Proper backspacing/offset for 35’s with no bulge

coukos34

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Don’t a lot of searching and viewing of other people’s setups, but can’t find the answer I’m looking for. Where I live there are new inspection retrictions that don’t allow tires to be any farther out than the fender.

I’m looking for the right 17” wheel backspacing/offset for a 35 or 315/70 tire that will be just at the edge of this limit. Anyone happen to know or have something similar?





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I use the stock Rubicon wheels on my Sport and 315/70/17's and 2.5" lift and the wheel/tire combo looks factory. I think they are 4.5" backspacing. If you have a Rubicon I bet you could just slap the tires on your current wheels and it wouldn't stick out.

I don't have many pics from the side but the tire sticks out maybe 1/4" tops.

20180505_095640.jpg


20180506_083812.jpg


20180506_122613.jpg
 
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coukos34

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Sorry I should have given more info. I have a JLUR, but not sure I want to chance mounting a 12.5 width tire on the stock 7.5 rim (nor do I know who would even mount for me). What I’m trying to find is a 17/18.5 rim with the proper offset for 35’s with no bulge. What you have is exactly what I want for a look, but just an 8.5” rim.
 

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If you go with a wheel that's 8.5" wide, then what you want is +25mm offset or greater.

If you go with a wheel that's below +25mm offset, you will start pushing tread outside of the fender flares.
 

Waiting

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I use the stock Rubicon wheels on my Sport and 315/70/17's and 2.5" lift and the wheel/tire combo looks factory. I think they are 4.5" backspacing. If you have a Rubicon I bet you could just slap the tires on your current wheels and it wouldn't stick out.

I don't have many pics from the side but the tire sticks out maybe 1/4" tops.

20180505_095640.jpg


20180506_083812.jpg


20180506_122613.jpg
ERROR CORRECTION: The stock 7.5" wide wheel have something like 6.1" or 6.2" back space.....NOT 4.5"; not even close
 
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coukos34

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If you go with a wheel that's 8.5" wide, then what you want is +25mm offset or greater.

If you go with a wheel that's below +25mm offset, you will start pushing tread outside of the fender flares.
Thanks, this is helpful. I don’t know that I’ve seen any with this offset, but it’s good to know
 

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Don’t a lot of searching and viewing of other people’s setups, but can’t find the answer I’m looking for. Where I live there are new inspection retrictions that don’t allow tires to be any farther out than the fender.

I’m looking for the right 17” wheel backspacing/offset for a 35 or 315/70 tire that will be just at the edge of this limit. Anyone happen to know or have something similar?
My 2 cents: Tire width is wider than wheel width, so I view calculations from tire dimensions. A 315 (approx 12.5") tire is about 1" inch wider than the stock Rubi 285 (approx 11.5) tires. To keep the same clearance as OEM on the inner side, you need to push the wheel away from Jeep 1/2" or one half of the increase in tire width.
I have not seen definitive specs for OEM wheels but is about 6.1" back space, which equates to about 45mm positive offset.
To move the wheel away from the Jeep by 1/2" or 12.7mm, Take the 45mm OEM offset and subtract the 12.7mm needed to push the wheel out 1/2". This gets 32.3mm. With all that said, it is unknown (to me at least) if a full 1/2" of additional backspace/offset is needed for a 12.5" wide tire because there is decent clearance on full lock with the stock 285 tires. To my knowledge no one has made a JL wheel to correctly tuck a 315 tire on a JL or if it is even possible. As noted above, you get minimal poke with 315 tires on stock wheels because the stock set up, unlike the JK, sits so flush with the fender. I'm waiting to see specs on new JL wheels from AEV. You can also search for images of JLs with Mopar wheels found in their 2018 Performance Parts cataglog. All of them are 8-8.5" wide with 12mm offset. Even they have some poke, that can be seen in press photos. I'll attach a photo I snagged on here of the 12mm offset Mopar Gear wheel with 12.5" wide Nittos
Lots of info and no help. Sorry
You may also want to consider Nitto sells a 35x11.5 Trail Grappler

D48B3666-188A-4887-A8A7-CF61729F5A79.jpeg


88E7AE0F-EA0E-4B0F-9DDA-F30962995671.jpeg
 
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coukos34

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My 2 cents: Tire width is wider than wheel width, so I view calculations from tire dimensions. A 315 (approx 12.5") tire is about 1" inch wider than the stock Rubi 285 (approx 11.5) tires. To keep the same clearance as OEM on the inner side, you need to push the wheel away from Jeep 1/2" or one half of the increase in tire width.
I have not seen definitive specs for OEM wheels but is about 6.1" back space, which equates to about 45mm positive offset.
To move the wheel away from the Jeep by 1/2" or 12.7mm, Take the 45mm OEM offset and subtract the 12.7mm needed to push the wheel out 1/2". This gets 32.3mm. With all that said, it is unknown (to me at least) if a full 1/2" of additional backspace/offset is needed for a 12.5" wide tire because there is decent clearance on full lock with the stock 285 tires. To my knowledge no one has made a JL wheel to correctly tuck a 315 tire on a JL or if it is even possible. As noted above, you get minimal poke with 315 tires on stock wheels because the stock set up, unlike the JK, sits so flush with the fender. I'm waiting to see specs on new JL wheels from AEV. You can also search for images of JLs with Mopar wheels found in their 2018 Performance Parts cataglog. All of them are 8-8.5" wide with 12mm offset. Even they have some poke, that can be seen in press photos. I'll attach a photo I snagged on here of the 12mm offset Mopar Gear wheel with 12.5" wide Nittos
Lots of info and no help. Sorry
You may also want to consider Nitto sells a 35x11.5 Trail Grappler

D48B3666-188A-4887-A8A7-CF61729F5A79.jpeg


88E7AE0F-EA0E-4B0F-9DDA-F30962995671.jpeg
Thanks, that’s great info/advice. It does make sense thinking about the added width affecting the interior of the wheel as well, I hadn’t really thought of that.

What I don’t understand though, is if you are adding a 35 to stock wheels, it’s splitting the extra inch in width between the interior and exterior without poking too much at all. If that’s the case, there should be an appropriate backspacing/offset that would allow the same thing, correct? That same 12.5 tire is not less or more wide on a larger 8.5” rim compared to stock.
 

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What I don’t understand though, is if you are adding a 35 to stock wheels, it’s splitting the extra inch in width between the interior and exterior without poking too much at all. If that’s the case, there should be an appropriate backspacing/offset that would allow the same thing, correct? That same 12.5 tire is not less or more wide on a larger 8.5” rim compared to stock.
To answer that question, I'd say "maybe". There needs to be more trial & error, research, etc with the JL. Check out AEV's website for their engineering argument for their JK wheels. They are testing the JL and it's also why they still haven't released a wheel for the JL. AEV's blog says they will release JL parts in Oct, at SEMA. Mopar performance wheels are close to flush which "may" indicate a 12.5" wide tire may not sit flush (because there is exactly or less than 1" - 0.75" of inside clearance; typical Jeepers need some additional inside clearance for mud, debris, etc.).
Mopar, to my knowledge, are the only manufacturer that has yet to design wheel with the JL in mind. On one hand, I suspect Quadratec and Mammouth/Extreme Terrain will soon follow AEV to release JL specific wheels. On the other hand, Quadratec recently released the '41 Wheel with specs extremely similar to their Hardrock wheel which was developed for the JL.
You can measure a full lock to get a rough estimate but things get complicate quick because different tire manufacturers have different actual measurements, articulating the axles and stuffing the wheels while disconnected, and axle shifting from lifting, and the axle hub height placement from lifting all affect proper clearance.
 

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This is spreadsheet I’m working on for 12.5” tires. It makes sense to me LOL but if you have any questions just let me know
 

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At 0:51 in this video, you can see what 17x8.5" wheels with +10 offset and 285/75 (34x11.50) tires look like. As you can see, there's some tread sticking out.

If you go 12.50 width, then you're adding another half inch of tread outside the flares. So that's why I said you really need to stick with +25mm or greater positive offset if you need to keep the rubber inside the flares.

 

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At 0:51 in this video, you can see what 17x8.5" wheels with +10 offset and 285/75 (34x11.50) tires look like. As you can see, there's some tread sticking out.

If you go 12.50 width, then you're adding another half inch of tread outside the flares. So that's why I said you really need to stick with +25mm or greater positive offset if you need to keep the rubber inside
That is a good video
 
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coukos34

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At 0:51 in this video, you can see what 17x8.5" wheels with +10 offset and 285/75 (34x11.50) tires look like. As you can see, there's some tread sticking out.

If you go 12.50 width, then you're adding another half inch of tread outside the flares. So that's why I said you really need to stick with +25mm or greater positive offset if you need to keep the rubber inside the flares.

Thanks this is helpful. The +10 with those 11.5 tires is the farthest out I think could possibly be acceptable, so with 12.5” wide 35’s, it would be just too much.

@Waiting I had saw the new Quadratec 41’s on their site, but didn’t check the offset. Looks like it’s one of the few decent options at this point. I’m a bit hesitant to wait much longer, as I wanted to sell my current wheels/tires while they are still very low mileage. Didn’t honk I’d have such problems finding a good wheel setup at this point.
 

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@coukos34 Nitto makes a 35x11.5 Trail Grappler in a C load rating. It will fit the stock 7.5" wheels. 11.5" vs OEM 285mm is negligible. I saw someone with these on stock wheels at a Jeep show and was just as tucked as stock......Just another option
 

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This is spreadsheet I’m working on for 12.5” tires. It makes sense to me LOL but if you have any questions just let me know
To Waiting. I'm trying to get this right so i need your help. I'm looking to put 17 x 9 on my unlimited sport. The tires that I'd like to get would be nitto ridge grapplers 315 70 17. I have the mopar lift, i dont want to stick outside the fender more then 2" would i need a offset of -12 ? Any and all help would be greatly appreciated. Thank you
 

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