geometry check/suspension upgrade advice please

Mario149 · Sep 14, 2009

on the last couple of track days i've been on, i've felt that my C4S was a bit "floaty" in the corners than maybe i thought it should be, but not having another C4S to compare it to, i wasn't sure. however, last fri at my track evening, i was taken for a spin in a 996 turbo (so obviously same suspension, brakes etc) and it seemed to feel more planted in the faster corners, say at 70mph+.

now, my rear tyres do need replacing soon, but i'm pretty sure they're not the cause (is this correct?), so it looks like it maybe that the shocks are worn out (car has done 53k miles and they haven't been replaced) or the geometry needs checking.

plan of attack is to get new rear tyres, get geometry checked, then see if the situation has improved on my track day. if not, new shocks may be in order.

so, i have 2 questions:

1. is someone like my local porsche specialist (chelsea carrera, sounds like a pornstar!) qualified to check and adjust the geometry, or should i go to a specialist in it like centre gravity?
2. if i am going to have to fork out £1k or so for new shocks etc, is it worth just getting a suspension upgrade to lower it and firm it up for track use (i'll take the day to day ride comfort hit) and if so, what is a reasonably priced system and where might i buy it from/get it fitted?

apologies for the long post!

Rodney Naghar · Sep 14, 2009

The floaty feeling is probably caused by your rear suspension sagging more than the fronts due to the engine load.(nose up) so under acceleration the front end lifts too much and you get that floaty feel and loss of control.
Call Chris at center gravity, he'll probably suggest you get your rear shocks reconditioned by bilstein (£65-120) odd each then go to him to get them fitted and geo'd.
Tell him I recommended him, he'll do you a top job.

Mario149 · Sep 14, 2009

ORIGINAL: Rodney Naghar

The floaty feeling is probably caused by your rear suspension sagging more than the fronts due to the engine load.(nose up) so under acceleration the front end lifts too much and you get that floaty feel and loss of control.
Call Chris at center gravity, he'll probably suggest you get your rear shocks reconditioned by bilstein (£65-120) odd each then go to him to get them fitted and geo'd.
Tell him I recommended him, he'll do you a top job.

that sounds like an idea, thanks. quick question:

is there any way to definitively check whether the shocks are worn out? it's only really noticeable on a track when i drive it, if that's what it is, and obviously i don't want to get them reconditioned/replaced unless necessary

Rodney Naghar · Sep 14, 2009

It would be difficult as you'd need to check the ride height on a perfectly level platform.
Visually if you were parked next to a low mileage C4S you would see your rears sitting lower.
But at 53k I guarantee they'll be sagging way beyond spec. Mine were miles off after 30k, and having them refurbed and geo'd totally
transformed the car.

You could always drive it to Chris and he could check It for you then you could decide what needs doing. I'm sure he wouldn't charge you for that.

Mario149 · Sep 14, 2009

ORIGINAL: Rodney Naghar
Mine were miles off after 30k, and having them refurbed and geo'd totally
transformed the car.

You could always drive it to Chris and he could check It for you then you could decide what needs doing. I'm sure he wouldn't charge you for that.

is he able to refurb them and fit them and do the geo in one day? tamworth is a bit of a trek for me as i'm in south london so would want to get it done all in one day rather than have to leave the car....

Rodney Naghar · Sep 14, 2009

Yes.

You call him and relay over your symptoms. If he suggests you get your rear dampers refurbed he will send some over that he has lying around from another customer to Bilstein. They will take up to 2 weeks to refurb them, he books you in for some time after that.

You see him then, he takes off your old dampers (his to keep for the next customer) and fits the newly refurbed ones (with a stats printout from Bilstein showing how they've precisely matched the 2 dampers). He then carries out a geo, job done.

Mario149 · Sep 14, 2009

i've had people recommend X73 suspension to me which apparently can be fitted on the 996 TT, so presumably it can be fitted to my C4S as well then? can anyone confirm this?

dilloncallum · Sep 15, 2009

I think that changing parts sounds a little dramatic to me, especially as the car has only done a little over 50,000 miles.

I changed tyres on my C4S when the car did a little over 20,000 miles and the garage asked me if I wanted the geomitry done. I said yes, sure and when they fininished and I drove 500 yards, I found that the car drove totally differently.

This was not for the better, as the car was all over the place. By this I mean it was 'floaty' and almost felt that it was driving on ice.

I took it straight back and we had all sorts of arguments. They showed me the before and after settings and said how the before settings wee mostly in the 'red'. From there, I faxed the settings to Porsche in Tonbridge and they confirmed that the new settings were within tollerances. However, the fact remained that the car was not correct and the garage put the settings more or less in line with the settings it started with. Hey presto, it drove as it did before.

I would suggest that you try to have a drive of another car or check your settings before parting with cash to change things, unless of course you have your mind set on the changes anyway.

Rodney Naghar · Sep 15, 2009

ORIGINAL: mt0859

i've had people recommend X73 suspension to me which apparently can be fitted on the 996 TT, so presumably it can be fitted to my C4S as well then? can anyone confirm this?

Yes it's possible, makes the car lower/stiffer and it includes 4 bilstein struts and 2 uprated engine mounts and thicker rear anti-roll bar.

ORIGINAL: dilloncallum
I think that changing parts sounds a little dramatic to me, especially as the car has only done a little over 50,000 miles.

I changed tyres on my C4S when the car did a little over 20,000 miles and the garage asked me if I wanted the geomitry done. I said yes, sure and when they fininished and I drove 500 yards, I found that the car drove totally differently.

This was not for the better, as the car was all over the place. By this I mean it was 'floaty' and almost felt that it was driving on ice.

I took it straight back and we had all sorts of arguments. They showed me the before and after settings and said how the before settings wee mostly in the 'red'. From there, I faxed the settings to Porsche in Tonbridge and they confirmed that the new settings were within tollerances. However, the fact remained that the car was not correct and the garage put the settings more or less in line with the settings it started with. Hey presto, it drove as it did before.

I would suggest that you try to have a drive of another car or check your settings before parting with cash to change things, unless of course you have your mind set on the changes anyway.

If you were to take your car to Chris Franklin and have him do your Geo for you, and you weren't amazed (not just happy - amazed) at the positive difference it has made, please send me a PM and I will personally video myself eating my own shoes and stick it on youtube for all to see! [

] I have yet to hear one bad thing said about him and his work. I've been there twice myself, he's totally transformed my car (not just for track use, but for day to day use it's completely different)

Jokes aside, just give him a call anyway, explain to him the problem, and he would be more than happy to discuss what he thinks the problem may be.