a pit crew or a Delphi analysis trailer tagging along. Of all of the kits that we’ve sold this year there have the TWO, I repeat TWO, people that changed their pads and Jay Lopez’s pads STILL HAD OVER HALF OF THE THICKNESS LEFT! Now according to Shawn, because I haven’t been a track groupie all of my life, I need to call all of my happy customers, and go out into my shop; and tell my brakes that they’re not supposed to work. Boooyaaa!

Shawn can’t say that my brakes ****! Can’t even imply it because on at least 5 occasions this year I’ve gone to driving events (Viper Days and others) and invited, even begged, Shawn to drive one of my cars. I ONLY WENT to one of those events because Shawn was going to drive my car. And although he always said that he would, he invariably turned out to be too busy to drive them. Hmmm?

However, as he mentioned in his posts, I can provide feedback on HIS BRAKES as I drove his car. The pedal felt rock hard. So hard, that at low speeds and temps it had NO FEEDBACK! I’m sure that at the maximum threshold with all of the parts warm (were we never went) you could feel a pebble in the road and that’s great for pure “Race Cars”. I, on the other hand would like to go on a date or to a local club meeting and I wouldn’t want his pedal feel for that. It felt “Racecar” and nothing else.

It’s also kind of funny that, once again, Shawn agreed to drive my 2000 GTS or my Z06 at VOI6. Although, he avoided his chance AGAIN, Tommy Archer did make a few laps in my car. He didn’t rant and rave about the brakes (because he drives freakin’ ORECA cars all day), but he something EVEN BETTER. During the course of maybe 10 or 12 laps, he took PASSENGERS! His crew told me outright that was the ultimate compliment coming from Tommy and that he MUST have felt secure in an unknown car to do THAT. His two passengers were coincidentally instructors from the VOI event (that drove Vipers all weekend) both excitedly commented that those were the “Best Brakes they have ever felt on a street car, period”!

Finally, in one of Shawn’s most recent posts regarding Lucky’s car he eluded that the brake system had problems and that the Wilwood calipers that were being used sucked! I completely understand the brake system that Shawn is referring too as I’ve completely replaced 4 of them this year. While you were applying your mystical master cylinder fix I hope that you noticed that the rear caliper is mounted as such an angle that the upper bladder is FULL OF AIR and will NEVER allow proper bleeding and will subsequently NEVER WORK. I also hope that you noticed the malleable steel plates that they use for mounting brackets will flex so much that the calipers can HIT THE ROTOR! And, rear caliper is designed for a lightweight car and has HUGE rear pistons that will totally jack up the balance of the car. Bottom line, if you care about your customers life take that crap brake kit off of that car and throw it in the trash! Use the old Adelberg technique and give the guy some new tennis shoes or even put your brakes on!


Wow, I almost out of SMACK BREATH!

Highlights:

1969…Born
1972…Drove bright red pedal car from Coca-Cola (No license)
1975…Motorized Tri-cycle (Big Red Flyer with washing machine motor, 12v battery and converter)
1978…Attached sail (sheet to broom handles) to bicycle handle bars and suffered injuries (Mailbox)
1979…Spent most of my time on a tractor.
1980…Still on a friggin’ tractor
1981…Paid $150 for 1970 Cougar with 351C with 14” wheels on left and 15” on right
1986…Finished the Cougar, Rebuilt Motor, Auto Transmission, etc by myself (Got Dirty)
1987…Went to College and had no money for cars, Cougar now had 450hp and got 8mpg
1990…Police interceptor Mustang
.
Self employed made a GOOD LIVING inventing and software for all industries while club racing for the last 4 Years
.
1999…********** at greedy brake manufactures and built a set of BRAKES THAT KICK ALL OTHERS A$$ES!
2000…Making happy customers and making $$$ making brakes

Now have brakes for Vipers, Vette’s, 300ZX, and AUDI’s and have more to come. And will be the FIRST fully functional brake kit for 2001 ABS equipped Vipers!

Regards, Tittle

WAR BRAKES!!!

P.S. Sorry for the length but I had corneal transplant surgery this morning and am typing this while under the influence of darvoset! WAR PAIN KILLERS!!!

 

[Bill Pemberton Woodhouse]

Dear Dave,
I too had a red pedal car, so I have figured out you really know yur sh......, er, stuff. My big problem is this entire topic has been about braking systems, and then I find out you have been playing in Roe's bathtub.OOOOOOOOO, not a good statement, as I am afraid when Mumford and Adelberg read this ,everyone will soon know all about it. I promise not to say a word, but please clarify if both of you were in the tub together, discussing stopping distances?

 

[Bob Woodhouse]

Your guys are insane, killin me, I am on the floor chokin on my sneakers. Tittle, you ping on Roe so suttle that it must still be sifting in. Mumford and Adelberg need to enroll him in Smack 101 at the Adelford School of lower education
How about Sean's resume' Dave, makes the rest of us look like we been playin Tiddley Winks huh? (Suttle enough Paul?) On those brake photos. They draw suspicions as to whether you have opened the ultimate can of whup-*** . I don't want you to snooze reading this so I'll just tickle ya. The front to rear pad size ratio could be a concern. Why would that be? Hmmmm.
It appears from the photo that pad material on front and rear pads is different. Brake pad torque changes with heat, different pads have different torque curves. Do we have some bias change here? Hmmmm........
There are several good suppliers with sorted out brake systems in the Viper Nation. Sean Roe, Dave Tittle (DeLussi Mtrspts), Stop Tech, and BrakeMan (ours).
Mr. Roe can't be too concerned with the ultimate brake system, he hasn't built a Viper that was fast enough to need much brake. OOOOOh, I owed you one tho Sean. Still luv ya tho.

 

[GTS Dean]

Wow!

I like both Sean and Dave, but this is bullcrap.


I think I'll just stick to my setup. No spring, AP600, BrakeMans and deflectors up front, PFCs out back. If I just learn to use the brakes less, I'll be faster. Darned thing seems to stop fine - no more probs at TWS or Cabaniss NAS and I haven't flat-spotted a tire since March.

I don't know what to spend my money on now - maybe I'll paint the car...

 

[Mark Young]

Oh yeah? Well I spent most of my time on a friggin' tractor from 1983-1992, plus a fair bit more from 1992-1997. So if anyone is looking to upgrade the brakes on their TRACTOR, I guess I am THE guy to talk to!!! whooo hooo.

Sorry, couldn't help myself, I am lovin this thread!!!

WAR TRACTORS!!!

- Mark ('99 ACR)

 

[Sean Roe]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Bob Woodhouse:
It appears from the photo that pad material on front and rear pads is different. Brake pad torque changes with heat, different pads have different torque curves. Do we have some bias change here?
<HR></BLOCKQUOTE>

Hi Bob,
The smaller pads in the photo are stock Viper pads. The larger ones are PFC Z rated pads (the street set). If there's any visible difference between the front and rear pads in the picture, it may be because of the flash from the camera.
The track pads we use are also PFC, 99 compound front and 90 rear. Both come on at about the same temperature, but 99's can operate at higher temperatures than 90's and offer excellent release characteristics. Therefore we use the 99's on the front where the brakes do most of the work and operate at higher temperatures than the rears. We could use 90's all around as well, but the 99's are a great pad and were what ORECA and most of the top NASCAR and CART teams used this past year.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>by Dave Tittle
Shawn was going to drive my car. And although he always said that he would, he invariably turned out to be too busy to drive them.<HR></BLOCKQUOTE>

Hi Dave,
Yes, I planned to drive your car at the Mid Ohio Viper Days event and am sorry I didn't get a chance. My main priority on the track was to work with John Hennesssey and Larry Macedo on the Venow 650 that we were testing and tuning for the week long Michelin One Lap of America. On Sunday, after we were done and the car was ready, as I recall, your car had an engine problem and was not running. If you would like to schedule a track day where I could devote all my attention to your projects, let me know and we can work out a schedule.


Regarding how this thread has progressed, I am not quote "P.O.'ed" at anyone and find the Mumford Adelberg "war of words" a fun read, though it took this topic in another direction. As I had mentioned in the original post that started it all, I hope you all take the time to read the article in the Viper Magazine titled "Brakes 101". If you're going to do much more with your Viper other than enjoy the pride of ownership, you would do well to educate yourself on the mechanics involved in how it works.
I think the VCA discussion board is proving to be a great place for fellow Viper owners to share experiences and information, as there is more that we can all learn.


Sean Roe aka "Obewan' Seanroebee, owner of Jedi Knight Vipers, May The Torque Be With You!"
Central and North Florida VCA Board of Directors Member under President Gary Lashinsky
VCA member: 1998, 1999, 2000 and just paid dues for 2001

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[kverges]

Holy Brake Rotor, Batman!

I actually have to call BS on just one thing.

No way Tittle could get a date to need them subtle brake feelins.

How 'bout we solve this whole thing with a Thelma and Loiuse chicken run kind of thing; all but the best brakes end up . . . .

 

[Jay Lopez]

There is a good article on brakes in the latest issue of Grassroots Motorsports. The article is not on their website ( http://www.grmotorsports.com/ ), so you'll have to make a trip to the store to get it.

 

[dtittle]

That's a great idea Verges! Why don't we schedule a "BRAKE OFF"!!! Get all of the players involved and do the test. I'd be happy to put my money where my mouth is and see if I can't "BRAKE IT OFF" on somebody. Frankly, I would rather do that than keep listening to Shawn imply I'm an idiot. I mean really, what's up with this:

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Remember, ANYBODY can buy larger calipers, take them to a machine shop and say "can you make brackets so I can bolt these on my Viper?". The difficult part is getting the master cylinder and booster mechanics right. After 15 years of professional racing, working on 3 factory road race teams and campaigning programs myself with factory support, I'm having a hard time watching people who have only been club racing a couple years telling you otherwise.
<HR></BLOCKQUOTE>


(Well I had absolutely NO EXPERIENCE with having kids and miraculously got it right the first time!)

And What's up with this?
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
"If you're going to do much more with your Viper other than enjoy the pride of ownership, you would do well to educate yourself on the mechanics involved in how it works."
<HR></BLOCKQUOTE>

Historically Shawn, because you're such a nice guy and because of your impressive resmume', I would've NEVER even thought of tossing stabs your way like you've been throwing mine. What gives dude? If I'm so inept, why do you EVEN CARE? It seems to me that if I'm so inexperienced and below your radar as you imply I'd be "Like a Button Off of Your Shirt". But instead, you'er like the "Little Boy that Cried Wolf" and you protest toooooo much about about my skills. Once again, if I'm SOOO illiterate to cars why would you bother even stabbing at me?

Here's the deal, go out and set your best car's alignment straight up and shoe on a fresh set of Hoosiers. Let's say 315/345/17 front and 335/17/35 rear on Purners rims. Get new pads or rotors or whatever you want and I'll do the same. We'll meet in the middle and get the VCA/ViperClub.org come to watch. I've got some cones, video cams and radar gun, and I understand that you've got data aquisition. Let's bring it all together and put one unbiasted driver in both cars, warm up the brakes, and beat the shuppee out of them for 20 to 30 bonsia, cranium crakin', eye poppin, skrot@m scrapin' runs and let see who emerges the illiterate. Heck I'm currently scheduling a review of my brakes systems on both my GTS's and the Z06 by a major magazine. Maybe they could do it for us? Or, just pick a Viper Days event that's a few days away (so I can recover from my eye surgery) and let's do this right!!!


WAR BRAKES!!!
WAR TRACTORS!!!
WAR INEPTITUDE!!!
and
WAR OBEWAN!!!

Just Havin' Fun, Tittle

 

[Bob Woodhouse]

TOO FUN!!!!!! Fellas, would you count me in, especially if it is a Viper Days event, Could you substitute this for the tire changing pit stop contest on Saturday?

Except, if we used my rules it would be who had the best brakes on lap 20 without using John's sand pile eeeyikes. Sign me and "brake man" up, Sean missed my comment completely regarding brake pad sizing front to rear so it looks like aside from John's bargain of a lifetime sand stop all I have to tremble over is you Mr. Tittle.

 

[Bill Pemberton Woodhouse]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by JonB-Pace Car Pilot:
I've been accused of having a memory like a steel trap, (nothing gets in!) And methinks Bob W. has already TESTED the "Sandtrap method" at a certain desert track near Pahrump, NV.......

Simultaneously testing aero-devices as I recall.........

<HR></BLOCKQUOTE>

Dear Jon,
Hmmmm, a Dear Jon letter, but I digress..................
I PERSONALLY AM VERY PROUD OF MY BOSS AS HE HAS PERFECTED HIS SANDTRAP BRAKING METHODS AT; GINGERMAN RACEWAY, ROAD AMERICA, HEARTLAND PARK-TOPEKA, MID-OHIO, TEXAS MOTORSPORT RANCH,SPRING MOUNTAIN MOTORSPORT RANCH, AND ROAD ATLANTA. HE PERSONALLY WILL NOT BE SATISFIED TILL HE HAS TESTED THE LIMIT AT ALL THE TRACKS IN AMERICA.BEWARE!!!

WAR WOODCHUCK!!!!

 

[Jim Hodel]

For those of you actually interested in a technical brake discussion, here are some real measurements and calculations that compare the piston sizes and areas of various brake calipers.

The stock Viper 4 piston calipers have 36 mm and 32 mm pistons for a total area of 18.21 sq.cm.

The AP 6 piston system (on a Mitsubishi 3000 GTVR4) has 38.1 mm, 31.75 mm, and 27 mm pistons for a total area of 25.04 sq.cm

An Alcon 4 piston system (on a Z28) has 42.0 mm and 37.0 mm pistons for a total area of 24.57 sq. cm

The stock 3000 GTVR4 4 piston calipers have 44.0 mm and 38.0 mm pistons for a total area of 26.55

The stock Z28 1 piston calipers have a 60 mm piston for a total area of 28.26 sq.cm

The Viper piston area is quite a bit smaller then the stock 3000 GTVR4 caliper, and is also smaller then either of the after market AP or Alcon calipers. The 4 piston Viper front caliper piston area is approximately 27% smaller then the 6 piston AP system.

Is this difference enough to require an increase in master cylinder size to retain similar pedal feel? I don't know, but a 27% difference does seem significant.

My brother and I have driven the Z28 and 3000 GTVR4 many times at PIR with the stock and upgraded systems. I have also run my stock Viper at PIR. If anyone wants to have additional discussions of the relative braking performance of these and other systems, please let me know.

Jim

 

[dtittle]

Shoot John, I totally forgot about that! Oh well, I dun upped and drawed the line in the sand and I can't back out now! I aint skeert'.


WAR BRAKES!!!
WAR TRACTORS!!!
WAR INEPTITUDE!!!
WAR OBEWAN!!!
and now
WAR GINSU!!!

You guys are awesome. T

 

[Supercharged Vipermad]

Well look who it is...John "Shirley" Mul-Hennessey!!!! You're not supposed to care about things like stopping or turning, John. I do like the optional pile of sand, though. Funny how this post was 2 days old and destined to be obsolete until they spruced it up a bit.


WAR ROAD-RACERS!!!!!!!!!!

 

[dtittle]

I think 10 but that's supposed to be a secret!!! The decals added 5 and the big tips he uses added 20. He cheating though, all he really did was grind the Hundia and Opel insignias off of the calipers and then attached the old awning from the track trailer to the rear tow hook. And he's putting VHT on his Nike's. No Fair!

TOO MANY WARS TO LIST...

 

[GTS Dean]

Jim,

You forgot to multiply the front piston area by two, because there are 2 pairs of pistons per caliper. However, ratios are directly proportional.

Also remember that the same front line pressure is going to both font wheels, so braking G is essentially controlled by the width, frictional coefficient and the vertical loading of both front tires.

Master cylinder displacement must allow ALL the system's pistons to move adequately without excessive pedal travel or exceeding the mechanical advantage of the pedal/booster linkage.

In the grand scheme of things, rear brakes typically don't do much useful work once weight is transferred and the chassis has taken a set. The time to maximize their effect is on initial application. This is why there is a proportioning valve - to keep them from locking up after the nose dives and the rear axle unloads.

 

[Jim Hodel]

Right you are Dean. The calculations were for one side only.

I was buying some brake fluid at the local race shop today, and they have the 6 piston GN III Willwood calipers. The Wilwoods have the largest total piston arrea of all the calipers I have measured, a total of 34.23 square cms for one side of the caliper. That is almost twice the piston area of the stock Viper caliper.

I am not trying to imply that piston area is the only factor in brake design. These statistics are more related to the discussion on whether increasing the number and size of pistons will require an upgrade to the master cylinder in order to maintain pedal feel and good control under threshold braking.

The stock 3000 GTVR4 brakes faded fast at PIR as well. The six piston AP calipers and stock rotors made a modest improvement in stopping distance and fade resistance. Adding 14 inch rotors made a significant improvement to stopping distances and fade resistance.

The stock 95 Z28 brakes were hopeless. The single piston calipers would fade in only a couple of laps. The upgrade to the Alcon 4 piston calipers and 13 inch one piece rotors was excellent. The stopping distances and fade resistance are excellent.

My first day in the Viper with stock pads and fluid, I tried to use the same braking point as the Z28, and I did not make it through turn one. I was going 20 mph faster at the baking point, but the stopping power of the stock Viper system just wasn't there. I have installed Poterfield R4 pads and Motul 600 fluid and will run another track day before I make any other upgrades to the Viper.

Jim

 

[GTS Dean]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Jim Hodel:
Sean and Dave, I still don't quite understand the relationship between the number of pistons per caliper, the piston caliper bore, and the piston area per pad.

I understand that multiple pistons and differential piston sizes can reduce pad taper, but help me understand how moving from the stock (or other) 4 piston caliper to a 6 piston Willwood, AP, Alcon, or other caliper effects fluid volume, piston area, and pedal feel.

The stock Viper pads are about 4.25 inches long, and I think the 6 piston pads are around 6 inches long (pads for Alcon 4 piston calipers are around 5 inches) I do not know what the relative piston sizes and overall piston volumes are between 4 *** and 6 *** calipers. How much larger is the total piston caliper bore, piston area per pad, and resulting fluid volume between the stock caliper and the 6 pots?

At what point does an increase in total piston area and fluid volume require a change (I.E larger) master cylinder? Also, do larger pads stop better, or is it more that they wear longer?

Thx, Jim Hodel


<HR></BLOCKQUOTE>

I'll take a quick shot at this. First off, larger pads wear longer and they are more consistent in performance. More pistons, as Sean said, are there to equalize the forces thru the backing plates of the pads into the lining.

Second, brake effectiveness is directly related to coefficient of friction between the lining material and disc at a given temperature. The main thing we are trying to do is to keep the grip vs temperature vs wear equation within a reasonable window.

Looking at Sean’s tables, you should notice some fundamental force relationships:

Larger master cylinder pistons reduce the line pressure available from a given input force. Larger caliper piston area (total) increases the net force applied to the disc with a given line pressure. If the pads are the same size and compound, then increasing the caliper piston area will make them more aggressive up to the point of temperature fade or a wear rate you can’t tolerate.

If you look at the pedal travel table, you will see that more caliper piston area (whether by larger pistons or more pistons) requires more volume of fluid to be displaced and that means more pedal travel. More pedal travel (smaller MC bore) will probably give you a more linear feel for pedal travel vs rate of deceleration as long as you don’t over-center the brake linkage.

The faster you enter a braking zone (at a given vehicle weight) the more kinetic energy you need to convert to friction and heat, because the car can only corner so fast. Faster drivers, or more horsepower on the straights, place higher demands on brake system performance. Assuming the factory engineers were reasonably close with their component sizing, the first thing you do is experiment with brake compound changes to get past the pad fade and wear problems. Then, you can experiment with different compounds front/rear to achieve better balance from the stock system.

If you want to (and this is the reason for this whole argument in the first place) you can buy a complete aftermarket setup that is focused on more specific performance objectives – like consistent track performance for hour-long (or day-long) races at ambient air temperatures of 120F running slicks and 700 hp with double element wings and 6” splitters sticking you to the track.

Do yourself a favor: analyze _your_ performance *requirements* (not necessarily your dreams). Talk to lots of people who have spent money in different ways to satisfy their own specific goals. Ask them why they did what they did, if they are happy now and if they would do the same thing again....