996 Geo

Author
Discussion

asbi

Original Poster:

107 posts

213 months

Wednesday 27th May 2015
quotequote all
All,
Developing a 996C2 for track, had KW Clubsports fitted and tracked the car for the first time last weekend.

Overall very pleased but noticed a slight steering pull to the left on the way home and after measuring the geo found that the NSR toe has gone from +5mins to +40mins - OSR toe has not moved and neither have the cambers.

The rear toe arms and bolts are new and AFAIK were torqued up correctly.

Questions: 1) would the above cause a steering pull and 2) what should I do about this - re-torque and try again?

Going to Spa in July so don't want the geo moving around and spoiling my days :-)

Cheers,
Kevin

PorscheGT4

21,146 posts

264 months

Wednesday 27th May 2015
quotequote all
Mono ball it and fit locking bolts.

fioran0

2,410 posts

171 months

Wednesday 27th May 2015
quotequote all
The method of adjusting and restraining the rear toe via an eccentric bolt is not very effective when it comes to the second part of its job. Sadly it doesn't take much for it to slip or be knocked out of whack rendering ones expensive geo useless. Off all the things on these cars that can be set, rear toe is perhaps the most important.

As mentioned, though not perhaps clearly, you can fit an adjustable rear toe arm and locking plate kit (tarett.com or others) to remove this issue. A plate and regular bolt/nut combo replaces the eccentric bolt, which becomes fixed, and the rear toe control arm is replaced with one that is threaded like a regular steering rack arm. Adjustment is now made on the arm itself.
This combination is both more resistant to self adjustment and easier to adjust when required.

sportsandclassic

3,774 posts

217 months

Wednesday 27th May 2015
quotequote all
Hi, As stated before the locking bolt and plate is a sure fire way of nothing moving BUT it is not necessary as I have done dozens of track days including SPA on sticky tyres with no movement in the eccentric adjusters.

Best thing to do is strip it apart clean the head of the adjuster as if it has any anti-seize compound present it WILL slip. I have seen this on more than one occasion.

Once the wheel alignment is finished then mark the adjuster with a marker pen in two places to see if it shifts.

The rear wheel alignment being so far off would cause a pull as the thrust line would be incorrect.

Mike


asbi

Original Poster:

107 posts

213 months

Wednesday 27th May 2015
quotequote all
Gents,
Thanks to all for the responses - will give it another go with the standard set-up, marking up the positions as Mike recommends and see how I go.

Shows I must have been trying (a bit at least :-))

Cheers,
Kevin

gordonc

264 posts

251 months

Wednesday 27th May 2015
quotequote all
where u based??

GT2rainge

189 posts

195 months

Wednesday 27th May 2015
quotequote all
Hi Kevin, did you have them fit new eccentric bolts and nuts?
If so I'd guess they either didn't clean and scrub the subframe where the bolts fit or/and they covered the bolts with copper slip crap. They need to be fitted dry with no lube etc on them then they shouldn't move.

Ask me how I know, plenty of tyres killed and European trips ruined because of toe moving.

GT2rainge

189 posts

195 months

Wednesday 27th May 2015
quotequote all
Also 5mins toe in isnt really enough on the rear, I'd run 12mins each side at least

asbi

Original Poster:

107 posts

213 months

Thursday 28th May 2015
quotequote all
gordonc said:
where u based??
Cheshire - so it's the 9m boys doing the actual work, as an engineer to trade though I like to get "involved" :-)

asbi

Original Poster:

107 posts

213 months

Thursday 28th May 2015
quotequote all
GT2rainge said:
Hi Kevin, did you have them fit new eccentric bolts and nuts?
If so I'd guess they either didn't clean and scrub the subframe where the bolts fit or/and they covered the bolts with copper slip crap. They need to be fitted dry with no lube etc on them then they shouldn't move.

Ask me how I know, plenty of tyres killed and European trips ruined because of toe moving.
Niel - I hope they did all the above given who is doing the job :-)

asbi

Original Poster:

107 posts

213 months

Thursday 28th May 2015
quotequote all
OK, so had the geo reset today to pre-Anglesey specs (when the car was driving fine)...

...and its no better - so I am guessing that the stress of the day has maybe bent something - I went onto the exit kerbs on the hairpin at the end of the loop a couple of times which are very mild and spun once at fairly slow speed (Rocket) whilst staying on the tarmac.

The pull is subtle but most defintely there - the car doesnt feel as neutral as it did before the trackday.

Gonna swap the front tyres (888s) round over the weekend but think this is unlikely to be causing the issue.

All suspension compnents were inspected prior to the polybushing and KW fit - ARBs are on centre setting F&R.

Ideas?

boxsey

3,574 posts

209 months

Thursday 28th May 2015
quotequote all
asbi said:
The pull is subtle but most defintely there - the car doesnt feel as neutral as it did before the trackday.

Gonna swap the front tyres (888s) round over the weekend but think this is unlikely to be causing the issue.

All suspension compnents were inspected prior to the polybushing and KW fit - ARBs are on centre setting F&R.

Ideas?
Brake caliper on the left side binding?

...I hear they're made by cadbury's whistle

asbi

Original Poster:

107 posts

213 months

Friday 29th May 2015
quotequote all
Slippydiff said:
What top mounts are you using with the KW's Kevin ?
KW, supplied fully assembled.

asbi

Original Poster:

107 posts

213 months

Friday 29th May 2015
quotequote all
boxsey said:
Brake caliper on the left side binding?

...I hear they're made by cadbury's whistle
No binding issues front or rear.....after a long run all hubs are similar temperature.....

asbi

Original Poster:

107 posts

213 months

Friday 29th May 2015
quotequote all
Had a look at the tyres last eve and the geo is goign to have to be changed notwithstanding the pulling issue.

Both the n/s tyres are visibly worn on the inner half which surprises me considering i have only done one track day and 300 road miles.

Current geo is -2deg fr and -2.5deg rear with 10min of rear toe in.

I am surprised at the tyre wear, on both RSs they wear very evenly and I get 8-9 days out of a set - these will be worn out by the time I get to Spa at this rate!

Is the current geo super aggressive or par for the course for 996s that are tracked?

Thanks,
Kevin

PorscheGT4

21,146 posts

264 months

Friday 29th May 2015
quotequote all
what's front toe ?

keep it lit

3,388 posts

166 months

Friday 29th May 2015
quotequote all
Not really what I'd call a super aggressive.. No way front tyre wear should be that heavy with those settings in such short mileage..
Again I'm not sure why someone would set your rear camber with with more negative camber than your fronts unless you specified this?

asbi

Original Poster:

107 posts

213 months

Friday 29th May 2015
quotequote all
PorscheGT4 said:
what's front toe ?
3min total toe in

asbi

Original Poster:

107 posts

213 months

Friday 29th May 2015
quotequote all
total rear toe 20min

asbi

Original Poster:

107 posts

213 months

Monday 1st June 2015
quotequote all
All,
Decided to try a different set of wheels with road tyres and found that the problem disappears and the car drives straight and true.

On inspection there is a clear wear profile on the NSR/F tyres with even wear on the OSR/F - called up Toyo and they confirmed that this could cause a steering pull.

So, I am going back to a less cambered geo as per my RSs which wear tyres very evenly - around 1.25deg front and 1.5deg rear - will use this until this becomes a limiting factor.

Thanks to all for the contributions.

Cheers,
kevin