Here is the short story on 10.5" wheels, wide tires and wheel spacers...
All Cobra replica 10.5" wheels on the market right now have the same offset/backspacing (+27mm offset, 6.9" backspace). I'm talking about the 10.5" wheels sold by AFS, Wheel Replicas, etc. Unfortunately, these wheels were never intended to be used on Mustangs with an independent rear suspension (IRS). This is why you often see a disclaimer with these wheels that says something like
"will not fit 1999+ Cobras." Nobody makes a wider-than-stock replica wheel for '03-'04 Cobras that has the proper offset and backspacing...so we're stuck using these wheels. The problem is, when you put
most 315-35-17 tires on these 10.5" wheels, you will run into two clearance issues with IRS Mustangs:
ISSUE #1 - Tires Rubbing the IRS Frame
When the car is sitting at normal ride height, the inner sidewall of the tire will rub the frame of the IRS. If it doesn't rub, it may still just barely clear it by 1/8" or less.
ISSUE #2 - Tires Rubbing the IRS Bolts
There is a suspension bolt head that sticks out into each of the rear fenderwells. These are 2 of the 4 bolts that connect the IRS assembly to the body of the car. When the rear suspension is unloaded (in other words, the car is lifted and the rear wheels are allowed to hang freely), the inner sidewalls of the tires will most likely rub against these bolt heads. This could cause serious damage to your sidewalls if it ever happened while you were driving.
To solve issue #1: You have to use wheel spacers. As long as your tires aren't really wide (believe it or not, all 315-35-17 tires are
not the same width...more info below), 1/8" or 1/4" spacers will solve that problem in some cases. Other times, you'll have to move up to 3/8" spacers.
To solve issue #2: You have to remove a little bit of material off the top of the bolt heads. It's pretty easy and can be done without removing the bolts from the car.
Another option is to replace the bolts with low-profile bolts like
THESE from Maximum Motorsports.
Other important tips when working with wide tires on 10.5" Cobra replica wheels:
1. If your car has been lowered, you actually gain a little extra sidewall clearance for the rear tires.
Many people who lowered their cars found that they didn't need to use wheel spacers for clearance any more.
2. All 315-35-17 tires are NOT the same width!
BF Goodrich and Goodyear 315s have a section width of 12.75" on a 10.5" wheel. A Dunlop or Sumitomo 315 only measures 12.25" on a 10.5" wheel. When you're talking about fitting wide tires on a Cobra with 10.5" wheels, 1/8" is a big deal. You can get away with using a more narrow spacer (1/8") if you stick with the Dunlop or Sumitomo 315s. If you go with the BFGs or Goodyears, you'll need at least a 1/4" spacer (and most likely a 3/8" spacer).
3. Sumitomo or Dunlop 315s (mounted on 10.5" wheels) should fit without any spacers on a stock Cobra.
The only problem you might run into is how much sidewall-to-IRS frame clearance you'll have. Sometimes it may only be 1/8" (especially on the driver's side)...and that's cutting it really close. You'll still have to address issue #2 with these tires.
4. As the rear springs of these cars are compressed, the action of the suspension will actually move the sidewall of the tire away from the IRS frame.
So while it may seem that you don't have much sidewall clearance (like maybe 1/4"), you will be fine.
5. If you move up to 18 x 10.5" wheels, you may not need wheel spacers at all.
18" wheels move the tire away from the IRS frame enough to keep it from rubbing in many cases.
6.The tire clearance is not exactly the same from side to side on a Cobra.
For example, many people have reported having an extra 1/8-1/4" clearance on the passenger side wheel vs. the driver's side. So when you test-fit any wheel/tire combination for clearance, always try it on
BOTH sides before you draw any conclusions about fitment.
7. If you just want to run 315 Nitto drag radials on 17x10.5" wheels, you will NOT need any wheel spacers!
Nitto 315s are a very narrow tire (see the section width diagram above) and will not rub the IRS frame when mounted on 10.5" wheels. You'll still have to deal with issue #2 above to keep them from rubbing the IRS bolt heads. You can also mount any 285-40-17 on a 10.5" wheel and you won't need spacers.
285-40-17 on 10.5" Cobra Replica Wheel (no wheel spacers required):
8. No two Cobras seem to have the same tire clearance.
There are some people who've gotten a specific wheel/tire/spacer combination to fit on their car, while others who tried the same thing said it didn't work. So just because something works on one person's car doesn't mean that same setup will work on yours. It
probably will, but it's not 100%.
9. You can solve both the wheel spacer AND IRS bolt head issue by using 1" (25mm) spacers with integrated wheel studs.
These spacers will give you enough space to easily clear the IRS frame and the IRS bolt heads without any modification. See 1" spacers
HERE. Many people don't use these with 10.5" wheels because they feel that they move the rear wheel/tire out too far and gives the car an "old school" look. You can check out a Cobra with 10.5" wheels and 1" wheel spacers
HERE
10. If you need a spacer thicker than 3/8", you need to install longer/stronger wheel studs.
Instructions can be found
HERE
12. If you need a spacer thicker than 1/8", then get some HUBCENTRIC spacers.
Flat wheel spacers transfer too much load to the wheel studs and may eventually break the studs. Read more about this
HERE.
THESE spacers are very popular in the cobra community.
13. If you use wheel spacers, be sure to install them properly and check the lugnut torque several times after you drive the car around for a few short trips.
If you don't do this, you could end up breaking wheel studs and/or lose a wheel!!!
14. If you decide to use wheel spacers, understand that they definitely have the potential to be dangerous.
If not used properly, they can introduce additional stress loads which may quickly exceed the tensile strength of the wheel studs and lead to a catastrophic failure. If you don't fully understand the implications of using spacers, then don't use them.
Here are 2 other good threads (with pictures) that are worth checking out...
315 BFG + 17x10.5" + Cobra IRS = tire rub (DUW)
My experience with 10.5 AFS rims, 315 BFG's and spacers...
Simple, isn't it?!?!?!?!
i have the 315 drags on an 10 rim, friggin sweet and no problems
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