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Front wheels locking up

Nathan Gould

New member
Hi there,

I had fairly old tyres on my 997 C2S and had experienced a bit of understeer, and most worryingly the front wheels locking up under hard braking. I recently got a pair of michelin pilot sport 4S fitted to the front in the hope that this would solve the problem however its still pretty easy to get the fronts to lock up. As I'm sure you can understand thats not really ideal! is this some sort of issue with the ABS, or just something that these cars will do being slightly lighter at the front?

thanks

Nathan
 
Hi Nathan,

That doesn’t sound right to me because the ABS should activate before the brakes lock-up. I assume that you’re not getting any ABS warning messages?

It sounds as though there could be a problem with ABS unit which needs to be checked-out using some appropriate diagnostics.

Jeff
 
Hi Jeff, I had assumed the same as well, but the car recently had a health check with Porsche Sheffield and they found nothing wrong, no ABS warning lights are showing at all. Might be worthwhile taking it to someone else for an independent inspection.

Thanks

Nathan
 
That is very odd Nathan. Are you not getting any ABS action at the brake pedal before actual lock-up?

An independent inspection would be a good plan; the question is where? Sheffield presumably have run a standard PIWIS diagnostic test and have found nothing wrong, so if you took the car to either another Porsche dealer or even a Porsche Independent you’d have to presume the same outcome. Assuming the ABS is a Bosch unit, maybe there’s a Bosch specialist somewhere who can run an independent test for you? This link might be a starting point:

https://www.bosch-repair-service.com/en/category/abs-and-esp-control-unit/

Jeff
 
How long have you had the car, how long has it been `doing` this ?

Are both wheels `locking up` together when on an even surface and in what weather conditions ?

It`s easy to `feel` a locking - tyre slipping sensation when the front is unevenly loaded

Is the brake pedal `pulsing` (ABS engaging) ... you should have to brake really hard for the ABS to engage when evenly loaded

Is the wheel alignment geometry OK and are the tyre pressures OK and even ? (New tyres can take some time to scrub in before they give of their best)
 
Hi guys- sorry for the late reply, i've been caught up with family stuff over christmas. Theres no discernible ABS pulsing through the brake pedal, the tyre pressures were OK and even, but i cant say for sure the geometry is. I have done a fair few miles on the tyres now and it feels better, but i can still get the fronts to lock up with a firm prod on the pedal.

https://www.bosch-repair-service.com/en/category/abs-and-esp-control-unit/- this is good link thanks for sending it over, i'll do a bit more research and see if i can find a specialist to investigate for me.

 
Thanks for the feedback Nathan. Unfortunately I can only repeat what I said previously that it should be impossible to lock the wheels if the ABS is working correctly, so clearly something’s not right. The ABS is an independent safety system and I can’t quite see how the geometry will have any bearing on it.

Hope you manage to find a solution … please keep us posted on any progress.

Jeff


 
Will do, hopefully this is just some sort of sensor or connector issue which should be easy to fix, its just the diagnostics which might be tricky- i'll let you know how it goes
 
You could start by disconnecting and reconnecting the front connectors to see if that clears the problem and if not buy a sensor and plug it in as a replacement. However if there is a sensor fault it should have been thrown-up by the diagnostic test.

Jeff
 

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