Hi Volts Z06

Racingswh

Nice lap time. Glad you are ok. If there's anything that scares me about that place you just showed it to me exactly how I envision it. At your pace I am guessing you would benefit from a proper motorsports ABS system.

OP hope you get your issues figured out next season.

fatbillybob

IMO stock brakes the issue is pad selection vs. tire selection and driver input

BBK's are all of the above plus improper section of piston sizes mated to master cylinder. Many BBK's have zero testing but empirical data crunching for appropriate match. When Stoptech developed the SCCA T1 brake kit on my car they brought out about 4 sets of calipers all set up to work. The finalist was chosen by testing on the racetrack. Then other guys went on to win National championships.

SouthernSon

I can only relate my person, anecdotal experience. I used to have a couple of hiccups with my OEM ABS module in my C5Z (2003). After it went completely out I sent it to ABSfixer. I am not sure what all they do but I no longer have any problems with the ABS module. I don't get the 'warm up' msg. I don't get any lockup. It is always consistent and dependable. Been running it for years with DTC70's/60's on R888's, R6's and R7's. I do go DEEEEP and have only experienced ice mode once in the last several years. You might give them a call and see what they do when repairing. At least I think this would get rid of any ABS unit problems you may be having.

Oh yeah, using WW SL6's on front.

1badtantrum

Billybob,
Agree, no matter what the options are, the application of the brakes is driver input. In my case, I have ST-60 up front w/ DTC-70's, stock rear caliper with DTC-60's. I know the 'ice mode' is waiting in the background. This is and has been avoidable. I have had the hard 'ice mode' pedal many times with the current brake setup at VIR over my 100's (>1000) laps. It was always recoverable with a release and reapply of the brake pedal. This time, I could not get the pedal back in time and had to make a course correction to avoid trees. No National championship for me, no scouts watching, no autographs... I could experiment with pads and I may do that. for now, just braking a little earlier.

1badtantrum

SouthernSon,
Thanks for the info and referral. I'll keep the ABSfixer in mind. I don't think there is a problem with the ABS unit. I have to make an adjustment with brake application (pressure and/or location) with my current setup. I was able to go pull some grass and dirt out of the car and run several <2:00:00 laps on Saturday and Sunday. I will give them a call and see what they do. If they eliminated the hard pedal no/limited brake result, that would be great.

96CollectorSport

I'd like to share a few things here - ABS Fixer doesn't do any kind of reprogramming of the module he simply replaces the old micro-relay in the ABS module which controls the ABS pump and puts an in line surge suppressor in if you choose that option - it in no way changes brake bias or any other performance settings.

Secondly if you are having issues with "ice mode" look at your brake compounds and tire choice - it seems like DTC70 Front / DTC60 Rear is the go to for these cars and that you need to run a less aggressive rear brake pad compound than front - this is not the case!

When GM racing came out with a different program for the ABS module for T1 racing they added 15% more rear brake. If the engineers saw the need for more rear brake under race conditions why do we run split compounds?

A few years back RX Ben did some data logging on his 03 Z06 and what we found was that in some cases the rear brakes took .4 sec to initiate after the front brakes initiated. So for almost 1/2 second you have no rear brakes just fronts - so the front brakes are trying to stop the whole car and the rear axle is trying to pass the front.

If you look at the bigger picture this is what's happening - GM/Chevrolet sells Corvettes to the general public maybe 10% will ever see the track - out of the 10% that see the track how many are actually pushed hard? The engineers designed the car to work well if granny was driving the car and a deer jumps out in front of her - the way the system is designed to work is to allow weight to transfer to the front axle so you have more control over steering in case you hit the brakes and try to steer around something - and that is exactly what it does - obviously this is a gross simplification - but you get what I mean.

You hit the brakes the ABS module initiates the front brakes - waits a few tenths of a second then initiates the rear brakes and then you get full braking - provided the active handling and ABS agree that the car can handle full braking. By staggering brake compounds you are making the front axle do more work in an already front biased system.

The rational behind staggered brake compounds is to prevent the rear brakes from locking up and causing the car to spin out - how can the rear brakes lock if they aren't even initiated?

Now lets take a look at this pad comparison of Hawk compounds



Since we are over working the front brakes they are going to run substantially hotter than the rears - I've seen rotor temps over 1400°F - so look at the bite level of DTC70's in the working range between 1000°F - 1400°F - then think about how hot your rears are getting more than likely not much over 800°F. So the front pads are at there highest bite level and the rear pads are near the bottom of their bite level - I don't see the rears locking up in this situation.

Also the rear suspension of a C5/C6 has anti-dive designed into it - that's why the front mount point of the rear lower A-arms are higher than the rear mount point. The rear axle is essentially going "up hill" - to test this take the car out in a parking lot and roll along at 5 mph - then pull the parking brake - the rear of the car gets pulled down - it doesn't just lock up - that pulled down feeling is the anti-dive geometry at work.

When people have problems with "ice mode" it's usually multiple things that all add up to cause the situation. In no specific order:
Brake pads with too much bite
Tires with not enough grip
Suspension that allows too much front / rear weight transfer
A driver that stabs at the brake pedal instead of squeezing on the brake pedal
Something slippery on the racing surface

When the ABS sees two or more wheels lock up at the same time it locks pressure from being applied to the calipers so you are "locked out" that is why you get the brick pedal the ABS module closes the wheel circuits off from the master cylinder. When your release the pedal it again allows you to modulate the calipers.

Ideally everyone would be able to sort out there brake system without ABS then add ABS after the balance is confirmed. Unfortunately with the dynamic rear proportioning in the 01+ cars that isn't possible. The best you can do is to put brake caliper temp stickers on your calipers and monitor your brake temps front and rear to find out if you are at or near a good balance.

1badtantrum

96Collector,
Lots of good info there. I'm not sure if I'm having issues with 'ice mode'. I've just found a limit with a bunch of variables...
Is the T1 ABS controller available for purchase? Does it remove the 'ice mode' (limit brake pressure)?
I run different compounds front/rear as that is what the community has mostly settled on. I have gotten specific recommendations from brake vendors with years of experience driving and selling brakes. I have taken the community input and vendor input and implemented it. Lot's of slop in the approach...
I get the big picture and of course it makes sense.
I'm a little surprised by the community, brake sales companies etc. and me as a result, being so ignorant of the brake bias, geometry etc and not recommending a correct pad compound match front to rear.
I have run into limits. probably a combination of the things as you mention. My immediate 'fix' is braking earlier to apply a slower deceleration rate to the pedal given the setup I have.
A Bosch Motorsports ABS controller, Chassis and brake engineer are on my Christmas list. thanks for the informed input.
I can put some brake caliper temp stickers and look at temps. Do you have any PIDS for the wheel speeds or brake pressures on the ABS CAN?

dfettero

I found St-43s too aggressive for the street on base model Stingray with stock MPSS and DBA 4000s.
Just initial strong grab, no modulation.

kdm123

How can you tell the difference between pad fade and "ice mode." I wonder if ice mode isn't a bit of a unicorn and what people are more commonly experiencing is simply pad fade.
I have issues with my brakes as well, but I've never experienced ice mode. I do see fluid fade, and on some very rare occasions I've seen pad fade. Maybe those instances of pad fade where in fact ice mode, but it does seem to me that the simpler explanation is simple pad fade. Just for the record I've been tracking my C5Z for 3 years and did 17 track days this year alone.

ShaWING66

I think we would need to know more about your setup. I personally do not think I have had any "ice mode" just an aggressive ABS unit. I run with Castrol SRF fluid and I have popped out my fog lights and ducted cooling directly to the rotors while also running on cooler days (50s) towards the end of the year and still having issues in my 2011 GS. I am going to get an AIM SOLO DL to try and diagnose which wheels are locking up (front or back or any).

fleming23

They are completely different sensations behind the wheel. With pad fade, you still apply normal pedal pressure but the car does not slow as fast, resulting in you pushing the pedal harder. With ICE mode, your pedal goes rock hard and you have very little brake pressure, basically unassisted, resulting in reduced braking. I don't think you would confuse the two once you experience one or the other.

1badtantrum

kdm123,
Like fleming mentioned, 'ice mode' and pad fade or are very different things and easily distinguishable. With pad fade, fluid fade/boil-steam/air, ABS you get pedal movement. With 'ice mode' the pedal will not move. The pedal is like it's obstructed or mechanically locked in place. If you release the pedal for some short? period of time and reapply without upsetting the ABS unit the brakes will work just like normal. It's a thing. "Ice mode" is a name given to the phenomenon by the 'community'.

kdm123

With fluid fade, you obviously get a soft, long pedal that needs to be pumped up.
With pad fade, you get a very hard pedal due to the gases between the rotor and the pad.
So, how do you distinguish pad fade from ice mode?
If ice mode happens when someone suddenly slams on the brakes, then this would happen all the time to soccer moms, right? But if you Google "ice mode," you don't get any stories about lawsuits against GM. Rather, the only info that pops up is guys on various car forums discussing it. I would like to see some information from knowledgeably sources, say like an article written by a brake engineer.
I'm not saying it doesn't exist, only that I have never experienced it and that I suspect it may be confused with regular old pad fade most of the time. Consider how many people likely forget to bed in their pads (or don't do so properly) and get green fade.
Has anyone with a C5Z experienced ice mode?

1badtantrum

ShaWING,
Sorry to have consumed the/your thread. Was sharing an experience that I had about ABS engagement and something else to eventually be aware of given your ABS thread. I think the real diagnosis and remedy to this issue is beyond my capabilities and budget. I'd love to have a chassis and brake engineer and racing ABS but, I'll have to just brake a little earlier and slow the rate just a little.

96CollectorSport

I sold a few of the T1 ABS controllers in the past - but there are no more left to sell - you would need to have your ABS module re-flashed and I haven't found anyone with the ability to do that reliably. That said - I really don't think that it's necessary. Some people actually have more instances of ice mode with the T1 module - so short of going with an aftermarket ABS controller there is no way to eliminate ice mode with the stock modules. I've actually had pretty good luck tweaking the brake system around the stock modules. Through pad compound or component replacement I can usually find a way to balance out a system.
I really believe that if we were able to simply pull the fuse and disable ABS to really see how the car behaved without ABS most people would be in for a rude awakening.

I think once people understand what is happening it will be easier for them to prevent it from happening and that is what we are trying to do as a community of Corvette racers.

Sorry I'm no help on the PIDS - RX Ben did all of that stuff himself - but I know he had to install in line pressure sensors to get the front and rear line pressure data that I was talking about above.

SouthernSon

For me the price difference in the rear 70's and 60's make the 60's a lot more attractive. But now I have gone with WW calipers at all four corners. There again, the price of the pads is very attractive with the WW setup. The rear 70's are cost prohibitive for the difference with OEM calipers.

96CollectorSport

If cost is an issue then I would suggest running DTC-60's all around that way you can save money on the front brakes as well as having a system with better balance.

I have several customers who actually prefer this set-up, one is a car that we removed the ABS from and found that DTC-70's were too easy to lock up - the DTC-60's made it much easier to modulate.

SouthernSon

I suppose that would be especially true for those with no suspension mods.

1badtantrum

Guys-thanks for the input and help with brakes and different considerations. My reference to cost and budget was related to the chassis and brake engineer and aftermarket ABS. I'll do fine with the DTC70's/60's and may try some other compounds. It is as simple as adjusting initial brake pressure and braking just a little earlier to make sure the ABS controller doesn't loose it's mind. Do I have to go this fast or brake this late...nope. Just trying to have fun and keep up with all the C7Z06's, C7ZR1's, etc... All that horse power yikes. Stay safe watch out for 'ice mode'.