Darren

I'll call Hoosier tomorrow to ask, but I thought the Grand Am slicks were the same compound as the R6's from my discussions with them. I'm using R80 front and R100 rear and they seem quite a bit grippier than the R6's.

From the feedback I've gotten so far, and thanks everyone for responding, even stickier tires are likely to make the problem worse. I know the problems are real.

I'm looking to install a Cup ABS unit if that turns out to be a technically feasible option. From what I've seen the connector to the ABS unit and the wire colors are the same for the 996, but there are way fewer wires in the Cup harness.

jakermc

I don't know much about the Grand Am slicks, but remember that one big difference between Hoosier slicks and Hoosier R-compound is the sidewall construction and spring rate. It may not be a matter of the rubber compound and grip, but the spring rate of the tire that may or may not cause problems.

The slick has a much higher spring rate. You then have to ask yourself if your car was set-up for slicks or R-compound, or a compromise solution. I'm guessing all of these things come into play. I know that changing my damper settings change how the ABS reacted, so I've got to think that the tire/spring pairing plays a large factor as well.

Darren

I'm sure the spring rate of the tire plays into it, I'm sure this is all very complicated at the engineering level. In my case, my car is setup to use slicks.

85Gold

I wonder if braking style, ie jumping on the binders, with out allowing sufficient weight transfer aggravates the problem. The reason I suspect this is one of the causes is mine and Ian's braking style are different, he is on HARD, and I ramp up a little slower. Ian has had more problems with Ice Mode than I have. Pre ABS we knew to not jump on the brakes and allow transfer for max grip. Abs has made us lazy.

Peter

Darren

Yes, I think that is true, if I'm more abrupt it is more likely to happen.

My problems are not exclusively ice mode -- the more recent problem is this issue where the "Steering Angle Sensor" code is thrown and the ABS turns off.

Krokodil

Absolutely true. A smooth transition to brake, vs an abrupt stab, all but eliminates the problem (at least for me). Tire size F/R ratio is also critical, as the 997/987 cars require a larger diameter rear.

As long as the ratio is near stock, and the brakes are applied progressively, the OEM controller seems to work fine, even on a stiff car.

This is all on R6s, slicks may be different of course.

Darren

I've heard that the Caymans are actually even worse with these issues than the 996. A local shop has been developing a Cayman for a customer with a pro racer as the test driver and they scrapped the ABS and went with dual masters from the 997 cup because of all of the issues.

997gt3north

I have found this to be 100% true in the 997gt3 - i.e. you absolutely cannot stab / be abrupt with the initial pedal - it will instantly "icemode" in this situation. The problem of course is safely finding the point of crossover from normal to icemode as it can be very dangerous because you go from 100% stopping to in certain situations to potential way less than 50%. This in a nutshell is my issue with the ABS unit in its current form. I have no idea who it was (Porsche, Bosche or combo Porsche/Bosche) that decided this was the preferable outcome to "flat spotting a tire because to me flat spotting a tire is a far far better outcome that losing potential 50% of your braking. Now, I'm sure it is no where near that simple as there are many many scenarios which come into play (car spinning, rotating, too much rear bias etc) BUT in the case of the GT3 where TC can be turned off for the 997.1 and TC SC can be turned off for the 997.2, it is the ABS control unit logic that in many very repeatable situations, which are not uncommon even while basic street driving, that the ABS software is making the wrong decision - it is choosing to reduce the requested brake level to "potentially" give you more steering control when the driver has asked for a higher level of brakes - in certain cases the difference in requested and the given level can be "extreme" and in my opinion that is crazy.

If the Chris Harris / Francois Delecour test drive 2010GT3/RS video mentions this issue (clearly on street tires) and WR is having it re-programmed to use for the 24Hr - then clearly Porsche knows there is an issue??????

I think the easy solution is for Porsche to put another button on the dash (or even better make it the PSM button found in 2010 gt cars) that changes the tolerances in the ABS module to make it far, far less intrusive

jakermc

is it possible you actually have a bad steering angle sensor?

I know when my MAF went bad it sent errors codes into the ABS system. ABS was fine though, replaced the MAF and all was well with ABS again.

Darren

Yeah the MAF lights everything up like a Christmas Tree when it fails. I don't think its the Steering Angle Sensor because it only throws a code when I corner at max g-force.

garrett376

Is this a problem only on cars that have the PSM from the factory?

Darren

You know the more I have researched and talked to people (and read replies from folks here, including an actual Bosch engineer here on the forum) I think we're just asking stock ABS systems to do things they were never intended to do.

I know the ice mode problem is very real on 993's also, so no it's not just limited to cars with PSM.

onefastviking

+1
It's a great stock system but as we change the tires, susp.,modify the eng., brake pads and calipers, etc, etc, we also must expect the need to modify the ABS also.

924RACR

Oh, so you don't actually have a code pulled for that? Ah, makes it a little harder to diagnose...

It's quite possible, perhaps even likely, that you are exceeding allowed range values for lat g's in that case. I seem to recall hearing something about such issues with fairly standard calibrations on full-race tires/slicks...

Not that there's much you can do about it.

garrett376

Darren, and Mr. Viking, do you guys know of anyone having this "ice" problem with a 996 with no PSM as an option? The ABS is a different part on those cars. Just curious (and that's the question I should have asked above!)