96CollectorSport

Jim,

Short answer is yes.

The 97-00 cars have an external mechanical brake bias, so you can either add a heavier spring, like the one DRM sells, or gut the block all together and add an adjustable brake bias valve like the one Wilwood sells - actually I perfer the one AP sells (I've had issues with more than one Wilwood valve in the past - but that one's $80 vs $300 with the AP)
You can pull the fuse, dial in the brake bias the way you would like and either run it that way or add the fuse again and run a more balanced system with ABS.
The issue with the 97-00 cars is that "ice mode" triggers at lower g-levels than with the later cars, the 97-00 ABS modules are also know to have internal faults and once the fault sets it's junk. So it's easier to sort out but also more likely to send you on a scary ride.

Obviously you know what I'm talking about there Jim!

I wish I knew more on how the 01-08 Delphi modules block off the rear circuits but I've never been able to find that out. All I know is that it makes the car a bear to drive, you can drive the car like that but you have to tip-toe around the track and you absolutely kill the front brakes, obviously not the best way to run fast laps.

jtmck

[QUOTE=96CollectorSport;1590008105]Jim,
I wish I knew more on how the 01-08 Delphi modules block off the rear circuits but I've never been able to find that out. All I know is that it makes the car a bear to drive, you can drive the car like that but you have to tip-toe around the track and you absolutely kill the front brakes, obviously not the best way to run fast laps.

Joel,
So......pulling the fuse on the 01-08 gives you only front brakes.
Could it be that normally there is very little rear brakes on the car and the module is just reducing the front in heavy braking? Pull the fuse and now you have full normal front braking?
Could dramatic increasing of the rear pad or rotor help?
I think I am reading that the rear should lock up if the fuse is pulled, but you have found that not to be the case. Correct?

RX-Ben

I drove my '01 w/o the ABS fuse for 2-3 events a few years ago when the ABS module was getting repaired. It was not that difficult to drive, but I did not A/B test vs a working setup on the same day. Without ABS working, I've only locked up the fronts (once w/the fuse pulled, due to nonsense traffic on a flyer, and once when a wheel sensor went bad under threshold braking).
I think the reason for this is that the ABS module defaults to a "safe" F/R bias with a bad WSS or a pulled fuse.

skxf430

Robert,

What pads are you using on your car? My front vs rear pad probably last 3 to 1 and maybe even more. I recall Mikymu saying the ZR1 calipers use pads that are slightly thinner than an aftermarket BBK so he is going through a lot of pads as well. From what I understand you are somewhat limited by the pad selection with the ceramic brakes so it has been difficult to find a good pad for street and track.

On my BBK, I have been using the Endless ME20's and N05S with really good results. I can get 12 to 15 days out of my fronts and there is still some pad leftover. I don't run them down to the backing plates because I have to still drive my car home but they would probably still last another couple of days.

Robert R1

Stock pads. There are no viable alternatives for the CCB's unfortunately. Atleast from the research I've done, no one is in any hurry to make one either.

If adding cooling and front downforce helps out my issues, I'm certainly game to try it out. Those two elements should beneift the car in general anyhow.

Wow at your pad life! And since I know your pace that's even more impressive. One of these days I might just have to sit down and do the math. I recall you stating your brakes being at a "press and forget" state which would be nice to achieve.

Then I'm sure there will be something else to deal with

DLC7

WOW. Now this is the kind of thread i was looking for....Thanks again...

96CollectorSport

Jim,

I think Ben's answer above is more accurate about the rear brake bias defaulting to more front heavy setting when the fuse is pulled, I've always looked at it as the rear brakes being "shut off" when in reality it's just a system that is already front biased becomes even more front biased.

Now it seems like there is a difference in opinion as to what happens when the fuse is pulled, I believe that the system becomes more front heavy and limits rear braking. Bill on the previous page believes that there is no rear bias at all and it will make the rear lock up first.

My experience is with Geff's ST2 car - a full aero 02Z running StopTech ST-60 front and ST-40 rear brake kits. When we would get an ABS code he felt like he had no rear brakes, lock up front tires, the back end wanted to pass the front and we would go through a set of front pads much quicker.

I can see how someone would think that the rear is locking up, especially if they trail brake, but I feel like the loose feeling under braking is because of too much front brake and not enough rear.

Bill Brinkop had his ABS go out on him at NASA Nationals a couple years ago and stated that his rear brakes locked up on him - that was probably true because he was running the stock fronts in the rear and a ST-60 kit up front. Those rear brakes were so much larger than a typical rear brake set-up that once the ABS stopped assisting he was along for the ride.

One side note, I don't think a lot of us realize how much ABS interacts with us at the track. You can learn a lot about your cars overall set-up when the ABS goes bye bye. There are so many things that contribute to how the car feels under hard braking. Alignment, ride heights, corner weights, spring rates and shock settings all have a part to play in this. That assuming that you don't have any mechanical issues like bushing deflection or play, loose/worn bearings, ball joints or tie rods. You can throw aero balance in the mix too. Everything works off one another and the ABS can mask a lot of stuff to make the car "feel" fine.

skxf430

There is always something to deal else with on these cars.

That's what makes them so entertaining. Lol

johnny c

We have some conflicting information. I wouldn't classify a ABS failure equal with pulling a fuse. a failure could be any number of things and All we know is that the unit isn’t functioning properly. it could be the electronic bias that failed to one side. Also another thing to consider. If the unit failed maybe the engineered balance for the ST kit is a heavy front bias. Maybe when the ABS called it quits it also quit compensating for that bias. The only way to know for sure is to put a line pressure gauge on the car and test it with (and without) the abs fuse pulled.
Anyone got a line pressure gauge?

96CollectorSport

As a matter of fact I do! I'll give it a try today and report back.

johnny c

now we are getting somewhere.

96CollectorSport

Here is the pressure gauge I used:



I took the bleeder out of the LR caliper and installed the gauge, turned the ignition on and pressed on the brake pedal.
I got 400 psi
Pulled the ABS fuses and pressed again:
I got 150 psi
With the ignition off:
I got 300 psi
If I pulled the connector off of a wheel speed sensor:
I got 200 psi

Now this isn't with the car running so I don't have the vacuum booster - but I think the results speak for themselves.

Please make sure to read the revised results below - See post 56

johnny c

OK, so it has been confirmed. pulling the ABS fuse kills 75% of the line pressure to the rear. SO we cannot pull the fuses on our cars. all the balance will need to be set up on paper first.

jtmck

Joel,

jtmck

Joel,

Damn computers

What year car did you test?
How would that apply to my 1998?

Thanks Jim M.

96CollectorSport

The car is a 2002 Z06 with StopTech ST-60 front and ST-40 rear calipers.

However I would take the above numbers with a grain of salt, I was trying to push on the pedal and read the gauge at the same time - so my level of pedal pressure may not have been as even.

So I re-did the test with someone else looking at the gauge as far as pedal pressure - I pushed pretty much as hard as I could.

Here are my revised and hopefully more accurate numbers.

Key off: 1150 psi

Key on: 1300 psi

Key on fuses pulled: 1000 psi

Key on fault set: 1180 psi

So here we see it's not as drastic as first thought.

Also for fun I fired the car up to see what the readings would be with the booster and I pegged the gauge!!! Well over 1500 psi!

For reference sake I will take some readings on the front as well just to compare.

96CollectorSport

Tell you what Jim, I'll bring the gauge to Road America at the end of the month and we can find out.

johnny c

it's still alarming to me that is changes 16%. anything over 5% is noticeable. if it where stable at 16% change we could run pad compounds square. (currently everyone likes to run lower tq rear)

parsonsj

In the thread below, I did a similar experiment to see what sort of caliper pressures were valid on a front caliper (2007 Z06, Wilwood Aero6 calipers). I only see about 1200 psi (1168, actually), with engine idling, ABS intact, and standing on the brake with all possible force.

https://www.corvetteforum.com/forums...re-values.html

froggy47

Good thread, thanks all.