I have a stock 2008 wrangler JK-X. I just installed a set of 17” Fuel Assault wheels 9 inch wide on 285/70/17 tires. Will increasing the wheel and tire size damage my suspension and suspension geometry? What about my gear ratio? It’s never taken off the road - no 4-wheeling.

 

No, that will not damage your suspension, and since there is no change in the suspension all your steering geometry remains the same. Increasing tire size will have a direct effect on performance, and I suspect that is why you question gearing as well. Changing the gearing will have zero effect on the suspension. The larger tires will add a bit more stress steering components, like ball joints, that are typical wear items.

 

Sis,

I have a 2016 JKU 75th Anniversary Edition and moved up to the 285/70R/17’s recently. I noticed a significant difference (loss) in power, primarily due to having a 3:21 gear ratio. Hitting a hill of any size sucked the life out of it, even more so if I was pulling a utility trailer! You didn’t mention if you had an automatic or manual transmission. Mine is an automatic, so the change in tire size probably effected it more than if it was a manual. To solve this power loss issue I had it regeared to Yukon 4:88’s. I was planning on going with 4:10’s but after speaking to “Randy’s” I followed their advice and put in the 4:88’s. They’re not as expensive and the difference between the two ratios is not as great as you might think. I also dumped the Clutch style rear differential for an Eaton TrueTrac. The gear change absolutely brought the Jeep to life! The 3.6 loves to rev and at 70 MPH it’s turning about 2700RPM’s, which is still in the “Green Zone” on the tachometer. Now on a long hill it might down shift to 4th gear. Pulling my utility trailer, same thing. Hardly know it’s back there. Passing on the highway, just give it the throttle and go!

Now this wasn’t a cheap project, but I would do it again in a minute! I love driving my Jeep more now than when I bought it! The gear swap has made it more responsive than before I changed out the original tire for the 285’s.

Sorry for the long post, but I wanted you to know the details and results of what I did to mine.