Help with rim sizing for an 05 Rubicon

rraulston

TJ Enthusiast
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Oct 12, 2018
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Sahuarita, AZ
So I just reduced the lift height on my Rubicon from 4.5" to 3". I want to run 33x10.5 tires. Half the comments I read say the 33s will be OK with 3" lift and half say you need 4". I will simply add a 1.25" body lift if they don't work so lets not go there. My question is I like my tires to be flush or close to it. Quadratec has the following rims I am interested in but am not sure which one would get me close and have the best clearance:

Steel Blackrock 15x8 3.75 back space
Steel Blackrock 15x8 4.00 back space
" " 15x8 4.5 back space
" " 15x8 4.75 back space
" " 17x8 4.5 back space

I really appreciate the knowledge!!

rr4.jpg

The current tires are 305/70-16 on the 3" Teraflex lift.
 
As far as the lift "requirements" are concerned, you need to start with the bump stop extension. 33s need extension to prevent them from mashing into the front fender sheet metal. Bump stops necessarily reduce suspension up travel. Adding lift is a way to recover the lost up travel from the required bump stop extension. If a stock TJ has about 4" of up travel and you want to maintain that, then you will need enough lift to create that up travel.

This is my thought process and this is why I don't believe 3" is enough lift for 33s with an unaltered body.
 
As far as the lift "requirements" are concerned, you need to start with the bump stop extension. 33s need extension to prevent them from mashing into the front fender sheet metal. Bump stops necessarily reduce suspension up travel. Adding lift is a way to recover the lost up travel from the required bump stop extension. If a stock TJ has about 4" of up travel and you want to maintain that, then you will need enough lift to create that up travel.

This is my thought process and this is why I don't believe 3" is enough lift for 33s with an unaltered body.
I know a guy who has one of those ramps you drive on to test flex. Maybe I can do a test utilizing that ramp and adjust bumps accordingly? Don't I want the tires on the Jeep and adjust the bumps to keep the tire out of the fender?, Can I get flat fenders for additional up travel?? And thanks for helping me get sorted!!
 
4.5" BS would get you flush with Rubi flares. If you want to see coverage with a 33x1050x15 tire on a 3.75 BS wheel with Rubi flares I can take some pics.

The best way to setup your bump stops would be to pull the springs and put the axle to full bump, then articulate the axle with the wheels on. while articulating, turn wheel lock to lock and note your restrictions. bump accordingly. with a 3" lift, you'll likely need 2" of added Bump.
 
I know a guy who has one of those ramps you drive on to test flex. Maybe I can do a test utilizing that ramp and adjust bumps accordingly?

A ramp won't tell you everything you need to know because it cannot replicate the dynamic movements of a Jeep on the road or trail. It also cannot demonstrate what happens when you hit a speed bump or a dip in the road when traveling faster than you should have been. ;)

Removing the coils, jounces and disconnecting the sway bar so that you can move the axle around with a floor jack is the only way to recreate what happens out in the wild. Move the axle and steering up and down and all around to see what gets in the way. Add bump stop or make adjustments where appropriate.


Don't I want the tires on the Jeep and adjust the bumps to keep the tire out of the fender?
Yes

, Can I get flat fenders for additional up travel??
If the flat fenders can do better than this, then there is an opportunity to increase travel. Many flat fenders actually reduce clearance because the outer tube is thicker than the stock fender lip.
85f91084a2e00b173590c205cc198202.jpg


And thanks for helping me get sorted!!

Happy to do it. There is a logic to all of this. Understanding the bump stops is the key to unlocking most of the mysteries of modifying a Jeep.
 
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4.5" BS would get you flush with Rubi flares. If you want to see coverage with a 33x1050x15 tire on a 3.75 BS wheel with Rubi flares I can take some pics.

The best way to setup your bump stops would be to pull the springs and put the axle to full bump, then articulate the axle with the wheels on. while articulating, turn wheel lock to lock and note your restrictions. bump accordingly. with a 3" lift, you'll likely need 2" of added Bump.
A pic would be amazing. Once I get the tire/rim package, the bump adjustment and potential body lift can be more accurately assessed....
 
A pic would be amazing. Once I get the tire/rim package, the bump adjustment and potential body lift can be more accurately assessed....

Cali is pretty strict on tire coverage, but you should only need coverage to here,
DSCN0858.JPG

As long as the tread blocks are covered you should be good.
DSCN0855.JPG

DSCN0857.JPG

as mine sits, I'm technically illegal, but haven't had any issues.
 
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So I just reduced the lift height on my Rubicon from 4.5" to 3". I want to run 33x10.5 tires. Half the comments I read say the 33s will be OK with 3" lift and half say you need 4". I will simply add a 1.25" body lift if they don't work so lets not go there. My question is I like my tires to be flush or close to it. Quadratec has the following rims I am interested in but am not sure which one would get me close and have the best clearance:

Others have given you advice on tire height clearance, and here's my experience on width. I have 32" x10" tires with 5.0" back spacing. I have 1" from tire edge to fender flare edge, using Rubicon flares. If my math is correct, and wheel with a back spacing of 3.75" or larger, would be ok with the wider Rubicon flares.

(edited backing measurement from 4.75" to 5.0")
 
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I'm still trying to decide backspacing for my next set as well. I'll also be running a 33 x 10.5 x 15. FWIW, you could run a 7" wide rim with a 10.5" wide tire and run a little less risk of losing the bead at low pressures. Your preference really though. I'm planning to run 7s. And again - completely just my own opinion - but I'm not big on the 17" wheels on TJs. They just look a bit odd in my old eyes. And they are heavier. And both the wheels and tires will run a good bit more $$.