I have a PSM or ABS issue on my 2002 C4S: front brakes come on hard for a split second.

It only happens when driving quickly on hilly, twisty roads with rough pavement.

It is very disconcerting and feels unsafe although it doesn't actually lock up the front -- but it unbalances the car.

No errors lights or codes, by the way.

Anyone have this issue?

More important, does anyone know how to start troubleshooting it?

Thanks in advance.

 

Are you still stock suspension and tire sizes? I noticed it more when I put on the 19"s with the big 315's in the rear.

Unfortunatly, I think it is normal under the right circumstances.

I have felt mine a couple of times. Usually in a very tight downhill corner....it feels like the load side front brake locks up for a split second and you are sliding. Then it lets go and straightens out. It freaked me out for a second the first few times it happened.

I think it is a combination of the ABS and PSM trying to optomize things.

I also set my adjustible H&R sways to soft front and med rear and it seemed to help some.

 

YES is normal,
friend of mine have the same problem with is boxster s on track ''le circuit Mont-Tremblant'' on namerow turn 14 ...downhill tight corner

 

I still have stock suspension and wheels. (Suspension may be getting a bit tired since its stock and has 78k kms or 48k miles.)

By the way, it happens under light throttle or gentle lift off the throttle -- and the car does not feel like its slipping at any wheel (i.e. this is not a unweighted four-wheel drift or understeer scrub).

A friend with a 996 turbo says he's never experienced it...

then again, these are much tighter, hillier corners than average (and not high speed either).

 

sounds normal.... especially when one wheel (yaw sensors) is loosing grip (gravel, dirt etc) on uneven pavement during a hill climb (slight acceleration) while turning (cornering)...

 

Many thanks all for answers.

It is more sensitive than I expected and than my Audi S. Oh well, that is what the PSM 'off' setting is for

 

Happened to me when i switched the rear tires with Kuhmos, and the fronts were still Potenzas. The rears were worn out and the fronts were okay. Trying to save a few bucks i just replaced the rears. I thinked the PSM sensed the difference either in tire diameters (front vs. rear), or tread compound which resulted in the same behavior you were explaining. I ended up replacing the fronts also and the problem went away.

 

Hmm. Interesting.

In my case it happened with Continental Contisport 2 that we all wearing fairly equally. Then, with new Sumitomo HTR Z III it happened also.

So it doesn't appear to be the tires in my case.

 

Turn the PSM off and hit the same route. Just be careful that the tail doesn't whip out on you.

 

Done and done!

With the PSM turned off there is no problem.

But its a nice bit of insurance... so I prefer to keep it on.

Oh well, I just didn't expect it to be as intrusive...

Thanks for answers.