33’s or 35’s? - Page 2 - Rubicon Owners Forum
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post #11 of 28 (permalink) Old 05-23-2019, 08:02 PM Thread Starter
Rubi Noobie
 
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Thanks. I’m running 4.88’s in a 6-spd manual trans.

(Yea, I’m over 30 - when I say “trans” I mean “transmission”. Old habits die hard.)


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2017 JKUR | 6-spd Manual | Rock Krawler 2.5" Flex | G2 4.88 Gears | Bilstein 5100s | Fox 2.0 ATS Stabilizer | Smittybilt Atlas F & R bumpers | Smittybilt X20 Winch | ARB Diff Covers | BesTop Sunrider | Woods 1310 F & R shafts | Magnaflow axle-back | K & N CAI | ARB CKMA12 | too many cheap light bars
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post #12 of 28 (permalink) Old 05-23-2019, 08:10 PM
Rubicus Maximus
 
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Yes JKs need 35s

After running 34s, (285/75-17) for 3 or 4 years and 45k I am switching to 35s which are marginally larger. In those 45k mles Ive had zero issues that would be tire size related from the stock 31/32 inch tires. The only thing I want is more gear, but you have that taken care of already.

If you have a lift existing and it is driving and behaving as it should now I wouldn't expect to see many problems related to tire size switch. If you don't already have one get a procal or something similar to adjust the engine/ trans parameters for the tire & gear combo.

Wheel choice and offset is key, taller wider tire needs more backspace to avoid problems, but not so much that the tires are way outside the fenders. The AEV back spacing on their wheels seems to work well with 35s I think its 4.625 off top of my head on a 8.5" wide wheel. Just remember that wheel width, tire width, back spacing and height are all related.

I too would love to find the elusive narrow 35/36 inch tire...super swamper makes em, but they are not appropriate for most uses.
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some scrapes, dents and some skids ,UCF high clearance skid, Hybrid 3" lift w/tera 3", Bilstein 5100s, F&RATB, JJ control arms , on 255/85 KM2's

2013 crush JKU AEV bling 285/75-17s

2006 TJ project truck GR8Tops, flat fenders , 34s , 6' bed are the plan
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post #13 of 28 (permalink) Old 05-23-2019, 09:26 PM
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I too would like a narrow 35/36 tire. A 12.50 tire around here can be a hand full when changing lanes. The pavement grooves tend to pull you around.
I can be hitting the bump stops on most gravel roads. Your springs might be stiffer or your shocks can play a role also. If I had 33's then I could get another inch of up travel.
I think the important thing is to figure out where you are going to end up. Doing things twice is a pain. Heck I may end up on 40's. It just depends how bored a guy gets in the winter.
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2014 JKU, JKS lift,Poison spyder flares, bombshell covers,Rancho D2 control arms, JKS adjustable track bars, 35" Tires. GrabBars, Crawler Conceptz rear bumper, Smitty front bumper, Winch. Rough Country inner fenders, Teraflex Disco Mud Flaps
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post #14 of 28 (permalink) Old 05-24-2019, 10:40 AM
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Getting back to your question about the belly skid. The issue here is that the wheelbase on the JKU is so long, it has a more difficult time clearing rocks and other obstacles than a shorter wheelbase jeep on the same sized tires. Consequently the under carriage will pay the price with extra abuse.


Based on the plan you wrote for how you plan to use the jeep, you shouldn't need to put skid plates on immediately. Until you do armor up the bottom you'll need to pay attention to the lack of protection and drive over obstacles with extra caution. Still, for long-term piece of mind I recommend investing in armor. Even if you only planned to drive logging roads there will be rocks, logs, etc. that will try to bite the bottom of your jeep.


As far as specific suggestions, I leave that to others on the forum. As with many jeep products, you can buy piece-by-piece or all at once. Designs run the spectrum from Gucci (aluminum) to more simplistic with matching prices. If the aftermarket changes as it did when jeep went from the TJ to the JK, in the next few years, JK parts will become more and more difficult to find as the manufacturers concentrate on the JL/JT market. With that in mind, I'd recommend trying to buy sooner, rather than later.
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1982 Red Jeep Scrambler, small block chevy on 35's.

"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety." -Benjamin Franklin
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post #15 of 28 (permalink) Old 05-24-2019, 11:29 AM Thread Starter
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Quote:
Originally Posted by Mouse View Post
Getting back to your question about the belly skid. The issue here is that the wheelbase on the JKU is so long, it has a more difficult time clearing rocks and other obstacles than a shorter wheelbase jeep on the same sized tires. Consequently the under carriage will pay the price with extra abuse.

Based on the plan you wrote for how you plan to use the jeep, you shouldn't need to put skid plates on immediately. Until you do armor up the bottom you'll need to pay attention to the lack of protection and drive over obstacles with extra caution. Still, for long-term piece of mind I recommend investing in armor. Even if you only planned to drive logging roads there will be rocks, logs, etc. that will try to bite the bottom of your jeep.

As far as specific suggestions, I leave that to others on the forum. As with many jeep products, you can buy piece-by-piece or all at once. Designs run the spectrum from Gucci (aluminum) to more simplistic with matching prices. If the aftermarket changes as it did when jeep went from the TJ to the JK, in the next few years, JK parts will become more and more difficult to find as the manufacturers concentrate on the JL/JT market. With that in mind, I'd recommend trying to buy sooner, rather than later.
Thanks. About 20 years ago I switched from short wheelbase 4x4s to a 4x4 VW camper (that thing was a blast, btw) to double cab trucks (mostly to accommodate family) so I've gotten very used to dealing with a long wheelbase. The JKU feels like a nimble little cricket in comparison to my old F250!



I do plan to add some armor to the bottom - that evap box in particular looks very vulnerable. I just spent the afternoon yesterday re-routing some aux light wiring installed by the PO that was hanging inside the front fender well and under the frame to instead follow the stock loom down the pax side above the frame & gas tank for this same reason (I also added a 20 amp power feed to have aux power in the back). Boy, there is some close clearance between the pax side resonator and the rear bushing on the UCA - I would imagine that bushing needs to be replaced often if one spends a lot of at low speeds in hot weather...
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post #16 of 28 (permalink) Old 05-24-2019, 11:36 AM Thread Starter
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Originally Posted by rlenglish View Post
I too would like a narrow 35/36 tire. A 12.50 tire around here can be a hand full when changing lanes. The pavement grooves tend to pull you around.
I can be hitting the bump stops on most gravel roads. Your springs might be stiffer or your shocks can play a role also. If I had 33's then I could get another inch of up travel.
I think the important thing is to figure out where you are going to end up. Doing things twice is a pain. Heck I may end up on 40's. It just depends how bored a guy gets in the winter.
I think you guys have convinced me to go with 35s. Now I just need to figure out the wheel/tire combo. It looks like there are a couple of ways to get to a 35" tire. Looking at tire rack's web site it looks like the vast (and I mean VAST) majority of 5x5 17" wheels are 9" wide and offer a -12mm offset. According to them that will provide 4.5" backspace, but I'm not sure how they do that math.

I notice that AEV's wheels (a trusted name, to be sure) are all 8.5" and they claim 5.2" of backspacing and that 37" tires will fit with these wheels. However, Rock Crawler advises 4.5" backspacing for tires up to 35" and 3.5" backspacing for 37's and beyond.

I realize I am now drifting into a topic that has probably be covered 10,000 times already ("wheel and tire choice with xyz lift"), so if anyone has a link to a good and authoritative answer on this topic, I'd be grateful.

I want to avoid the mall crawler 'tires sticking out 4" past the fender' look
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post #17 of 28 (permalink) Old 05-24-2019, 02:38 PM
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Quote:
Originally Posted by sbsyncro View Post
....I want to avoid the mall crawler 'tires sticking out 4" past the fender' look
That is actually quite functional and not just to impress the mall crowd. Wider track mean more stability off-camber plus with minimal backspacing you won't have interference when making a tight turn (or not much interference.)
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post #18 of 28 (permalink) Old 05-24-2019, 04:02 PM Thread Starter
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Thanks John. Had a long (and great) conversation with Paul at AEV this AM about their wheels. They make an 8.5” (17) with 5.2” backspace and they say that it is the ideal geometry for 35-37” tires based on the concept of “scrub radius”. This keeps the wheels in tight but gives enough clearance for all the suspension components with a lift (2.5” to 4.5”). Sounds like a lot of thought went into their design for the JK.

I think I’m headed in that direction now... there’s a guy about 100 miles away from me selling a set of 5 AEV wheels and 315/70 BFG KO2’s with 10k miles on them for $1800. I might head down that path or buy new....


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post #19 of 28 (permalink) Old 05-25-2019, 12:36 AM
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The closer in your wheels the less stress on your axle and ball joints.
I have a 4.5 backspace and on turns (lock to lock) I have barely any clearance. If I went to a 5.2 BS then I would rub on the frame. I have not modified my steering stops.
Keep us informed.
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post #20 of 28 (permalink) Old 05-25-2019, 03:49 PM
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I think the AEV wheels are a good choice. I went with them because they were specific to the JK, designed with JK geometry and tire sizes in mind. An excellent value for what they are, JK specific wheels. I believe that extra design thought brings less wear and tear and better handling.
There are tons of wheel manufacture's but the back spacing and offsets are all compromises for the numerous applications that a 5x5 bolt pattern fits, not that most of them are bad they just are not vehicle specific.

Narrow tires and the wheels that fit them are just not popular, my ideal would probably be a 35/6 tire on a 7.5 or so wheel with 5 inches back space, no such animal unless I custom build a wheel and buy a container full of specially built tires...
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some scrapes, dents and some skids ,UCF high clearance skid, Hybrid 3" lift w/tera 3", Bilstein 5100s, F&RATB, JJ control arms , on 255/85 KM2's

2013 crush JKU AEV bling 285/75-17s

2006 TJ project truck GR8Tops, flat fenders , 34s , 6' bed are the plan
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