Oi, Manfred! Whats with the torque steer?

[ThirstyMoose]

On a recent trip to Europe my 993 turbo has been exhibiting some quite serious torque steer characteristics. Pulling sharply right under hard acceleration and then back to the left under deceleration. It runs, and stops, perfectly straight and the handling is otherwise excellent - crisp turn in and nicely planted.
I've never noticed this to such an extent before and I'm curious as to how to dial it out. I'm guessing that its a castor angle issue.
Any wise or experienced Carrera 4 or Turbo drivers (or geo experts) who can help??

[Saddlebag]

Well on my C2 it was a knackered rear shock absorber and I had exactly the same symptoms as you.

Problem is, to look at they were fine, but I just changed them as a last resort and it sorted it straight away.

[ThirstyMoose]

Interesting, thanks Sb. Had a set of PSS10s, new bushes, top mounts, arms etc done about 800 miles ago at Centre Gravity. Maybe a call to chris is in order...

[BIG GT2]

i had a 993 turbo that the front diff was playing up on that had bad torque steer. a customer who is a friend had his front diff go and it had no torque steer just spun the rear wheels like a 2wd so may or may not be the diff. worth a look though sir!

mark

[ThirstyMoose]

OK, I'll throw that into the mix too. It had new front diff seals, fresh diff oil and also a new steering rack at the time of the suspension rebuild, so there has been some messing about in that area.
I was wondering whether there might be an issue with the front wheels being driven all the time, rather than simply when the rears lose traction.....

[sportsandclassic]

Hi, check your tyre pressures...

If ok, swop tyres side to side and see if the thrust direction changes.

Mike

[RatBoy M3CSL]

..Sounds like a worn bush or joint somewhere, resulting in 'variable' geometry under load.. I've had similar issues and what felt like rear wheel steering thro' worn joints..

[graemel]

sportsandclassic said:

Hi, check your tyre pressures...

If ok, swop tyres side to side and see if the thrust direction changes.

Mike

+1 and add. Have all the tyres got equal tread depth. If so talk to Chris but it could be that your caster is out. Effectively one side of the car is longer than the other.

[Pope]

My money is on a tyre issue.........

Do as Mike says and swap the wheels left to right, I've had brand new tyres exhibit this complaint and had tyres tested to find a 'soft' sidewall which essentially reduces the circumference of the tyre under load causing the handling issue.

If the pressure(s) is found low in the tyre bear in mind that the inside wall can damage very quickly so is worth checking after too.......

[ThirstyMoose]

Thanks all.

Tyre pressures checked and all good. The tyres (P-zero's) are directional, so swapping from side to side is likely to be problematic. The only anomaly is that the fronts are newer by about 2000 miles so they have about 2.5mm more tread.

All bushes, rod ends, arms, top mounts, etc are less than 1000 miles old, so I suspect either a geometry or maybe diff issue....

Plan to talk to Chris and a couple of others today so I'll post an update later.

[RatBoy M3CSL]

..Did the car behave like this before on the same tyres..?

[cd1957]

Hi we used to have this issue when the turbo first came out,we had to reset the "Kinematic" toe setting on the rear.

Chris

[supermono]

I'm pretty sure I saw your car in CG when mine was there, was it a polar 993 turbo?

Looked superb.

SM

[sportsandclassic]

Pope said:

My money is on a tyre issue.........

Do as Mike says and swap the wheels left to right, I've had brand new tyres exhibit this complaint and had tyres tested to find a 'soft' sidewall which essentially reduces the circumference of the tyre under load causing the handling issue.

If the pressure(s) is found low in the tyre bear in mind that the inside wall can damage very quickly so is worth checking after too.......

I had this on my GT3 with a Michelin Pilot Sport tyre... Was replaced and issue resolved.

[ThirstyMoose]

S&C - RatBoy - Graemel - Pope - cd1957:

Thanks for all the ideas and input, Just been out and checked over the car again. Tyres are spot on for pressure, not showing any signs of uneven wear. Put the car up on the lift and all of the yellow tell-tale marks on the geometry adjusters are unchanged. No apparent play on any bushes, ball joints etc (they're all new anyway).
The tyres haven't been replaced since before the issue arose - by the way, what happens if I do swap them over and run them 'backwards' ??http://www.pistonheads.com/gassing/imgs/4.gif

Had a nice long chat with Chris and I'm booked beginning of sept. He guarantees to fix it!!

Kinematic toe, castor angles, tyres etc all discussed and it seems that all could be candidates in some way or other. First-hand testing by an expert should reveal all..

Update to follow.

Supermono - No, mines a red one; red ones are faster!!

[ThirstyMoose]

Images of Manfred. Maybe. No idea how to do this....

[ThirstyMoose]

[sportsandclassic]

800 miles ago and you can only be seen next month? Well I could not run a business like that!

There is something wrong and it needs sorting, I would be devistated if I had set that car up and now something was wrong.

Where abouts are you in country as we can take a look sooner than that for you.

Mike

[Pope]

Running tyres backwards for a test will be fine - if the issue is transposed then you know where you are.......

Try it yourself - you'll feel great if you fix it....

[ThirstyMoose]

Ah, 800 miles but also10months! Last week was the first proper run out since the work was done (and was about 700 of the miles) and I think he's on holiday before that.
In fact he's been very helpful moving stuff to fit me in asap.

I'm going to swap the wheels tomorrow though, just to be sure...