turbite

mumzer,

ah yes, I do remember reading something about this.
I'll check and see, I'm not sure what the PO put in there.

It seems the best route would be for me to do this and put street pads in the front.
Then I'll definately be able to lock the rears, so I'll just throw in the adjustable and balance it.

Thanks for your help guys!

Oddjob

As long as you have the ATE brake master cylinder and booster, there is no difference in parts between an 87 944T and an 89TS, ABS or No ABS. Same master cylinder 951 355 011 01.

Do you happen to have the Girling master cylinder and booster in your car (rare after '86)?

special tool

Oddjob - I have the Girling stuff on my racecar. Why - you got some info, man??? Spill it!

mumzer

i thought so also...im not sure where it came from but i wound up with an MC that had a 2MM larger main bore...

instant brake pedal...had to change 1 hard line i think.

made a huge improvement...i do think it is an ATE part.

ninefiveone

Hearsay? I speak from experience. I've been doing this for years.

Alan C is the only person I know of on the boards running "no" bias valve and he is running a bias valve although it is open full to the rear. I can only surmise there are other issues at play with his system.

So one guy is your evidence, eh? Yeah, all the other people at the track simply don't know what they're doing. A couple feeble stops from street speeds? You've definitely got enough info to refute years of track experience. (And yes, anything less than honest to god firm application at 100mph+ is pretty feeble)

You may not like my tone or my delivery but I'm just the messenger. The facts remain the facts.

turbite

mumzer:
I'll get you to check out my system at the meet sunday if you're around, otherwise whenever you check out my car. I have no idea what I have in there.

nivefiveone:
I'm not going to get into it with you. If you looking to rant and rave, there are several street racing threads where you can join the lynching party with all your facts.

Oddjob

Special Tool: No, Im not really sure of any performance difference between the ATE and Girling parts.

I believe the Girling parts were more common on earlier cars, and the factory was just using up inventory of these parts after ’86.

For ABS cars, only the ATE parts are listed (which are the same ATE parts as for a non-ABS car, so Im not sure why the Girling parts that are interchangeable for non-ABS, would not work with an ABS car).

I have only worked with the ATE parts on my cars (an 87 S, 87 Turbo, and 2 89 Turbos: all came with them OEM) and I have replaced one master cylinder with a factory new part, and it was the same as all the others. The S2s and 968s all use the same parts too.

Mumzer: I wonder if you have a 928 or 911 master cylinder (I have no idea what parts those models use). The ATEs will have ATE written in the casting, usually on the bottom of the master cylinder.

I have also played with various factory brake proportioning valves. The 5/18, 33, 45, and a 55 bar (the designation is a reduction ratio pressure in bar, not a %). I believe the aftermarket adjustable valves are just a pressure regulator, and flatline the pressure the rear brakes see, where the factory proportioning valve limits the rate of increase to the rear as the overall pedal/brake pressure increases. But someone here has to know for sure.

I used the 33 bar on the 87 turbo and one of the 89s (OEM was 18 for both). The 33 bar on the 87 turbo will still definitely lock the fronts first. I never tried the 45 bar on the any of the turbos, but it might work on the 89s w/o locking the rears first (obviously less of a concern w/ ABS).

I tried the 55 on the 944S (OEM was 33) but it would lock the rears, so I used the 45 and that seemed to work well. Interestingly, the 944S has the same brakes as a plain 944, and a plain 944 does not use a brake proportioning valve at all. I did talk to one 944 racer who said when he locked a wheel under braking, it was a rear. But as squirrely as my car was with the 55 bar, I never considered trying w/o the bias valve.

I have no experience with upgrading to larger (than 928S4) front calipers, so I cant comment on what bias you want to try. But I will recommend this: unless you try threshold braking (on the track) with the track pads and tires you plan to use, you wont know how the car will act at the limit. When I said the 944S was squirrely with the 55bar valve, that means the back end was a little tail happy when trail braking, or occasionally I would chirp a rear tire in the brake zones for major braking corners. Also if there were any pavement changes or uneven ground in the braking zones, the car would dance a little. I don’t believe you can (or should) recreate these kind of extreme braking conditions on the street to test the braking balance of a track car.

Chris Prack

absolutely untrue! A very good friend of mine who started out as a customer has an 88 non ABS non S 951 that I installed big reds all the way around on and the OE master cylinder is more than enough to stop his car. It's a full blown race car that has won it's class running ITE with SCCA two of the past three years.

The biggest issue with all that I am reading on this thread is everyone is making blanket statements (for the most part) and lumping all of the models together to some degree.

For example, you are going to have one hell of a time locking the brakes on an 89 951 regardless of what you install for bias or pads or anything else. The ABS will not let that happen! I know this for fact as I own one and track it regularly.

You need to "tune" your brakes to not only fit your car but also your driving intentions and style. turbite if you have big reds on the front and stock on the rear with no ABS and run competition pads (PF 97, Pagid Orange) you will get rear lockup under heavy braking guaranteed. Adding more bias to the rear will make this worse. You need to balance the braking system and experiment with different set up's to find what is right for YOUR car. Tires, suspension. LSD and weight all will have a dramatic effect on your braking. I have had to do all kinds of different set up's for track cars such as running steel braided hose in the front and stock style rubber in the rear, comp. pads in the front and stock street pads in the rear with and without steel braided lines etc.

For my 89 car I used steel braided lines all around with PF 97 pads and a 33 bar bias. I can jump on the brakes going into T1 @ SP with all the confidence in the world and more often than not the ABS does not cycle. Sometimes going into T5 down the chute I will get a little ABS action but never any lock up. That's the beauty of ABS. I can out brake most cars in my group.

Your mechanic wasn't incorrect in telling you to run your front's on the rear. I would do this with no hesitation. I do it all the time. You just need to be though in the install and not just install calipers and let it eat or you most likely will not be happy with the results.

I am not a big fan of the adjustable bias. It's installed under the hood of the car right? So you drive it and the brakes don't feel so good so you have to stop and get out and adjust it (by how much?), drive it, adjust it and so on. Then the next day when it's raining the brakes suck again and you have lock up. btdt. It's no fun. If you are only going to drive it on the street then I couldn't imagine why you would both with the whole process, at the track you Wilwood bias is going to be a big PITA.

mumzer

then ill add simply "in my opinion"


i never suggested that the big reds wont stop the car...i think they are likely to allow inexperienced drivers to overslow the car.

a major part of a brake systems function is pedal feel and the drivers confidence in what will occur when he pushes the pedal...and a low mushy pedal doesnt inspire confidence. It leads to unconcsious "confidence taps" on the pedal, and driver's overslowing cars in the braking zone for the vintage cars because rather than getting on the brakes hard and applying maximum deceleration for minimum amount of time.


further, a soft pedal and pedal travel combined with modern pads with high initial and non linear coefficients of friction make it very difficult to allow a transitionally locked (ie an inside front) wheel to start rolling again without coming almost entirely off the pedal. this problem gets worse with lighter tires with softer carcasses (like hoosiers)

I would care less about this if i were running higher speed longer tracks, but at places like Sears and Laguna, and even here at Thill with 2nd (1st if the car is geared properly) corners, where a driver is likely to really need HEAVY braking at low speeds, and is likely to have his very best overtaking opportunities under the brakes, the ability to get that locked up wheel turning again is the difference between successful overtaking and flat-spotted tires.

there is no conjecture involved in my assertion that i dont consider the pedal feel of the big red/stock MC combo to be adequate for use on my race car....thats my observation of the facts.

2mm was the measured difference in bore diameter of the unit that came off from the one i replaced it with. Both were marked Ate.

i run a 5/55 prop valve on the car ( the same size tire front arn rear and 51% rear weight)

Chris Prack

Your experience is your experience. I can't argue with that. My buddies car with four big reds being pushed by a stock 951 m/c has a high firm pedal. I would suggest if the result of a soft/low pedal with stock rears indicates another issue.

What kind of brake hoses were being used? If they were worn rubber hoses, this would give you the pedal feel you described.

mumzer

-3 teflon lined stainless...maybe we have a different idea of what is an acceptale pedal.

Oddjob

>"Sometimes going into T5 down the chute I will get a little ABS action but never any lock up. That's the beauty of ABS. I can out brake most cars in my group."

Chris - where were you when I started a thread a few months back about retro-fitting ABS onto a non-ABS equipped car? Having had it on my 89TS, I wanted to add it to my 87T club racer to avoid the possibility of lockup while trying to overtake/pass under braking. I was looking for anyone that had done it from a technical standpoint, but all I got was people telling me not to do it. The consensus from a couple of the replies, was that a good driver can out brake ABS by modulating a 15% lock/slip (point of maximum braking ability of a tire), and that I should just learn how to drive....

When referring to running the front calipers on the rear, this is to take advantage of the larger pistons (36/40 front vs 28/30 rear)?

Chris Prack

Who was telling you that? Maybe I am incorrect but don't F1 cars use ABS? Anyone telling Schumi that he should lean how to drive? Whatever. I would bet that most of those people are just pissed that they don't have it. You know?

I would also like to know how a human being is going to control lock up better then a electo-hydralic devise? With everything going on around you, including driving your own car, if I have one less thing to think about all the better for me.

Installing ABS in a non ABS car is not a big deal. I reinstalled the ABS system into the Tilo SC 928 when I rebuilt the car 3 or 4 years ago.


Yes. The idea is to use the larger pistons.

turbite

I have been told you can mount the adjustable in the cabin. I am not positive on how this is done on a 944, but I am going to try it.
The problem I also foresee here, is that I will be tempted to fiddle with it too much, and I don't want to do this.

In other news, I did get the backs to lock up. I went to my old favorite brake testing spot (280 woodside exit) , and did get them to lock once before the fronts.

Oddjob:
Some people suggested moving the fronts to the back because it has larger pistons.
It seems the stock backs have enough to lock the backs, so I don't see a huge need, except it may effect the pedal feel.

All in all, with my current setup, the brake pedal is pretty high and stiff, but I've never driven another car with big reds. I've got about 1 cm of no action, then it comes an hard and fast.

Great info in this thread!

Chris Prack

Sure you can mount the regulator anywhere you want, it's not a problem. If you are going to use an adjustable, I would not waste my time with it unless it was in the cabin and in reach of the driver.