Quickshift_C5

I didn't compare the two (I agree, that would be silly), just said I owned one. Related topic though, the C5 brakes feel far far better than my 86 did...since I'm using the AP Racing kit. I was comparing the brakes to my other C5 ZO6 that I still have and have tracked as well with the only difference being OEM hardware and using Carbotech XP12 pads. This was in reference only to stopping distance and early ABS activation. Pedal feel, stiffness, range of motion, etc are all a different topic.

It's difficult to tell what someone is doing without being in the car, and it's easiest to blame it on their incompetence (jumping brakes, not managing pressure, etc). I'd say the same thing if someone asked this question. I feel I've exhausted that possibility, or it IS the case and ABS is just engaging far too easily...which it shouldn't be.

So, I'll focus on that. Again. But, I'm curious what some other guys might suggest on what could be checked in the ABS system and if there is anything that might trigger it early. It could be the square tire setup since that's the only thing I've changed, but lots of guys use it without issue. At this point, it looks like a tradeoff between heat management and stopping distance. Strange. Thanks guys!

KNSBrakes

www.rentatechII.com?

RagingGrandpa

Be careful with this method: removing electrical power from the brake manifold disables rear proportioning, so you're likely to get premature rear wheel lock. Unplug the rear wheelspeed sensors if you want "no ABS" while keeping proportioning.

Quickshift_C5

Not a route I want to take then, thanks for the info. There is only one track day left for the year, so I'll give that a shot and report back.

JRitt@essex

As we discussed previously, this just isn't an issue that our other customers are having. We talked about the tire rolling diameter possibly being a problem, but you checked that and it's close to stock. Our systems offer almost identical brake torque output as stock. I talked to our engineering director again on this one, and we're a bit stumped. Here's what he said:

"I suspect that the ABS light coming on just means that the driver is pushing hard enough on the pedal to activate the ABS. When it comes on the deceleration should not be limited. In fact, the ABS should be doing a good job of holding the car near its deceleration limit. If the car was going into ice mode, the car would not make the corner. That creates a huge decrease in brake torque.

The ABS is likely working primarily at one end of the car. I suggest that the driver get a feel for which end of the car is having the ABS kick in most of the time and switch to a pad that has a lower friction coefficient on that axle.

If the ABS kicks in at both axles with the same amount of brake force after the tires have warmed up and the pedal is just too sensitive, then go to a lower friction coefficient at both axles. Not everyone prefers the same pedal sensitivity and sometimes a little tuning is need to make a driver happy."

The tricky part is finding a pad with a lower coefficient of friction that can still handle the heat of track duty. I believe you told me that you tried Ferodo DS1.11. The mu of the DS1.11 really isn't that high compared to many other race pads. DS2500 would be even lower mu, but it's really not up to extended lapping on these cars.

We will keep trying to help you if we can!

96CollectorSport

If you have access to a Tech 2 take a look at the accelerometer and yaw sensor readings when the car is sitting on a flat level surface. I believe they should read 2.50 volts (the accepted range is 2.3 - 2.7. You may have a bad sensor which thinks the car is pitched differently than it actually is.

Another thing you could try is to disconnect the steering position sensor, since the EBCM needs the steering position sensor to calculate corrective action - more for active handling but I'm wondering if there is some cross talk to the ABS - if disconnected it would solely make adjustments based on the wheel speed sensors.

Lastly you could replace the ABS jumper harnesses for the front wheels and (if you want to go extreme - replace all four wheel speed sensors with the SKF HD race bearings)

After all of that you may have a EBCM that is a little jumpy - you could try swapping the EBCM from a known good car into yours to see if it makes a difference.

These are all things to try but some cars just seem to be a more sensitive - I've done all of the above on a customer car and ended up removing the ABS all together and just plumbing up standard power brakes.

Good luck - it's a PITA

jtswenson

I have 2 brake questions on my 2011 ZR1. First, I'm running the Kumho ACR tires in the rear for the first time and I'm concerned about ICE MODE. I'd really like to find a way around ICE MODE as it's incredibly dangerous on the track, (and frankly a stupid feature IMO)...although I understand its use on the street.

Secondly, I feel like my brake bias is far too heavy in the front. I've been playing around with different carbotech pads but nothing seems to help what feels like a crazy bias towards the front.

Thanks in advance! The car will be at SEMA and will be racing in the Optima Ultimate Street Car Invitational following SEMA. I'd really like to have braking confidence!

Rx7Rob

Don't know if this has already been discussed, 78 pages are a lot to look through...

Any info on pre-bedding pads / rotors?

Typically I'm tossing in the pads at the track with no time to bed them in. I do have access to computer controlled furnaces that can achieve several thousand degrees and any temperature ramp profile desired.

I see that Pagid offers pre-bedding, anyone know the technical details?

Thanks

I just found another thread indicating the PFC01's that I run come pre-bedded. Still interested in knowing what is done.

KNSBrakes

Carbotech offers pre bedding. It is in an oven but I don’t know the temp/time etc.

PFC when ending in .44 means race ready which I think is a baking process and they also offer actual dyno bedding which I assume is for professional racing and may or may not be with the actual rotors. The dyno bedding is as you would expect costly.

In to hear Johnny clarify

Quickshift_C5

Thanks! Tested as much as I could on my last track day of the year with the same results using the DS1.11 pads. I used very little pressure, then slowly applied more, etc. doesn't seem like its a matter of stomping on the pedal or it being too sensitive. The ABS light simply turns on constantly. I also tried ignoring it to see what happens and used even more pressure, and there was a lot more brake left in the car. While the light was on, it didn't seem like ABS was actually intervening. Odd.

Dont know what else to do on this one, but it doesn't seem like swapping pads is the answer. Sounds like that's trying to get around an existing problem rather than fixing an underlying issue. As you and your engineer mentioned, this setup should work. As always , I appreciate the help and suggestions. The system is working fantastic otherwise. I literally never have to worry whether or not the brakes will be there and yet...I never have to do any maintenance beyond a simple general safety check I like to do before each track event. The system is phenomenal...just need to figure out this ABS light. I could link the latest video, but I don't think that will do much good since I wasn't logging brake pressure.

Bill Dearborn

When I autocrossed my C5s or C6Z I always used the ABS to stop quickly. Every now and then I would get Iced Mode and the car wouldn't stop.

When ABS is active and you are pressing on the pedal hard it is a very violent stop. The car is shaking, shuddering and making lots of noise while the brake pedal sinks a little and is vibrating like hell. It is like somebody threw out an anchor.

My experience with Ice Mode is the brake pedal doesn't vibrate it is very high and feels rock hard. No matter how hard I pushed on the brake pedal the car wouldn't slow. There was no action pressure increase/decrease you get when the ABS is working. Just the high hard pedal and a slow reduction in speed that might be more from engine compression than anything else. I have never seen an ABS light or ABS Active message when this happens.

As for stopping on real ice with ABS the pedal will start to vibrate as soon as you touch it as the individual wheels experience pressure decrease and increase although if you are on water covered ice (my favorite is refrozen packed down snow when it is raining, where it is so slippery you can't stand up) most of the time all 4 wheels will lock immediately as the grip level is so low it doesn't generate sufficient difference in wheel speeds to activate ABS.

Bill

romandian

would anybody know if my 99 c5 has electronic proportioning and what the contraption that looks like a proportioning valve near the master cylinder does? there is a small hole in it thats quite deep. wondering what that is for also.

Bill Dearborn

The C5 didn't get DRP until the 2001 model year. Before that it had a mechanical spring loaded proportioning valve. That is probably what you are looking at. DRM used to sell a modified spring that permitted more brake pressure to be applied to the rear brakes. If you want more rear braking it might be worth your while to check their web page to see if they still sell the product. I imagine there hasn't been much call for it over the last 7 or 8 years so they may not carry it anymore. If you don't see it on the web page you may have to call them.

I installed one of those springs in my 97 about the time your car was built so can't remember much about it due to the passage of time.

Update: I just looked on their web page and they still have the spring. Here is a link to it: http://dougrippie.com/products/drm-brake-bias-spring-3/


Bill

romandian

thanks a lot. so the contraption is a proportioning valve. still wondering about the hole. maybe its adjustable?

Bill Dearborn

It has been 18 years since I replaced the GM spring with the DRM spring so can't comment on the hole. The bias is only adjustable as far as I know by replacing the spring with a spring that has a different compression.

Bill

dfettero

What are the options to upgrade the base 2016 Stingray to Z51 brakes and keep the same wheels?

Bill Dearborn

Wheels should fit. In the front you will need Z51 caliper brackets, your old front calipers, new brake pads with different brake compound and two of the front Z51 rotor. In the rear you will need Z51 caliper brackets, the Z51 Calipers, the Z51 rotors and the Z51 brake pads. The rear Z51 calipers aren't the same as the base calipers as they have smaller piston diameters so the car's brake bias remains the same.

Here is a list of parts showing base and Z51 part numbers as best as I can make out from the Cultragfactory parts web site. Some of the parts are not listed. You will need to have your VIN and a C6 Z51 car VIN to try and make heads or tails out of this at a parts department.




Bill

jmmy

On the way in to work this morning I heard a blower running in the driver side rear duct.
Never knew a blower was in there, but it's very loud now. Has it been running unnoticed for two years? Or did it start because it thinks the brake is hot? The rotor felt just barely warm to the touch.

ErnieN85

it's the trans cooler

CJKC6

I have a C6 base 6 speed. The brakes squeal which drives me nuts. They are currently at ~6%. I have read that many people are happy with the Duralast Ceramics for taking away the squeal. However, I dislike the looks of the stock brakes - especially the small dia rears. Anyone have exp with these: https://www.ebay.com/itm/WILWOOD-DIS...%257Ciid%253A1