981 tyres scrubbing when turning
Discussion
nsm3 said:
If its in the manual, why is it even being discussed?
This 981 on 20's is the worst for doing it, forwards or backwards, hot or cold, even compared to my GT3 on 19's, a previous C2S on 19's, an M3 on 18's and an Exige on castors - they all exhibited some form of it, although the M3 and GT3 also had an LSD lock up thing going on in reverse as well.
If anyone thinks their car (981) has a problem over and above what has already been mentioned on this thread, they had best make a nuisance (or eejit) of themselves at their dealers?
Well - I did some experiments in the cold this morning - and the result? The clunks on my car ARE due to PSM - traction control. How do I know? Because that little light on the dash says so - happily flashing away. Of course it might well be it's set off by tyre scrub - but since it causes tyre scrub itself it impossible to tell just by listening when that happens on my car. This 981 on 20's is the worst for doing it, forwards or backwards, hot or cold, even compared to my GT3 on 19's, a previous C2S on 19's, an M3 on 18's and an Exige on castors - they all exhibited some form of it, although the M3 and GT3 also had an LSD lock up thing going on in reverse as well.
If anyone thinks their car (981) has a problem over and above what has already been mentioned on this thread, they had best make a nuisance (or eejit) of themselves at their dealers?
I think we MAY now have an explanation that actually meets ALL the facts, which we did not have (here) before.
No mention of either effect as far as I can see in a 981 handbook. Anyone know where it's supposed to be....
Edited by bcr5784 on Saturday 6th December 15:38
Ozzie Osmond said:
Congratulations. You appear to have the first front wheel drive Boxster!
Alternatively please explain to me: How do you trigger traction control braking at the front of a rear wheel drive car at parking speeds?
Who said it was at the front? If PSM is doing anything to (it thinks) sort out the drivers issues it flashes. Alternatively please explain to me: How do you trigger traction control braking at the front of a rear wheel drive car at parking speeds?
anonymous said:
[redacted]
Since you appear to have the clonking too then presumably YOU need your PSM attended to. Or perhaps you haven't noticed the odd flash. I suggest rather than continue to make simplistic and unhelpful statements you do some controlled experiments of your own and see if the clonking (as opposed to, but possibly at the same time as the scrub) you apparently experience is indeed PSM intervening. You're very good at talking the talk, but walking the walk seems beyond you.bcr5784 said:
Well - I did some experiments in the cold this morning - and the result? The clunks on my car ARE due to PSM - traction control. How do I know? Because that little light on the dash says so - happily flashing away. Of course it might well be it's set off by tyre scrub - but since it causes tyre scrub itself it impossible to tell just by listening when that happens on my car.
I think we MAY now have an explanation that actually meets ALL the facts, which we did not have (here) before.
No mention of either effect as far as I can see in a 981 handbook. Anyone know where it's supposed to be....
So how come you get it on TVRs which don't have PSM?I think we MAY now have an explanation that actually meets ALL the facts, which we did not have (here) before.
No mention of either effect as far as I can see in a 981 handbook. Anyone know where it's supposed to be....
Edited by bcr5784 on Saturday 6th December 15:38
Lets keep this simple. Tyres do not clonk only metal does. If you get something that is a metallic clonk it is NOT tyre scrub. You say you have experienced a clonk. I have established that my "clonk" is caused by PSM intervention. You have asserted that the problem occurs on a 986 which doesn't have PSM. But tyres don't clonk ... So
Either 1) The noise you have heard was not a clonk
2) There is yet another source of clonks which is not tyres.
I am perfectly prepared to accept that 986 (or 7 or 1) may be subject to tyre scrub on lock. But I am not prepared to accept that tyres clonk.
So - have you heard clonks as you imply or not? If so on what car and can you reproduce it? Unlike you I actually want to understand what is going on.
And just so YOU understand what I'm trying to understand the handbook says:
"Examples of PSM control operations
If the front wheels drift (POSSIBLY WHAT IS HAPPENING IN THIS SITUATION) on a bend the engine power is reduced and the rear wheel on the inside of the bend is braked if necessary......"
So it perfectly possible that tyre scrub (whether audible or not) will cause PSM to intervene - since tyre scrub will cause understeer.
If you are REALLY interested in understanding how the car works, I suggest you read that a couple of times so you actually understand it rather than come back with yet another silly comment.
So I ask again do you get clonks and if so on what car and under exactly conditions?
Either 1) The noise you have heard was not a clonk
2) There is yet another source of clonks which is not tyres.
I am perfectly prepared to accept that 986 (or 7 or 1) may be subject to tyre scrub on lock. But I am not prepared to accept that tyres clonk.
So - have you heard clonks as you imply or not? If so on what car and can you reproduce it? Unlike you I actually want to understand what is going on.
And just so YOU understand what I'm trying to understand the handbook says:
"Examples of PSM control operations
If the front wheels drift (POSSIBLY WHAT IS HAPPENING IN THIS SITUATION) on a bend the engine power is reduced and the rear wheel on the inside of the bend is braked if necessary......"
So it perfectly possible that tyre scrub (whether audible or not) will cause PSM to intervene - since tyre scrub will cause understeer.
If you are REALLY interested in understanding how the car works, I suggest you read that a couple of times so you actually understand it rather than come back with yet another silly comment.
So I ask again do you get clonks and if so on what car and under exactly conditions?
Pope said:
Thanks - at last someone else is trying to CONTRIBUTE to the discussionDefinitely thump and definitely tyre scrub. Not a clonk nor a PSM intervention as far as I can see.
anonymous said:
[redacted]
Yes. Mid-engined cars can be "a bit of a handful" at speed. Once they start to rotate they love to keep going round. So the manufacturers do what they can to suppress nasty high speed behaviour by introducing some nice friendly understeer. The flip-side is that you get the tyre jumping/clonking/scrubbing effect at parking speeds. There's nothing wrong, it's just the way the cars are set up. You could completely disconnect all the electronics and it would still happen. It's a physical effect. In other words, reality.anonymous said:
[redacted]
As usual you half read and half understand (on a good day). I always said it wasn't as simple as that ON MY CAR - and in my case it clearly and provably isn't . If you take the trouble to look at the video you will hear nothing that I would call a Clonk - nothing metallic. I REPEATEDLEY said it was a metallic noise which you insisted was poor Ackerman induced tyre scrub. Which IT IS NOT.But I can't be bothered arguing with you any more. You would insist black was white,and rather than admit that your assertion was wrong (I'll let you get away with SIMPLISTIC and INCOMPLETE). Clearly you can detect at great distance what MY CAR is doing. It's gift!
If anyone else has witnessed PSM intervention under those conditions, I would be interested to here..
Edited by bcr5784 on Sunday 7th December 08:45
Therein lies the issue.
No one here has experienced your scenario. Their experiences tie in with the examples and descriptions discussed and their concerns have been allayed. Their experiences is of around a third of the vehicles weight being shunted left/right around the tyre with most grip which brings with it some pretty alarming noises.
Post up a video showing the problem; this will help get distinction between what is normal and what is not.
PSM intervention is a normal occurence given the right conditions (lack of traction/excessive yaw and other forces).
If you are experiencing understeer - however fast/slow - then driving through it will give rise to a PSM intervention (the system's way of bringing the vehicle back into line).
No one here has experienced your scenario. Their experiences tie in with the examples and descriptions discussed and their concerns have been allayed. Their experiences is of around a third of the vehicles weight being shunted left/right around the tyre with most grip which brings with it some pretty alarming noises.
Post up a video showing the problem; this will help get distinction between what is normal and what is not.
PSM intervention is a normal occurence given the right conditions (lack of traction/excessive yaw and other forces).
If you are experiencing understeer - however fast/slow - then driving through it will give rise to a PSM intervention (the system's way of bringing the vehicle back into line).
bcr5784 said:
No mention of either effect as far as I can see in a 981 handbook. Anyone know where it's supposed to be....
Page 198, top right hand corner, under (i) information....."For example, juddering noises caused by the tyres can occur while manoeuvring the vehicle or accelerating out of bends on both dry and wet road surfaces."Page 206 in my book (Cayman, Cayman S, Cayman GTS Driver's Manual)
"The summer tyres of your sports car have been specifically developed for high performance. The tyre characteristics change at low outside temperatures (below 15 deg C). This can result in noises when parking or manoeuvring at low outside temperatures"
Since fitting winter tyres, I have not noticed any noises when parking. It would happen every time with the 20" summer tyres on
"The summer tyres of your sports car have been specifically developed for high performance. The tyre characteristics change at low outside temperatures (below 15 deg C). This can result in noises when parking or manoeuvring at low outside temperatures"
Since fitting winter tyres, I have not noticed any noises when parking. It would happen every time with the 20" summer tyres on
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