Bump Steer w/ Leveling Kit - Caused by Factory Tie Rod Angles ? - Chevy and GMC Duramax Diesel Forum
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post #1 of 16 (permalink) Old 03-29-2019, 09:19 PM Thread Starter
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Bump Steer w/ Leveling Kit - Caused by Factory Tie Rod Angles ?

I put a Tuff Country leveling kit on my 2019 Silverado 3500HD last fall.

The leveling kit included new upper a-arms, torsion keys, shock drop spacers, limit straps, and front differential drop spacers.

Lifted the front of the truck just under 3 inches ... leaving a slight rake to the truck (1/4 inch).

I now have a very slight bump steer, especially when going over bridge transitions at highway speed.

Nothing significant or dangerous ... just annoying.

I do however want to verify what is causing the issue ... and fix the problem.

My personal theory is the factory tie rods ... and the steeper angle placed on them after lifting the front end.

What are your thoughts ?

Has anyone else had this issue ?

Appreciate the kind feedback.

2019 Chevrolet Silverado 3500HD 6.6L Duramax (L5P) Crew Cab 4x4 SRW Standard Box High Country Loaded w/ Rear Entertainment Package, Fabtech 4” Suspension Lift w/ Heavy Duty Tie Rods, 35” Tires on 18x8.5 Vision Valor Wheels, Luverne Grille Guard w/ Parking Sensor Relocation Kit, Rhino Roll Bar (Sport Bar 2.0) w/ 8” Hella Off-Road Lights, Banks Derringer / iDash / Intake / DPF Back Exhaust, Fabtech Stealth Shocks w/ Front Limit Straps, Front & Rear Hellwig Sway Bars, Airlift Air Bags w/ Wireless Air, DuraFlap Mud Guards, S&B MAP Sensor Spacer, Kryptonite Heavy Duty Pitman and Idler Arm, Centramatics
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post #2 of 16 (permalink) Old 03-30-2019, 12:47 AM
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Did you have the steering aligned after changing the ride height? If you didn't then that is the first thing to do.

If the control arms were the same length the wheels would move together whenever the suspension compressed or extended. This would produce extra wear on the tires and suspension joints. To minimize this wear the suspension has a shorter upper control arm and longer lower control arm This causes the top of the suspension to pull in quicker as it compresses, tipping the wheel inward. This allows the tire contact patch to stay in nearly the same spot instead of scrubbing in and out.

By changing the angles on the suspension with a lift you have messed with this designed function of the suspension and thrown it out of wack. That can lead to the sort of thing you are experiencing. This isn't usually enough of a problem to cause concern but maybe you are more sensitive to these things than most.

You could have worn suspension parts that are acting up now that the angles have changed and you may need to replace a bunch of them to fix it. I don't think so though.

I don't know if what follows is your problem of course but is sure sounds like it.

When I was in school to become a for real Mr. Goodwrench we had some pretty smart people lecture to us. One talked about the problems that can come up with conventional parallelogram steering.

When you have a pitman arm and idler arm attached to the frame and a cross link between them they form a parallelogram. This is the foundation of our type of steering. From this parallelogram extend two tie rods that transfer steering to the wheels. The tierods need to pivot in line with the other suspension joints or they will swing in a different arc and steer the wheels as the suspension moves. All of the parts of this setup have specific geometric requirements and if they are not met the steering will not work correctly.

One common complication of messing with the suspension and steering is something called orbital steering. This happens when a bump in the road cause the steering to turn one direction and then a dip in the road causes it to turn the opposite direction. When you go over something like an expansion joint that isn't perfectly aligned the steering will turn aside without moving the steering wheel. After going onto the new piece of pavement the suspension will rebound and the steering will turn to the other side. If the shocks are weak it can continue to cycle from side to side as the suspension bounces up and down.

In stock configuration the suspension is designed to sit near the center of such irregularities so that they have minimal effect. When you change the angles on the suspension components it can put things into a condition that is less favorable.

These are the things to check.

Inspect the cross link to be sure it is the same distance from the frame on both sides where the frame passes between the pitman arm and the idler arm. If one side is even 1/4 inch higher than or in front of the other it will cause orbital steering.

Verify that the length of the idler arm from it's pivot to the ball joint on the cross link is the same as the length of the pitman arm from its pivot center to its ball joint on the cross link. Inspect that nothing is bent and that both the idler arm and pitman arm are solidly bolted in. Also verify that the steering gear isn't loose.

This next part is tricky. You need to know that both tierods are the same length. It isn't easy to find a place to measure from but you must do it. The stud on the tie rod ends might work. If they aren't the same length then they will swing in different arcs and steer the wheels differently as the suspension moves.

This is even trickier. You need to verify that the inner tierod ends line up with the control arm pivots when the steering is straight ahead. If the tierods ran at the same level as the control arms you could just sight along the control arm pivots and see if they intersect the tierod ends but they don't. You will have to find a line between the upper and lower control arm pivots in front and in back and then sight along that line to see if the inner tierod ends are in the right place. If they aren't then you will need to find out why. Is something bent? Is there a wrong part in the system? Is something worn out? Is the frame bent?

With a lifted suspension your steering will never be as it should be but it should be good enough that you don't notice it without looking for it. The better way to lift the front end is to use new suspension components that are designed to keep the geometry the same and just move the wheels. Anything that cranks up the torsion bars is messing with the geometry.

Last edited by mizterwizard; 03-30-2019 at 12:51 AM.
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post #3 of 16 (permalink) Old 03-30-2019, 06:47 AM
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I found that a pisk kit improved my steering situation. I am not cranked as high as your truck is but I’m about 1 3/4 inches higher in the front. Also added differential drop spacers. Had a little more play in the steering wheel and installed the pisk kit and went away. Drives like a stock truck now. Alignment after the install of pisk kit is necessary.
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Last edited by dasbill; 03-30-2019 at 06:51 AM.
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post #4 of 16 (permalink) Old 03-30-2019, 08:39 AM
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May need to de-crank your torsion bars some, can you post a picture of your angles? Sometimes the included diff drop doesn't bring the angles into acceptable range for the IFS to work well. If it were me, I'd replace the shocks and spacers for the adjustable shocks, add the pisk kit, upgrade tie rods and drop the torsions down an inch. What pressure are you running in your tires?
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post #5 of 16 (permalink) Old 03-30-2019, 06:26 PM Thread Starter
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Quote:
Originally Posted by TX_DMax17 View Post
May need to de-crank your torsion bars some, can you post a picture of your angles? Sometimes the included diff drop doesn't bring the angles into acceptable range for the IFS to work well. If it were me, I'd replace the shocks and spacers for the adjustable shocks, add the pisk kit, upgrade tie rods and drop the torsions down an inch. What pressure are you running in your tires?
Answers to questions:

1. Alignment was done immediately after leveling kit install. (of course)

2. Cognito PISK was installed same time as leveling kit.

3. Already replaced stock junk ACDelco shocks with 5100-series Bilsteins (no quality 3 inch longer adjustable shock I could find)

4. Tie rods are a planned upgraded in May ... probably ReadyLift tie rods designed for 2 to 6 inch lifts.

5. I agree in retrospect should not have went 3 inches of lift ... probably should have stayed around 2 inches ... was simply trying to level truck as much as possible front to back since I have air bags to avoid rear end drop when towing.

6. Running 70 psi all the way around. Replaced the junk factory Goodyear’s with Michelin Defender LTX M/S tires. I tow on a regular basis ... and have found this tire pressure to work the best avoiding airing up and down between towing. Carry 600 lbs of sand bags for winter traction in 2WD and to soften the ride of the rear leaf springs (it is a 1 ton).

Appreciate the feedback, and will let you know if the upgraded tie rods fix the problem. If not, going to lower the front back down an inch.
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2019 Chevrolet Silverado 3500HD 6.6L Duramax (L5P) Crew Cab 4x4 SRW Standard Box High Country Loaded w/ Rear Entertainment Package, Fabtech 4” Suspension Lift w/ Heavy Duty Tie Rods, 35” Tires on 18x8.5 Vision Valor Wheels, Luverne Grille Guard w/ Parking Sensor Relocation Kit, Rhino Roll Bar (Sport Bar 2.0) w/ 8” Hella Off-Road Lights, Banks Derringer / iDash / Intake / DPF Back Exhaust, Fabtech Stealth Shocks w/ Front Limit Straps, Front & Rear Hellwig Sway Bars, Airlift Air Bags w/ Wireless Air, DuraFlap Mud Guards, S&B MAP Sensor Spacer, Kryptonite Heavy Duty Pitman and Idler Arm, Centramatics
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post #6 of 16 (permalink) Old 03-30-2019, 06:56 PM Thread Starter
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Quote:
Originally Posted by mizterwizard View Post
Did you have the steering aligned after changing the ride height? If you didn't then that is the first thing to do.

If the control arms were the same length the wheels would move together whenever the suspension compressed or extended. This would produce extra wear on the tires and suspension joints. To minimize this wear the suspension has a shorter upper control arm and longer lower control arm This causes the top of the suspension to pull in quicker as it compresses, tipping the wheel inward. This allows the tire contact patch to stay in nearly the same spot instead of scrubbing in and out.

By changing the angles on the suspension with a lift you have messed with this designed function of the suspension and thrown it out of wack. That can lead to the sort of thing you are experiencing. This isn't usually enough of a problem to cause concern but maybe you are more sensitive to these things than most.

You could have worn suspension parts that are acting up now that the angles have changed and you may need to replace a bunch of them to fix it. I don't think so though.

I don't know if what follows is your problem of course but is sure sounds like it.

When I was in school to become a for real Mr. Goodwrench we had some pretty smart people lecture to us. One talked about the problems that can come up with conventional parallelogram steering.

When you have a pitman arm and idler arm attached to the frame and a cross link between them they form a parallelogram. This is the foundation of our type of steering. From this parallelogram extend two tie rods that transfer steering to the wheels. The tierods need to pivot in line with the other suspension joints or they will swing in a different arc and steer the wheels as the suspension moves. All of the parts of this setup have specific geometric requirements and if they are not met the steering will not work correctly.

One common complication of messing with the suspension and steering is something called orbital steering. This happens when a bump in the road cause the steering to turn one direction and then a dip in the road causes it to turn the opposite direction. When you go over something like an expansion joint that isn't perfectly aligned the steering will turn aside without moving the steering wheel. After going onto the new piece of pavement the suspension will rebound and the steering will turn to the other side. If the shocks are weak it can continue to cycle from side to side as the suspension bounces up and down.

In stock configuration the suspension is designed to sit near the center of such irregularities so that they have minimal effect. When you change the angles on the suspension components it can put things into a condition that is less favorable.

These are the things to check.

Inspect the cross link to be sure it is the same distance from the frame on both sides where the frame passes between the pitman arm and the idler arm. If one side is even 1/4 inch higher than or in front of the other it will cause orbital steering.

Verify that the length of the idler arm from it's pivot to the ball joint on the cross link is the same as the length of the pitman arm from its pivot center to its ball joint on the cross link. Inspect that nothing is bent and that both the idler arm and pitman arm are solidly bolted in. Also verify that the steering gear isn't loose.

This next part is tricky. You need to know that both tierods are the same length. It isn't easy to find a place to measure from but you must do it. The stud on the tie rod ends might work. If they aren't the same length then they will swing in different arcs and steer the wheels differently as the suspension moves.

This is even trickier. You need to verify that the inner tierod ends line up with the control arm pivots when the steering is straight ahead. If the tierods ran at the same level as the control arms you could just sight along the control arm pivots and see if they intersect the tierod ends but they don't. You will have to find a line between the upper and lower control arm pivots in front and in back and then sight along that line to see if the inner tierod ends are in the right place. If they aren't then you will need to find out why. Is something bent? Is there a wrong part in the system? Is something worn out? Is the frame bent?

With a lifted suspension your steering will never be as it should be but it should be good enough that you don't notice it without looking for it. The better way to lift the front end is to use new suspension components that are designed to keep the geometry the same and just move the wheels. Anything that cranks up the torsion bars is messing with the geometry.
Appreciate the detailed response. Good to see this type of technical feedback on the forum ... not just opinions.

My truck has seen almost no off-road (only maintained gravel roads) ... and has been driven like an adult ... I have a Polaris General UTV to be stupid off-road with. So highly unlikely anything is broken, bent, etc. Also, all parts were double checked and installed correctly (and meticulously) by myself and a friend who is an ASE certified mechanic (who is anal like me regarding proper installations). We even fully articulated the steering and suspension after the install to ensure no drivability issues existed.

I agree with you that it is likely related to a geometry change that occurred after the leveling kit install. In stock form, the tie rods were almost level from the center link to the knuckle connection at the wheel. As you know the out tie rod connects from underneath on the knuckle ... it would now be almost level if it connected from the top ... that is how much the tie rod angle has changed.

My theory is the factory outer tie rod cannot articulate far enough when the suspension drops now that the tie rod is at such a steeper angle than the factory ride height.

Will try to get some pictures this evening to better illustrate my theory and follow up on this post ... but thanks again for the detailed response ... made me think about some other possibilities to look at if upgrading the tie rods does not fix the problem.
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2019 Chevrolet Silverado 3500HD 6.6L Duramax (L5P) Crew Cab 4x4 SRW Standard Box High Country Loaded w/ Rear Entertainment Package, Fabtech 4” Suspension Lift w/ Heavy Duty Tie Rods, 35” Tires on 18x8.5 Vision Valor Wheels, Luverne Grille Guard w/ Parking Sensor Relocation Kit, Rhino Roll Bar (Sport Bar 2.0) w/ 8” Hella Off-Road Lights, Banks Derringer / iDash / Intake / DPF Back Exhaust, Fabtech Stealth Shocks w/ Front Limit Straps, Front & Rear Hellwig Sway Bars, Airlift Air Bags w/ Wireless Air, DuraFlap Mud Guards, S&B MAP Sensor Spacer, Kryptonite Heavy Duty Pitman and Idler Arm, Centramatics
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post #7 of 16 (permalink) Old 03-31-2019, 09:02 AM Thread Starter
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Attached is a picture of the tie rod angle on the driver’s side.

Also attached is the tie rods I am looking at ... notice the angle on the outer section to help avoid binding issues.
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2019 Chevrolet Silverado 3500HD 6.6L Duramax (L5P) Crew Cab 4x4 SRW Standard Box High Country Loaded w/ Rear Entertainment Package, Fabtech 4” Suspension Lift w/ Heavy Duty Tie Rods, 35” Tires on 18x8.5 Vision Valor Wheels, Luverne Grille Guard w/ Parking Sensor Relocation Kit, Rhino Roll Bar (Sport Bar 2.0) w/ 8” Hella Off-Road Lights, Banks Derringer / iDash / Intake / DPF Back Exhaust, Fabtech Stealth Shocks w/ Front Limit Straps, Front & Rear Hellwig Sway Bars, Airlift Air Bags w/ Wireless Air, DuraFlap Mud Guards, S&B MAP Sensor Spacer, Kryptonite Heavy Duty Pitman and Idler Arm, Centramatics
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post #8 of 16 (permalink) Old 03-31-2019, 01:56 PM
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So based on what you are saying, we need to buy longer tie rods any time we lift our trucks?

Or is this just a problem because the keys have been cranked so much?
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post #9 of 16 (permalink) Old 03-31-2019, 04:04 PM
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Not typically. It all depends on how much you lift, if you relocate the steering components to compensate and where the inner tie rod pivot is in relation to the control arm pivots. Typically there is enough adjustment in the tie rods to get a good alignment with a reasonable lift.

Ideally you would drop the steering gear box and the idler arm mount the same amount that you lift. Also the control arm pivots would also move the same amount. Doing this you would not have to turn the torsion bars at all. This takes a lot of heavy duty parts to work right though so most people just crank up the torsion bars and live with the consequences.

As an intermediate solution you can use drop arms on the pitman and idler that will put the cross link in the same relative position to the wheels as it was originally. There is a limit to this though because if the pitman arm gets too long it becomes flexy. If it extends out further, rather than just straight down, it will reduce the leverage of the system, which is the last thing you want with the typical taller tires that accompany a lift.
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post #10 of 16 (permalink) Old 03-31-2019, 05:18 PM
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That's why the tie rods are adjustable, as you crank the torsion bars to change the suspension height, the tie rods should also be adjusted to compensate for the change in geometry. Most people don't do it though or they buy the "upgraded" tie rods which also just so happen to align closer to instant center, this is how to limit bump steer. The change in the angle of the "outer section" (steering knuckle) improves that instant center geometry and improves bump steer, almost impossible to remove completely in a truck but you can get close.

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