Pneall and bumpsteer on Classic Revival.

[Treeve]

Originally Posted by Tenrocca

Some more tinkering and measurements today.

Definitely no go on turning the pivot bolt around Mike, so got some half lock nuts - thanks for the tip. Heaps more room there now.

Took out the single 25mm spacer on the rack and got a bunch of 3mm washers to muck around with spacing the rack. I also took a measurement with the rack not spaced and the rod end on the top of the steering arm - result was as bad as it looked to the naked eye. Im probably running a bit more castor than standard now so again it might not be the same result for everyone, but worth taking a measurement if you have done this.

My question is which of the 2 lines (with the rack spaced 12mm and 15mm respectively is better. The ride height is around 240-250 on the x-axis in the graph. With the 12mm spacer I get <=1mm toe from 20mm drop to full bump, but at full droop it toes out to 9mm - this to me looks a little better than the 15mm spacer which has a lower maximum toe, but is not as flat around the ride height.

I dont think I can get much better unless I shorten the rack which isnt going to happen (power steering)

I'm used to seeing these charts with the axis the other way around, as it gives you a neater representation of the vehicle arm movement as you would normally look at the front edge of the tyre.

Also, normally you put the 'ride height' at 0, bump as positive and droop as negative from there. This helps evaluate how much of your suspension movement you're using - let's face it, you're rarely at full bump or droop, more likely within +/-50mm.

[Bender]

My 2 cents.
It is always better to have the least amount of toe change in bump.
Bump is when the tyre has the most load.
Compared to droop (less load than ride height).
Toe change in bump will cause darting when hitting one wheel bumps.
Also the front to squirm under brakes.

Bender

[Tenrocca]

All back together, did a quick fishing line wheel alignment (easier on a hoist) and took it for a spin today. Feels a lot better with the extra castor and urethane bushes, has a real go kart feel now and wheel centres much easier on the straight. Steering is maybe just a touch heavier - not sure how it would feel if you had a manual rack.

Final rack spacing I went for was the 12mm lower than stock, and a 10mm cone spacer with the rod end. I also machined the head of the bolt down to a chamfer to get enough misalignment clearance and meant I didn't need another spacer in there.