Why do we have such bad brakes?

[Ron]

<FONT face="Comic Sans MS">Was flipping through the latest issue of R&T and came across the Road Test Summary. Always fun looking at how many cars we're faster than....

Anyway, while knowing we aren't the best in braking, I was shocked to see that we're pretty much the worst!

Why I ask, do we take 20% more road (47 more feet) to stop from 80 than a Subaru wagon?

Why does a Volkswagen Beetle GLS stop 44 feet quicker?

Mercury Cougar, 48 feet quicker.

At least we're 17 feet better than a Rolls Royce....

I know the R&T tests were 1999 Vipers without ABS, but if ABS helps that much, somebody please design a cost effective retrofit system quick!

I also know brakes are a very controversial topic around here, but could someone explain why stock Vipers are so brake deficient? Our brake system specs seem impressive, but what is the Achilles heel and what is the best way to address it (cost effectively) WITHOUT COMPROMISING ONE PERCENT OF RELIABILITY?

Thanks!</FONT f>

 

[JimDavis MT 97GTS 650R]

I blame vehicle weight. Of course I could stand to loose some pounds myself!

 

[Mike Brunton]

I'm curious too..

I know the Viper can lock it's tires up at 60mph easily, so it should be capable of braking as good as other sports cars of similar weight - but it isn't.

The problem seems to be that it locks up the wheels WAAAY to early. Sometimes it's only one corner (bias problem?), sometimes it's both fronts. but that's the problem.

My first guess would be that the way the weight is distributed in the car, it doesn't transfer forward over the front wheels effectively during braking. The car doesn't "dive", it just pushes forward. I think the Viper is so low, and the center of gravity is so low, that the downward force on the front tires is not as great as in something like a Vette, or a 911, or even a Subaru wagon. I'd love to hear force #'s over the wheels during braking for various cars.

Friction is a function of the coefficient of friction, the surface area, and the weight. Less weight pushing down means less braking force, which is why the #'s **** so bad. I bet if more weight was over the front wheels, and the car was a little higher up, the braking #'s would be a LOT better.

 

[Mike Brunton]

The thing is, if you can hit the lockup point at 60mph, then the car has the ability to provide maximum braking potential to the tires from 60 all the way to 0. Since we know the tires provide good grip (from acceleration and lateral grip #'s), we know it's not a traction issue due to the tire choice. I hear what you're saying about the "balance" of the brakes, but I've found it easy to modulate the brakes to the lockup point on my '98, I never felt it was an on/off switch between medium braking and lockup. Also, I think the reason we go with larger rotors is because they provide a larger heat sink with more capacity. Meaning you can brake harder, more times before you start to get brake fade.

K Adelberg is completely right too, that the rear brakes are basically worthless. But I think even those that have good rear brakes can't stop as good as a Z06 or a 911. I think it's a fundamental problem with the car. Hopefully the 2003 will have it "fixed"

 

[Hiper]

I realized the same problem with my brakes! Although the 2001, in my opinion, seems to brake better than the 2000 thanks to the ABS, it still isn't satisfactory enough for such a car! My Porsche feels MUCH safer and better at braking, although it has the standard brake system. Porsche is even outdoing itself with its new Ceramic Brake System, which is supposed to give 30% shorter stopping distances and much more life on the pads and discs. Now that is amazing!!! Dodge should really do something with the brake system for the 2003! But even if it doesn't, I'll still get one

 

[dtittle]

Okay, here are some reasons:

Although the Viper has huge tires and "should" have tons of traction it also has tons of anti-dive built in to the suspension geometry and under "normal" driving, (on the street) the tires don't get more traction than the grabby stock brakes do...then...lockup.

The big tires actually hurt the Viper under normal conditions due to the weight per square inch of contact patch.

Most people actually use pretty agressive track style alignments
on the street reducing the contact patch (force) issue even more. If you're cornering (trail braking) some of the tires will have excellent traction (hopefully) and won't be easily overridden by the brakes.

The front brakes are grabby and don't release well and the rear brake totally *****.

Get better brakes and set up your suspension and alignment correctly.

Just some extra .02

Regards,
Tittle

 

[K Adelberg]

This is a big problem with the car. The main problem is the rear brake, which is worthless. The front caliper is a Brembo 4 piston. Its decent, but the car has really no braking capability in the rear. I feel like the brakes were taken off a Ram Truck. My Suburban will out brake a stock Viper.

Now I have the Stop Tech Brakes and WOW what a difference.

This is total ignorance, but looking at the pictures only of the new race only GTSR, it looks like the front calipers are the same as the rear. May be a balanced system, but I was hoping for Porsche braking ability. Maybe I am wrong.

 

[YellowSnake]

I DONT STOP.

 

[Richard K]

Just a further confirmation that the front Brembo's are pretty descent, but the rears are useless. In fact I think it's somewhat humorous that the stock rear brake caliper now sits on the opposite side of the rotor and acts strictly as the parking brake on my car after installing an aftermarket big brake package.

 

[Mike Brunton]

1 bad,

I don't see how caliper size matters? I mean, if I can lock the brakes up at 60mph and keep them locked down to 0 (which I can), then obviously I have the ability to reach threshold braking the entire time, therby maximizing my stopping distance.

Given that, what would bigger calipers do? Make me lock my wheels up more?

I think Tittle is right on the money here (I think he is saying what I said before), that the car does not trasfer weight effectively, an so it "pushes" forward rather than putting weight over the front wheels, adding traction, and stopping quicker. I am positive that is the biggest factor. Add in the evident suckiness of the rear brakes (which only give you 10% of your braking force anyways), and you're not stopping so quick in the ol' Viper.

Let's HOPE Dodge has addressed this in the '03. I can't imagine they wouldn't, since it's the lifelong beef about the Viper - the brakes.

 

[Steve-Indy]

...and doesn't the current 996 (2001) Twin Turbo Porsche currently weigh over 3400 pounds as well ???

 

[YellowSnake]

GLAD TO SEE YOU DONT GET FLAMED LIKE I DID IN "VIPER IS HELD TOGETHER WITH PLASTIC AND LUCK" http://vca1.viperclub.org/ubb/Forum14/HTML/008276.html WHEN YOU SAY SOMETHING THAT MAY BE NEGATIVE ABOUT THE VIPER.

 

[Bob Woodhouse]

Mike and Dave and all, you are getting warm here but the real reason our cars suffer in stopping distance: Brake balance front to rear. You are right, caliper size does not matter when referring to the ability to lock a wheel. The problem we have is that our brakes are designed with 80% of the stopping power in the two front wheels and the rears, well hey who needs to work, we are only being asked to do 20% of the work. When you get all four corners to exploit their maximum traction available you will stop a car fast. Yes of course there is much more to this, like weight transfer (a whole nother world in suspension design etc.) but that is not a major concern. Our street cars can be improved without changing suspension etc. The brake system needs to be balanced in around 65/35. So for the simplest "where do I start" ask some of the brake guru's here how you pull out your o-ring from your metering block. From there be prepared to spend some money with Stop Tec or Brakeman or Dilusi

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

I don't see how caliper size matters? I mean, if I can lock the brakes up at 60mph and keep them locked down to 0 (which I can), then obviously I have the ability to reach threshold braking the entire time, therby maximizing my stopping distance.

Given that, what would bigger calipers do? Make me lock my wheels up more?

I think Tittle is right on the money here (I think he is saying what I said before), that the car does not trasfer weight effectively, an so it "pushes" forward rather than putting weight over the front wheels, adding traction, and stopping quicker. I am positive that is the biggest factor. Add in the evident suckiness of the rear brakes (which only give you 10% of your braking force anyways), and you're not stopping so quick in the ol' Viper.

Let's HOPE Dodge has addressed this in the '03. I can't imagine they wouldn't, since it's the lifelong beef about the Viper - the brakes.

<HR></BLOCKQUOTE>
Yes, O3 has it right.

 

[kverges]

Bob and David are on target.

I have done the calculations - the stock viper calipers are set at 71% front bias for the '92-'00 cars; the front bias is 63% on the '01-'02 cars. Now, with a Viper stopping at 1g and if the center of gravity is about 15-20 inches high (I don't know the precise number), the weight transfer to the front results in about 62-66% of the weight on the front tires. Voila, the late model cars are set up with exactly this range of bias and so lockup is far less likely (also assuming equal grip front and rear). Add that to ABS and the new car is substantially better, at least on paper. Oh, and also figure less chance of fade, as the larger-bore rear calipers dissipate more heat into the rear rotors and less into the front.

I somewhat disagree that the anti-dive affects weight transfer, as weight transfer is simple physics caused by the center of gravity being above ground level and the car's wheelbase acting as a lever. Anti-dive also keeps the front from squatting and squatting causes camber changes, which can in turn reduce the contact patch of the front tires. All modern cars of which I am aware have anti-dive built in and in theory anti-dive should reduce camber changes under braking and increase the weight transfer rate, since the suspension does not have to travel as much. But then again the suspension geometry is altered in order to keep that weight transfer from causing the suspension to compress(front) and rebound (rear), so there is some loss of transfer to the contact patch, it would seem.

Finally, note that the basic StopTech kit (the front caliper kit) uses SMALLER bore sizes than stock to improve bias. I have this basic kit on my older RT/10 and it works very well, although I go through rear pads much more often, as you would expect. A four-wheel setup with carefully desigend bias and fluid volume to match the master cylinder is best. But never jump on the bandwagon that bigger is better, even in brakes. Hopefully the '03 SRT/10 will have all of this squared away.

Nerd boy out.

 

[Gavin]

Good input there - here is a bit more!
1 bad gts raises the point regarding the size of Porsche rear calipers (they being roughly equal in size to the front calipers). Note these are rear engine cars (more weight on the rear tires) therefore the rear tires can handle a much higher percentage of the overall braking than a front engined car.

Sean Roe has an excellent solution for the Viper- that is a complete braking solution. i.e. six piston fronts, four piston rear calipers, pads, braided lines (have to have these), new master cylinder - front to rear proportioning valve (adjustable)- add a set of Porsche air deflectors and you will be guaranteed to STOP - downside - carry a spare set of rotors (cheap from Dodge) - a couple of open track events and they warp and start to crack - (the harder you are able to brake - the more heat generated)(StopTech has rotors that can handle the extra heat better than stock rotors)

Regarding the conversation "can lock up the fronts with the stock system so why do larger front calipers make a difference?"

I don't know that they do - what makes the difference is having effective rear brakes - this allows for overall harder, shorter, and more effective braking and more front braking- therefore you can add bigger front calipers. (some will disagree - they add bigger fronts only and feel they improve braking - personally I beleive the increase the "out of balance" situation by doing just the fronts)
Look at it from this point of view:

Long straightaway - stock brakes- gotta get on the binders early to get the thing slowed to turn
Same Straightaway - a fully balanced brake system like Seans - We are still on the gas accelerating at the "stock systems" braking point - braking is now much later, you can brake harder without lockup (balanced system)and I think carry a little more speed through the turn as the car is not as much in a nose dive condition (it is more in balance, front to rear) therefore the front is less likely to push (car will turn in better) and the rear is less likely to get loose as the rear tires are more firmly planted and have more grip.

hope this little bit helps

 

[Ron]

<FONT face="Comic Sans MS">Lots of great feedback! Thanks to all.

Now how about some hard facts.

How many out there with upgraded brakes can provide G-Tech or better, 60 ~ 0 distances, or 80 ~ 0 or something, anything, that will help us evaluate the effectiveness of these changes?

In addition, could some of you that unfortunately experienced brake failure share with us (even without mentioning the vendor if you prefer) the ultimate cause of the failure so again, we can make the best and safest decision for our own cars.

The shortest stopping distance system is worthless if it fails on the way home from the track.

Many thanks.......</FONT f>

 

[ACR Joe]

This is a very compelling thread that is well worth absorbing. I've had brakes on my wish list for some time. The information posted will be most helpful in providing direction and expectations.

Thanks to all contributors .....

 

[K Adelberg]

This is a great thread. I have had experiences with a tuner, whose brakes I had on my car, which turned out to be a nightmare and potentially life theatening.

Now I use the Stop Tech Brakes, which are really something. Most of the race cars at Viper Days are using them. Now even my little follower, Mumford, is using them with great satisfaction. I personally feel they make the best kit for the Viper. I think the Porsche kit is well favored too, but more expensive initially and to maintain.

 

[Bob Woodhouse]

Yikes Sam,
This brake company you just bought has some of the better sorted out brakes on the market for a Viper, but you need to read up on them brakes my friend.
To all my stock-brake Viper associates: DO NOT install a proportioning valve in your system. We will be sending your spouse flowers. There is no way you can put an aftermarket proportioning valve in your system and make it work, the explanation is long so I will spare you all. A few have cheated the grim reaper and live to substantuate this advise. Call Ron Adee the man who won "One Lap" in his Viper. I have his number at work if you would like to follow up.
Regarding the original stock proportioning valve, I have written the explanation and removal procedure a couple of times over the years and am too lazy to offer it again here tonite so if you cannot dig it out of the archives using key words, like proportioning or maybe by my name, then check with Jay Herbert or Joe Houss. We should put it in the do it yourself section of this site.
RE: the comments on evaluating brake performance with stopping distances, that's OK I guess, but I don't think you will learn much. If I wanted to spike all you brake tuners including the ones I represent which is Brakeman and Stop-Tec, I could do it with stock brakes and just two things: allow me to pick the master cylinders and the tires.
The main reason all these aftermarket brakes are justified is to keep stopping you after 30 consecutive laps at your favorite track.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Venom 650R:
Why tamper with the metering block? Install a prop valve and make adjustments as necessary for the driving task at hand. Glad to hear K.Alderberg is so enamored with the Stop Tech kit. It does buy you a point at Viper Days. Go figure. I've heard they're great brakes. However I also believe the Dilusi brakes are as good or better. K. did you install that Stop Tech kit yourself?


Sam Sloan

<HR></BLOCKQUOTE>

 

[Ron]

<FONT face="Comic Sans MS">
While one goal might be to continue to stop after 30 laps on the track, another for street use might be to just stop quicker.

I've got to believe shaving 50 feet off our 80 ~ 0 distance might have saved a few of our departed Snakes........ </FONT f>

 

[Frank Parise]

GODFATHER, great to hear from you! You have valuable data that I'm keenly interested in. I'm curious as to what the operating costs have been on the Stop Tech system. I guess my main question is how often you have to replace front pads, rear pads, front rotors, rear rotors...and what is the cost of each? How often do you have to change the hats, and at what cost. When will you need to replace piston seals, and at what cost? Also, what is the complete up-front cost of putting the entire 4-wheel system on. Sorry for all the questions, but I'd like to know how it compares to my Brembo/Porsche system. Can the Koreans really outdo the Germans? Thanks in advance.

 

[dmora]

Because its an $8000 upgrade. Ceramic brakes are too new/expensive to be brought to the larger consumer market. i know companies like brembo, willwood and baer are all in development for these brakes.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Hiper:
I realized the same problem with my brakes! Although the 2001, in my opinion, seems to brake better than the 2000 thanks to the ABS, it still isn't satisfactory enough for such a car! My Porsche feels MUCH safer and better at braking, although it has the standard brake system. Porsche is even outdoing itself with its new Ceramic Brake System, which is supposed to give 30% shorter stopping distances and much more life on the pads and discs. Now that is amazing!!! Dodge should really do something with the brake system for the 2003! But even if it doesn't, I'll still get one

<HR></BLOCKQUOTE>

 

[dmora]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 1bad gts:
Guys getting back to what Baer Claw said ,could someone please explain to me why all the calipers on the Porsche are much larger than ours.Does it have something to do with fade?

<HR></BLOCKQUOTE>

It has nothing to do with fade. There are cars with smaller brakes that do better than a viper. The opposite is also true. Theres a lot that goes into whats classified as a great brake system. The pad, the rotor, the lines/fluid, calipers, braking electronics.

Im not sure how big the vipers brakes are, i think i heard 13"? i could be wrong. I know i can out brake a c5 in my supra, and im using stock rotors/pads. Supra rotors are "Front four-piston 12.6 spiral vented disc; rear twin- piston 12.6 spiral vented disc." according to tech sheets.

 

[StopTech Service]

Maybe the question to be asked is “Can an American engineered, designed and manufactured product using a small portion of foreign content materials possibly compete with Italian and German companies?” We believe American engineered and manufactured products can compete with anyone.

Lets get the facts straight, StopTech rotors are cast in Oakland, and finished machined in Harbor City (Los Angeles adjacent) at a division of TRW-Kelsy Hayes . Both facilities are QS 9000 certified. All hats and brackets are machined from billet aluminum in house. All hardware is also US made. StopTech brake calipers use castings produced in Taiwan by a company that supplies OE components to other manufacturers including a well known US Motorcyle company. StopTech receives, inspects and then finish machines all critical dimensions in house (that would be Torrance, CA USA).

Our kits have approximately 86% US content.

I spoke with both Paul and Mark Schley this morning to get the exact details of their component usage. Paul asked that I answer some of the questions posed on the board concerning component costs.

The Schley brothers have had our 4-wheel kit longer than any other customer. Here is a break down of parts they have used to date:

First set of front rotors and pads went 684 track miles. They were both replaced at Road America when the pads went metal to metal on the rotors. These were Pagid 4-4 Club race pads that were not up to the task at a hard braking track like Road America. They replaced them with the Pagid RS-14 full race pads.

They have since logged 693 additional track miles. The front rotors look fine and front pads are ½ worn. Rear rotors and pads (also Pagid 4-4 Club race) are still from the original install. Rotors look fine, pads are about ½ gone.

Rotors are $279.00 each. (14”) Hardware kit is $30.00 per corner if using the same drive pins, $60.00 per corner if replacing pins and hardware. Pagid 4-4 Club Race pads are $252.50. Pagid RS-14 Full Race pads are $277.50. Hawk or Porterfield race pads are available at a much lower price but we believe Pagid is the best pad available for a Viper owner that wants to win a Viper day event. We offer an excellent street pad for $95 made by AXXIS.

As far as installation; an experienced shop would take 3-4 hours to do a front kit installation. Add maybe 3-4 hours for the rear kit. These time estimates are at the high end and allow time to inspect other suspension components and not rush things. Add an extra hour for a complete brake fluid flush and cleaning the master cylinder if necessary.

List price for a StopTech 13" front kit is $2295.00, 14" front kit is $2595.00. 4-wheel kit is $4495.00 without parking brake brackets, $4995.00 with parking brake brackets. (2001 Vipers must supply early model rear calipers to use as parking brake)

StopTech is dedicated to providing top quality American made brake systems to the Viper community and we have numerous Viper class wins by our customers.

If you have any further questions, please feel free to contact us directly, we'll be happy to reply.

Sincerely,

Matt Weiss, StopTech Customer Service Manager
[email protected]

 

[Bobby Likis]

It amazes me to hear that so many folks are not happy with their brakes. For the record, mine worked perfectly when I got into a "situation." Unfortunately, I still lost my car because I was going faster than I should... given my limited driving experience, very fast new car, and road speed! I'll know better next time.

 

[99t1]

according to a scientist with the initials EM, number of caliper pistons, amount of contact surface and rotor size does not matter in stopping distance if you can fully brake to lock the wheels...it only matters in heat dissipation.

 

[speedshftr]

as the car evolves i guess the brakes will come.its funny i often wondered why my durango outbraked my viper.i took it as a price to pay for such a mean machine.

 

[Tom and Vipers]

Regarding "weight doesn't transfer to the front"

The only time this can happen is if the CG of the car is on the road surface (zero height.)

If you draw a free body diagram, you will see that either rear or front braking force will produce a forward weight transfer.

Regarding "dive"

Actually, during the dynamic portion of braking, dive delays weight transfer into the front tires because the front springs are being compressed.

If the front springs were solid, the weight transfer would appear at the tires instantly.

 

[Ron]

<FONT face="Comic Sans MS">Thanks Matt!</FONT f>

 

[Frank Parise]

I'd like to commend Stop Tech for sharing such detailed information on their brake systems. The fact that they monitor our message board and respond on a timely basis tells me they are really interested in serving the Viper community. Thanks for your response.