Car becoming very unstable when accelerating???

[996dom]

My 996 GT3 has started to feel very unstable when accelerating, it sort of feels like the car is pulling to the right when pushing on and then it sort of snap's back when you take your foot off the throttle......any ideas?

[Trev450]

When did you have the geometry last checked?

[Scooty100]

996dom said:

My 996 GT3 has started to feel very unstable when accelerating, it sort of feels like the car is pulling to the right when pushing on and then it sort of snap's back when you take your foot off the throttle......any ideas?

Yup Geo or check the tyres. I had similar few months back turned out to be a rear tyre

[supermono]

Additionally bushes may be worn and shocks too. I took my GT2 (same chassis but obviously lots more torque for it to deal with) to Center Gravity and ended up spending the best 3500 (IIRC) I ever spent, rebuilt shocks, a few bits and pieces replaced and adjustment with meticulous attention. Now it accelerates hard in 2nd and you could almost let go of the wheel even over bumps.

These cars go off tune gradually so you'll probably be surprised at how much better it can be.

[996dom]

Trev450 said:

When did you have the geometry last checked?

I had all 4 shocks refurbished last year and had Jaz do the geo, the car had quite an aggressive set up when I got it so I got Jaz to wind it in a bit as I've got no plans to track it. The problem was even with all the spacers removed then could only reduce the front camber to -2.5 each side.

I have been told that a knacker plates in my LSD could cause the car to feel very unstable, could it be this?

[Trev450]

996dom said:

Trev450 said:

When did you have the geometry last checked?

I had all 4 shocks refurbished last year and had Jaz do the geo, the car had quite an aggressive set up when I got it so I got Jaz to wind it in a bit as I've got no plans to track it. The problem was even with all the spacers removed then could only reduce the front camber to -2.5 each side.

I have been told that a knacker plates in my LSD could cause the car to feel very unstable, could it be this?

I 'tightly' set-up LSD can cause some instability but not generally a 'loose' or worn one. If you tyres are well-matched and not showing any signs of uneven wear, then I would be looking towards worn suspension components or the geometry having gone out.

[sleep envy]

Your geo will be out. Mine handles like rubbish when the geo's out - pulls right on acceleration and left on a trailing throttle.

Jaz when they were in Wembley? If so they used to sub it out to Neasden Tyres, they had to have my car back as I wasn't happy the first time.

IIRC Jaz now do geo on site so this should improve.

[PorscheGT4]

could be diff on a car that old, top mounts, shocks, geo, control arms ,toe links, bushes, engine mounts etc etc.

too much camber for road use only also.

Some thing not right if no spacers and still -2.5 !

Edited by PorscheGT4 on Tuesday 21st July 14:44

[supermono]

996dom said:

I had all 4 shocks refurbished last year and had Jaz do the geo, the car had quite an aggressive set up when I got it so I got Jaz to wind it in a bit as I've got no plans to track it. The problem was even with all the spacers removed then could only reduce the front camber to -2.5 each side.

I have been told that a knacker plates in my LSD could cause the car to feel very unstable, could it be this?

Apologies, my post sounds patronising in the light of your post here.

[boxsey]

Loose wheel bolts on one wheel? Removing wheels during a service and forgetting to torque one up is an all too common occurrence.

[996dom]

supermono said:

Apologies, my post sounds patronising in the light of your post here.

Not at all, love the fact I can get so many responses in such a short time

[996dom]

Right I've had the car in the air and checked all of the bushes/mounts and everything seems ok, the rear tyres are a bit worn on the inner edge so might get a new set of rear boots.

One thing we did notice is that it looks like the top mounts have been swapped to opposite sides, this would answer why the car has over -2.0 of camber without any spacers...can you swap the top mounts left to right?

I'm going to get another Geo done, I know COG are the most respected but is there anyone else nearer West London who anyone can recommend?

[Trev450]

996dom said:

the rear tyres are a bit worn on the inner edge so might get a new set of rear boots.

This is to be expected running over two degrees of negative camber. Once you have it reduced the wear should even out a bit.

[dom1102]

Cars with LSD fitted are very susceptible to tyre pressures and tyre wear on the driven wheels. Try to borrow a set of rear wheels with good tyres, check the tyre pressures and try it with those.

[LaSource]

NineExcellence are a bit further than West London (they are near Gatwick) but have sorted this out on previous 996 GT3s for me.

In my experience it could be 'all of the above'. i.e.:

1. tyres (not as round as they should be)
2. diff
3. suspension/arms

I've had exactly the same symptom with uneven tyres (brand new but not as 'round')...and also with a rear diff.

[keep it lit]

sounds like a tyre issue to me.

[graemel]

Your caster is incorrectly set or gone out of adjustment. One side of the cars wheelbase is longer than the other.

[996dom]

LaSource said:

NineExcellence are a bit further than West London (they are near Gatwick) but have sorted this out on previous 996 GT3s for me.

In my experience it could be 'all of the above'. i.e.:

1. tyres (not as round as they should be)
2. diff
3. suspension/arms

I've had exactly the same symptom with uneven tyres (brand new but not as 'round')...and also with a rear diff.

Thanks for the recommendation, I'll give them a call and have a chat.

[rb5er]

I've heard good things about Wheels in Motion in Chesham in regards to Geo. Not used them myself though.

[red997]

Hi Dom
it was Chris @ CG that did all the work on the car - and yes you are right, it was very track focused!
the top mounts were swapped round to increase neg camber;

Try JZM - very good - and although being near Watford it may be easier to get to them;

If it's feeling loose at the rear, my guess would be the bushes

(I'm back in a GT3 now - 991 CS)