FireRescue42

I have a 2014 Mustang Gt Premium. I am getting new aftermarket rims for it and the measurements are 8.5 width all around. I am swapping to a 10 in the back because I want more traction. I am unable to find how wide a TIRE I can go without it sticking out from the wheel well. I was wandering 325? or is it lower? If anyone has any knowledge of this please let me know its the last step I have.

Horspla

With the correct offset wheel, a 315/35/20 will fit in back but there isn't much room for error. You would need an adjustable panhard bar at that point to center the rear end nearly perfectly.


John

FireRescue42

Okay thanks ill look into that then

Blown CS

325 is too large for a 10" wheel. I wouldnt go much bigger than a 295 and you probably could get by stretching a 305.

kcoTiger

315 is as wide as you can get underneath the rear. You'll need at least a 10.5" rim, but you're much better off with an 11".

2k7gtcs

This man knows

He goes through wheels like toilet paper

m05fastbackGT

Gary ! I'm looking to go from a staggard setup back to square.. My current setup is 285/30/20's on 20x10's rear and 255/35/20's on 20x8.5 up front..

So here's my question.. If I'm interested in going with 20x9.5 wheels all around, will there be any clearance/rubbing issues if the offset is between 45 and 59mm ?
My concern is my current 20x8.5 wheels up front have a +35mm offset at approx 6.4" backspace.. Therefore I'm unsure as to whether or not I should remain at same offset and backspace or if it's really nothing to be concerned about..

Anyway, I'd really appreciate any feedback that you may be able to provide..

Thanks, Rocky

UOP Shadow

I had to sign the work order at the tire shop authorizing them to mount a 295/35 on a 10" wheel because that is right at the limit of their recommendations. They told me they wouldn't mount a 305 on a 10".

Bert

You should go by the tire manufacturer's recommendations for wheel width. Look up the tires on Tire Rack or anywhere else that you can get the full specs. Then look at the "specs" or "sizes" tab to see the recommended wheel width for the tire size you are considering. I'm pretty sure you will find that 295 is about the widest tire that any manufacturer will recommend a 10" wheel for.

Last1

This

MRGTX

That Scion appears to be optimized for handling now.

FireRescue42,
It might be worth talking to the guys at http://www.vorshlag.com/index.php
They have put a lot of work into finding the optimal widths/offsets for stuffing huge rubber under these cars.

Good guys over there...no affiliation.

2k7gtcs

I'll have to research this. Had 9.5" wheels with the rtr's on the car but don't remember their offset as its been a while. I would think whatever their offset was it would be better if they had tucked them about 5-10mm further inside the fender.

m05fastbackGT

I completely agree, as I'm also concerned that going with a 20x9.5" wheel in the front might not be tucked inside the fender enough.. So I'm also considering 20x9" but I don't know if they'll be quite wide enough for the rear and IIRC most 20x9" applications recommend 255/35/20" tires anyhow which IMO would leave too much of a gap in the rear.. IMHO I believe the ideal tire size for those interested in running a non-staggered setup is 275/35/20" in all 4 corners..

In the meantime, I'll be looking forward to what you find out from your research..


Thanks once again Gary.... Rocky

gruiz_06

I have a 315 35 20 tire on a 20x10.5. It looks beast but going to remove my lowering springs soon because there s only about a 3/4 inch gap between tire and fender.

kcoTiger

Bert

The correct offset for the wheel width positions the wheel correctly in the wheel well; not sticking out too far and not in too far but just right. I don't know off the top of my head the correct offset for 9.5" wheel but it is no big secret so should be no problem to select the correct offset. The same offset that is used on the GT500 9.5" OEM wheels should work perfectly. I have those on my car and they are just right.

Then you match the tire to the wheel. If the tire is not too wide for the wheel, again there should be no problem. Or you can go in the other direction-- select the tire size first, and then select a wheel that is within spec for that tire and has the right offset for the car.

When you go outside the manufacturer's recommendations is when you might run into trouble.

m05fastbackGT

Bert ! I came across both the offset and tire sizes for the 07-09 GT500.. Here's the specs from LMR and Shelby's websites..

PRODUCT DESCRIPTION

Ford Racing Shelby GT500 Wheel
Check out this silver machined & black Ford Racing Shelby GT500 wheel and tire kit (M-1007-S1895) for your 2005-2014 Ford Mustang. This is the original equipment wheel on the amazing 2007-09 Shelby Mustang GT500. This kit includes (4) 18x9.5" silver 5 lug 07-09 Shelby GT500 style wheels & (4) 275/40/18 Sumitomo HTR Z II tires mounted, balanced, & ready to go. Also includes SVT center caps! Fits 2005-2010 Mustang V6 equipped with M-2300-D brake kit. Fits M-2300-S Brembo brake kit. Band TPMS Compatible. Not compatible with valve stem mount TPMS.

Wheel Specs

Size: 18x9.5
Backspacing: 7.125
Offset: +45mm
Lug Pattern: 5x114.3
Weight: 28lbs
--------------------------------------------------------------------------------------

Applications:
Shelby - All Models (2005-2014)
Ford Mustang - All Models (2005-2015) (Narrow Shaft Lugnuts 14mmx1.5 are required for 2015

Introducing Venice, the first in a line of premium, one-piece forged wheels from Shelby American. Made exclusively by Weld Racing for Shelby American, these wheels are some of the strongest, lightest 20" offerings ever to be available for the '05-15 Mustang. Offered in two sizes and three finishes, the staggered fitment allows you to maximize the amount of rubber you can fit under your Mustang and Shelby for optimal performance. Wheels are treated with a proprietary crystal-clear ATC Nano-ceramic barrier for a long lasting shine. Suggested tire sizes are a massive 305/30ZR20 for the rear 20"x10.5" and 275/35ZR20 for the front 20"x9.5" to achieve that perfect profile.

NOTE: Lowered 2005-14 vehicles require an adjustable pan-hard bar or watts link, available separately from Shelby Performance Parts.


P/N AF9.5.2014 Size 20"x 9.5" Backspace (in) 6.778
Offset (mm) [+] 40 RMOI (lbs*sq.in.) 1715 Weight w/ Caps (lbs) 28.1
---------------------------------------------------------------------------------------
P/N AF10.5.2014 Size 20" x 10.5" Backspace (in) 7.671
Offset (mm) [+] 50 RMOI (lbs*sq.in.) 1782 Weight w/Caps (lbs) 28.4
---------------------------------------------------------------------------------------

So according to these specs, these are the recommended tires sizes and offsets for either an 18x9.5 or 20x9.5 wheel setup

2k7gtcs

You found it

Doesn't matter if it's 17 or 18 or 19 or 20 those offsets work for 9.5" width front and back

m05fastbackGT

So here's my concern Gary.. Does the offset have to be exactly +40 as recommended or will an offset of +45 be just as acceptable ?

My reason is.. I'm interested in the Steeda Spyder 20x9.5 wheels, however the offset is +45 rather than the recommended +40 offset.. I also don't know what the backspacing specs are, as it's not listed on the Steeda website..

2k7gtcs

Back spacing and offset when looking at a 9.5" wide wheel are two sides of the same coin

Backspacing and offset as long as you are talking about the same wheel width are essentially the same thing. Move the offset and the backspacing changes.

To me backspacing is the old school way and offset is the new school way.

Now if you change wheel widths then the numbers for both change and a 9" won't be the same as a 9.5"

The stress wheels are good. They know what they are doing and you can trust their offsets.

Honestly in 9.5" there's a little bit of play in the numbers because they are not pushing the edges like a 10" front or 11" rear would.