Suspension geometry, wheel offset

I know wheel offset has been much discussed here, but I wonder if anyone knows how the suspension geometry would be affected by different offsets. I have a '99 C2 and am looking at original 977 Carrera III wheels, fronts are 18X8, 235-40-18 tires, offset of 57mm. Rears are 18X10, 265-40-18 tires, 58mm offset. The sole purpose of fitting 18"'s on my car (standard factory 17"'s on it currently) is for improved handling. I like the look of the 5 spoke wheel, and I believe it is also one of the lightest available. The shop that has the wheels says there is no problem putting them on the 966, that the increased width of the wheels and tires make up most of the difference. I know I could use a spacer on the fronts, but would rather not. Apparently, there is not a problem with the rear offset, only the front. Would my handling be adversely affected by putting on these wheels with the 57mm offset? More understeer? Like I said, I want an improvement, and you'll have to excuse my ignorance on this, but I am not sure exactly how the geometry/handling works! This is my first P-car an I love the handling, and can't wait to improve it!

They'll hit the springs/shocks in the front because the wheel is set too far in. you HAVE to use spacers with that setup in the front. Andy

Well, thanks! I guess that sews that up!

You need to run a spacer in front for sure. If you want to go with OEM spacers (which I suggest), the 17mm spacer would be perfect up front as you would effectively have a 8" wheel with a 40mm offset which is only 6mm "in" front the factory GT3 sizes. In the rear, to compliment, I would suggest 5mm spacers to help balance it out a bit and bring the 10" wheel to an offset of 53 which would be just 3mm "in" from the GT3 offsets. IMHO, that would be a great looking setup both from an aesthetic look as well as a functional geometric application. With the 17mm spacers you just run your old bolts but with the 5mm spacers you will need the longer bolts.

Thanks Dell. So 53 in the rear would be OK, huh? One more question, would I be better off getting the regular 996 18"s with the 50/65? Or will the handling be better with the above mentioned wheels, or about the same? The wheels seem to be a fairly decent deal, which makes me keep revisiting this. I just want to make sure whichever wheel/offset combo I get, it's the right choice for the handling/geometry. I am just learning how to drive this car and don't want to upset the newbie-friendly handling! At least that's what I've heard it described as compared to prior 911's. Mitch

If you can find some wheels with 50/65 offsets (front and rear, respectively) then you won't HAVE to use spacers. Later if you want a more agressive (wider) stance, you CAN opt to add some spacers.

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53 in the rear would be just fine. Honestly, I don' think you will notice any handling differences between the offsets. Especially not on the street.

6ocyclehum, Here is a link to someone selling 996 5-Spoke wheels 8" with 50 mm offset and 10" with 65mm offset. FYI. 996 5-Spoke Wheels

The main reason I was looking at the Carrera III's with the wrong offset was they are new original Porsche wheels for the same price as aftermarket. The aftermarket ones I'm looking at are the Italian ones sold by Wheel Dynamics. I though it could be worth the trouble with the spacers to get the factory wheels. Good point with the fact spec offset and being able to add spacers if desired. Tim- when I try to open the link you posted, I get a message saying I'm not authorized to view that page. I'm also considering the aftermarket GT3 wheels with the 11" rear. Any downside or benefit to running an 11" on the rear? They are almost the same weights as the 5 spoke, with the exception of the 11" is maybe 5 lbs more than the 10". Mitch

Mitch, OK, I looked and he has them posted on the For Sale Forum, which only paying Members can access. Here is a link to his thread here on the 996 Forum. 5-Spoke Wheels

Thanks, I sent him a PM.

FWIW, H&R TRAK spacers are something to check out as well if you go for the 997 wheels. They use longer bolts,are hub centric, and should save you a little weight.