HDK Bump Steer 101

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autoxcuda said:
But I was just afraid someone reading this would assume you had .000"
toe change or .00 degree toe change. Then see some other suspension
with .040" toe or .05 degree change and think that was bad.

People in this thread are trying to draw comparisions to other K-members,
kits, and suspensions. Nothing wrong with that. But please just compare
apples to apples or put things in the same apple level.
Click to expand...

Thank you for the information; that is a valid point.

I think Denny originally performed this test as he did because the request
for that information was mentioned numerous times in various threads here
as time passed.

However, before commenting, I looked at the RMS and QA1 sites (I'm afraid
I didn't know where else to check) and didn't find any bump steer specs on
any of them. The RMS site in particular has a lot of information but try as I
may I couldn't find comparative bump steer data. (Please correct me if I am
wrong).

I realize that this is primarily a function of how well the rack is positioned.

That is why I stated early on that it would be nice to see results from other
kit mfg's and I am still waiting to see if they compare favorably.
 
autoxcuda said:
They just did that to replicate the factory upper control arm ball joint angle. It just keeps the ball joint sleeve closer to perpendicular from the spindle at ride height. Some compensation for the tilt the anti dive angle put on the upper control arm.

Nothing to lose sweat over, IMHO.

It really doesn't matter. Because that angle from the side view doesn't change enough to over extending the angle of the ball joint stud to the sleeve. That angle doesnt change much at all. And an upper ball joint tilted a little is fine. That why it's a ball joint.
Click to expand...

Steve,

I see...perhaps the application being for rear steer spindles is what threw me off. I am not used to looking at tubular UCA for them.

I am always curious when I see a non-stock part....thanks for replying
 
DR HEMI said:
Thank you for the information; that is a valid point.

I think Denny originally performed this test as he did because the request
for that information was mentioned numerous times in various threads here
as time passed.

However, before commenting, I looked at the RMS and QA1 sites (I'm afraid
I didn't know where else to check) and didn't find any bump steer specs on
any of them. The RMS site in particular has a lot of information but try as I
may I couldn't find comparative bump steer data. (Please correct me if I am
wrong).

I realize that this is primarily a function of how well the rack is positioned.

That is why I stated early on that it would be nice to see results from other
kit mfg's and I am still waiting to see if they compare favorably.
Click to expand...


Dr Hemi, you are correct, my intention is to show that there are NO bumpsteer issues with the HDK, not necessarily that the wheels stayed 100% perfect thru over 6" of travel, but I did get any see-able toe movement...let's just say c-hair close (WV technical term)....I will let the pics speak for themselves.

I think Steve has a valid point for comparison sake.

thanks all for your comments.
 
HemiDenny said:
Steve,

I see...perhaps the application being for rear steer spindles is what threw me off. I am not used to looking at tubular UCA for them.

I am always curious when I see a non-stock part....thanks for replying
Click to expand...

They threw me off too when I first saw them. That's exactly why I took the picture of them next to a stock A-arm. Then they didn't look so strange to me. :D

Same idea would work for any UCA bolted to factory located UCA pick up points on the chassis. It's just not a necessity.
 
No argument that the results using a digital instrument are inherently more
precise than with an "analog" method. However, at least the fact that you
were checking 13" out from the tip of the spindle insures an extra measure
of accuracy compared to if you were using 7.5" as your reference point.

Kind of like using a 12" degree wheel to set up a camshaft vs. using a 6"
wheel.

Thank you. Good information from all.
 
Hard to tell from your photos Denny, but it appears the tie-rod remains quite parallel to the LCA. This is key to minimizing bumpsteer! Since most cars don't have equal length tie rods and LCA's, the pivots change during the arc of travel. If you set ANY suspension up with the tie rods parallel to the LCA with vehicle sitting on all fours you will have your best shot of minimizing bumpsteer through travel under both bump and unloading.


And was that a bch or a rch?
 
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