Question from Member - noise on full lock?

[Mark_Bennett]

I have received a query from a member via the Submit a Question facility on th Club's website, I've never heard of this before - has anyone here?

I have a porsche boxster 2001 model. Recently i have had noises coming from the front end when steering at full lock. The car has gone to an approved Porsche dealer in Chiswick and they say this noise is common on a boxster and 996, as this is the tyres scrubbing. Do youi have any knowledge of this? or should i pursue this further?

 

[thboxster]

I get it from time to time when I turn round in our close. I can't recall it happening in reverse, only forward, but could be wrong. The other thing I noticed was that you can put it on full lock and drive a short way without knocks, then there seems to be a clunk and it goes quite again for a short while.

Off full lock though, no probs. It's never concerned me as previous cars have made odd nooises on full lock. Mine's 2.5 years old, it's always done it and i've never experienced any problems.

 

[Dapster]

Similarly, I've experienced this and asked my OPC who explained that the combination of the suspension offset and fat tyres cause the knock at low speed on full lock (ie walking pace). I was preparing myself for full open wallet surgery and new front wheel bearings so this was a very pleasing response.

 

[Mark_Bennett]

Thanks all - I'll let him know he's not alone!

(Feel free to continue posting if there are any more comments)

M

 

[graemewf]

We have a 2002 Boxster 3.2 S that does it, have had a 2010 997 911 C4S that did it and also an 2012 Audi S6 that does it. Just fat tyres scrubbing round a tight circle. The inner edge of the tyre takes a tighter radius on the turn than the outer edge so the tread pattern has to give a bit on some surfaces. Was a bit disconcerting to start with when you heard it giving the odd thump as you manoeuvre in car parks or in front of the garage.

 

[SamanthaHewit]

Am I remembering correctly, isn't this something called the Ackerman Effect? X

 

[waxman]

Yes this is the Ackerman effect and I believe is caused by the wide tyres scrubbing at low speed on max lock or close to it in this case. It is perfectly normal.

 

[ralphmusic]

....perfectly normal but seems mechanically unsympathetic to do it.

 

[Glyn]

Its the Ackerman principle.
The inner wheel when on full lock has a greater angle than the outer as it has a smaller radius to turn, however, with such wide tyres the angle calculation is only spot on for one particular point - which is the centre of the tyre - Therefore the inner and outer edge of the tyre scrubs a little.
The noise is simply the tyre scrubbing over the road and is more noticeable on loose surfaces/gravel etc, When driving forward it is less obvious than in reverse.
All perfectly normal - the wider the tyre the more you can feel and hear this.

 

[Mark_Bennett]

Wow - A 9 year old thread resurrection!

Someone's been reading in depth or making use of the fact that search now works []

 

[BartyB]

Yes, it happens to me too. A couple of observations: It's always worse when the tyres are cold (when driving off the drive in the morning) and Pirellis seem slightly noisier, although in all fairness our road's been resurfaced since the car was shod with Michelins.

 

[Wollemi]

Yes, I've been getting it as well when I have to do a bit manoeuvring in reverse to get the car out in the mornings. Thanks for dredging up this nine year old post to explain it all.

 

[Motorhead]

A recurrent post on this forum, although it's interesting to note that we've only seen posts more recently when we've had some frosty mornings, so as Alan says, low temperature plays its part too.

Glyn's explanation is correct, although I believe that manufacturers use a modified, rather than pure, Ackerman set-up these days.

Jeff