38mm rear caliper information sheet error

[Tom F&L GoR]

Achilles99 pointed out a transcription error in the table I used to explain the 38mm and 40mm calipers. Here's the correction, or if you want a the new Word document, let me know. Sorry for the confusion.

(last row, third column is changed)

Needless to say, StopTech neither endorses nor provided information for this table. Good thing, huh?

 

[jcaspar1]

Do you have info on the Stoptech 4 wheel setup? Seems small but what a difference going from 16 to 18% rear bias makes!! The Stoptech fronts make a huge improvement.

 

[Tom F&L GoR]

The StopTech rear calipers are bigger than the perfect mechanical balance, so you would also use an adjustable proportioning valve. Now we introduce another variable - the brakes are bigger, but we're using them at less than 100%. That is fine, and it is the way to dial the balance in perfectly, but now you can't look at the area ratios alone.

 

[Achilles99]

Might I add that the error wasn't in the final numbers, but only in the formula leading up to it (as Tom mentioned, he made the calculations correctly all along. He just copied the formula he used incorrectly). I was just being anal

I can't wait to try out the new calipers. I'll be sure to post impressions afterwards. Thanks for answering ALL of my questions, Tom!

jcaspar1 - Do you have the Stoptech fronts on your current GTS? If so, can you try to describe your experiences with them?

 

[jcaspar1]

I do have the Stoptech Front 13" setup with rear SS lines and rear slotted rotors. Works great. It has given me much mor confidence in braking. With the stock setup I would lock up the fronts far to easily, particularly in panic situations. It was hard to find the threshold braking point. I always felt like I was braking on ice. Now the fronts feel much more proportional with a larger area for threshold braking. I also seem to stop much faster with far less chance of front lockup. The fronts still do lock up first. This is using the stock Axxis Ultimate pads. I have not experienced fade except during brake-in but I am not really aggressive at the track.
Installation was easy other than a minor error in the instructions. Pedal feels very firm with the SS lines.
The larger rear pistons sounds like a great idea. Better in theory than going with smaller front pistons but the nice thing about the StopTech setup is you get the proper bias with much better cooling rotors/calipers and SS lines all by just doing the fronts. Everyone should be sure to upgrade to SS lines with whatever upgrade they do as it makes a big difference

Do you think there is any advantage of 38 rears with Stoptech fronts? Might be too much for a non ABS car.

 

[Tom F&L GoR]

Actually, if I did the math correctly, the rear piston size ratio using StopTech fronts and 38mm rears is 20%, same as the OEM fronts with 40mm rears. You'd be on the edge as far as needed some adjustable proportioning valve, or at least the stock proportioning valve functional.

That's an interesting combination. I pursued the 38 and 40mm rears ($600 for either size) because it was far less expensive than the StopTech fronts alone ($2200?) However, the above combination might be an expensive version of the StopTech 4-caliper set up, since (with their rotors) you'd have the cooling capability at all four corners, you'd have sufficient brake torque capacity at all four wheels, but you be saving about $1000 (assuming the StopTech 4-caliper system is about $4400, the new combination is $2200 + $600 for 38mm calipers, then add $500? for the rear rotors.) On the plus side, you wouldn't have to cut the rear knuckles to install the ST calipers (save install labor $), you wouldn't have two calipers on the rear (since you still need the OEM calipers for parking brakes) and the resulting weight. On the minus side might be whatever structural improvements ST has made in the design of the rear calipers they produce - and I just don't know what that may be or what the effect is.

Jeff, at first I thought your idea was a little odd, but please excuse me since I obviously was approaching this by being as cheap (too cheap?) as I could. A 40mm rear for $600 was pretty cheap for near-ideal (pseudo-ST) balance. However, your idea is still less expensive than the 4 caliper system and includes the cooling superiority from ST (since you already have the rear rotors.) That would actually be a pretty good setup.

 

[Nadine UK GTS]

Was out today and reminded myself just how good Toms rear brake improvement is when a car pulled out on me! No sudden front lock up, pedal easy to modulate at the point of lock up, and brakes that stop! Thanks Tom, a most worthy, efficient and cost effective improvement.

 

[Bugeater]

Tom,
For somebody that already has the front ST setup (2000 GTS) with what I presume is a 38mm rear, what would you consider as an upgrade to my current setup to try and emulate a 4-wheel ST setup?

I too would be looking at the best bang-4-buck option. Upgrading to ST 4-wheel isnt simply just adding 2 more of their calipers since the 2wheel kit uses a diffeent caliper than they use in combination with the 4-wheel kit.

The balance of my car is pretty good, but am always looking to achieve better braking. Its not perfect.

 

[Tom F&L GoR]

Bugeater,
You have the ST front-only kit, but aren't sure about the 38mm rears? Nadine and I are the only ones I know of that have made larger than 36mm calipers.

Sorry, in my rambling above I was comparing prices more than sizes. You're right, can't just add ST rears to the ST front kit.

Here's my order of things (ignoring heat/rotor issues):
#1 {OEM front and OEM rear}= the original front lock up setup

#2 {OEM front & 38mm rear} or {ST front & OEM rear} = same front to rear braking balance, which is much better than stock.

#3 {ST front kit & 38mm rear} or {ST 4 caliper kit} or {OEM front & 40mm rear} will all allow ideal balance because the rear calipers in every case is now large enough to provide the potential for rear lock up. Therefore, a proportioning valve is used to dial in the ideal braking balance.

Add in the rotors from ST, and braking should be better yet.

What I was trying to get at was that the least expensive, ideal balance, good rotor set-up might be the ST-front calipers, 4 ST rotors, and the 38mm rear calipers. You'd have both the cooling improvement and the braking balance, for (I guessed) about $1000 less than the ST 4 wheel kit.

 

[Bugeater]

Tom,
I believe Woodhouse stated that the 2000 cars received a 38mm piston (maybe the 99's too)?

Assuming I have ST front only kit and stock 38mm rears,
is there an upgrade path for the rears, keeping the front ST setup?

Are you getting a 40mm piston from the abs cars, or are you making them?

 

[Tom F&L GoR]

Buggie, I think someone at Woodhouse slipped Bob a bad number. The caliper for all non-ABS cars is the same. PN 4723606 and 4723607 from 1992 up through 2000.

The ABS cars are completely different, there is an additional bracket to position the pads and caliper. The ABS caliper is a 43mm single piston and the brake hose attaches on the top, which then interferes with a 17" wheel. I know, I tried. Anyhow, the non-ABS caliper isn't thick enough to use a 43mm piston.

To get to 40mm, we sleeve the 36mm OEM piston. The piston isn't simple to duplicate because of the internal cavity to accomodate the parking brake adjustment mechanism. So it's easier to re-use it, sleeve it larger, and hence the price for either 38mm or 40mm conversions are the same. The machine shop (and other auto restoration places) has used this procedure for years to rebuild vintage car calipers.

To answer your question, then, adding 38mm rears to your ST fronts (and rotors all around) would be the upgrade. (With a proportioning valve.)

 

[Bugeater]

Thanks for the explanation Tom. May try this sometime down the road. Whats the cost and turnaround time on rear calipers, or do you do exchanges?

 

[Tom F&L GoR]

John, you have mail.