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No control after adding 35" tires

35K views 73 replies 27 participants last post by  Laggy 
#1 ·
Ok so we added a 3.5" Rough Country lift to our 2015 Sahara Unlimited and it was fine, a few weeks later we took off the stock rims and tires and added 35" Toyo mud tires and 18" Fuel Rims (18" were also stock on this Jeep). Now I feel way to much play in my steering, and if I hit a bump while doing over 45 it wants to jump into the other lane??? I called the 4x4 shop that put the lift and tire/wheels on and they suggested adding a dual stabilizer bar??? Suggestions please???? I'm just wondering why it wasn't mentioned when adding these tires, they seemed to think they would be fine. And yes I know it's not gonna ride like a Cadillac but it would be nice to feel a little more in control of which lane I'm driving in.:confused: Thanks, Donna
 
#3 ·
If you have the Toyo Open Country MT's I have the exact same tire. They need to be run at a lower PSI as was stated above. I run mine at about 28-30 PSI, depending on outside air temp. Mine came from the shop inflated to 39 PSI and the ride and bump steer was terrible. 10 PSI in a 35" tire makes a huge difference in ride quality.
 
#5 · (Edited)
Yeah that is way high! Drop down to 30 and see how it rides. You may have to play around with the PSI to get it right but that will help a lot.

Also, your PSI will be higher if you've been driving around a lot today. So re-check it in the morning on cold tires and see where it is.
 
#8 ·
Yeah keep us posted. It should help a lot. And also FYIW, if you get your oil changed at a shop, they'll air them back up to the door sticker PSI. They have to by law I believe. But just make it a habit to check them after it's in for any work and air them back down. Your TPMS light *looks like this (!)* on the dash will come on below 35 PSI. But I find that far less annoying than dealing with terrible handling.

I was nervous about running mine in the 28 PSI range until I read around on here and found out a lot of guys run that pressure with these tires. So don't be afraid to experiment with different pressure til you find something you like.
 
#9 ·
Also, Check your Caster it could be your issue and may need to add Adjustable Lower front Control arms to get more of positive caster angle.
 
#13 ·
I agree. I did that just to try and be able to hold the steering wheel with 35s. helped somewhat. I went somewhere else and had the tires rebalanced and dropped to 29 psi. rode and drove like a new freaking car. the only problem then was the dual stabilizers. I found myself sawing the steering wheel, two was too much. back to one and everything is golden.:happyyes:
 
#14 ·
It sounds to me like you have Bump Steer not "play in the steering". Bump steer occurs when you hit a bump and the steering wheel turns. It is caused by the change in steering geometry introduced by RC 3.5" lift. Consider installing a "high steer kit" which corrects the geometry (track bar and dragline should be close to parallel and equal in length). AEV, Synergy and RockKrawler are some of the best ones. Keep in mind they are expensive compared to your lift kit.

Lowering the tire pressure will just create more friction (damping).
 
#22 ·
It sounds to me like you have Bump Steer not "play in the steering". Bump steer occurs when you hit a bump and the steering wheel turns. It is caused by the change in steering geometry introduced by RC 3.5" lift. Consider installing a "high steer kit" which corrects the geometry (track bar and dragline should be close to parallel and equal in length). AEV, Synergy and RockKrawler are some of the best ones. Keep in mind they are expensive compared to your lift kit.

Lowering the tire pressure will just create more friction (damping).
It could be bump steer, or it could just be tramlining. Tramlining is the tendency for a tire to follow ruts or grooves in the road surface. A wide tire with a short stiff sidewall tends to tramline more than a narrow tire with taller sidewalls. Toyo MT's tend to do this even with just a 17" rim, and would tend to do it more so with an 18" rim. Lowering air pressure will effectively give the tire a softer sidewall, which decreases the tendency to tramline. So there is more to it than lower air pressure creating more friction (damping).

I just changed from 35" Toyo MT's to 37" Toyo MT's, and I noticed an improvement in driveability, especially in less tendency to tramline. But when I got home from the tire store and went to measure how tall the tires were, to set my Procal, I found out that the 37" tires were exactly 37" tall. Wait a minute, since when were 37" tires 37" tall? Never! I checked air pressure, and the tire store had 55 psi in the tires. I aired down to 29 psi, and now the 37s are even better than they were before. Taller sidewalls and less air pressure definitely decrease tendency to tramline.

Tramlining is different that wandering. Wandering is caused by inadequate castor. And both tramlining and wandering are different than bump steer. Bump steer is caused by non-parallel alignment of the track bar and drag link.
 
#16 ·
I agree tire pressure may help relieve/reduce the problem but that would mean the JK is on the ragged edge of steering stability and something else is wrong. It's an RC lift ...

Either way, I hope it fixes the problem. :thumb:
 
#17 ·
I wonder what the net lift was. Handling/geometry gets progressively worse is lift height increases.

I run my 35" Toyo MTs at about 27psi but it also depends on the width of the rim, right? Chalking the tire is the only way to be sure. But yeah, 40psi is stupid high. The way it was explained to me, each one of these tires could support the entire weight of the vehicle - and then some. They're a bit overbuilt for our application.
 
#18 ·
Did the shop do a wheel alignment after the lift/tire install? If they did check your caster specs.
 
#21 ·
Start by dropping your tire pressure, since that's free. Then, if that doesn't do the trick, look at things to improve your caster, like the AEV or Rancho geometry correction brackets or adjustable control arms. Caster has a lot to do with directional stability, i.e., how easy it is to keep your jeep in its lane. The more you lift, the worse your caster gets, and less stable your jeep is at speed.
 
#39 ·
I am going to get one of those attenuators to help with the on road manners of mine. I saw all the positive reviews. Also, I have noticed that ASE Mastertech does not just give out compliments on things that don't deserve them and he had nothing but positive things to say. I figure of all the reviews I read on it the only negative ones seemed to be from people who hadn't actually tried it. For $129 it is worth a shot, I will be ordering after Christmas.
 
#40 · (Edited)
Congrats on the new Wrangler!!!!!!

Any time that you install larger wider tires, they just won't hold the road as well. Your square inch tire foot print is now larger on the pavement, and the tires just have a tendency to follow the imperfections and contour of the road more and this is normal. It's just a trade off.

There are a few area's of improvement available to you.

1. Chalk test your tires, to find the optimum pressure for them. This may vary somewhat front to rear.

2. Your caster (the angle that your wheel protrudes out in the front) should be 3.7 to 4.7 Degrees. If you have adjustable CA's, have it set to the max allowed, without screwing up your drive line angularity. You will need a reputable shop set this up for you, that understands Caster and Drive line Angularity.

3. Toe in should be for large tires 1/16" to 1/8", but no more than this!!!!!

4. Ad the Steering Attenuator, because it will also improve your feel at the steering wheel.

Good Luck on your new ride.........:thumb:
 
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