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Old 05-16-2013, 07:41 AM   #31
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Quote:
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35 years of experiance and a degree in automotive engineering.

In a perfect world you would want the center line of your tire to be equal with the center line of your bearings but even in the stock configuration this isnt really possible so you try to keep it as close as you can.
In the real world I normaly just use common sense but there is actually a formula for calculation stress muliplication due to lateral force changes.
You'll have to do a considerable amount of measuring to use it but here you go -

(sigma1 - sigma2)^2 + sigma1^2 + sigma2^2 = 2*sigma(y)^2
sigma1 = x-direction max shear stress
sigma2 = y-direction max shear stress
sigma(y) = yield stress
Also an engineer myself (Mechanical) and we both know that real world scenarios dont always match theoretical calculations. If running these wheels was such a huge issue more people would be crying about wheel bearing failures. 3.75-4.5 are common backspacings run on aftermarket setups in order to reduce if not completely remove the risk of rubbing. It would also behoove a manufacturer to do some over engineering in primary failure points of which wheel bearings yield a high risk. While I dont believe its triple the stress on all the componenets you listed earlier, I will agree there is a risk of increased stress. Without actually working out the numbers I don't think throwing out finite answers is necessary.

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Old 05-16-2013, 09:14 AM   #32
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If you go back to the OP he is talking about 3.25-3.5 backspacing not 3.75-4.5 he did'nt mention wether he was going with 8" or 10" rims I'm hoping 8" 10's with that kind of backspacing would be even worse yet!Then add in that where talking about 33x12.50x15 or even 35's tires not the stock P215/75R15 or even the optional P225/75R15 tires. All that extra width means more leverage adding in the grip that heavy lugged "Offroad" tires have multiplies it even more.
Then you have the added weight of the vehicle when you start adding on heavier aftermarket bumpers, tire carriers, rock sliders, winches and other miscellaneous gear......not to mention how we actually Wheel or Jeeps, It's a damn wonder they hold together at all!

I believe my Estimate is resonable and if you've never seen Jeeps with broken/worn out axles, studs, bearings, hubs, knuckles, balljoints even bent housings....well you have'nt been wheeling with the same type of Jeepers I wheel with.

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Old 05-16-2013, 09:21 AM   #33
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All of which I am sure is completely related to have low backspacing......

If we didn't expect things to break when we wheel, then we wouldn't wheel. Having low backspacing isn't going to be the cause of 90% of the breakages on the trails. This discussion just went bonkers, I'm out.
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Old 05-16-2013, 09:25 AM   #34
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3.75 backspacing, locked d30 on 33s. No breakage
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Old 05-16-2013, 09:31 AM   #35
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Also an engineer myself (Mechanical) and we both know that real world scenarios dont always match theoretical calculations. If running these wheels was such a huge issue more people would be crying about wheel bearing failures. 3.75-4.5 are common backspacings run on aftermarket setups in order to reduce if not completely remove the risk of rubbing. It would also behoove a manufacturer to do some over engineering in primary failure points of which wheel bearings yield a high risk. While I dont believe its triple the stress on all the componenets you listed earlier, I will agree there is a risk of increased stress. Without actually working out the numbers I don't think throwing out finite answers is necessary.
In an 8" width wheel, 4" BS would result in a center mounting point. +/- .5" from that is a non issue. Your main concern for wheel bearings is lateral force due to cornering with large diameter tires.
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Old 05-16-2013, 11:33 AM   #36
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What about gears?
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Old 05-16-2013, 11:46 AM   #37
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What about gears?
4.10 w/ the 6spd (lower first). I don't plan on changing them.
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Old 05-16-2013, 02:17 PM   #38
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4.10 w/ the 6spd (lower first). I don't plan on changing them.
it will be kinda sluggish but it will work my friend is on 35s on his street jeep with the same gear/engine combo as you. may I remind you my friend NEVER wheels his tho.
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Old 05-16-2013, 02:22 PM   #39
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4.10 w/ the 6spd (lower first). I don't plan on changing them.
4.10's on 33's should be livable. Nice purchase BTW! You'll love the handling those JJ's provide. Might corner as nice as your M3, lol!
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Old 05-16-2013, 03:16 PM   #40
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4.10's on 33's should be livable. Nice purchase BTW! You'll love the handling those JJ's provide. Might corner as nice as your M3, lol!
It's pretty flat around here. When I'm in SF stopped on one of those ridiculous hills I usually drop it into 4Low because the e-brake is pretty weak -- I don't think it'd even hold 33s/35s on a decent slope. Really looking forward to turning lower RPMs on the freeway though.

My M3 is just happy that I'll be driving it while I'm waiting on the CV shaft.
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Old 05-16-2013, 03:29 PM   #41
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I just installed f/r metalcloaks no lift 33 12.50 15 goodyear wranglers mtr new wheels with a 4 in back space I love it rides like stock no rubbing I send photos if you like.
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Old 05-16-2013, 03:50 PM   #42
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I just installed f/r metalcloaks no lift 33 12.50 15 goodyear wranglers mtr new wheels with a 4 in back space I love it rides like stock no rubbing I send photos if you like.
Yeah, post some pics, would like to see what wheels you found with 4" BS.
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Old 05-16-2013, 05:10 PM   #43
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What kind of wheels are you looking at? Mine have 3.75" BS.
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Old 05-16-2013, 05:22 PM   #44
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Yeah, post some pics, would like to see what wheels you found with 4" BS.
Cragar 365 V5 black 15x10 $ 70.99 at quadratec
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Old 05-16-2013, 05:36 PM   #45
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What kind of wheels are you looking at? Mine have 3.75" BS.
I think I'm going to go with the Mickey Thompson Classic III's in black.



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Cragar 365 V5 black 15x10 $ 70.99 at quadratec
Nice -- are those the 6" or 4" flares? They look like 6 to me.
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Old 05-16-2013, 07:09 PM   #46
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Yes 6 in. And I put the cut mod in the back. Took about 6 hrs to change the finders and install all for tires. Love that I have the stock smooth ride and handling. My wife drives a 08 rubicon 6in lift and rides hard.
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Old 05-16-2013, 07:29 PM   #47
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Yes 6 in. And I put the cut mod in the back. Took about 6 hrs to change the finders and install all for tires. Love that I have the stock smooth ride and handling. My wife drives a 08 rubicon 6in lift and rides hard.
do you have a zoomed in cut of the back? I had to cut mine too.
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Old 05-16-2013, 07:34 PM   #48
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It was just a little sliver about a inch and about 5i inches not at home but I will take a photo and post it for you
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Old 05-16-2013, 08:41 PM   #49
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Old 05-21-2013, 12:22 AM   #50
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oh I see... you trimmed the rear of the wheel well. I trimmed the front of my wheel well to my my 35s fit.

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