Spyerx

Can someone explain this to me?

Today, last run of the day, at Streets of Willow, going down back straight into waterfall, I brake before the turn in, at about 105mph or so (will check gps data later). I push brake, car isn't slowing, very stiff pedal, I release and get into it again and it's fine, and fine rest of run but I'm a little trigger shy now, point by a couple cars and slowly pickup the pace again.... I do not stab the brakes hard, easing in and then apply hard. This was an immediately very stiff pedal, didn't feel any ABS sensation.

First time using PFC 08 pads and I really like them so far.

has anyone had this happen recently?

mdrums

Yep...happens on very hard very late braking and small ripple bumps on the track.

I know brake a tad bit earlier and also a tad smooth into the brake...more like a fast hard squeeze instead a fast jab and that cured my ice mode issues. My ice mod happened with Pagid Yellows and it's not a pad issue.

Spyerx

Ok, that situation describes this corner well, I think I might have got a video of it (kept forgetting to turn on damn go pro... ) But it's a downhill and it's a bit bumpy, I am mostly braking earlier and am trying to be very smooth and fast on braking as you describe, not "jabbing" the brakes but I carried a lot more speed this time as I've finally started to figure out the chicane before this downhill section and I think I did get on the brakes late so very possible the car was over the bumpy parts. It definitely had a sensation of "ice" very stiff pedal and very little braking feel with no ABS sensation, quick get off then back on and it was fine.

993Brendan

This happened to me on the street today- scared the **** out of me. I remember reading posts about it a long time ago before I got may car and had forgotten. Yikes.

mooty

did u glaze the pads?

skxf430

I have had this both on my GT3 and Z06. mdrums describes it pretty well above. Also, as explained by a mechanic, when you transition from full acceleration to hard on the brakes, the system doesn't have enough vacuum pressure, and you will end up with a stiff pedal, and you will have to pump the pedal to get pressure back. The best thing I have found is to just brake a bit earlier and smoother.

Spyerx

Not that I'm aware as this issue literally went away after I lifted the pedal and got back in it and never reappeared the rest of the session.

What the others have described highlights the situation exactly:
Fast downhill, on full throttle
Transition quickly do full brake
Bumpy track in braking zone

I'm looking at my GPS data now and it looks like I carried the braking zone a lot further than I had been all weekend and must have stabbed the brakes.

996FLT6

If pads glazed u be feeling all the time. Been there done that. Abs went in dizzy mode. Mike

fc-racer

I experienced that the first time I used 08 pads as well. To prevent it, load the front tires a bit before going hard on the brakes. I was locking fronts up by using similar pressure as Pagid.

Jake951

I've had this happen two or three times. It's happened at the same spot every time (at the end of the braking zone entering turn 3 at NHMS) where I'm hard on the brakes and the track surface has a series of bumpy ripples.

TAI2

Much written on the subject. Do a search and you will have plenty to ready. I can reproduce the ice mode coming in to turn 5a at Mosport....

This happens to Caymans as well.......

Protocav

Happened to me on Saturday at the same turn. The car becomes very unstable through the T1 kink, and it is followed by bumps. Your brain tells you to put the brakes on, which is what i did early in the day, and the car does not like what is going on. The only way to get out of it is to let off the brakes, but this is very difficult, mentally. It works though. I began to use no brake through there and wait until the car settled down before applying the brakes. It seems like T2 is coming up very fast but there is actually a lot of track left before you have to get on the brakes.

Nice meeting you BTW.

997gt3north

Welcome to 6 years ago - completely normal.

Bumps, Downhill with changing tire traction levels = ice mode.

Once you know the types of corners it happens on you work around it.

You also made a very critical statement that when you checked the data later you saw you were braking later and going faster than expected. This is a critical observation. It shows that a corner at a certain speed, line, braking point may not show up as an ice mode candidate but as you start to go faster in may become one - this happened to me.

The reason this is critical is that as you go faster there is clearly less time and space to correct things if they go wrong - i.e. having no brakes when you need them.

Dumps and downhill with bumps are the very well known candidates. There is another more dangerous type of situation - and that is braking on what looks like a relatively flat surface that then changes to slightly less flat to slightly downhill during the brake zone - followed by a corner that goes extremely right or left with not a lot of space for error. This type of situation I would suggest the utmost type of caution as your speed picks up as the potential disaster outcome soars. When the ABS system senses a change in load on the wheels as the surface level changes to 'slightly downhill' you are going to get reduced braking force to the rear wheels to prevent a potential spin. If you are really, really on it, and now braking later and later and harder and harder to push for that last 1/2 second, your car will need to be doing more of the braking on the section of the track where the change in level is happening - and as that spot in the track gets closer and closer to where the initial brake point begins you run the risk of a catastrophic result - sort of the braking over the hill feeling to make the point more clear - you really, really need very good braking technique to keep maximum deceleration happening without getting ABS interference.

The best thing about Ice mode is that once you know about it you should be able to predict where it happens and then you just adjust your strategy for the affected corner to maximize your car's ability to go quickly through the corner on whatever line is required to make it work.

I actually got to the point of enjoying practicing dealing with it. Certain tracks have these unload types of situations where you constantly have to deal with ABS intervention. When you find these spots, you can actually use the opportunity to practise your braking technique - i.e. trying to find the optimal point where you don't trigger computer intervention - i.e. one more % brake pressure kills the corner - or, brake, sort of release, brake again, etc.

The reality is that you have a street tuned ABS system and it works as designed - i.e. not optimal in my opinion but it is what it is. So, like practicing driving in the rain for car control, use these spots on the track to work on your brake pressure skills - this is where the Pros are way better than DE drivers - way better.

Spyerx

Totally 6yrs ago. I read all the old threads on this and there was a lot of back and forth that almost seemed like speculation as the situation had just been 'discovered', but what I'm hearing now in this thread are some very definitive thoughts on when and how it happens. Or at least it seems clearer to me in reading this :-)

Its interesting looking at the data, I plotted my accel position, braking against lon accel (using AIM Solo DL wired into CAN, what a fantastic tool) and you can see very clearly I was accelerating harder, further, and I braked harder, and later. You can also see a dip in braking, then a bigger dip that appears when the accel didn't happen due to the stiff pedal. Fascinating to recount the experience in the data.

Appreciate the feedback, as I'm very new to this it's good to understand these limits and situations is key to the learning experience. Every time I've gone out I'm getting quicker, but more than that I'm starting to learn what the car is doing and why it is doing it.

utkinpol

do not stab brakes, develop a habit to apply bit of pressure first to load front and then very quickly give full press on a pedal. when you stab your brakes at same exact moment when car was bumped up into air (during suspension rebound cycle) and front wheels have much less traction than rears computer initiates ice mode.