Wheel tech

[JLMounce]

Well unfortunately I've come upon a small (yeah rigth) wheel issue with my Cobra. The previous owner apparently had no periphreal vision and every wheel on the car has signs of being curbed. I've now discovered that one of the wheels has been damaged enough that the tire's bead has backed away from the wheel causing a flat.

Although I could just have the tire remounted and I'm sure the wheel would hold the bead for at least a little while, I don't feel safe putting the car on-track with the wheels in said condition.

So I'm looking at some new wheels. I have some questions before I buy however.

Staggered fitments: Generally I hear that the staggered wheels don't perform well on track because of traction differences front to rear. What's everyone's opinion on this? Staggered fitment for my car would be a 9" wheel up front with 275 section width rubber and a 10.5" out back with 315 section width rubber.

17" vs 18": The stock wheel size for this car is a 17x8 with 245/45 tires. At the last NASA event even with cheap street tires I experianced no fold over conditions from teh stock sized tires. Is the shorter/stiffer sidewall of the 18" rubber going to perform better if I'm not already having issues? If so will it perform well enough to negate the rotational mass that the 18" wheel will add over the 17" wheel?

Thanks in advance.

[bpanther]

You might also check out Wheels America. The owner Bob Stretch is a NASA racer. They work miracles on wheel repair.

[bobcowan]

I havn't seen a folded over tire in quite a while. Technology is good enough that it just doesn't happen that often. You really have to be driving on the ragged edge.

18" tires will give you better performance with a little more predicatbility. But you also get a harsher ride. If it's your daily driver, I would stick with 17".

Staggered tires sizes are not a big issue. It's very common on performance cars. You can use the tire size to tune the handeling a bit. Think about how your car was handeling the last time. Did the back end try to swing out? If so, then a wider rear tire might help. I don't think it can ever hurt you.

[JLMounce]

Car was pretty neutral last time out. Maybe bordering on slight oversteer.

We'll see what I can find tire wise. there's not a lot of choice in the 315/35/17 size. Wish Kumho made the MX in that size.

[leggwork]

You could also show them to these guys - I hear they have a good reputation.
bruce

(303) 853-9978
Spec-Wheels Of America 5750 E 58 Av
Commerce City, CO 80022 - 3967

[MHISSTC]

The Mustang/Cobra generally understeers even with a mildly modified stock suspension at stock power levels. Depending upon the tires, track, etc., you can sometimes induce some power-on oversteer. Adding a wider rear tire may get rid of that sometimes desirable effect. If you were developing 400-500 RWHP, I'd say go ahead and widen up those rear tires as far as you can. Also, unless you are upgrading to larger brakes that require a larger diameter 18" wheel, I'd suggest sticking with the 17" wheel, but possibly going to 275's on a 17"x9" instead of the stock 245's on 17"x8". If you want to push the rear wheels out further towards the fender lip, the type of stagger I'd suggest is getting a slightly different offset 17"x9" wheel in the rear. That way the car will remain more balanced, but look a little cooler.

The one big problem I see with different wheel offsets, sizes and tire sizes is that you wont be able to rotate the tires as easily. If you are trying to even out the wear on the outside edges of the front tires that the Mustangs will always have, your only choice is to dismount the tires and swap sides if they have directional tread, or flip them on the same rim if they don't have directional tread. Another consideration is that 18" tires, especially the wider ones, are more expensive than the 17" tires.

However, you can't ignore the "bling" factor of 315s on 18" rims in the rear. :cool:

[JLMounce]

Well I did order wheels. And soon I'll be ordering another set.

I saved so much money buy going with a cheaper street wheel that I'll be able to do so. Maybe not prior to PMI in July but hopefully around that time.

For the street I purchased a set of deep dish 95 R replicas from OE Wheel Distributors. The wheels are your standard 17x9 front and 17x10.5 rear. I also picked up the Maximimum Motorsports buttonhead IRS bolts and a set of H&R sport springs.

For my track wheels I'll be going with the Konig Villian that MM sells. at 21 lbs a piece it will account for about 20-25 lbs of rotational mass removed for tracking events. I'll wrap those in Kumho MX tires 285 section width at the corners.

So this kind of gives me the best of both worlds. The nice bling wheels for street use and a decent set of track wheels as well.