305 on stock SL rims

See this thread - REAR TIRE, my post # 15. While I haven't' found a specific formula describing the relationship between tire profile width and wheel width, based on the Budnik chart I copied the info from, as tire sidewall height increases the minimum required wheel width decreases. When matching wheel width to tire profile, always try to stay within the tire manufacturer's recommended sizes for safety and warranty reasons. Using a wider tire on a narrower than recommended wheel width increases the possibility of breaking the tire-to-rim seal with negative consequences and would probably void any manufacturer responsibility or warranty.
As I posted in a different thread, I have read about folks running 305 tires on 9.5" rims (Mustang forums, IIRC), but that is generally a smaller wheel width than most tire manufacturer's would recommend and probably wouldn't be recommended by the tire manufacturers.

Actually, the stock SL rear rim is 20 x 9." See - Specs: 2018 Slingshot SL - Sunset Red | Polaris Slingshot.

Here's the Nitto specs for the 255/35R20 and 305/35R20 and 305/30R20 tires -

Increasing sidewall height allows use of a narrower wheel, so you might be able to fit a 295/45R20 (if anybody makes such a size) on a 9.5" wide rim, but a 9" wide rim will probably never be a good fit if you're trying to maintain a somewhat accurate speedometer reading using the Stock SL ECU tire settings. A wider wheel wouldn't affect your speedometer reading, but going to a much taller tire will definitely mess around with your speedo/odometer readings. I'm not sure if Polaris actually offers an SLR tire size for the ECU (I doubt it since the tire is only a little bit larger than the stock 255/35R20 tire). Just looking at Polaris' use of a 20 x 11" wheel with the 305/30R20 tire on the SLR would cause me to think trying to fit a 305 tire on a 9" wide wheel is too far outside any reasonable fitment. Some people may have done it, but that doesn't mean it's a smart thing to do. Most responsible tire shops wouldn't mount a tire that is significantly different from the manufacturer's fitment recommendations. Looking at the last line of Nitto's 555 info chart above tells me you should probably go with a 10" wide wheel, minimum. The least expensive wheel which I think might look ok with the existing front SL wheels would be this American Muscle 20x10 48mm offset wheel at $185 - Mustang AMR Charcoal Wheel - 20x10 (05-14 All) - Free Shipping. Generally speaking, you can usually trim about 2-3 mm from the Offset which would make this wheel a proper fit as a rear wheel or you could just leave it as is since it would only shift the center of the wheel a marginal amount to the right, but you might still find that it or all 3 wheels need repainting for a better match (or you may think it's just too different). I hope this helps some. Just remember this is my opinion and worth every penny paid for it!

1. I highly advise against putting anything larger than a 285/35/20 tire on a stock 9 inch wide wheel. It is too far out of recommendation and the tire is considerably bulged. They last thing anyone needs is the tire de-beeding under extreme use.

2. Widening a stock wheel makes very little sense. The stock wheels aren't that nice to start with and it is expensive compared to other options. If you widened the wheel 2 inches to a 11 inch rear wheel, you would be inch too far towards your shock. This would mean that you need a big 1 inch spacer and new wheel studs or a spacer that converts to new lug studs.

3. The best matches for a rear wheel are likely...

• The Rohana RFX5 you listed about
• The XO Verona (found here -https://www.xoluxurywheels.com…rona-xo-custom-wheels.php)

4. If you want wide, just run what everyone else runs - 20x12 rim (one of the two above) and a Toyo T1R 345/25/20 tire

5. I have a black Rohanna RFX5 with setup listed in #4 for sales if your interested - shipping probably isn't favorable though...

I pretty much agree with what @TravAZ posted. Before I bought the American Muscle 10th Anniversary Cobra Style 17x10.5 28mm offset wheel, I had thought about widening a stock front wheel to 10.5", but decided against it for 2 reasons, primarily because that would have been a 50% widening which I felt was a little too much and because of the need for a spacer. In the end, the Am wheel does center to the left over 1", but that doesn't bother me since I've experienced no handling problems and the wheel only cost $150 compared to $around 400 for widening plus the cost of the spacer. Iwas able to add that wheel and a Nitto 555 G2 315/35R17 tire for around $400 all-in, which fit my budget constraints.

I researched this quite a bit a few months back and went with a 285/30/20. It's about the max that is recommended for a stock SL rim and doesn't change diameter too much (speedometer error). If you go wider, it will fit but the tire contact surface will egg out and be reduced as well as cause faster, center tire wear.

I must be the odd ball in the group since i really like the stock 2015 SL wheels. It's not a matter of cost since having the wheel shipped out, made 2 inches wider, shipped back, powder coated brings up the cost to almost double of what one new wheel would have been. But I'll tell you this; The look on people's faces (those who know slingshots and what the stock wheel looks like) is priceless when they see this big fat 345 tire on a stock appearing wheel. Even this past winter during Bike Week in Daytona, both Polaris people and a customizer of sports bikes were impressed to see that tire on a stock wheel. The small changes that yields huge results shouldn't be overlooked by the fact that there are other choices in wheels.

Quote from funinthesun

I must be the odd ball in the group since i really like the stock 2015 SL wheels. It's not a matter of cost since having the wheel shipped out, made 2 inches wider, shipped back, powder coated brings up the cost to almost double of what one new wheel would have been. But I'll tell you this; The look on people's faces (those who know slingshots and what the stock wheel looks like) is priceless when they see this big fat 345 tire on a stock appearing wheel. Even this past winter during Bike Week in Daytona, both Polaris people and a customizer of sports bikes were impressed to see that tire on a stock wheel. The small changes that yields huge results shouldn't be overlooked by the fact that there are other choices in wheels.

Pretty cool! Didn't know you could do that...I like the older SL rims also and have 2 sets of them. Where did you send the rim, how much did it cost if you don't mind and how was the offset affected??thx

AFAIK, http://www.weldcraftwheels.com is the only national wheel widening company. There may be others, but these guys are usually considered the goto company for wheel mods.

Quote from BKL

AFAIK, http://www.weldcraftwheels.com is the only national wheel widening company. There may be others, but these guys are usually considered the goto company for wheel mods.

Correct, but Stickerdick has used another company to have his wheel done. Not usre of their name, but he's been happy with the results. As long as you get a wheel adapter that spaces the wheel back outward the same amount it came inward, you'll have the same offset as the stock wheel was.

Quote from funinthesun

Correct, but Stickerdick has used another company to have his wheel done. Not usre of their name, but he's been happy with the results. As long as you get a wheel adapter that spaces the wheel back outward the same amount it came inward, you'll have the same offset as the stock wheel was.

Hopefully, he'll post the name.

After reading that @StickerDick had used a different company to widen his wheels, I Googled "Aluminum wheel widening" and I found these listings -

Michigan - Welcome to Weldcraft Wheels | Weldcraft Wheels

California - eric vaughn machine: aluminum wheel widening and narrowing

Texas - RimSpec - Wheel Repair & Rim Repair Specialist Bent | Damaged | Curb Rash | Cracked | Powder Coating | Classic Wheel Restoration (also list a Miami phone number)

I also found several sites that repair wheel damage, but none of them mentioned anything about widening.

Eriv Vaughn is who i use... but i beleive he is laid up for a while after some surgery.

I just emailed RimSpec (Texas) and requested cost info on widening my 18x9.5" rear wheel to 18x11". I assume I'll need a 3/4" spacer similar to this one - B07DWK6YM3. It uses 12x1.25 studs and has a 66.1 mm bore to match the stock wheel.

Quick response (just over 1 hr) - $300-350 per wheel.

I may just try this since it will cost (wheel mod + spacer) about the same as buying a single wheel while matching my stock front wheels. I want a wider 18" wheel so I can try an Achilles ATR Sport 2 305/30R18 tire at a cost of $102-150, but most sites currently have them out of stock. Catch 22 - Don't want to mod the wheel until I know the tire I want to try is available.

After some searching, I found one at Onlinetires for $133 including shipping and road hazard coverage. Guess once I get the tire, I'll have the wheel modded.

But, you would still need to re-paint or re-powder the wheel too, right?

Quote from TravAZ

But, you would still need to re-paint or re-powder the wheel too, right?

Depends on how much the weld appearance bothers me. Probably just some paint touch-up since I'm modding an existing stock rear wheel.

if done correctly, you will hardly notice the widening. and the face of your wheel should at the most only be slightly marred or nicked... you should be able to use touchup paint.