I challenge you to unhook abs and see if you think its front bias. I dont see it. Niether did the Grand Am team. Its heavy rear bias. Most of us are dragging rears and system is releasing things to keep the car from spinning.

I originally thought it was front bias until I unhooked abs and tested the car with fast stabs and threshold braking on the track. And I have huge clampers in the front. Its lighter rear end with pretty aggressive rotors and calipers that cause rear to lock up from what I see.

Grant Am guys are pretty sure most of issues will go away with rear caliper change but I havent had a chance to make the change yet. Also have been waiting to see if there are any other solutions before I commit.

That is one of the most common triggers, pad fade is the other time I have experienced it but it feels slightly different in the way that it recovers.

Yes, I had the G35 with the crappy calipers like your 350 and never ever had a problem despite getting the brakes to the point of smoking. People were impressed with the stopping power. Did any 350 owners with the fixed caliper Brembo's experience ice-mode? I'm not sure if we can use their ABS controller however thanks to the newer sensors (yaw etc) and if it would be compatible with the ECU.

My brake pad experiments in the 370 have had the opposite results to yours though. I tried running the same compound front and rear for a session and it was pretty difficult. Minor ice-mode every time you stepped on the brake too hard too quickly. With a lesser pad in the rear it doesn't happen as much. Basically the same problem as the Corvette just in reverse.

How about this?

Turner Motorsport | Racing ABS Wiring Harness

In August 2003, Stewart McColl died sa a consequence of an accident in the braking area into turn 4 at Philip Island whilst competing in the Australian Production Touring Car championship in a Volkswagen Golf (I think an R32 from memory, but I may be mistaken).

The coronial enquiry concluded (based on datalogging presented to the court by "specialist engineers" whose attribution does not appear in the court records) that the root cause of the incident leading to the driver death was small bumps in the circuit on drivers left (T4 is an 80kph right hand hairpin) approached at ~200kph that triggered the ABS in such a manner as to present a confusing set of circumstances the the electronic programming of the ABS controller "which were outside the paramaters for which the programming was created". The flag marshalls reported that the nose of the car dipped as the brakes were applied but once past the bumps, the car's rate of deceleration wsa not maintained. The vehicle impacted head-on into an earth filled tyre bank at relatively undiminished speed (data logging confirmed impact speed of 138kph - at whcih speed the driver suffered unspecified "internal injuries" which were the cause of death - such decsriptions are usual for a ruptured aorta).

There were 3 major consequences of the race incident:
1. Volkswagen withdrew their team from the championships forthwith (and have not re-entered as a distributor backed team in the Production Car championship since that date - and IMHO never will) given (my opinion) the issues associated using an OEM ABS system in a rce environment.
2. The circuit was modified to add large areas of gravel traps to pull cars up before they can impact the barriers, AND the earthen bank barriers have been moved further away from the race-track proper.
3. The sanctioning body removed the previously mandtory requirement for ABS-equipped cars to have the electrical system present in its entirety (which forced entrants to leave the ABS intact), by allowing the ABS to be "removed or disabled" provided that the brake lights must remain functional.

I make this comment only because the only time I have experienced "ice-mode" in my Z34 was at Philip Island on entry to T4 on literally "the perfect lap" where I got T2 and T3 absolutely right and and carried 9kph addiional speed thru T3 and kept the car all the way to the left and ran the left-hand side of the car down the LH edge of the track and hit the same bumps as in the McColl incident - about 12-15m into the braking area). I stood on the brakes - right the the threshold of lock-up, did not initially trigger ABS, but when the LH wheels hit the bumps, it this triggered the ABS and the pedal almost instantly went rock-hard and the ABS "went nuts" but the car did not slow. The situation was resolved by lifting off the brakes and re-applying with a shallow entry/deep trail brake and hard right to recover back onto the circuit when enough speed had washed. This was on the 4th lap of a 5lap run so everything was nice and hot. I run Endless 462TR pads front and rear and Direzza tyres (245/40R18 front and 275/35R18 rear). Pads give good initial bite, tolerate heat, have reasonable CoF and don't chew the rotors to death in road driving.

There is no doubt in my mind that "ice-mode" is an unintended consequence of an OEM requirement arising from the EBD implementation.

Whilst I run my Z34 on the track with VDC off, I have not bothered to disable the ABS but if I were to run the car in open competition (eg: full-on race champioships) then there is no doubt that I'd throw the standard brake setup away, go for ALCON/BREMBO/AP calipers and a stepper-motor driven balance bar assembly.

IMHO, the ABS/EBD logic works OK for the road, but is problematic on the track, and there is lots of good info inthe thread for how to best "manage" it - because that's the price of using a "road-car" in a track situation, the fact that it still needs to serve on "the road".

It is worth noting that the factory GT4 race-car (NISMO Fairlady Z RC) is Bosch MotorSport ABS equipped - details on the NISMO.CO.JP site.

For me, I know I have to stay off the bumps in braking areas on the track, and if not avoidable, I have to ease the brake pressure a little - might cost a tenth inlap times, but that is better than being in the fence.

I have my real race car for serious track work in any event.

Bottom line - everyone who tracks a Z34 needs to be aware of what ice-mode is (and this thread is as good a write-up of what it is I've ever seen) and how to react when it happens, andif serious about their track work, lots of ideas about brake balance that can/will help.

My thanks to the key contributors for an entertaining and informative read - a real gem of a thread ..........

RB

Thanks you RB, an insightful commentary.

In addition to EBD I think Brake Assist is also a potential culprit. The brake controller can decide to boost brake pressure based on how sharply you stab the brake pedal regardless of how hard you pressed. Useful on the road but madness on the race track.

Interestingly enough though, the 350Z and G35 both had EBD and BA as well yet didn't seem to exhibit these problems. They used a slightly older revision of the Bosch brake controller.

I recall reading somewhere else today that there are no real experts posting on forums b/c they are all off doing what they do... well we have at least one here, so thanks RB for your thoughts!

(once I get a working engine!) I'm going to look into getting a proper proportioning valve setup... it'll be interesting to see what we learn about this issue by modulating bias

I am with RB that I have just learned to accept the flaw and move away from the "hotspots" where I know the car will get into ice mode most of the time.

I still believe the 350Z I had didn't have the same problem as my 370 and Corvette is because I was riding on the smaller single piston caliper. Despite having nearly the same power, the 350 just didn't have the stopping power to lock up my RA1s where the Corvette and 370Z could. I have to look at the datalog to see exactly how many Gs as it happened.

I can say that whatever spots I hit ice mode with in the Corvette, I did the same exact thing in the 370.

Interesting... on the site it says the controller is an extra $6K, however, so likely it ends up being $10K as well

I wrote them. They indicated harness works with e46 m3 that uses same bosch system so if you could find an m3 parts car you could pull system but what is likelihood of this.

I think ATE system is what grand am team used. So I wonder if ate makes full system?

Well what that site offers could amount to a complete ATE system for this car as well, but yes it does come out around 10K if you're not putting it in an appropriate BMW that already has some of the parts (sensors, etc) installed.

So, in my C6 and this car, this really hasn't been an issue for me. I wonder why? I'm not the fastest out there, but far from the slowest. I run stoptech ST60 front and ST42 rear trophy calipers with equal compound pads front and rear. My only problem is getting more than a couple days out of a set of XP12s on the fronts.

Okay there's one vote for equal compound pads...

Mike, do the braking zones at your most frequented tracks have bumps or anything that would unsettle the rear? Also, do you tend to brake straight line only or use trail braking at all?

I run on XP 8's at all four corners with sport brakes and haven't had this issue at all. That's why I'm so interested in this thread. I've only done three track days. Two at Road Atlanta which has about three hard brake zones which none have bumps or anything that would upset the car as you said. I do brake hard and late and thats all in a straight line myself but no trail braking as of yet. Haven't reach that skill level yet.

Mike, what did u run on your c6 for brakes?

for me, ice mode usually happena at the initial brake contact, not under trail braking.

I run the same compound on the 350 rx8 370 and c6, I think the xp10 have too mich bote for non slicks

For comparison with the icing I was seeing this past weekend (also XP8x4 and stock calipers, can't be far from Spohn's overall setup, except perhaps in rotor heat capacity / cooling), my most common (only actually) track surface is in fact quite ripply and bumpy, and notably so in the one section where I first had the major ice-mode problem.

In that section the weight transfer is not only heavy to the front from the braking itself, but is also heavy to the right from having just barely completely a fast left sweep before getting into the brakes. There's also a decent chance that during that initial problem stop, I hadn't quite finished rotating the car to its new straight-line direction before jumping into the brakes, by a scant few degrees. I'll probably know better once I have all the video processed.

Also my LSD helps aid in slowing being it locks at 50% during braking. Might not be a factor but I thought I'd throw that in there.

And Spohn, if I could offer any advice from this past weekend, it's this: if you ever do feel like the brakes just didn't work when when you asked them to, lift and reapply/modulate to regain power, don't panic and keep your foot in the brake pedal hard like I did :)

Yea I did know that. That's why I'm so into this problem with you guys. That way if it ever happens it will be in my head. I know a lot of you guys have this issue not sure Mike and myself haven't experienced it before. Especially Mike. He has lots of track days and on about three different brake setups at that.

alright, so do you guys think me running DTC60 up front and stock compound in back on a street tired stock suspension 370 is a ok idea, or just bad to begin with? Im running buttonwillow this sunday, if you guys think i should get a pad for the back with a little more bite, ill figure out how in the next few days, but if not im going to leave the stocks in the rear. This is the first time tracking my 370, so thats why im asking you guys, but i do have alot of track experience, so my pace will most likely not be slow. let me know what you guys think

Doesn't make much difference, just means that the rear wheels are tied together to the drive shaft and engine braking effect will be distributed more evenly to the rear wheels. The stock VLSD unit will have a similar effect just not as strong, but in a straight line this isn't a huge factor.

:tup:

I don't think that most braking zones at my tracks (VIR, Barber, Road Atl, Little talladega) have many bumps. Maybe at Roebling, but I've only been there the one weekend and don't think it did at all.

I do 90% of my braking in a straight line, stabbing the brakes hard and then trailing off into the turn. I used to street brake, but Sharif and Bryan Settle cured me of that. I actually think that I am only able to keep up with faster cars because I brake much later and make up lots of time there.

Cossie,
On the C6, I had a widebody conversion and ran Z06 brakes for 2/3rds of the time I owned it. On both the Z51 and Z06 calipers, I ran hawk HP+ pads, but until my last year in the C6, I was only doing 2 track days per year and not at the level I am now. 3 years ago, my last year in the C6, I started doing two per month for 6 months a year. The only brake issue I ever had on the Z06 is when ALSM driver Shields Bergstrom took me out for a session at VIR driving my car and he boiled the fluid, but had no ice or fade issues either.

Just a thought I had that I posted in another thread. It could be total BS though, I really don't know, just kicking around an idea.


OK, its been in my head stewing for a bit, but I think I know why I am against a lower compound in the rear and why a proportioning valve won't work.

The car has EFBD. it senses each wheel and applies more brake as needed. I'm not 100% sure on this, but I do think, even with a proportioning valve, it will still direct more braking to the rear or front as needed, so with a valve, you may actually decrease brake performance, as it will be reacting to the lower or higher rear brake pressure.

Even with different pads, its still reacting, which is why I use the same compound all around.

I did some hot laps with Shields at Autobahn in Joliet. We were in a race-spec Audi TT. That dude can drive...

He was about 30mph faster than me everywhere, but he gave me the confidence in my car that I picked up about 10mph throughout the track.

T1 at VIR is bad. You get in at the wrong spot and you will get ice mode. I had a Z51 C6. The brake issues on that car is the same thing as my 370Z. The C6 did have more front bias and carried way more speed down the straight, it can be nerve racking going into T1 at 146mph! I have gone as deep as the 4 marker, but the brakes would burn right up and I would get nothing for the next corner.

I used the same Carbotechs on both the C6 and 370.

Speaking of EBD, I don't know if you guys had an issue with the car grabbing to one side under braking. For some odd reason, my car loves doing that at Watkins Glen. I am not sure why, but it sure flips me out to get the car grabbing right at over 100mph. 0411 370z WGI Unstable brakes.avi - YouTube

It's the pavement there, concrete patch on one side and asphalt on the other. One side has more traction than the other and it pulls as a result. Fortunately it pulls you towards the corner so it's not all bad and it is after the initial braking application.

Interesting, never thought that would make a difference. It was nerve wrecking the car kept pulling to the right

Yeah it can definitely throw you off. There are concrete patches everywhere at WGI, some of them are grippier than the asphalt and some are polished smooth and less grippy. Some are grippy in the dry and then slick in the wet, so you have to learn multiple lines.

Drove buttonwillow raceway park config #13 clockwise(dubbed the time attack config ) Sunday. Ran dtc 60s front, Oem rear pads, bridgestone Re11 street tires._No ice mode all day even over the brake zones that were bumpy. Ran 2.04:140 best lap time, oil temps hit 230 max just a few times with the Nissan motorsports oil cooler

Hmm, for my next event, I'm seriously considering leaving my front XP8's in place and using my Bobcat (CT street pad) on the rear and seeing what happens. Worst case I burn up my rear street pads over the course of one weekend and have to get new ones. I'm also planning to making some ducting improvements in the front before then, but I don't think I'll have a solution that brings air fully into the spindle, just into the wheel well for now.

This is what Grand Am team did to address rear bias issues. They used 350 Z nismo rear brake caliper and rotor. Well that and an $8k racing abs system.

http://lh3.googleusercontent.com/-s3...88CEB24959.JPG

Mmmmm, inverted coilover. Me like

Hey Guys and Gals I had a 350z 35th anniversary and was running track pads and RE01R tires. Anyways I had the problem that Car and Driver had with the 370z at their lightning lap. Now maybe we are talking about two different things. But per their investigation they reported that the problem was the 370z did not have proper brake cooling. So is that something separate from Ice Mode? Or is it the same thing. Because when I had my experience it was exactly how C&D described theirs, I pushed the pedal down and got no breaking power whatsoever, therefore I had to go off course. I'm concerned because I want a 370z, but do not want to relive this again. I saw that stillen now makes brake ducts has anyone tried those, if so do they prevent the problem.

Two different problems. The C&D problem was boiled brake fluid accelerated by using the stock pads well beyond their designed operating temperature causing them to wear prematurely (thereby eliminating the insulating pad layer that protects the caliper). Heat is definitely an issue with the 370Z brakes so by adding cooling you are less likely to boil the fluid. Whether or not it will help with ice-mode remains to be seen as the kit was only just released.

Well, even if you don't get to the point of boiling off the fluid, just fading out the front pads from overheating them a bit can get you into ice mode easier. The fronts fade first, and then the rears lock up before the fronts do, etc...

Yes this is true, especially for the less worthy track pads (streetable track pads etc).

Ice Mode = super hard pedal, car wont stop.
Brake Fade = super soft pedal, car wont stop.

It's my opinion that the Ice Mode problem is a software issue. We're running Hawk DTC 70 (f) and DTC 60 (r) on the World Challenge car with Racing Brake 2-piece rotors and am still able to get Ice Mode easily, even before everything has overheated. We're working on a solution, but I think it's going to involve proportioning the brakes properly and installing an ABS disable switch in the cockpit (probably not something you can easily do or even want to on a street car).

It's all about overall pedal pressure, how quickly you apply it and the initial bite on your pads. When it happens you have to give up the pedal and re-apply ... kinda like you do in a non-ABS car :shakes head: Problem is that takes some quick thinking as you're hurtling towards certain doom.

^ Yeah, I get that they're distinct. But fading the fronts on relatively low-end pads isn't a binary condition. As they get "a little" faded, where the pedal's a little softer and your braking distance gets a bit longer, the bias shifts to the rear and then ice-mode kicks in sooner than it did on the previous lap, causing the "omg what happened to my brakes" reaction :).

And with pad fade the pedal still feels relatively firm thanks to ABS kicking in at the rear. From the driver's seat you just feel ABS and reduced braking performance.

Also stupid Brake Assist activates the ABS prematurely if you jump on the brake pedal swiftly but haven't pushed the pedal hard enough to activate ABS. Unfortunately Brake Assist is counter productive to what we are taught as proper on-track driving skills.

The ABS system in general does not deal well with grippy track pads and/or low grip conditions. Short of going to a full-race spec ABS system I think you are better off disabling the ABS if you can get things proportioned properly.