2006 987 on full lock at low speed....crunchy feeling???

[Tiggsy]

First spotted this reversing off the drive under full lock in the winter - the sensation was that the tyres where "crunching" on ice or snow on the drive. I assumed, as they are pretty fat/wide tyres they just had more resistance to the ground when going slow on full turn.

But weather is now fine and its still doing it...so starting to think it may not be the tyres/road surface! What would make it feel like that....full lock, slow in reverse....feels like tyres are going over hard packed snow.....but assume it may well be feedback coming from elsewhere in the steering system and not the rubber (or even wheels) themselves???

[kingston12]

I am not sure what it is, but my 2005S does it as well when cold.

There was a thread on it a while back that seemed to conclude they all do it. I am sure someone more knowledgeable will be along shortly...

[Greshamst]

Yep, most do this on full lock, mine does it reversing out of my space. It's a common thing, It's something to do with the ackerman effect.

[guards red]

It's nothing to worry about, it will be the tyres.

The tread blocks are sat on very cold ground overnight and stiffen up a tad. As you move off on lock the tread is being asked to flex which they are not happy doing and make that sound. This goes when they are warm.

[T1PAU]

https://en.wikipedia.org/wiki/Ackermann_steering_g...

This'll explain it.

[PaulD86]

Experienced it in 4 or so Porsches. They tend to start doing it when the tyres are getting worn.

[bcr5784]

PaulD86 said:

Experienced it in 4 or so Porsches. They tend to start doing it when the tyres are getting worn.

Happens with new tyres too - at its worst when the weather is cold on Summer tyres. Hasn't occurred at all on my Winter Dunlops so far (but it's never been very cold) - but was pretty bad on P Zeros on even coolish days. As has been said it's due to lack of Ackermann (the inner front wheel should describe a smaller circle than the outer one when turning a corner and so should have more lock applied to it). It's used on some race cars to aid cornering on hairpins - and on road cars to limit the amount of wheelarch intrusion into the footwell area (a particular problem with rear and mid engined cars where the driver sits well forward between the wheel arches)