boomer46

I really want to get the PP for my 15 I am going to order but in that I may be taking some long trips with it am really bummed you can't get a spare. The mobility kit just doesn't cut the mustard on long trips. I was thinking of just ordering a PP rim & putting the same Pirelli tire on it, but then, of course, the rims are 2 different widths between front & rear. Does anyone know if you had a smaller PP black front rim/tire for your spare & had to put it on the rear if that would mess with the workings of the Torsen rear end??? I would think a different inch rim (in height, i.e. 18") would but not sure about width. I wouldn't think so but don't know for sure. May not order the PP just because of this.

srichard

I think it would be OK to get you where your going in an emergency. I can tell you that the front rim from the PP will not fit under the carpet in the truck. You'd just have remove the cover.

boomer46

Yes, I'm pretty sure you're right about the spare fitting in the under the carpet. I don't think it would damage anything on the rear end either if you would use a front tire as a spare but I assume no one knows for sure. I would probably just put the spare in the trunk off to the side as much as possible on trips. Around town take my chances with the mobility kit they give you. Thanks Dennis

srichard

I'm hoping the aftermarket will come up with something.

kn7671

If the primary concern is spare, being complicated more by unequal sizes front to rear with a Torsen diff, then get the PP car and swap out the differential with a non-Torsen type.

guitar

I have posted the info on this forum of a wheel and tire that folks are using on Boss 302s that should work. Not sure if the set-up has been tested though. This wheel is 18" and the tire can be squeezed into the trunk. This set-up should be within Torson's tolerance. Don't know why Ford did not just supply a spare.

boomer46

My question though was if you just bought a "front" smaller width OEM 19" PP black rim & Pirelli tire for a spare and you had to use it as a spare for the rear, would the diff in width mess with the torsen rear end?? I don't think width would do anything but if it was a different height, yeah, I would think that probably might not work too well. Your thoughts???

kn7671

Running different diameter rear tires for anything other than a short emergency with the Torsen differential in the Performance Package GT's could cause excessive wear and heating of said parts, failure, and warranty denial for repair.

If you're not certain how a Torsen differential works compared to a clutch type limited slip, do a little research and it will be clear why the diameters from left/right cannot vary much at all.

MuddyLX

Sell the tires and replace with runflats.

boomer46

I'm not talking different diameter/height, I'm talking different width. I would think width would not make any difference to a Torsen rear end.

SINBUSTER007

So according to the video I watched as long as the wheel diameter is the same you should be fairly ok... Unless you have a huge difference in widths then you are putting more load on the one wheel. If you are only going a short amount of miles and time then the stresses shouldn't be a factor. Only thing I see is if your losing traction in the one wheel and the other side compensates for that traction loss.
So for me it brings up the question... My boss does not have the Torsen since I did not get the recaros and it's not listed on the window sticker so in theory I should be able to use a front wheel on the rear if need be..
My 15 has the PP and Torsten so we need to verify if the small width diff would really make an impact.

boomer46

The front Performance Pkg tire size is: 255/40R/19
The rear Performance Pkg tire size is: 275-40R19
(this info from a different thread w/folks that own a PP 15 Stang)


So if one had a front tire the same as what is on the vehicle, w/the front Ford PP rim for a spare, I don't think that would make much of a diff for a short period, IF you had to use it on the rear, until you could replace the tire or have it repaired. I assume that's a 20mm diff in width but don't know for sure, I'm not a tire guy. Anyway, that's the only way I would think you could have a spare for the Performance Pkg, IMHO.

SINBUSTER007

Yea 25.4mm is one inch so your talking less than an inch. You can make that diff up with just a slight change in your tread width. The rim is only 1/2 in so I would assume a front wheel can be used for a spare in order to get your original fixed in a couple days. If I'm wrong then someone needs to chime in here. Brake clearance shouldn't be an issue if it's the exact same wheel as the front. From what I've read the Torsen shouldn't have any issues.

Cobrakev

The .4 to . 7 OD difference will not matter to the rear diff. Just think what the difference would be with the space saver tire. I just bought the 19" AM wheel for 179.00. Put a new 265/40/19 tire on it. I throw it in the trunk when I go on long trips.

boomer46

Good idea... buying that 19" AM wheel is even better in that if you bought a PP Ford rim, they're almost $400.00 alone. I assume, if you had to use it on the front, it will fit over the Brembo brake though right??

Cobrakev

Yep, look on their web page. They have the 19" wheel on a red brembo brake 15 gt mustang.

guitar

As long as the circumference of the tire is within 10% of the factory rear the Torsen should be happy. You may have to put powder on the tire to squeeze it inti the well. It might stick up an inch or so in the well. Please let us know how it all works out.

kn7671

Can you quote your source for the 10% you state?

guitar

I talked to a person and he told m 10%.
I looked hard and posted all the info I had on the subject. I may have kept some not sure. I became frustrated and decided not to get the PP.

boomer46

Do you have a link??