Rim widening to run 335/30/20s on an '09

[FHATTCATT]

Seems like most people are saying the offset should be et56-62. From all the rims I see widened, it doesn't look like the barrel is affected at all- the added width is added to the back of the rim so the face of the rim and tire sit where they did prior to the rim being widened... is that correct?

I have 2013-2014 20x9.5" GT500 rims on my 2009 GT500.

I tried running 305/35/20 Micky T drag radials and took them off in less than 50 miles. The car hooked better, but lane changing at 80+mph was sketchy at best- softer sidewalls = less turning control and stability at higher speed. So I put on 305/35/20 Goodyears and now might as well have hockey pucks wrapped around the rims. No traction even in 5th and 6th gear. The car has a 2.9l Whipple, cams, full exhaust, tune, 3.73's, etc....

I have done tons of searching here on SVTP and elsewhere, but no one definitively says what the offset should be once the rim is widened to 11.5" or 11.75". I'm looking to run 335/30/20 Michelin Pilot SuperSports- sounds like people have good control with them and hook fairly well.

https://www.svtperformance.com/forums/threads/335-30r20s-on-custom-widened-forgestar-f14s.1108795/

Can anyone say with certainty how the rims should be modified? The above post shows 335/30s being run on an 11.75" rim, but doesn't say what the offset should be. When I send these to Weldcraft, I want to make sure they are done right. Not looking to run 315s or 325s. Since not running drag radials, I really want the widest possible street tire on it.

Thanks for any info.

 

[Catmonkey]

The change in offset with be half of the increase in wheel width. On the 9.5x20, you have a stock offset of +50mm. Adding an 1.5" to the wheel will get you to a +69mm offset. It's likely to result in the use of a spacer to get it away inner fender wall. My SVTPP wheel is widened to 11" and I'm using a 1/4" spacer to position the wheel/tire where I want it. People that go wider than 11" usually are working with a shallower offset and a wider wheel to begin with. I think a 325/30-20 Michelin Pilot Sport Cup 2 will give you better traction than a 335/30-20 Michelin Pilot Super Sport because it's a softer compound.

 

[klb2sweet]

Don't think you can widen more than 20x11 without having any issues as I run 18x11 by Weldcraft and have two different sets of tires I run. A 345 and a 315 in the winter. Still had to cut bumpstop off and reinstall on rear diff.

 

[DutyCalls]

thanks for checking out my thread....I know it wasn't totally helpfull because i didn't include the offsets, but at least you know what it takes to fit 335 and it can be done.

The best way to figure out how much you can widen your rims is to actually pull the tires off, mount them on your car and measure...this is what I did. I would make sure to leave at least 3/4" of clearance between the back edge of the wheel and the fenderwell.

I wanted to go 3/4" wider....so I taped a piece of 3/4 wide foam to the back of the wheel and spun it while mounted...it showed where I would need to make clearance like the shock boots.


hope this helps......

 

[FHATTCATT]

Thanks. Have been super busy so haven't had time to touch base with any of the shops to see if they have experience with widening 13-14 rims for an 09. Would really like 11.5" minimum and preferably 11.75" to make mounting a 335 a little easier. Really would like 335s in that they seem like they may fit, and if so they'd be the widest. If not, I think a 325 on an 11 or 11.25" might be an unhappy compromise. I know the Goodyear are pretty hard compounds, and I know I'll spin even Michelin 335s probably in 1-3rd gears. But chasing your rear bumper at 100+mph is no joke. And... I might be upping the power soon....

 

[DutyCalls]

Thanks. Have been super busy so haven't had time to touch base with any of the shops to see if they have experience with widening 13-14 rims for an 09. Would really like 11.5" minimum and preferably 11.75" to make mounting a 335 a little easier. Really would like 335s in that they seem like they may fit, and if so they'd be the widest. If not, I think a 325 on an 11 or 11.25" might be an unhappy compromise. I know the Goodyear are pretty hard compounds, and I know I'll spin even Michelin 335s probably in 1-3rd gears. But chasing your rear bumper at 100+mph is no joke. And... I might be upping the power soon....

I know you will like them....im at 725 rwhp and when they are warm, they bite hard in second and no spinning in third

 

[paluka21]

Thanks. Have been super busy so haven't had time to touch base with any of the shops to see if they have experience with widening 13-14 rims for an 09. Would really like 11.5" minimum and preferably 11.75" to make mounting a 335 a little easier. Really would like 335s in that they seem like they may fit, and if so they'd be the widest. If not, I think a 325 on an 11 or 11.25" might be an unhappy compromise. I know the Goodyear are pretty hard compounds, and I know I'll spin even Michelin 335s probably in 1-3rd gears. But chasing your rear bumper at 100+mph is no joke. And... I might be upping the power soon....

FHATTCATT- I know you want the fat tire look, but also more meat for traction and safety. One other option you may consider is a "narrow" Toyo R888 in 315/30r20 if you go with an 11 or 11.5" tire. If you go with a 335 on an 11.5" wheel, your contact patch isn't going to be maximized hence yielding tire bulge. As I mentioned in another thread, you will have to space the 13/14 GT500 wheels away from your inner fender/bump stops because the widening will all be done on the inside of the rim. When you're making more room inside, you'll be pushing the tire/wheel near the edge of the fender. If you're flush against the fender with the wheel you want the tire to also be flush and not bulge, or else you risk scraping the tire against the fender under suspension compression. In addition, you also have to consider the compound of the tire; I prefer a softer compound which yield better traction but less tire life.
Personally, if you're hell-bent about going with a 325 or 335 on an 11 - 11.5" wheel, you could consider the Michelin Pilot Sport Cup 2 tire. But as mentioned above, if you go 11.75 or even 11.5" with a 325/335 tire, you may run into rubbing issues either on the inside or outside on the fenders.
Otherwise, I would look at the ToyoR888 in a 315.
Here is a "narrow" Toyo 315 on an 11.5" wheel:

 

[enormous]

My friend with a 14 Shelby widened his rear factory rims to 11" to run the Michelin Sport Cup 2 in 325 30 20...no rubbing.
Another good option to consider.

 

[FHATTCATT]

I think I have up to 1/4" to play with front side for a spacer if needed. Having seen DutyCalls run 335s on an 11.75" rim, I'm really tempted to try it but probably would want one of the widening shops to offer more testimonials (if they've done it) that it'll work with my wheels on an 09. 325s might be an ok, and necessary, compromise. I should have time Friday to make calls to try to get more confirmation. Chasing your bumper 1/8 mile at 100+mph too often probably isn't a wise course of action. Would like a stiffer sidewall with tread that bites. Genuinely appreciate all the input.

 

[DutyCalls]

Just so you know....Before I widened my rims, I was going to sell them and order custom width rims. I spoke to a few shops and no one would guarantee fitment over 11.5" wide.

 

[biminiLX]

First, are you more interested in traction or the look?
(I doubt much will hook in winter temps and cold roads)
I run widened factory wheels on my '14, made a few posts about it.
I found acceptable street traction with the rears widened to 20x11" by Weldcraft with 315/35/20 Nitto NT05Rs. Like you I loved MT traction but not the other compromises (handling, vibration, etc), and find the Nitto a better street DR.
I also run a 5/8" billet hubcentric spacer and ARP studs.
I use the spacer for the flush look, it's perfectly at the fender and probably could go to 20x11.5-11.75".
Another option if you want both looks and traction is to go factory front 19x9.5" wheels (available by Ford Racing in black only) and go 11.5" with the 345/30/19 Nitto NT05R.
The drag radial will obviously give you the best traction, and the factory 19" is better backspacing for widening and I've really been thinking of the 345 option in 19"
Last, as guys mentioned, true street non-DRs will vary on actual width (despite number designation). Michelins tend to run wide and the 325 cup 2s might actually work better for you as the right compound is key for your goals.
Got any pics?
-J

 

[JB_2010GT500]

FWIW, last month I sent out OEM 19"s to get widened to 11.5" from 9.5". Did the bump stop relocation in preparation. I'm going to try the newer Mickey radials (SS) in 325 and hope they are more round than previous generations of their radials. I really wanted to do the 345 NT05r as I also think Nittos are more streetable. But, balked at the section width. I should be able to report back on fitment and if a spacer was necessary for inside clearance in the next few weeks.

 

[Catmonkey]

Maybe this photo will help. This is an SVTPP wheel widened to 11" with a 315/35-20 MPSS mounted on it. There is no spacer in this shot.

Yes, it's that tight. Another .5" of width and it will move the tire roughly half of that distance closer to the inner panel. The cross section on this combination measured 12.6" on this set up. I moved the wheel/tire further out using an 8mm (.31") spacer. I have since gone to the 325/30-20 Michelin Sport Cup 2 and the cross section width comes in at the same 12.6". It just has a much wider tread width.

 

[JB_2010GT500]

What a difference. Here is mine currently, 18" x 10" replica 2010-2012 wheels with 305 Mickey ET Street 2s. Car is on jacks in this pic.


Sent from my iPhone using Tapatalk

 

[Catmonkey]

At a 12.6" cross section, it's more like a 320mm. It seems all the MPSS have a rim protecting outer lip that adds girth to the tire. Now, I must confess that it's been too long to remember if the rear end was centered at that time. I'll snap a couple of current pics with the 1/4" spacer I'm running now.

 

[FHATTCATT]

Have been too dang busy with work. Hope to have time to make calls tomorrow morning. Traction and looks kind of goes hand in hand with this deal. But... traction is paramount. Sideways in 1st and 2nd is one thing. Sideways literally at 100+mph is playing with fire. Am thinking that I'm seeing a fair number of posts where people are going with 11.5" rim and 325/30 tires. That might be worth giving a shot and then seeing if I have room to go 335 the next time I need tires.