New wheels/tires

[4Scargo]

Okay-I'm the FNG. **/@# New Guy. I bought an '03 C4S from Capitol 1- salvage title and a hit to the left front. I'm not a body guy and it is in the shop. On Ebay, (I couldn't help myself) I bought a set of 4-20 inch wheels from a TT owner. Fronts are 8.5 inches wide with 245 30's and the backs are 11 inches wide with 295 35's. Did I screw the pooch as this is AWD? Help.

[mathism]

If the offsets are correct, the wheels will probably fit. One of the other C4S guys could help you with that.
I think the tire sizes are wrong. They are probably too tall by about 3/4".

[Ray S (Chicago)]

20 inchers on a 996? Bling city baby, don't forget the chrome curb feelers.

[4Scargo]

Yeah baby-Dubs! Teenies are so '00! Really, $1000 for wheels and tires...I am strong and yet sooo weak.

[Purplxd]

The only thing is that technically the 996 was only designed to run 18" wheels at a maximum.

I've heard rumors that 19" wheels can even lead to the windshield cracking due to increase body stress as a result of lower profile tires. I haven't actually seen this happen on 19" upgraded 996s. I'm upgrading to 19" but I'm going with OEM rims from a 997 C2S with OEM tire sizes (Pirelli Rosso).

My understanding is that even 19" will ruin some of the natural characteristics of the car as it is past design. I'm compensating by upgrading to a coil over suspension.

Now 20" seems way over the top. Again from my understanding, the 997 was designed to run up to 20" as it was assumed that people would do this to them.

If you plan to cruise more with it, I'm sure it will be fine if the tires and offsets are correct. If you plan to track it, keep the original 18" ones around and put some R-comps on them.

PS The other reason why 19" is a bit nicer is that if you swap to 18" rims for the track, the difference is so minor that an alignment isn't really necessary.

My two bits...


A

[mathism]

I've never heard of a plus-1 change causing those kinds of problems on a 996 or any vehicle. As long as the proper offsets and tire height are kept with each rim diameter increase, you should not need to realign the car.

[Redridge]

Tires are way off spec... usually under 4% error is fine. For performance 18" is the way to go.

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
245/30-20 2.9in 12.9in 25.8in 81.0in 782 0.0%
295/35-20 4.1in 14.1in 28.1in 88.4in 717 9.1%

[Ray S (Chicago)]

Like Redridge said those tires are waaaaaay off spec. You've got almost an 8 inch difference in circumference front to rear.

Do yourself a favor and get some properly sized 18's (or 19's if you must). Leave the "Dubs" to the SUV crowd.

[4Scargo]

Thanks Guys. I wondered if they would work. Oh well, they are due here in sunny Minnesota tomorrow. We'll see. It has 18's on it now with Turbo Twists and P-Zeroes. Thought it would be cool with the 20's. No big loss. Thanks again.

[zdr2k]

Originally Posted by Redridge

Tires are way off spec... usually under 4% error is fine. For performance 18" is the way to go.

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
245/30-20 2.9in 12.9in 25.8in 81.0in 782 0.0%
295/35-20 4.1in 14.1in 28.1in 88.4in 717 9.1%

DING DING! what he ^ said.