Tire Sizes

Quik95SC

SCCoA Member
Have a question about tires sizes. I noticed a lot of SC'ers are Running 17X9 Wheels with the Mustang 245/45/17 Tires. This seems to be too small of a tire compared to the stock 225/60/16 that came on the SC's. It shows about a 3.5% difference in Speedo Reading and about a full inch difference in a shorter tire. I want to stick with the same ride heigth, and it looks like the 245/50/17 tire is almost an exact match, but it only recommends a 7-8.5 inch rim. I have the 17X9's and would like to go to the 255/50/17 which are about .4 larger diameter which may compensate for 3.73 gears installed before Iowned it, woithout the proper speedo gear in tranny.

Bottom line question is will this tire fit OK under a stock suspension (not lowered) without any tire rub problems.

Any thoughts.
 
Yes, it should be fine on a stock ride height car. If you decide to lower it later on, you may need to do some fender lip trimming or rolling.


cheers
Ed N.
 
Thanks Ed,
I just wanted to make sure before I spent money on tires that don't fit. By the way what size combo are you using for your Sc in the Pics. Just curious. Looks great by the way.

Smitty
 
Quik95SC said:
Thanks Ed,
I just wanted to make sure before I spent money on tires that don't fit. By the way what size combo are you using for your Sc in the Pics. Just curious. Looks great by the way.

Smitty

255-45ZR18 Goodyear Eagle F1 GS-D2 tires, mounted on Fittipaldi Force machined-finish 18x8.5" wheels (+35 offset) -- still the only SC so equipped

Check his member page. Those are his road rims, the ones in the pic are his 17" racing ones, not sure what size tire.

Yes, I am WAY too into Fast Ed's tire/rim setup :)
 
Smitty, my 255-45-18 tires would be pretty much the same overall dimensions as the 255-50-17 you're thinking of (27" diameter and 10" wide roughly). With my car being lowered 1-1/2" with aftermarket springs, we trimmed the rear fender lips a bit, and I'm also running AirLift bags in the rear coils, to help keep the fenders off the tires when the car is loaded up.

At stock ride height, it should fit fine.


cheers
Ed N.
 
That hasn't been my experience however...

Qwik95SC: If I had to do it again, I'd actually go with the 245/50/17 Tires.

I've got the 17x9" Rims and the 255/50/17 and I've run into rubbing on the rear fenders when going over high speed dips as well as a very nasty front rub that actually "chunked" the tire when I took a dip in the road at 30 MPH.

In fact the front rubbing was so bad that it pulled the lip down a little bit, I had to roll it a little bit to get it back up.

I got the rear fenders trimmed (Rolling WON'T work right because there is way too much fender gap) AND I am running -1.5º rear camber to compensate too.

So basically, there isn't rubbing in the back anymore, and I don't take any dips in the road at anything over 20mph.

With the 16" tires I didn't have these issues.

If you are asking about Turning and Steering angles, the Tires and wheels WON'T rub. I haven't had an issue there.

My suspension is stock and I am NOT lowered. Sometimes the actual width of the tire will vary from manufacturer to manufacturer. The tires that I have been running are BFGoodrich G-Force KDWS tires.

My Rims are the 03' Cobra style and I think they are a 36mm offset, I can't remember.

Up front the inside top lip of the rim comes about 1/4" to the front spindle. I'm sure a little more "meat" could be shaved off of the pedistal of the wheel but then I'd be running dangerously close to the spindle. Maybe the spindle would need to be ground out a little bit too. Oh and the bottom part of my upper ball joints needed to be ground off to prevent rubbing too. But that wasn't such a big deal.

I'm really starting to think that the rest of the SCCOA'ers who run 245's up front do so for these reasons. Out back you can go hog wild and that's why alot of guys will run 275series in the back and staggered up front. I wanted to keep the tire rotation that's why I went with consistant sizes all around. You'll also notice more that the front track of the car is wider than the rear, hence the reason why the front tires bulge out a bit more. Kinda makes it look like a front wheel drive drag ricer errr... Racer.

I'm also pretty sure that you can easily fit 245 series tires over a 9" rim without any issues.

ALso another reason why some guys run the 245/45/17 tires is because the tires are overall 1" shorter, it gives natural lowering to the car. And they compensate with a different speedo gear.

Oh and last but not least.... that smooth creamy cadillac ride you've come to love from these cars and was probably one of the reasons why you got it in the first place? Forget it. It'll ride like a nasty F-150 with the 17x9's, 255's and 35psi cold pressure. Garunteed.

It will however take off-ramps at 70mph without batting an eye and will probably be the BIGGEST increase you'd get from any suspension modification out there.

So the choice is yours. Just thought I'd let you know the ups (and mostly downs) of my experience thusfar.
 
Good additional info. For what it's worth, the BFG KDWS tires tend to be very large in section width compared to some other brands and models. I had a pair of 285-40-17s for another car, and they were huge!!

Air bags inside the rear coil springs help a lot for keeping the fenders off the tires. If I didn't have them installed on my SC, I'd be getting more rubbing for sure.


cheers
Ed N.
 
I have a 91 sport (sc springs) with a 5-4.5 bolt pattern conversion. I'm running 95 cobra rims and 255/50/17 Kumho 712's. I've had the drivers rear tire rub on the fender lip on a really big bump on the highway. So far that's the only rubbing I've had and will roll or trim the fender somehow this weekend.

Those of you who trimmed the fender what did you do exactly?
 
I had the local rice shop do it...

I think that they jacked the car up and removed the rear tires. Then they either used a plasma torch or cut-off tool to trim about 1/4" of the fender lip on the inside off. They then applied a anti-rust compound to the exposed metal.

That and in combination of running 1.5º of Negative camber in the rear has eliminated rear fenderwell rubbing.
 
New tires on

I finally went with the 255/45/17 cause i wanted the xtra width for the 17X9 wheels and I only had about a 1/4 inch between the tire and upper ball joint, so I'm glad I didn't go with the 255/50's

Thanks for all the input from everyone.

Smitty
 
I run 255/50/17 tires no problem. I could show you pics if you'd want to see. Perfect size for non lowered cars in my opinion.
 
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