Ford Shelby GT500 Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
Hello all,

I have a new set of F-14's 19x9.5 (F) and 20x11 (R) for my 2012 SVTPP (Not lowered-factory height)

I am planning on buying a set of Michelin PS4's 275/40/19 (F) and 305/35/20 (R)

Have any of you run these tire sizes?, if not should these be fine on my Stock height SVTPP?

Thanks for your time,

John
 

·
Registered
Joined
·
1,641 Posts
I’m very close on the sizes: 275/35/20 F, 305/35/20 R (Firestone Indy 500’s). I hear the Michelin’s run a bit wider than others, but if your wheel offsets are correct you should be fine.
This question is right in @Catmonkey ‘s wheelhouse so I would expect him to share some of his knowledge.
 

·
Registered
Joined
·
6,639 Posts
Like @TedShred mentions, wheel offset is a critical component in fitting wider tires. There's ample room in the wheel well, if the tire is properly centered between the fender walls. There is a lot of room in the rear if your wheel width goes toward the inside of the wheel. This will increase the offset. It makes little sense to me to go with an offet less than your stock wheels to start, which will be 45mm or 50mm depending on whether you have a standard model or a performance package in the '11 up cars and all '13-'14 wheels.

The problem with wider tires is there is a bracket welded on the inside that is used to move the body around in the manufacturing process. It can be safely removed, if you need the clearance. You tire can rub on that bracket if the axle drops down out of the ride height position. This thread covers that process. If your wheel is within 1/2" of the bracket, it could end up damaging your wheel. The more offset you have, the closer you wheel will get to the bracket. The less offset you have, the more your tire will stick past the outer fender. Only problem with that is looks IMO, and the potential of burning the paint at the point of contact with the tire. Depending on how bad the impact, it could potentially damage the tire's inner core.

Do you have offsets in mind or quoted to you?

I'm currently running 325/30-20s on an 11.5" wheel. I've seen some install 335s, but I think that's pushing it. There's ample room for a 305, but they are NOT intended to fit on the factory wheel width and probably need a minimum of 50mm of offset. I would tell you to try and find a wheel with at least 55mm. These are my current tires and wheels which have a 63mm offset.

193880
 

·
Registered
Joined
·
9 Posts
Discussion Starter #4
@Catmonkey Thank you for the reply.
The front 19 x 9.5's are a +29mm offset
The Rear 20 x 11's are a + 55mm offset

My GT500 is a 2012 SVTPP that has not been lowered.

I feel fairly confident that the 275/40/19's will fit alright in front, I think that is just up one size from the factory 265/40/19's.
I wasn't sure if the SVT Performance Package changed ride/suspension height at all, but it seems like many guys are running 305's and larger on the rear even with lowered cars.
One thing I don't want is any rubbing anywhere.

Thanks Again (y);)
 

·
Registered
Joined
·
6,639 Posts
I have run a 285/40-19 up front on mine without lowering and have 285/35-20s on it now and it's lowered. The mounted tires have the same dimensions. I have no rubbing issues. I'm running the stock offset (44mm) up front too on 10" wide wheels. 29mm is much shallower than the stock wheels. I'd shoot for something no less than 35mm. If you're running SVTPP wheels and tires, take a look at where the tire will be if it was mounted 5/8" further outboard with the existing tire. Figure another 1/4" going to a 275. You might want to stick with a 265 with that offset. If you never lower the car, you may not have any issues with a 275.

Many guys ignore the manufacturer's recommendations and many tire shops won't install tires outside of those recommendations. I widened my SVTPP wheels to install wider tires and don't encourage anyone to put tires on rims that are outside of the manufacturer recommendation. It will have an impact on the cross section width. Give up 1.5" in rim width is likely to make the actual mounted cross section 1.25" narrower, so it may not rub in that scenario and could on the wider rim.

I haven't seen any manufacturer recommend anything larger than a 285 for the for a 9.5" wheel. It will physically fit, but you're subjecting the tire to forces it wasn't designed for. To test that theory squeeze the beads of a 305 to 9.5" and see how much it fights you to get there.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #6
@Catmonkey
I purchased the wheels from American Muscle......they state the recommended front tire for the 19x9.5 Forgestar to be 275/40/19 with the offset they recommend? You now have me concerned about the +29mm offset. You would think those guys at AM would have sold enough of these over the years to get the offset correct for the S197's?
Also, I wouldn't stretch 305's on my factory wheels, which is why I went aftermarket (20 x 11)

Thanks again for your info, this Forum has been a great learning experience.

John
 

·
Registered
Joined
·
6,639 Posts
The Shelby Alcoa wheel and similar knock-offs use that offset, but it's a 9" wide wheel. I'm not sure what tire Shelby recommended with these. I doubt they will rub since there's a lot of tendency toward negative camber should the front suspension bottom out. The sidewall may just stick out a little past flush. If you look at mine in the picture I posted, the sidewall is likely to be sticking out 7/16" further outboard. To me, the rear is a much more critical measurement.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #8
@Catmonkey
Should I just order the 295/35/20 PS4's instead of the 305/35/20 just to be on the safe side? (On the rear)
I don't want to have to hassle with cutting anything underneath to make tires fit. If you think the 305/35/20's would work I would rather go that route and have a little more rubber on the road to hopefully aid in a little better traction under acceleration. I have the BMR LCA's & UCA that I plan on getting installed in the near future as well which leads me to yet another question. Is the adjustable Pan hard bar necessary for a car that is not lowered or changed from stock configuration other than the LCA's & UCA? Off topic but would appreciate any input you or anyone else may have on the Pan Hard bar.
 

·
Registered
Joined
·
6,639 Posts
While it defies logic, it won't make any difference. The wheel width has more to do with the actual cross section than you might imagine. When you look at cross section widths, pay attention to what wheel it's measured on. To illustrate, here is my widened SVTPP wheel with a 325/30-20 and the True Forged I purchased with 295/35-20s. Both wheels are 11" wide. Both measured 12.6" at the widest point.



So going to a 295 won't change anything. Many guys leave the bump stop bracket and claim no rubbing; however, they will well you they have to jack up the axle to remove the tires, because when the tire drops down a couple inches there's no clearance. Now they don't experience that scenario in real life driving experience. Before I removed mine I had the same issue, but I removed them shortly thereafter. While they've been rare circumstances, but I can't imagine I would not have made contact with the bracket had it not been removed. They just pour asphalt or concrete on top of waterlogged organic matter down here and call it a road, so I expect I drive much worse conditions than most.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #10
@Catmonkey I really appreciate your time and effort.

Originally I was just going to leave this car stock except for maybe a CAI and mufflers.......Well, like probably everyone else on here it got addicting to throw $$$ at it, why should wheels and tires be any different ;) Next Spring adding a TVS and a few suspension goodies, then I'm DONE . Can't hook up very well now with the stock Eaton but that's the way it goes!

Cheers,

John
 

·
Registered
Joined
·
6,639 Posts
So tread lightly on the mods or you'll make your tire exercise all for naught. I can't hook at my power level. I may put a set of drag radials on my old SVTPP wheels and see how that works out. It rains too much here to do that on a full time basis.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #12
@Catmonkey
Currently I'm at 605RWHP/600TQ and I'm finding some reluctance in installing the Trinity 2.3 that's on my shelf.
I've done all the supporting mods properly setting the car up for the TVS but am having second thoughts due to the lack of traction I have with the stock Eaton.
I currently have Michelin PS4's on it with stock wheels and stock tire sizes and while the PS4's are a night and day difference from the original Goodyears, traction on acceleration could be better but the handling improved IMMENSELY with the PS 4's.
I use the car mainly for some spirited weekend driving, out of town cruising......that's about it.

I've rambled this thread off topic, but appreciate the comments.
 
1 - 12 of 12 Posts
Top