Well, yesterday I finally had a hard ice mode condition on the track. It was a pretty scary experience. Now that I know for sure that this was ice mode and exactly what ice mode feels like, I know I've hit it before a little, too, just not as critically.

Luckily, this track I'm running at always has easy run-off on the braking zones (extra pavement, or at least grass). The setup was a long straight with a straight brake zone to scrub a little speed (~115 -> ~80), then maintenance throttle for a gradual sweeper to the left, then straighten up and a hard, short straight braking zone down to ~35-40-ish for a hard right. It was in that second braking zone that I hit it. I had been gradually raising my speed coming into there on each lap, and backing up my braking start. Then I nailed everything really great one lap going into there a bit faster than before, and the brakes just iced up. Hard firm pedal, ABS pulsing like crazy, and little to no braking force.

I wasn't really ready or expecting it, so I didn't even try to re-apply or modulate. I blew past my intended turn-in spot still going too fast for the turn, so I just held straight past it and then turned right a little for a bit of an angled slide, and eventually the brakes semi-fixed themselves and killed my speed just in time to bring the car to a stop at the brink of the pavement (and then I rolled it off the edge of the track to get out of the way and find a good time to re-enter).

It was the 3rd of 4 sessions, and I was able to avoid it on the 4th run by taking that spot a little "easier" and less aggressively. Going back out today on the same equipment, same track, so I came here to read back through all of this. Having done so, I think the trigger was that my initial pedal stab was a lot sharper than I normally do. Usually I'm pretty good about rolling into either pedal instead of stabbing them, but in this particular case I knew I was set up straight and perfect and had a lot of speed to scrub in a short distance, so I stabbed pretty hard.

I'm on half-decent street tires (Conti DW) and XP8 all around, stock calipers, RBF600 fluid, braided lines, and RA's 2-pc slotted rotors (which seem like they have a better-than-stock cooling vane setup), but no ducting for the fronts.

So for my sessions today, I think my focus for preventing a repeat will be (1) Don't initially stab too hard, and (2) if I feel it happening, try to re-apply / modulate repeatedly to kill it, and (3) Try to engine brake a little later (I normally downshift pretty much at the moment I'm getting on the brakes, when applicable).

In the longer term, I'm going to need to fix this up a little better though. I'm figuring bias is one of the key issues, but I don't think on these street tires it would be wise to go XP10 front, right? So that probably leaves me with downgrading the rear pads from XP8 to... I don't know. Something that can take the heat, but doesn't lock up as easy as XP8 rears do. Or do you think XP10+XP8 might fix it and not be too grabby for the tires?

That or try disabling ABS. I'm willing to learn to live without it, I hate it when it does engage. The simplistic "pull the ABS fuse in the center console" thing also kills your brake lights though, right? Is there a better way to disable it that I could put a dash switch on?

Glad you experienced it safely... today would be a good opp'n to make it happen intentionally in a safe spot and then try to recover... might want to tell the session organizer you are doing this as a heads up

If any of the wheel speed sensors stop working, ABS is disabled... one could wire a switch to any of those sensors... I don't recall if that dash light comes on, however... also, the car requires a restart to get ABS going again - likely will not be able to toggle it back on as a hot switch

Aggressive engine braking was one of the triggers for me, as even with the throttle blip it can cause the rear wheels to lock up when trying to brake with maximum potential (as the ABS tries to maximize rear braking potential). I downshift a lot later now so as to not send the RPM's too high.

Brake balance is critical. I can get the ice-mode a little when cold if I'm running different pad compounds front and rear that come up to temperature at different rates and have different sweet spots for their torque curve. When hot it is usually later in the session when the front pads get overheated and the ABS system has too much rear bias dialed in causing the rear to lock up especially if you stab the brake.

With the right pad setup and more calculated application of the brake pedal I can avoid it 99% of the time. Some brake ducting would help a lot as well I think.

I have donr the xp10 and stock pads setup, you will dtill get ice mode

so the trick is to not have the rear bias get to high?

Aggressive bit pads with street tires is a tough combination as well. It is very easy to over apply the brakes too quickly before the weight has transferred forwards, especially in the wet.


It is not a solution but it does help.

very true! particularly with stiff springs up front and aggressive front pads - this car has forward weight bias and will bite hard... I found that by playing with tire pressures and dialing in the front dampers I was able to deal with it somewhat

tempting to run very soft brake compounds front and rear to see if the car behaves better... how much ice mode have we seen on completely stock brakes? there was that media incident... others?

Could you please explain this more? It's obvious to me our cars have forward weight bias. So how does having stiffer springs up front effect weight transfer towards the front? Never really thought about this before so I don't really know. Seems it would be the opposite. But I also know how that goes.

In my experience it is worse with softer springs as there is more compression and a longer time period during which the weight transfer is occurring. I can reproduce this somewhat if I run the dampers near full soft as I do sometimes in the wet. With the stiffer setup there is less dynamic weight transfer and the time period during which the transfer occurs is shorter which means you can get on the brakes harder and sooner.

This is one of the reasons I like the lower torque compounds, however it can be tough finding a low torque compound that can handle the heat. Last year I ran an endurance racing compound, the (CL Brakes) RC6E which is only 0.5 on the friction scale but can take a ton of heat and is very consistent. It's probably a little harder on the rotors, but for me after a season they are done anyway from heat fatigue. I think the RC6 compound is very similar but more rotor friendly (and wears twice as fast). Next season I will compare them with the slightly more aggressive RC8 compound (about 0.62) and see if I have more difficultly staying out of ice mode. The comparable information I got about Carbotech is XP8 = 0.55, XP10 = 0.60, XP12 = 0.65.

This is how I would think of it also.

Stiffer springs up front along with stiffer damping would only allow slower resistance of weight transfer.

I'm running 18K springs up front and so load transition to front tires happens fast... would agree that soft springs also present a problem, as they can result in nose dive, which can shift the cg forward. My current thinking is that 16K/10K is just about right for this car.

Good lord. I'm running 13K up front and I thought I was doing something. I know a lot of people love how planted my car is compaired to the rest.

18K is a little too twitchy! :)

16K is about right I think

I found 12K soft for track use, but it may be fine if you have high quality dampers and are running on tracks that favor a more compliant setup

I have Stance true type coilovers. I know I like them. But I know they could be better. In the begining I didn't know the route I was heading and just settled. Only because I've ridden in a 370 with JRZ's. Mostly will be running at Road Atlanta.

I have Stance true type coilovers. I know I like them. Only because I've ridden in a 370 with JRZ's. But I know they could be better. In the begining I didn't know the route I was heading and just settled. Mostly will be running at Road Atlanta.

^ I did the same... BC Racing are just fine, but not JRZ's... or Penske... etc

Well I got to think on (and play with) this all day, and I think my initial reaction to "oh no I have to deal with ice mode" was overreaction. There's a few layers of analysis here, not sure what order to put it all in, and I'm trying to avoid my tendency to get really long-winded :). But the bottom line in my case I think is:

An additional major contributing factor was front pad fade on the XP8s, even on my street tires. When the fronts start fading, of course the bias goes to the rear, which helps kick on the ice-mode.

Based on that alone, it would seem like it would be best to up the fronts to XP10 (at least) and get my brake ducts finished, which should lessen both the fade and bias contributing issues.

But, a major contributing factor to the pad fade (well, aside from lack of ducts) was that I was carrying around a lot more speed due to some skills improving, but I was abusing the brakes way more than I should have had to. We corrected some of this today, and I was able to make even faster lines with less brake abuse, and it helped a lot. I still got some ice-mode late in a hot session, but I was able to modulate through it and come out ok, and after pushing through that barrier for a bit, the XP8 front pad fade of course starting becoming increasingly obvious.

So really, learning to use the threshold better (so I'm not dipping into ABS in the first place), and not abuse my brakes in ways that aren't even warranted will go a long way towards fixing this for me on a practical level, although the ducts certainly can't hurt as well. Even then, I'm still going to be pushing the limits of the XP8's on street tires, but I think trying to upgrade the pads too far against these tires is probably a bad idea (just going to be a lot more touchy and sensitive on the ice-mode line when it does hit it), and I also think I haven't learned enough of the limits of these tires to consider upgrading to slicks either.

Really, where that leaves me for reducing the overheating problem is I need to not go balls out on the straights. If I held back at say 70% throttle on those long straights instead of flooring it, I wouldn't have as much speed to shed, and the braking system and the tires would all line up with my driving skill in the corners and work properly. In other words, even my lowly NA V6 really has a little too much power on tap for an ideal learning environment at my level of skill, if I want the rest of the system to hold up to a long session.

One way or another, I can play with modulating through the fade + ice mode and/or reducing my straight speeds and mitigate the ice-mode while continuing to learn how to push these tires to their fullest, and then consider further true tire+brake upgrades later when I'm ready, I think. The ducts will go on ASAP though :)

I run completely OEM brakes and get engage ice-mode at will. I've learned to drive around it and it is rarely a problem anymore.

I had it on the OEM setup at auto-x as well. It would only present itself towards the end of the session when things were warmed up. Everything in auto-x is much more deliberate and sudden that I think it was just easy to catch the ABS system off balance. When I went smoother on the brake pedal it was avoidable in this case.

well im going to buttonwillow sunday, stock suspension and wheels with RE11 street tires. I got DTC 60s for the front, was going to run the OEM pads in the rear. ill let you guys know how it goes

What I found that was causing the ice mode was that the rear brakes were stopping the rear wheels/tires faster than the front. Because of that the car would release the brakes causing the "ice mode". This was from my brake test last year. I mean we tried everything from pulsing the brakes to me standing in the car on the mothers. Once the rear tires locked up or got really close to lock up "Ice Mode" came into affect. I think because of the bias in braking power from front to rear it causes this affect. we tried it on a stock car with upgraded pads and lines and my car with the alliance BBK. The BBK under the right circumstances was able to trigger it alot easier since we were running bigger rotors and calipers in the rear... This also depended on the ground composition as well... if it was dirty and sandy it happened a lot faster. If it was clean it didnt happen at all on the bbk and stock. With all the weight shifting forward under hard braking the rear end has less friction from the ground under braking thus allowing less effort to stop the rear wheels and causing Ice Mode...

My hypothesis on the solution is to run a stiffer front than rear bias and to run less aggressive pads for the rear.

Mike

Ohh and DO NOT DISABLE YOUR "ABS OR ABS MODULE" you will lock all four wheels up in an instant even at slow speeds like 35mph!!! Trust me I ruined a set of $1200 tires testing that theory out. The car went immediately sideways. I tried a modular increase in brake pressure and lock up. I also tried pulsing and with each pulse the wheels locked up. It is almost like an instant on/off switch with the abs disabled...

Yeah, I meant to mention that in my above post. When I mentioned the idea of disabling ABS to a few others at the track event, the advice I got back was "Yeah that's great, except one little screw-up and you'll flat spot and ruin a tire, better to have the ABS as a backup at that point and not ruin tires."

You know what... I agree that it is "easy" to lock up and flat spot w/o ABS on... but that's the best training in the world and your ABS is only masking the situation... I was able to improve my setup a lot w/o ABS and then turned ABS back on, making the whole thing much smoother under braking

Yeah but what's the practical difference between saying to yourself, "Oh I screwed up and managed to engage ABS" when you feel the pulsing, and saying to yourself, "Oh I just screwed up and now I need an expensive new tire?". Well, aside from the $$$ :)

I ran with the ABS disable once because of a faulty brake solenoid that told the abs computer that the brakes were always on and therefore wouldn't allow full throttle. Pulling the brake-light fuse tricked the ECU into allowing full throttle but disabled the ABS in the process. It wasn't that hard to modulate the brakes even with Hoosiers on the car.

Now that you mention it though the one time I saw my codriver lock up the brakes during that event it was the inside rear tire, not the inside front that you would expect.

so so far no ice mode solution ? really makes me wish i'd bought a different car to do track days with. Being a noob and all just a little scary .
dont know if this helps http://www.lotustalk.com/forums/f100...-solved-36810/
or this http://forums.rennlist.com/rennforum...ly-got-me.html and
http://forums.corvetteforum.com/auto...ere-a-fix.html

Not the same problem as the Lotus, more like the problem with the Corvette.

Hmm yeah the Corvette issue is obviously related. These posts in particular are interesting:

Corvette Forum - View Single Post - ICE MOde ! ... off track event :( is there a fix ?

Corvette Forum - View Single Post - ICE MOde ! ... off track event :( is there a fix ?

They seem to be focusing in the other direction (increase rear bite to lessen the problem), but that's probably just differences in the overall setup and use of the vette versus ours, and/or some minor revision to ice-mode programming in some shared ABS controller code.

I think the bottom line for both cars is roughly what that second link talks about though: if one or two wheels wheel decelerate/lock *much* faster than the others (and probably if all 4 decel/lock much faster than should be possible on a grippy surface), the car assumes it's on ice and limits overall braking force heavily. When you think about it, with all four wheels firmly planted to the pavement the wheels should be decelerating evenly. Their (the ABS programmers') logic almost makes sense, except they're not accounting for the possibility very uneven dynamic corner weight loading, and they're not accounting for the possibility of a bumpy but otherwise grippy surface (esp combined with harder suspension setup).

Stabbing exacerbates this, and it makes sense to me that higher rear bias (due to grabby rear pads, due to front fade, etc) would exacerbate it in many common scenarios, since the initial stab will unload weight from the rear wheels, allowing them to lock up quickly under reduced weight with a hard-biting pad. Having wheels unloaded due to bumpy pavement, suspension setup, and brake timing relative to all of that would exacerbate it as well.

And really, I'm not buying the idea that this is a good tradeoff on the street, either. It might be a good tradeoff for Nissan and Bosch's wallets from a lawyer perspective when running some statistics on which scenario results in more total lawsuit damages, but even a consumer street driver shouldn't have to take the tradeoff of "ABS might totally screw me if the pavement is too bumpy or I was cornering hard when I first hit the pedal" just to get it to work right in icy conditions.

I guess they figure in those scenarios anyone driving fast enough on bumps to feel them hard, or anyone braking while still under dynamic loading from a hard corner, could probably be written off as "it's your own fault you wrecked, you weren't driving safely on the street to begin with"? Their code works great for probably the two most common ABS lawsuit cases for them: straight line stabbing-the-brakes stop in commuter traffic way too late because the driver wasn't paying enough attention, either dry or in slippery conditions.

EDIT: I wonder if it would be possible for someone to dig up a Bosch (or other ABS mfg) engineer to discuss this on the side and confirm exactly what the behavior is and why?

I don't think the car ever determines it is on ice, however the controller does have a wide traction range (too wide IMO). The fastest way to stop on ice and gravel is full lock up, ABS can extend stopping distances by 2x to 3x if improperly applied (not allowing enough lock between releases).

I think it is a flawed design, but you are probably right that it goes back to liability. If it was a true 4-channel ABS controller then it can individually give full stopping potential to each corner. However doing that could cause the car to pull in one direction or the other so they create artificial limits on how much the bias can be left to right, front to rear. Given the large rear brakes, their maximum limit may not be enough in the extreme cases especially front to rear.

I just spoke with Bosch and with the head of their major west coast distributor

Not going to quote anyone directly but basically the theories discussed in this thread are correct. The DOT approved versions of Bosch ABS induce ice mode when the wheel rate sensors detect variation across the four sensors. I am not clear if it is front/rear overall or any one wheel or both, nor did I find out what % difference the computer looks for nor timing involved in the algorithms... but it is a safety mode designed to help in the majority of street situations... hard to blame them for that

There are two systems available for dedicated track vehicles. One produced by Bosch and one produced by Continental. These systems are only provided for vehicles not used on public roads and purchasers are required to sign a waiver that is kept on file with the mfgr. The systems are sold through distributors. The Continental system is apparently a modified BMW ABS that is not configurable. The Bosch system is a bottoms-up race ABS with config options. Bosch has two major US distributors, one east coast and one west coast. The west coast distributor is Brian Sekata with MS Electronics.

I realize this is not all that helpful for those of you that will keep your cars street legal. Sorry, I have nothing to offer you folks. The only possibility I can think of is to find someone that can crack the computer and re-write the code... but then there is an issue of liability and intellectual property

For anyone reading this that has a dedicated track Z (either 370 or 350), it may be possible for us to work out a group buy on Bosch Motorsports ABS systems. I have no commitment from Brian or from Bosch, but they are interested in starting the conversation with us and asked me to carry the idea forward. If there are enough of us willing to sign that waiver, there might be a break off the system price... as many of you know, it is $10K today :thumbsdown: ... but what if it were $6K ??? better braking performance and safe guard against ending up in a concrete wall... the system is also highly configurable - from the cockpit you can adjust proportioning and how the ABS reacts

In any event, please spread the word if you know anyone else with a dedicated track Z

Thoughts?

Here's the Bosch ABS race system overview FYI
Bosch Motorsport - Chassis & Brake Control

I think the Grand Am team found a differnt motorsports abs solution for around $7K. I can ask but they indicated it was one of the best race oreinted abs systems they have ever used.

The problem using the stock system on our cars on the track is that they have terrible rear brake bias. Just disable your abs and stopm on brakes and you'll understand issue that our system is dealing with when we get good pads and bigger tires on the front.

Suspect the Grand Am team got a killer deal on the Bosch system or more likely they bought the Continental system... anyone found a link to the Conti system?

Not too sound like a noob but if the source of the problem is poor factory brake bias front to rear then wouldn't the simple and cost effective solution be to add a brake bias proportioning valve to the car. Yeah it might take a little trial and error to dial in but I would guess a hell of a lot cheaper than one of these ABS systems.

Thanks for making the calls Travis!

I remember we all had discussions about the Motorsport version of the Bosch controller before. Looks really nice, just really expensive. Even at $6K it is a tough pill to swallow, more expensive than the entire BBK! If it were $2K or $3K it would be a no brainer.

If you did an ABS delete then that would be the best solution, but not sure how well that would work in conjunction with ABS.

I have owned all the cars you mentoned. C6, 370, 350, elise. The problem is notiable on the 370 and c6, not so much on tje 350 or elise. while most believe the problem is likely due to the brake bias and abs on the 370, I personally dont believe they are the main reasons, definitrly a factor. Here is why

1. The 350 non brembo had way more rear brake bias than the 370, yet ice mode isnt quite as bad.

2. The corvette has way more front bias, the problem is as bad as the 370.

personally here are a few things I have learned on the 370

Almost all the ice mode occurance happened on bumpy area or low grip surfaces.

I have three set of pads and I have mix and match with different combo. Running oem fronts and xp10 didnt throw the car into ice mode frenzy and my datalogger showed a slightly better stopping distance. Thats why I still believe the brakes have too much front bite and it is flipping the system out. With all that said, I feel like the giant brakea and aggressive nature on race pads are locking the front wheels too easily and quickly, causing the ice mode. Of course that's just my opinion and I could be way wrong on it. It's just some of the things you guys are experiencing are different than mine. Btw I ran the 350 with the same pads and never really experiences ice mode. I am curious if nissan patched the abs software or maybe the little calipers I had didnt have the stopping power like my 370s akebono?

Sry typing on a phone

As little off topic but do you think the ABS is configured different from base model to sports?

That or smaller 350Z Bermbo caliper and rotor