Bump steer ?

[VA6489]

Bump steer will not be corrected by adding a Hydro assist. The track bar is shorter than the Drag link meaning that they swing in two different arcs. This delta is what causes bump steer. Adding shocks and hydro cylinders doesn't change that fact. By adding 7-8 degrees of caster you will mitigate the tendance to steer with every bump but you will not eliminate it.

Simplest way to visualize is take a long straw and a short straw. with a common pivot point move them thru their arcs. The short track bar has more side to side movement than the long drag link. This causes the steering to react to the bump and required driver input.

Adding a slave cylinder to this will only slow you input to correct.

Another way to mitigate this is to install a long arm front suspension, one that locates at the transmission crossmember. Remember this is all about geometry lessen the arcs reduced the bump steer.

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[VA6489]

Look at this video Bump steer explained visually start around 5:48

 

[Zachanadandy]

Bump steer will not be corrected by adding a Hydro assist. The track bar is shorter than the Drag link meaning that they swing in two different arcs. This delta is what causes bump steer. Adding shocks and hydro cylinders doesn't change that fact. By adding 7-8 degrees of caster you will mitigate the tendance to steer with every bump but you will not eliminate it.

Simplest way to visualize is take a long straw and a short straw. with a common pivot point move them thru their arcs. The short track bar has more side to side movement than the long drag link. This causes the steering to react to the bump and required driver input.

Adding a slave cylinder to this will only slow you input to correct.

Another way to mitigate this is to install a long arm front suspension, one that locates at the transmission crossmember. Remember this is all about geometry lessen the arcs reduced the bump steer.

Have you run a hydro assist? The cylinder is resistant to movement due to the pressurized cylinder. The 2" ram on my old XJ absolutely eliminated any bump steer or shimmy. Even when a tie rod end was worn out or the drag link was bent and the alignment was jacked. No it won't eliminate the effect of the diffrence in length, but it slows the movement so much you won't feel the bump steer in my experience.

 

[Kyle10]

Look at this video Bump steer explained visually start around 5:48

Okay thanks

Have you run a hydro assist? The cylinder is resistant to movement due to the pressurized cylinder. The 2" ram on my old XJ absolutely eliminated any bump steer or shimmy. Even when a tie rod end was worn out or the drag link was bent and the alignment was jacked. No it won't eliminate the effect of the diffrence in length, but it slows the movement so much you won't feel the bump steer in my experience.

Thats what I’m being told also

 

[VA6489]

Have you run a hydro assist? The cylinder is resistant to movement due to the pressurized cylinder. The 2" ram on my old XJ absolutely eliminated any bump steer or shimmy. Even when a tie rod end was worn out or the drag link was bent and the alignment was jacked. No it won't eliminate the effect of the diffrence in length, but it slows the movement so much you won't feel the bump steer in my experience.

Why yes I have and do run Hydro assist from my favorite company PSC. I do not use it to fix bad bad designs. While it might give an impression of helping it really does very little. The bump steer problem is one of mismatched geometry ( even you acknowledge that in you response). I am not sure why that is so hard to wrap ones head around. As the axle swings up/down the axle moves right or left. It has to due to the track bar ( Fixed link) the drag link in this case longer move in a different arc and hence you get uncommanded steering input due to rigid mismatched length. Preventing the Tie rod movement (hydro assist) slow the response to the axle movement. Simple mechanical engineering.

Exacerbating the problem is a big lift and short control arms. Now not only do you have bump steer but axle steer as well. Both react together to make for very uncomfortable tracking over bumps.

As with most builds, folks just start throwing stuff together with little to no knowledge of how all this interacts. OP has a beautiful rig from what I can see but there are several problem that can be addressed to limit the bump steer/axle steer issue.
1) Extend the track bar 4+ inches to the passenger side. Yes fabrication is required.
2) with 4.5+ inches of lift the Control arms should be lengthen to reduce axle steer. Assuming the current ones are OEM replacements.

Lots of work? Yes. Additional Cost? Yes. Cheap simple work around? ..no.

 

[Kyle10]

Why yes I have and do run Hydro assist from my favorite company PSC. I do not use it to fix bad bad designs. While it might give an impression of helping it really does very little. The bump steer problem is one of mismatched geometry ( even you acknowledge that in you response). I am not sure why that is so hard to wrap ones head around. As the axle swings up/down the axle moves right or left. It has to due to the track bar ( Fixed link) the drag link in this case longer move in a different arc and hence you get uncommanded steering input due to rigid mismatched length. Preventing the Tie rod movement (hydro assist) slow the response to the axle movement. Simple mechanical engineering.

Exacerbating the problem is a big lift and short control arms. Now not only do you have bump steer but axle steer as well. Both react together to make for very uncomfortable tracking over bumps.

As with most builds, folks just start throwing stuff together with little to no knowledge of how all this interacts. OP has a beautiful rig from what I can see but there are several problem that can be addressed to limit the bump steer/axle steer issue.
1) Extend the track bar 4+ inches to the passenger side. Yes fabrication is required.
2) with 4.5+ inches of lift the Control arms should be lengthen to reduce axle steer. Assuming the current ones are OEM replacements.

Lots of work? Yes. Additional Cost? Yes. Cheap simple work around? ..no.

EVO adj. control arms but they are not long arm

 

[Kyle10]

Why yes I have and do run Hydro assist from my favorite company PSC. I do not use it to fix bad bad designs. While it might give an impression of helping it really does very little. The bump steer problem is one of mismatched geometry ( even you acknowledge that in you response). I am not sure why that is so hard to wrap ones head around. As the axle swings up/down the axle moves right or left. It has to due to the track bar ( Fixed link) the drag link in this case longer move in a different arc and hence you get uncommanded steering input due to rigid mismatched length. Preventing the Tie rod movement (hydro assist) slow the response to the axle movement. Simple mechanical engineering.

Exacerbating the problem is a big lift and short control arms. Now not only do you have bump steer but axle steer as well. Both react together to make for very uncomfortable tracking over bumps.

As with most builds, folks just start throwing stuff together with little to no knowledge of how all this interacts. OP has a beautiful rig from what I can see but there are several problem that can be addressed to limit the bump steer/axle steer issue.
1) Extend the track bar 4+ inches to the passenger side. Yes fabrication is required.
2) with 4.5+ inches of lift the Control arms should be lengthen to reduce axle steer. Assuming the current ones are OEM replacements.

Lots of work? Yes. Additional Cost? Yes. Cheap simple work around? ..no.

If I order long arm. Do I just need lower front only ?

 

[VA6489]

If I order long arm. Do I just need lower front only ?

Do some research. Long arm systems remove both the upper and lower OEM mounting points and in favor of new mounting points closer to the Transmission cross member. Can this be done in the driveway or garage on jacks? Yes but I would rather be on a lift to do so. A front end install will take between 8 to 14 hours and welding is required.

An option is Artec bolt on system. I have not used this on any of my installs this kit is more user friendly ( read garage install) and can be bolted on. cutting the old mounts is still required. This should be follow up by welding to ensure nothing comes loose.

https://artecindustries.com/product...MI7qa_xb3XlAMVCTgIBR2N9RfCEAQYBSABEgI5m_D_BwE

AMW uses Teraflex in some of their builds

https://teraflex.com/jt-alpine-long-arm-bracket-kit-8-arm-3-6-lift.html

 

[VA6489]

Something else to consider is the rear track bar. This is shifting the axle in the opposite direction adding a Yaw component to the bump steer problem. In effect it magnifies it.

Not sure what you end goal is.

Tackle the front first. Then look at Rock Crawler or Artec for a upper triangulated rear suspension. this delete the rear track bar and improves the yaw (cross talk) between the front and rear axles.

Just finished up my JTRD long arm install (Artec Kit)

https://www.jeepgladiatorforum.com/forum/threads/another-gladiator-build-white-jtrd.89867/page-4

 

[Zachanadandy]

The bump steer you feel driving on road is in no way related to axle steer. Yes it's a real phenomenon, but you have to stuff 1 side and droop the other to get any significant axle steer even with short arms. Hitting a speed bump or pothole isn't causing any measurable axle steer unless you're control arms are very steep. I don't think many are running 6+" of lift on stock arm geometry so I'll bet that long arms will do little to nothing on road as far as bump steer. Bump handling is better as the axle doesn't try to move forward when impacting bumps/potholes. Of course geometry correction brackets have the same effect at 10% of the cost. No they aren't as good as long arms, but they are far more cost effective.

 

[VA6489]

The bump steer you feel driving on road is in no way related to axle steer.....

.....Hitting a speed bump or pothole isn't causing any measurable axle steer unless you're control arms are very steep.....

No way related, but then you say that it is.


There is a lot of math that goes into a good handling suspension system. Simple geometry plays a very important role in handling. Simple correction make a huge impact on how a vehicle handles. I am sure you have are at least familiar with NASCAR, a simple 1/4 turn of a Jack screw can make an ill handling car perform better.... 1/2 lb of air pressure solves a cornering issue...

Long arm suspensions swing thru a flatter arc than a short arm system does. Simple mechanical engineering. Move on side up or down and that moves that side forward or back a small amount. That DOES affect the steering. The less fore and aft movement the better the steering simple mechanics.
The angle at which the control arm also plays into the calculation. 4-5 inch lift in a short arm system has some rather steep angles and thus lots of fore and aft movement over bumps. Add to that the resistance to ride over the bump is greater. A flatter control arm will ride up and over a bump with much less resistance and have less movement fore and aft.

I do build a fair number of 4 link style suspension systems. I have never unsatisfactory result.

- Converted my Gladiator Daily to a Long arm system , removed about 70% of the unwanted steering input required. Softer ride over sharp bumps.
- Building a J20 Project Skelator with a good friend, designing and building the triangulated 4 link rear and 4 link front suspension with 14 inches of useable travel.
- 2017 JKURR double triangulated rear suspension and long arm front on D60. Runs more like a trophy truck than a Jeep .12+ inches of travel
- 56 F100 complete 4 link system front and rear. Yes it is a 4WD on tuned Coilovers.
- 2008 F450 Parallel 4 link Front and rear suspension on Air.
- Deleted a few AEV lifts ( geometry location systems) in favor of long arm and mid arm systems due to horrible handling characteristics and mount flexing.

Yes are there are "more cost effective" solutions... Cheap doesn't always relate to better. you get what you pay for. I will say that most owners do not know that a Jeep doesn't have to ride and drive like an Ox cart. Cheap fixes are seldom a long term solution thus not really cost effective.

But you did fix the 2KSB w/blow out front suspension and bent components solving bump steer issue with the addition of a Hydro assist Cylinder....

 

[Zachanadandy]

No way related, but then you say that it is.


There is a lot of math that goes into a good handling suspension system. Simple geometry plays a very important role in handling. Simple correction make a huge impact on how a vehicle handles. I am sure you have are at least familiar with NASCAR, a simple 1/4 turn of a Jack screw can make an ill handling car perform better.... 1/2 lb of air pressure solves a cornering issue...

Long arm suspensions swing thru a flatter arc than a short arm system does. Simple mechanical engineering. Move on side up or down and that moves that side forward or back a small amount. That DOES affect the steering. The less fore and aft movement the better the steering simple mechanics.
The angle at which the control arm also plays into the calculation. 4-5 inch lift in a short arm system has some rather steep angles and thus lots of fore and aft movement over bumps. Add to that the resistance to ride over the bump is greater. A flatter control arm will ride up and over a bump with much less resistance and have less movement fore and aft.

I do build a fair number of 4 link style suspension systems. I have never unsatisfactory result.

- Converted my Gladiator Daily to a Long arm system , removed about 70% of the unwanted steering input required. Softer ride over sharp bumps.
- Building a J20 Project Skelator with a good friend, designing and building the triangulated 4 link rear and 4 link front suspension with 14 inches of useable travel.
- 2017 JKURR double triangulated rear suspension and long arm front on D60. Runs more like a trophy truck than a Jeep .12+ inches of travel
- 56 F100 complete 4 link system front and rear. Yes it is a 4WD on tuned Coilovers.
- 2008 F450 Parallel 4 link Front and rear suspension on Air.
- Deleted a few AEV lifts ( geometry location systems) in favor of long arm and mid arm systems due to horrible handling characteristics and mount flexing.

Yes are there are "more cost effective" solutions... Cheap doesn't always relate to better. you get what you pay for. I will say that most owners do not know that a Jeep doesn't have to ride and drive like an Ox cart. Cheap fixes are seldom a long term solution thus not really cost effective.

But you did fix the 2KSB w/blow out front suspension and bent components solving bump steer issue with the addition of a Hydro assist Cylinder....

You described exactly what I said in long form. It's not axle steer under small suspension movements on road, it's control arm angles. The forces being transmitted almost 100% vertically due to flat arms is the improvement you feel on road. You get the same improvement with drop brackets. I've never run AEV brackets but looking at them next to the metalcloak ones I could see them flexing. Nobody is arguing that they are better than long arms, but only a fool would argue that everyone needs long arms and $5k in shocks for their Jeep to handle well. Some don't even wheel. Others don't drive their rigs over 65mph even on the freeway. Even with 3.5" of lift and drop brackets the JT handles great. Is it as good ad it would be with long arms and ADS triple tube bypasses? Of course not.

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