My local shop has a set of 04 GT3 18' Wheels (brand new) for sale @ $1800. Would they improve the handling of my 02 C2 Coupe, currently fitted with 18' Carrera 5 spoke with 225/285 P-Zero Corsa? More importantly, would they make the handling worse assuming that I would use 235/295 tires? Many thanks

 

I'm not sure 235 will fit the front without rubbing when turning lock to lock. Only 225 is tested and recommended by Porsche for the 02. You may have issues with it. I would make an effort to find weight differences between the two wheels before buying them as well. Anything less than a five pound difference between wheels will offer very little, if any performance difference.

 

I'am running 235 fronts, 295 rears on my 02C2, no problems, they fit fine , no rubbing. With the carrera wheel, I don't know about the GT3 wheel.

 

you'd be adding quite a bit of unsprung weight (both in the wheel and the tire) which should hurt handling, braking, ride, and acceleration though braking and handling may be helped by the larger contact patches (probably not as much as hurt by weight though).

 

Thanks for all your assistance. Will the decrease in offset increase the handling performance?

 

Thanks for all your assistance. Will the decrease in offset increase the handling performance?

 

The difference in offset if not the same to the oem rim at 52 with the gt3's being 40 will produce bump steer this is an issue I am having and have been with a set of rims I have and just now know why it has been so unhappy to balance the car midcorner at speed.

 

What is bumpsteer and how can I eliminate them?

 

I raises this issue with my locl shop today and the mechanic says that there won' t be any bumpsteer with the GT3 wheels with offset 40mm/63mm vis a vis Carerra 5-spoke with 50mm/65mm. Is he right or is he just trying to sell me those wheels? Any comments is appreciated.

 

The Net: here is that this mod might look cool, but it's likely to decrease your car's performance overall. Given your car's performance envelope, you don't "need" the 235/295 mix. IIRC, Porsche doesn't recommend going more than +5mm from stock offset. The GT3's suspension, on the other hand, was designed w/geometry to take advantage of this particular wheel offset.

it would look cool, though

 

I have my local shop installed the 04 GT3 Wheels yesterday and the shop agreed that I can test the wheels out for one week and if there is any problem, I can return the wheels. Meantime, I still keep my Carerra 5-spoke. Since I do not want to spend any money on new tires (235/295) yet, I reuse the tires on the Carrera 5-spoke which is PZero Corsa 225/285. I went for a casual drive after the installation and at this stage, there seems to be no problem with the wheels: the tires are not touching the fenders from lock to lock. I will go for a hard drive this weekend to see whether there is any bumpsteer.

The shop does not have any access to a bumpsteer measuring device. What does a bumpsteer feel like?

 

matching the wheel offset to the suspension geometry goes well beyond "does it rub?". It's fairly complex, but imagine an axis around which your front suspension turns, then picture this against the center of your tire's contact patch. What you've done is move your contact patch away from (IIRC) the kingpin axis? Whatever it's called, in effect you've changed the dynamics of your front suspension.
What you'll likely notice is:
- different steering feel
- more wandering on uneven pavement
- more kickback in the wheel when hitting bumps

For purity of handling, IMO the stock offset is important. If you're going for looks, and hoping not to break anything, then just check to see if it rubs

 

yup exactly what I noticed indeed. But more importantly is the nerviousness and constant mid corner correcting you must do to make it track correctly through line.

 

I too am in a similar situation.. I have placed an order for a set of wheels and am wondering if I will suffer the bump steer problems using the following spec wheels.. Front 8.5/41offset and Rear 11/60 offset.. Additionally, what would be the ideal tire size for this setup .. I have a choice of 8.5/54offset and10.5/54 offset.. I am looking for the most aggressive look while preserving the cars natural characteristics.

I've done a few searches and it seems the stock offset is the ideal way to go.. but again since i'm putting new wheels on I am hoping to find a happy medium of have a full wheel look and maximizing performance...
Any feedback is much appreciated.