Bump Steer

H

HondaXR250

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So i just got a 1999 TJ yesterday. I have done alot of reading on the bump steer, but im still not quite positive where to start or what to order/change. It does look like my drag link and track bar arent quite in parallel. If you look to the right (driver side), the drag link seems to go a little higher out of parallel. I thought a lower pitman arm would help. But have seen alot of people telling others to go back to stock. The guy told me it had a 4" lift. But after measuring the spacers on the springs, they are only 2". Might have a 2" body also, but i didnt look for it. Its sitting on 33x12.5x15. It looks a little like i might need to get control arm drop brackets, because they do angle upwards a little. As far as the castor, i wouldnt have a clue. The steering wheel is a little to the left when going straight, so may be alignment. It does drive straight, but the front wanders everywhere. Also does it look like i need longer sway bar links? Any help on where i should start, would be greatly appreciated. Thanks

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Looks like a budget boost. AFAIK, none of them come with a dropped pitman and it doesn't appear you have one either. You also don't appear to have a body lift, judging by the way the rubber inner fender guards are sitting on the frame.

You said you had bump steer...but then said it wandered all over. Bump steer means that the jeep will steer on its own when you go over bumps. It appears as though you have factory geometry in your front end, so you should not be getting bump steer.

Your control arms are fine. Don't move the mounting points. That is a thing on JK's for some reason, but not TJ's

If you have a wandering problem its possible you have worn tie rod ends, ball joints, bad alignment (toe) or some other loose or worn component up front. Search dry steering test and see if you are getting movement somewhere. Also look in the How-To section for DIY Alignment instructions.
 
You're not experiencing bump steer which is caused by improper steering geometry. You geometry is fine, everything is fine there. You can't 'eyeball' the drag link and track bar angles as their physical angles don't correspond to their actual operating geometry. The track bar especially is bent to clear components so that will fool you as to its real angle. The real angle can be described as what it'd be if you connected a string between its two mounting points.

By the way, the actual bump steer symptom is this... when driving over a bump or dip in the road fast enough to cause the front axle to move up/down, bump steer would be when the steering is forced left/right when driving over that bump/dip in the road. If you were to be able to physically raise/lower the front axle, the steering wheel would rotate left/right as you moved the front axle up/down.

I suspect your steering issue is alignment related. And since you're running stock control arms without an excessively high lift, your caster angle is likely still within specifications. So at this point I'd be checking and setting the toe-in angle so it's correct. No need to measure its actual angle though, all you have to do is measure between the fronts of the front tires then between the rear of the tires. You want the fronts of the tires 1/16" to 1/8" closer together than the rear... giving you the right amount of toe-in. Just a tape measure, wrench, and a big pair of pliers is needed to do this. And with a little care your toe-in adjustment will be every bit as accurate as what the best alignment shop can produce.

Here's a thread that goes into how to do it with very little fuss.... https://wranglertjforum.com/threads/how-to-align-your-jeep-wrangler-tj.85/
 
Thank you both very much for your info.

When i go over bumps and small dips, my steering does jerk left or right. But when i let go of the steering my jeep stays straight (as long as road is ok). My steering wheel is a little to the left when driving straight. Im suspecting that my toe is off also. I will try adjusting it when i get time to.

One last question....When i take off from a stop, i get a excessive rattling sound from under the hood. It sounds like my motor mounts might be bad. I ordered new ones, and a new transmission mount. Wouldnt hurt to replace them. But when i push side to side on the engine with my hand, im actually able to move it more than i think i should. Im guessing weak mounts are making the engine vibrate when taking off?
 
Bad transmission/motor mounts can cause several problems like that. Make sure you go with rubber replacements like the factory installed, aftermarket polyurethane mounts will pass buzzy vibrations into the passenger compartment.
 
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One question on the toe in. How exactly would i measure to be within the tiny measurement of 1/16-1/8"? I tried measuring earlier, and couldnt really get a good reading. Measuring a round edge of a tire, with tread sticking out here and there. Would it be best to use a sharpie, and make a centerline on each tire, and go from that? Still seems like it would be rough to get them 1/16-1/8", such a minute measurement. Thanks!
 
So long as you measure between the same points on the treads, it doesn't really matter where you measure between. Like the outer point of a tread block to the same outer point of the tread block on the other side.

Or you can buy a pair of 1" square aluminum tubes and after clamping them to the rotors, measure between them like here. As in that link I provided to you up above.

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I figured so. Ill measure from the same points.

I dont have a garage, so taking the wheels off out in the mud isnt an option right now :D
 
Ok so i dropped the tire pressure down to 26psi, adjusted the toe (twice), adjusted the steering wheel (twice), replaced front and rear sway bar links, replaced motor and transmission mounts. The mounts definitely took away alot of vibration, motor hop on take off, and even made the ride a little smoother. The steering wheel i still cant get straight, im guessing i gotta keep playing with it until its straight. The toe is now right, but it still wanders around on the road. When going over bumps, dips, etc., it will jerk left or right, just like when the wind blows hard. It doesnt seem quite as bad as before. But maybe there is a way to make it even better. Would replacing the old (possibly stock) steering stabilizer help any? Picture just because.

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I don't know if you have any trouble with those fender flares, but I raised mine 3" with 33's and tore em' to hell when I hit deep holes, scrapped em' out for flat ones
 
HondaXR250 said:
Ok so i dropped the tire pressure down to 26psi, adjusted the toe (twice), adjusted the steering wheel (twice), replaced front and rear sway bar links, replaced motor and transmission mounts. The mounts definitely took away alot of vibration, motor hop on take off, and even made the ride a little smoother. The steering wheel i still cant get straight, im guessing i gotta keep playing with it until its straight. The toe is now right, but it still wanders around on the road. When going over bumps, dips, etc., it will jerk left or right, just like when the wind blows hard. It doesnt seem quite as bad as before. But maybe there is a way to make it even better. Would replacing the old (possibly stock) steering stabilizer help any? Picture just because.

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How thick are your wheel adapters? Those wheels already have a bit of offset and if the adapters are too thick you have probably moved your wheel centerline too far from ideal.
 
Me and my girlfriend took it out night riding the other night. We ended up trying to go up a steep field, and it's rained alot lately. We had to back out, and we tweaked the body a little to the passenger side while backing out. We heard a noise slam the back, and figured it was a stick. Got out and looked, and the tire had grabbed the flare, ripped it off everytime except one. I ripped it rest of the way off, the yesterday morning remounted it with bigger washers and different bolts. I don't really off-road much, so should be OK. And thing is, those flares are absolutely the only thing I like on a wrangler. I don't like the look of anything else.
gatertamer said:
I don't know if you have any trouble with those fender flares, but I raised mine 3" with 33's and tore em' to hell when I hit deep holes, scrapped em' out for flat ones
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They are 2". They came with the jeep like that, and they convert to 6 lug Chevy rims. Explain what you mean when that happens please. I have 2" spacers on my Nissan frontier, didn't change anything handling wise. Thanks!
Blackjack said:
How thick are your wheel adapters? Those wheels already have a bit of offset and if the adapters are too thick you have probably moved your wheel centerline too far from ideal.
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HondaXR250 said:
They are 2". They came with the jeep like that, and they convert to 6 lug Chevy rims. Explain what you mean when that happens please. I have 2" spacers on my Nissan frontier, didn't change anything handling wise. Thanks!
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Usually a spacer is used to make a negative offset wheel fit a given vehicle setup rather than purchasing wheels with a positive offset. But there is a relationship between the distance of the wheel centerline and the ball joint centerline known as scrub radius. Your combination looks like you are pushing the wheel centerline too far out and this increases the leverage your tire puts on the wheel bearings, ball joints and steering linkage.
 
That makes sense. Unfortunately I can't do anything about that. I'll probably just have to deal with the steering. It isn't horrible, but will take some getting used to
Blackjack said:
Usually a spacer is used to make a negative offset wheel fit a given vehicle setup rather than purchasing wheels with a positive offset. But there is a relationship between the distance of the wheel centerline and the ball joint centerline known as scrub radius. Your combination looks like you are pushing the wheel centerline too far out and this increases the leverage your tire puts on the wheel bearings, ball joints and steering linkage.
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HondaXR250 said:
That makes sense. Unfortunately I can't do anything about that. I'll probably just have to deal with the steering. It isn't horrible, but will take some getting used to
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You will want to address this at some point as your current setup will increase wear on all the front end components and make the issue you have worse over time. In the meantime you might try increasing your toe in by an extra 1/16 and see if that helps.
 
Definitely will keep it in mind. They were toed in 3/8, I brought them out to 1/8. Taking them in another 1/16 won't be an issue, I'll give it a shot
Blackjack said:
You will want to address this at some point as your current setup will increase wear on all the front end components and make the issue you have worse over time. In the meantime you might try increasing your toe in by an extra 1/16 and see if that helps.
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