Offset - Backspace - ideal fitment - Calculation chart - Page 5 - Jeep Garage - Jeep Forum

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  #49  
Old 05-05-2016, 01:59 PM
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Re: Offset - Backspace - ideal fitment - Calculation chart

SYDERTRAX only makes them in 1.75" for the Jeep WK2.

BORA ( motorsport-tech) will make any size you want but say 1.25" is the most popular. I believe this is do to, not having to trim threading on factory lugs. Although it has been reported that some minor trimming may be required on back wheels at 1.25" and it will not affect the threading.
Lenny at BORA is good to work with and on top of his product and service.
I am new and this is my understanding after recently investigating.

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  #50  
Old 05-05-2016, 04:08 PM
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Offset - Backspace - ideal fitment - Calculation chart

I have the Bora 1.25" with factory 18s on my 11 Overland. No trimming is required front or rear. The studs do stick out just a bit, but the wheels have a notch in the back and nothing touches. ImageUploadedByJeepGarage1462478853.912691.jpgImageUploadedByJeepGarage1462478877.111047.jpgImageUploadedByJeepGarage1462478906.313210.jpgthe middle is the before.
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  #51  
Old 05-06-2016, 10:07 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

I might be slightly slow but I'm having a hard time figuring this out. I plan on running the same tires as you(atturo trail blade xt 33x12.50-20) However, I'd like to get a slightly wider stance. Can I run 20x9 or 20x10 wheels with these without rubbing?

I have a 15 altitude and will be installing the rro2.5" lift with the wheel and tire package.
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  #52  
Old 05-06-2016, 11:42 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

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Originally Posted by chunkyblamm View Post
I might be slightly slow but I'm having a hard time figuring this out. I plan on running the same tires as you(atturo trail blade xt 33x12.50-20) However, I'd like to get a slightly wider stance. Can I run 20x9 or 20x10 wheels with these without rubbing?

I have a 15 altitude and will be installing the rro2.5" lift with the wheel and tire package.

slightly wider stance means.... less offset, wider wheels or both. What I am giving you is what is technically ideal. if you find a 8.5"wheel you want, and you want more stance, you will go lower than the +31 I stated. If its a 9 inch wheel and you want more stance youll go lower than 25 offset. I cant guarantee you wont rub with those offsets. But, if you dont go too far, your rub will be minimal and easily fixed. if you start to go in to the teens as far as offset goes, you will need to bend or cut your pinch and pin back the felt. if you go even lower than that, youll have to worry about your front plastics. increasing stance does look good, but is harder on the rest of your suspension, and will fling a lot of crap on to your Jeep, especially rock chips at the bottom of the rear door. just fyi
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  #53  
Old 05-06-2016, 11:47 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

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Originally Posted by carmstrong33 View Post
Question for Alludc.....

Thanks for all your info on this thread you certainly are a wealth of knowledge on this subject and have built an amazing GC!

I have a 2014 Limited...I want to install the $400 RRO 2.5" lift, no new shocks for now. I want to use the ATX Atrillery wheels in a 20x8.5x20 with a +35 offset and Toyo AT II tires....Can I fit a 33x12.5x20 (or 305x55x20) without any rubbing or additional modifications?

they dont seem to have a 33x12.5-20 but the 305/55-20 is technically a 33.2 tire. vs my 32.8. however, they dont seem to show the exact specs of their tire, and all manufacturers differ. it could larger or smaller by a 1/2"or more. if its exactly 33 (unlikely) and you have it on a 20x8.5 +35 you will be right at the edge of minor rub. Again, easily fixable. The point is to try to stay near these ideal numbers and if any rubbing occurs it will be very easily fixable. if you can find the exact OD of that particular tire you want, youll see it a bit more clearly.
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  #54  
Old 05-06-2016, 11:48 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

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Originally Posted by shubba75 View Post
Ok...guys im new here and could use some help on tires. I cant seem to wrap my head around what is being said here.

I have a new 2016 JGC HA 44 with QL on order.
I plan on changing the stock rims with 20x10 spider monkey wheels...SRT replicas. What is the biggest most agressive tire i can use and also give it a wider stance? Can i put a 275/55 20 on it? Do i need a spacer? Should i do something else? Im a bit confused on exactly what i need.

likely the 275/55 would be no problem, but would need the offset of the replicas to calculate
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Old 05-06-2016, 11:53 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

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Originally Posted by VWTG View Post
Alludc I keep coming back to this thread. Am I correct in my understanding that the optimal set up is a wheel 8.5" with +30 offset. Obviously your opinion but a close look at your set up and real world experience gives this alot of validity.
My question is what criteria are we looking at.
1. assuming we select a wheel that clear the calipers whether stand or HD. This resolves that potential problem.
2. We then need to look to clearing UCA bolt when going Bigger
3. Try to stay inside the fender trim with wheel Offset in combination of tire width.

Is there anything else to be aware of out side of these 3?

nope that pretty much settles it up. I suppose you could factor in sidewall deflection if you use 17 or 18" tires with large sidewalls. In the case that you are going for minimal offset, and you end up very close to uca bolt, you could deflect a larger sidewall tire. But in most cases this is absolutely no worry because most of the aftermarket wheels available for us will all be in teh 30s or lower and youll get a good bit away from that. even with my 33x12.50 im nowhere near the bolt

staying inside the fender trim is preference, in most cases. when suspension compresses the upper tire naturally progressively tucks both inward and upward. so you may seem like youll hit the fenderlip, but possibly not. in my case, its very very close. in slow situations, not a big deal. if you are high speed offroad it could be an issue.
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  #56  
Old 05-06-2016, 11:55 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

Quote:
Originally Posted by bandwagn View Post
Is 1.25" the only option on spacers? I wasn't looking to get that extreme - could I go with 1/2" or does that throw off the hub centering and/or lug thread length?


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1.25 and 1.75 are generally the most popular, but in most cases uninformed decisions.

if someone wants to run a 33, on a stock oem wheel a 1" Bora spacer would be my prescription. anything beyond that is a bit too far IMO
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Old 05-07-2016, 10:02 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

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Originally Posted by alludc View Post
1.25 and 1.75 are generally the most popular, but in most cases uninformed decisions.

if someone wants to run a 33, on a stock oem wheel a 1" Bora spacer would be my prescription. anything beyond that is a bit too far IMO
Alludc, as for going over 1" on the spacers. Is this a fitment thing or a concern for the geometry of the components and the various forces that will increase in exertion on said components?
I value your real world experience as it always is more reliable then the math and engineering.
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  #58  
Old 05-07-2016, 11:56 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

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Originally Posted by VWTG View Post
Alludc, as for going over 1" on the spacers. Is this a fitment thing or a concern for the geometry of the components and the various forces that will increase in exertion on said components?
I value your real world experience as it always is more reliable then the math and engineering.

1" is fitment, to reach near ideal. I do believe that very aggressive offset reached via an aftermarket wheel (think 0 to +12 offset), or big spacers (1.5-1.75), will add increased stress on other components of course. Especially when you are also adding more weight with the wheel/tire combo.
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  #59  
Old 05-09-2016, 10:03 PM
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Re: Offset - Backspace - ideal fitment - Calculation chart

Alludc,

The spec sheet for the Atturo Trail Blade XT in the 33x12.5x20 calls for a 9.5"-10.5" wheel. Have you had any issues mounting these tires on your 20x8.5 Rhino Wheels??
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  #60  
Old 05-10-2016, 01:52 AM
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Re: Offset - Backspace - ideal fitment - Calculation chart

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Originally Posted by carmstrong33 View Post
Alludc,

The spec sheet for the Atturo Trail Blade XT in the 33x12.5x20 calls for a 9.5"-10.5" wheel. Have you had any issues mounting these tires on your 20x8.5 Rhino Wheels??
the call out for a specific wheel size is more for getting the maximum out of the tire. To get its true size, and full width...its best used on that size rim but by no means at all was it a difficult fit or a bad fitment on my 8.5s. The sidewall bulge is just perfect, and at nearly 10k miles on em, the wear is even.
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