Wheel offset opinion

[bluebullitt256]

I realize this is probably not the right section to post in but the Mach 1 specific section doesnt get much traffic and i need a quick reply from the wheel gurus.

Car: 2003 Mach 1 SRA

Looking at a set of 18x9.5 front, 18x10.5 rears. Tires will be 275/35/18 fronts, 295/35/18 rears. BFG KDW's.

Offsets available: +22 or +30 for the front and rear.

Car is lowered on H&R SS springs with no isos so its decently low. Which offset would you pick without having to do any fender rolling or any other modifications? I realize there is only 1/3" or so difference in the two different offsets but i wanna make sure before i drop the cash on the wheels. Thanks for the opinions and sorry this is the wrong place.

 

[SpectorV]

I can give you some info based on the IRS in 03/04 Cobras. Some say the rear width is the same others say its off. Figure that out and adjust as needed.

For the IRS a 3.5 in frontspacing is good, 3.75 is pushing it (may not have to roll but you may)

Frontspacing = Rim Width - Backspacing.

18x10.5 rim with +30 offset is
-----------------------------------
30/25.4 = 1.2 inches

Center line = 10.5/2 or 5.25

Center Line(inches) - Offset(inches) = 5.25 - 1.20 = 4.05 inches

4.05 inches = Frontspacing
6.45 inches = Backspacing
10.5 inches = Width

4.05 inches is fender flush for an IRS car, will require fender rolling on an IRS car


8x10.5 rim with +22 offset is
----------------------------
4.35 inches = Frontspacing
6.15 inches = Backspacing
10.5 inches = Width

Thats even worse....

can someone double check my numbers?




To obtain a 3.5 front spacing you need 5.25 - 1.75 = 3.5

1.75 = 44.45mm offset~ for the 10.5 rims you can push another .25 inches (or .9mm) to 38mm if you wanted but you still might have to roll (if the tire pushes past the rim lip a good bit you for sure will)


maybe SRA are sunk in more if so you can adjust the numbers by that much per side. If you look at my rims I am sitting at 3.75 frontspaced and I had one fender that rubbed the other didnt. If you have to choose I would choose the 30mm offset over the 22mm

 

[bluebullitt256]

Thanks for the reply. All the mustang specific wheels have the offsets listed as:

9" front wheel: +24 to +30 so the +30 on 9.5" is what i would need for the outside position to match exactly what the 9" +24 is.

for 10.5" mustang replicas most are listed as +25 to +30 but many people fit alot wider of a tire than a 295 so i think the 10.5" +30 with the 295 would fit just right.