First triangulated 4 link Dana 60 axle

[JerryG]

Thanks to Liquid Iron Industries in Berlin, NJ we were able to modify the RK Suspension Pro-X Triangulated suspension to be adapted to a Dana 60 axle. I haven't had a chance to test the flex yet but on road rear bump steer is a thing of the past.

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[SierraBronco]

Niiiiiiiiiiiiiiiiiiiiiicceeeeee!!

Any idea what the weight difference is with the 60? Find all kinds of different numbers online

 

[JerryG]

Niiiiiiiiiiiiiiiiiiiiiicceeeeee!!

Any idea what the weight difference is with the 60? Find all kinds of different numbers online

I don't know the weight difference but I know it is now a 5600lb 2 door.

 

[SierraBronco]

I don't know the weight difference but I know it is now a 5600lb 2 door.

 

[Neps]

Bump steer from a rear axle, did you add rear steering too?

 

[SierraBronco]

Bump steer from a rear axle, did you add rear steering too?

Not bump steer in the conventional use of the word. Something that seems to be affecting a lot of bronco owners is the rear end stepping out when running over stuff like expansion joints or railroads. Our bronco didn’t have the problem, but my 2018 and 2020 rappy F150’s both did. 2022 is fine.

 

[KABQ]

Not bump steer in the conventional use of the word. Something that seems to be affecting a lot of bronco owners is the rear end stepping out when running over stuff like expansion joints or railroads. Our bronco didn’t have the problem, but my 2018 and 2020 rappy F150’s both did. 2022 is fine.

I've definitely experienced this (r/h lane westbound Montgomery at I-25 in front of the Maverick station, every single day), but I wouldn't call it bump steer.

 

[5GENIDN]

I've definitely experienced this (r/h lane westbound Montgomery at I-25 in front of the Maverick station, every single day), but I wouldn't call it bump steer.

I do call it bump steer. When the rear suspension cycles up and or down with the 5 link, that Pan Hard will pull the body and frame of the bronco to the passenger side as it travels on an arc. By pulling the frame to the passenger side a half inch or an inch that in turn angles the front tires to the driver side. Then as the Pan Hard returns to it's neutral position it reangles the front tires back passenger. The shorter the wheel base the more pronounced the frame angle is (and therefore front tire angle). Because the Pan Hard moves on an arc, when the vehicle is lifted and the Pan Hard is further away from horizontal in it's neutral position that same movement is larger.

So to me.... I hit a bump that cycles the rear suspension, the Bronco actually begins to steer driver and then back to straight ahead without adjusting the steering wheel at all... That is what I call bump steer. I minimize it by keeping my Pan Hard as flat as possible with a relocation bracket. You do not get any of that with a triangulated 4 link. The only other bump steer is associated with the geometry the IFS goes through during a cycle.... I find this to be less than what an angled Pan Hard puts me through. But I have that short wheel base that exacerbates that Pan Hard movement.

 

[Silver-Bolt]

Very odd upper link configuration. Never seen "bent" upper links. Looks like it starts as triangulated and ends up parallel.

 

[Arokcrwlr]

Triangulated in that the axle end is inboard from factory. The frame end uses the same mounts...

 

[5GENIDN]

Very odd upper link configuration. Never seen "bent" upper links. Looks like it starts as triangulated and ends up parallel.

The physics (active and reactive forces) still act on a straight line between the ends.... The "bent" bars are that shape only for clearance of existing parts.

 

[Demon4x4]

What modifications did you have to make to the RK Crossmember?

 

[KABQ]

I do call it bump steer. When the rear suspension cycles up and or down with the 5 link, that Pan Hard will pull the body and frame of the bronco to the passenger side as it travels on an arc. By pulling the frame to the passenger side a half inch or an inch that in turn angles the front tires to the driver side. Then as the Pan Hard returns to it's neutral position it reangles the front tires back passenger. The shorter the wheel base the more pronounced the frame angle is (and therefore front tire angle). Because the Pan Hard moves on an arc, when the vehicle is lifted and the Pan Hard is further away from horizontal in it's neutral position that same movement is larger.

So to me.... I hit a bump that cycles the rear suspension, the Bronco actually begins to steer driver and then back to straight ahead without adjusting the steering wheel at all... That is what I call bump steer. I minimize it by keeping my Pan Hard as flat as possible with a relocation bracket. You do not get any of that with a triangulated 4 link. The only other bump steer is associated with the geometry the IFS goes through during a cycle.... I find this to be less than what an angled Pan Hard puts me through. But I have that short wheel base that exacerbates that Pan Hard movement.

That's exactly what's happening to the rear suspension, but I think that's technically called roll steer (check me, though). Bump steer is caused by the front suspension cycling, not the rear.

 

[5GENIDN]

That's exactly what's happening to the rear suspension, but I think that's technically called roll steer (check me, though). Bump steer is caused by the front suspension cycling, not the rear.

It may well be called roll steer.... I just know when I hit bumps... It steers me. That is just how I remember what is going on.
Roll steer just sounds so gentle compared to how it feels.

 

[87-Z28]

I think the nuance between bump steer and roll steer are best described in how they can be quantified or measured.

Bump steer can be quantified by measuring toe angle as a function of front end linear suspension travel or degrees per inch. Under jounce the front wheel will change its toe angle inward for oem suspension and outward during rebound. A suspension can be designed that has very little or a great deal of change in toe with respect to travel. By changing kingpin axis and link geometry.

roll steer can be quantified by measuring toe angle as a function of vehicle roll angle or degrees per degree. As the vehicle rolls, one side of the front suspension experience jounce and the other rebound. This causes the same changes in toe angle but quantified differently.

“Rear” bump steer could be quantified by measuring changes to steering angle as a function of rear axle lateral travel. So not technically a change in front suspension travel that affects wheel toe angle. But instead changes in rear axle lateral motion that puts stress on steering angle inducing an effect. Hence a different fundamental response. As @5GENIDN pointed out, wheel base and axle lateral motion are big players in this response.

EDIT. A horizontal panhard bar is optimal configuration to minimize lateral axle motion.

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