Backspacing for 34" Trxus

Hey All,

I'm shopping for new tires and am thinking of either 33" mtr's, or 34" Trxus.Right now I'm on 33x10.50 TSL Radials on 7" 4.5 backspaced rockcrawlers, the lift on my 96 is a 5.5" RE Extreme Duty short arm kit with Acos added up front (wound all the way down) and a 1"
block added in the rear.No fender trimming as rubbing hasn't been a problem with these skinny swampers.

I guess if I go with the 33x12.50 mtr's, from the post I've read an 8" wide rim with 4.5 backspacing is what I should go with, and then trim fenders to stuff.But if I go with the 34x12.50 Trxus can I use that same 4.5 backspacing?If not what would you guys reccomend.

P.S. How true to size do the mtr's measure to 33", my swampers are exactally 32" with the vehicle loaded at 28 lbs. pressure.

Thanks!....................Chris

I have the trXus mt's, but 4.5 of backspacing will not be enough. That is pretty much close to stock, so you might end up with rubbing issues if you air down to about 15 or so. I run my 34x12.5x15 trXus tires on 15x10 rims with 3.75 of backspacing, and I don't rub anywhere. My tire actually sticks out a bit farther since it's a wider rim, but if you can find a 15x8 with 3.75" of backspacing, it will be a perfect setup, with no rubbing. The MT/R's will measure about 32.7" tall, which is what most tires measure that are 33x12.5; the trXus however, measure 34" exactly.

Nothing 12.5" wide will work with 4.5" bs unless you have 10" minimum.
YMMV.

12.50" wide tire WILL work with a 15x8 wheel and 4.5" BS. You will have slight rubbing in the LCAs at full turn and will rub the tops of the coil tower at full stuff.

3.75" BS will be better. Thats what I have now (well the equivalent anyways with the Warn hub kit) and I don't rub anywhere.

EricsXJ said:

12.50" wide tire WILL work with a 15x8 wheel and 4.5" BS. You will have slight rubbing in the LCAs at full turn and will rub the tops of the coil tower at full stuff.

3.75" BS will be better. Thats what I have now (well the equivalent anyways with the Warn hub kit) and I don't rub anywhere.

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Well I spent hours surfing through post on backspacing and it seems like quite a few have run 33x12.50 on 4.5 bs.I'm trying to keep mine as close in as I possibly can.Its just with these 34x12.50 that I'm still confused as its seems like kind of an odd size.Interco states that they measure 34" OD, and that their TSL 33x12.50 measure 33.7 O.D.So thats what like a quater inch difference?So if a rim fits a 33x12.50 swamper and stuffs well, is the 34" Trxus going to pretty much be the same?

Also on another note, as far as a spare if I go with the 34" Trxus, am I going to need another 34" Trxus, or could I use maybe a 34" LTB even though Interco states the 34" LTB is 33.7 O.D.How about using one of my 33x10.50 TSL Radials as a spare and airing down the other three 34" Trxus?

Thanks guys for the input

With as much lift as you have, why would you want your tires in as much as possible? With 34's especially, you are going to have to trim, no way around it. Might as well make up for your poor COG by widening your stance and get some wheels with as little BS as possible so you don't fall over. I have 34" Trxus on the wife's XJ with 15x8" rims and 4" BS, and I would rather have around 3.25" BS like on my XJ. I would get different wheels, but I am going to throw my 37" MT/R's on 15x8" 3.25"BS wheels on the wife's rig since I am probably going to get rid of my XJ. Both of our XJ's have the RE 6200 5.5" kit without additional spacers or what not. Here are some pictures of my wife's rig with the 34" Trxus:




If you are trying to keep your tires under the fender flares for legal purposes, then more BS would be somewhat understandable, but BW or TJ flares would be better to invest it and get wheels with less BS.
Just my thoughts.

EricsXJ said:

12.50" wide tire WILL work with a 15x8 wheel and 4.5" BS. You will have slight rubbing in the LCAs at full turn and will rub the tops of the coil tower at full stuff.

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I don't consider rubbing to 'work' at all.
Settling for rubbing and such is an option for some, but not for me.
YMMV>

bgcntry72 said:

I don't consider rubbing to 'work' at all.
Settling for rubbing and such is an option for some, but not for me.
YMMV>

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Understandable. However, I could have eliminated the LCA rubbing by extending my steering stops a bit but with the RE LCAs the rub was harmless so I left it as is. Believe me, I hate fender rubbing and will not stand for it on my rig, but some types of rubbing is worse than others. We agree that less backspacing is better and thats what I now have... :thumbup:

cloudswimmer - one other thing to keep in mind (and you brought this up) is that actual tire sizes will vary between different manufacturers. Just because a tire says 33" on the sidewall doesn't necessarily mean it measures an exact 33".

I have not used them but I believe Interco makes tires that are more true to stated size but you will have to check to make sure. Goodyear MT/R's run a little small. My 33" tires have an actual diameter of 32.8".

The larger the diameter, the more chance you'll have rubbing on the LCA when the tire is turned. So a 34" Trxus might rub quite a bit more than my 33" MT/R's but how much I don't know since I have never used the Trxus. Your options are: put up with the rubbing, lengthen the steering stops to increase your minimum turning radius, or use wheels with less backspacing. I agree with GottaBeJeep that a wider stance is better, but just be prepared that the wider you go, the more fender trimming is required but thats really not that big a deal, really.

with 4.5 bs my 33x12.50 where pushed right into the rear spings . i think i have 3 or 3.5 bs now and they fit great they do rub the lca a bit but i have not adjusted the stops

massxj said:

with 4.5 bs my 33x12.50 where pushed right into the rear spings . i think i have 3 or 3.5 bs now and they fit great they do rub the lca a bit but i have not adjusted the stops

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What I'm a little confused on here is this:I have 33x10.50 TSL Swampers on white Rockcrawler 7" 4.5 BS Steelies.On a 6.5" lift I can completely stuff these things with no rubbing anywhere, not on on the LCA or the Springs.Now isn't 4.5
backspacing 4.5 backspacing no matter what width rim I have?Another words if I were to get tires wider, lets say 33x12.50, and put them on 8" 4.5 backspaced riims it seems to me that the clearance of the tire hitting anything on the back side (control arms, etc.) is going to be the same as before, only difference now is the tires are going to stick out more on the front side causing rubbing issues with the fenders.Correct me if I'm missing something here :lecture:

Thanks!

I have 33X12.50s with 15X8 and 3.75 BS. I am not sure how much less will work!

cloudswimmer said:

What I'm a little confused on here is this:I have 33x10.50 TSL Swampers on white Rockcrawler 7" 4.5 BS Steelies.On a 6.5" lift I can completely stuff these things with no rubbing anywhere, not on on the LCA or the Springs.Now isn't 4.5
backspacing 4.5 backspacing no matter what width rim I have?Another words if I were to get tires wider, lets say 33x12.50, and put them on 8" 4.5 backspaced riims it seems to me that the clearance of the tire hitting anything on the back side (control arms, etc.) is going to be the same as before, only difference now is the tires are going to stick out more on the front side causing rubbing issues with the fenders...

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Yes 4.5" BS is 4.5" BS regardless of what wheel its on, but the width of the tire in relation to the width of the wheel still plays a minor part.

10.50" - 7" wheel = 3.50"
12.50" - 8" wheel = 4.50"

So assuming everything else is the same (air pressure, load rating, etc) there is a 1" difference - split between both sides of the wheel is 1/2" per side. Maybe that difference was why your 33x10.50's don't rub the LCAs and my 33x12.50's did...

4" bs on 10" rim. no rubbing lock to lock.