991 GT3 Wheel Alignment - Play in Rear Wheel Steer

[blueSL]

Took my GT3 to Centre Gravity today to set it up and everything ground to a halt when we found play in the rear-wheel steering. Lift the car off the deck, grab a rear wheel at Quarter to Three and you can rock the wheel, we measured it as 0.1 to 0.2mm at the rim. Seems to trace back to the rear wheel steering actuator and they told me the play was enough for the car to fail the MOT. Since this movement is greater than the setting tolerance, there was no point in continuing. The car pulls to the right, especially under heavy acceleration.

So now the long slog to get the OPC to replicate the problem (assuming it is such) and fix it. The OPC said the key has to be out of the ignition for the test to be valid, CG says the ignition has to be on. Who is right?

Anyone else seen this problem?

[sportsandclassic]

Hi,

The ignition must remain on when adjusting the rear toe according to Porsche working instructions.

You MUST also calibrate the steering angle sensor once the alignment is completed.

Mike

[blueSL]

Thanks, so the OPC were talking nonsense. i expect there is some sort of reset of the RWS when you switch the ignition on. Thanks for the tip about the steering sensor.

[996TT02]

Is that really 0.1mm or do you mean 1mm?

[PorscheGT4]

if it's only 0.1 mm then screw buying one of these 4 years and older.

way to much tech to be a nice buy in 5 years :-(

[Trev450]

This was something that was discused when they were first launched and IIRC it was Foran0 that pointed out the potential for alignment issues if any wear was to occur.

[Taffy59]

Took my car to CG in October last year en route to my PEC visit. Chris diagnosed slight play in the o/s rear rws motor. Mine was the first 991 GT3 he had seen.
When I returned home, the issue was reported to the OPC where I purchased the car and it was replaced without any hesitation.
I believe that the part number has had a number of iterations, so one could assume that any issues should by now be sorted. However I will be keeping an eye on them.

[Taffy59]

BlueSL, having read your post again, my car accelerated (hard) and braked (hard) without any pull left or right both before and after the actuator was replaced. Would doubt that the actuator would cause the symptom you describe. Did Chris offer any thoughts?

[blueSL]

With the wheels off the deck, you can grab them at quarter to three and push and pull in the direction the RWS operates, clonk, clonk.

It was only 0.1mm, 0.2 on the other side, but I'm hardly exerting the same forces as it would see on the road. Car has done 3500 miles.

The geometry is out, CGs view was that there was no point doing it because they do the back first, then the front and this play would create a dead zone around the centre.

Thanks for the info on the replacement, I'll get in touch with my usual dealer and see what they say.

[sidicks]

blueSL said:

With the wheels off the deck, you can grab them at quarter to three and push and pull in the direction the RWS operates, clonk, clonk.

It was only 0.1mm, 0.2 on the other side, but I'm hardly exerting the same forces as it would see on the road. Car has done 3500 miles.

The geometry is out, CGs view was that there was no point doing it because they do the back first, then the front and this play would create a dead zone around the centre.

Thanks for the info on the replacement, I'll get in touch with my usual dealer and see what they say.

Seriously? 0.1mm?

Surely you'd struggle to feel a 'wobble' of 1mm given the potential flexibility in the tyre itself - I'd be amazed if you could you detect a 0.1mm movement by feel alone.

Chris is good but not that good!

Edited by sidicks on Thursday 11th June 18:09

[Trev450]

Toe is adjusted in increments of 0.1 mm.

Edited by Trev450 on Thursday 11th June 19:04

[Taffy59]

sidicks said:

Seriously? 0.1mm?

Surely you'd struggle to feel a 'wobble' of 1mm given the potential flexibility in the tyre itself - I'd be amazed if you could you detect a 0.1mm movement by feel alone.

Chris is good but not that good!

Edited by sidicks on Thursday 11th June 18:09

Yes he is!

[sidicks]

Trev450 said:

Toe is adjusted in increments of 0.1 mm.

Edited by Trev450 on Thursday 11th June 19:04

But surely measured by laser / computer, not by 'feel'?!

[Taffy59]

sidicks said:

But surely measured by laser / computer, not by 'feel'?!

In my case he detected it by hand and then measured it using a dial gauge onto the rim.
Can't remember the exact measurement right now, but it was minimal

[sidicks]

Taffy59 said:

In my case he detected it by hand and then measured it using a dial gauge onto the rim.
Can't remember the exact measurement right now, but it was minimal

Wow!

He's very good!

[blueSL]

Same as Taffy59, you can feel the rim moving, not just the tyre. We measured it using a dial gauge and also reproduced it exactly with the Hawkeye attached and running. Grasp the rim and the figures change.

[GR GT2RS]

The car pulls to the right, especially under heavy acceleration.



Anyone else seen this problem?
[/quote]

Are all the tyres the original fitment Michelins or has one been replaced? (Have you had the car from new)
Does the car pull to the left when you come off the power?

[BertBert]

sidicks said:

Wow!

He's very good!

Not really, even very small amounts of play give thank "donk" feeling when you tug the wheel.
Bert