ABS FAILURE SYMPTOMS

[tiskev]

If i brake hard and make the car skid I presume all 4
wheels are locked .Should i get the juddering noise caused by
the wheels being released for milliseconds ?
She just skids and stops so maybe the ABS is up the shoot as shown on
screen as i do not get the judder.?

 

[paulus]

Your tyres shouldn't lock / skid at all with ABS - unless it gets confused by unusual road surfaces.
If it does there is probably a fault & associated warning light.
The ABS should cut-in before the tyre starts sliding & then it will release the pressure on the relevant wheel(s) & re-apply it again very quickly - maybe giving you a pulsing / juddering feeling at the brake pedal while it is working (dependant on ABS system). The juddering is not the tyre, it is the pump in the ABS system.

Dependant on how hard you push the brake pedal the system may be operating on anything between just 1 upto all of the tyres - eg on a 911 you often only get 1 or both front tyres trying to lock up because there is so little weight on the front. You have to push very hard to cause the rears to try to lock up - unless its very greasy / icy.
For the Cayenne, I would imagine the weight distribution is very equal, but the brakes will be biassed to wards the front - so front tyres are most likely to lock first, but dependant on road surface, any could lock up.

Paul

2004 996 C2 40th Anniversary

 

[tiskev]

Thanks Paul,
It sounds like there may be a problem. and a check is needed

 

[tiskev]

Paul I am told that some manufacturers fitted an SBS system which takes away
the juddering as this was causing a lot of drivers to brake too softly.
Do you think Porsche fitted it as thinking back i cant remember my Cayenne ever judddering
?