Caster and bump steer

[connor grimes]

after going to the 35's i'm noticing alot of shimmy when hitting bumps and especially when taking turns. front end is tight, hubs are good, just had it aligned when i got the new wheels. when i had it aligned my caster read 4.8 and 4.9. i'm wondering if more caster will help with this or am i chasing the wrong thing? considering getting the wheels balanced again. also i have adjustable arms all around

 

[BuildBreakRepeat]

Bump steer is almost always caused by aftermarket parts that affect the steering or track bar. Do you have pics/any info on what you have installed on steering or font track bar? That caster is just fine - and would only really affect the jeeps ability to return to center.

 

[Steel City 06]

Caster mainly affects return to center. You can try additional caster, but if you go too far, you could get driveline vibrations.

Consider getting Centramatic wheel balancers instead of continuously rebalancing the tires. The Centramatics will automatically rebalance every time you start driving.

 

[connor grimes]

Yeah my only gripe with the centramatics is the sound at low speed especially on trails , I’ve read it can be quite annoying .

 

[BuildBreakRepeat]

Yeah my only gripe with the centramatics is the sound at low speed especially on trails , I’ve read it can be quite annoying .

I’ve wondered about that - others like @jjvw have said it’s only noticeable sometime and not annoying, but I haven’t had the chance to give it a test.

 

[connor grimes]

My front end is:

zj tie rod /drag link
New ish ball joints
Adjustable track bar
OEM pitman arm

 

[jjvw]

Occasionally noticable, but not annoying. I need to be rolling next to a wall without windows before I remember the are there.

 

[connor grimes]

So you wouldn’t call them annoying ? I hate noises as I am always chasing them on my Jeep só the last thing I want is another sound to deal with but if it means always having a perfectly balanced wheel ; might be worth it . After owning them would you recommend them ?

 

[BuildBreakRepeat]

Interesting that you have stock location for track bar and pitman without a different style of steer and are still getting bump steer. I’m not an expert on other causes so I’ll let other chime in.

 

[Steel City 06]

I never found them annoying. I know exactly where the sound is coming from, and once you exceed about 5 mph or so they become silent. If there’s nothing for the sound to reflect off, I can’t hear them at all.

Imagine a pipe full of tiny beads. It’s not loud or annoying at all.

 

[Jerry Bransford]

What symptom exactly are you calling bump steer? Bump steer is caused by a steering geometry problem that forces the steering left/right as the axle moves up/down over bump/dips in the road.

Your 4.8/4.9 caster angle is a bit light for 35's, 5.5 would be better and make your Jeep track better. The only way to increase it however is via either adjustable length control arms up front or adjustable ball joints.

Shimmy when hitting bumps could be caused by something loose. Do this... with the tires on the ground, have a helper repeatedly make quick left/right turns with the steering wheel while you closely look at the front-end steering components for side-to-side slop or unusual movement seen at the tie rod ends, track bar mounting points, drag link mounts, or ball joints. Keep in mind that the tie rod and drag link are both mounted on ball joints so rotational slop/movement you'd feel by grabbing either and rotating them back & forth around their long axis is normal.

 

[connor grimes]

@Jerry Bransford that was the first thing i diagnosed having my buddy back and forth the steering and everything seemed tight no play, to make sure i torqued everything to spec in the front. thinking its a tire balance issue. i would like to get the caster adjusted, is it possible to adjust caster without having to get it aligned again ?

 

[Steel City 06]

@Jerry Bransford that was the first thing i diagnosed having my buddy back and forth the steering and everything seemed tight no play, to make sure i torqued everything to spec in the front. thinking its a tire balance issue. i would like to get the caster adjusted, is it possible to adjust caster without having to get it aligned again ?

Put an angle finder on the flat machined spots on the front of the differential. Shorten the upper control arms to add angle. You know the starting caster so just add a degree to the measurement off of the front of the housing. It will affect axle positioning slightly, but probably not enough to be concerned with extending the lowers.

After you're done, verify that the angle between the front driveshaft and the pinion is not excessive. Ideally it needs to be 3° or less.

 

[connor grimes]

Thanks !