flanders

I'm in the process of upgrading my suspension bushings and at the same time I also went with new toe arms (also called bump steer correction kit).
These arms can be set in a couple of ways and since I like to be a accurate I did some measuring to find the best setup, or the least bad one
I went with Hardrace but they are pretty much identical to Megan and maybe others as well.
Here they are with stock toe arms for comparison, I checked the weight as well, stock 900g and Hardrace 1200g.


Closeup, there are two different spacers included to offset the ball joint more or less.
The small one is 5mm and the big one is 10mm.


Here is my measuring setup, coilover and sway bar removed and spherical bushings installed in the control arms so nice and smooth movement.



This is what I got.

Since I'm measuring this at the brake disc it might be more at the wheel but relative to each other it should be pretty accurate.
Some calculator I used online said 1mm toe at 11" diameter is 0.103° and at 17" that would be 1.552mm.

Only curve I found to compare with was from this post https://www.s2ki.com/forums/s2000-ra.../#post21371536


My curves illogically converted for easier comparison

What I found a bit to late was that I should probably have measured at more droop but I'm not sure it would be relevant in real world.
My car sits at ~330mm ride height and full droop with no roll bar connect was 385mm.
I was a bit surprised that the small spacer seems to be the better choice since most people probably went with the bigger one instead.
Thoughts or flaws I might have missed?
Would be very interesting to have same measurement made on a facelifted rear end, I read someone claimed AP2 had no toe change at all which I find a bit hard to believe.

twohoos

Great stuff, thanks for doing this.

Could you clarify:
What's the difference between "spacer top" and "spacer bottom"?
Why do all the curves converge at one end? (Is this a coincidence? Are the measurements relative to the first point?)

flanders

Thanks.
All measurements have the same starting point at 360mm ride height
Big spacer on top means the toe arm sits further down from the hub, and small on top means it's closer to hub.
Here is a picture from robrob for easier visualization, it looks like the big spacer sits on top here (it's also an older designed toe arm but still same principle).

DanielB

From what I see in the picture, it looks like the dial indicator base is sitting stationary on a block on the ground. If that's correct, then I don't think you're measuring toe properly.

Toe is the difference in track between the leading and trailing edges. It looks like you are only measuring the leading track (using the disc as a proxy). As the wheel moves up and down, some of that change will be due to camber change and some due to toe change. In order to isolate the toe, you need the trailing edge measurement too (so you can calculate the difference).

An alternative would be to mount the dial indicator base to the suspension so it moves in sync with the hub assembly. I think that would be ideal, but not sure how you would actually do that with what you have.

Disclaimer: I have not done this myself so hope I am not missing something with the mental model I have in my head.

flanders

Yes dial indicator was on ground.
I was thinking the same thing about some of the toe change might be to the camber so I think you are right.
Should have put a bit more thought before measuring and maybe used two dial indicators setup one on each side of the disc.
Maybe the numbers are a bit off, but the results relative to each other might still be useful for comparison.

circuitclub

circuitclub