Getting The Most From Your '07-Present Wrangler's Suspension
For some reason, many JK Wrangler owners insist on installing tires larger than 35inches tall. This often results in a lot of axle-related failures, including prematurely worn ball joints, broken axleshafts, broken lockers, and bent front axle housings. The commonly adored 37-inch tires only net you about 1-inch more ground clearance than the 35s, but the 37s add quite a bit more weight and increased leverage that wreak further havoc, degrading the JKs steering and axle assemblies. To get the most out of your JK in factory trim, we think it's best to stick with 35s or smaller. That is, unless you plan to replace your axles with something more robust.
After accumulating about 30,000 miles on our lifted JK with 35s, some of our aftermarket suspension components were worn out beyond useable condition. During that time we came to the conclusion that we liked the way our JK rode and drove better with the stock suspension on it. However, we appreciated the additional clearance that the 35s afforded. So we set out to find a way to keep the big tires and regain the factory-like ride, handling, and performance both on- and off-road. And since the '07-up Wrangler is already a bit portly, we investigated wheel and tire selections to save weight and regain a small amount of lost engine performance. Here's what we came up with after a bit of testing and wrenching. In this case, less is more.
But I Really Want 37s!
Of course you do, but maybe you're not totally aware of the worm can you're opening when you step up to 37-inch tires. The drawbacks outweigh the benefits of the bigger meats for most of us. The truth is that if you really use your Jeep you'll likely bend the front axlehousing and prematurely wear out steering components with 35s anyway. But consider that a typical 37-inch mud tire weighs about 10 pounds more than a typical 35-inch mud tire. That may not seem like much, however it's rotating weight, meaning it's added weight that your engine has to turn and your brakes have to stop. The general rule of thumb is that every 10 pounds of wheel weight equals 100 pounds of carried weight inside the Jeep. So by going with the 37s instead of the 35s, you effectively add another 400 pounds of cargo to your Jeep. That will be a significant drag in the horsepower department, and we haven't even considered the gearing situation yet. A 35-inch tire is about 8 percent larger than the stock Rubicon tire. You can, in many cases, get by with the stock axle gears (less true if you have an automatic transmission). The 37-inch tires are over 14 percent larger than the stock tires and will require a gear swap to make your Jeep more drivable and less of a pig on-road. If you plan to stick with 37s, are you sure you want to toss money into those stock axles that likely won't hold up?
Up front we pitched nearly all of our 3-inch lift kit. The only things we retained were the brake line extensions. Our Jeep has an aftermarket steel front bumper and a winch. The factory JK front coils are incredibly light to provide a good ride but they will compress under this additional weight. So in place of the aftermarket lift coils we installed the stock coils along with Daystar 3-inch urethane coil spacers and bumpstop extensions. We reinstalled the factory JK upper and lower control arms as well as the original forged track bar and sway bar links. The stock shocks were reused too but we fitted them with Rubicon Express extensions (PN RE2003). With everything in place we set the Jeep back on the ground and centered the steering wheel by adjusting the drag link. Make sure you get this adjustment as close to perfect as possible or the Jeep's Electronic Stability Program (ESP) will freak out.