Uneven tyre wear

[JohnD]

Swing axle cars must use shims, Rotaflex have a turnbuckle in the radius arm.   You could use the latter on a Herald, but would need to relocate the bolt holes in the rear outrigger, as the arm runs at a different angle, and in that system is more for adjusting toe.

johnny, sorry, I missed your question in answer to my post about raising the spring.   The camber change on swing axle cars is excessive, as the axle rotates in an arc centred on the U/joint.   Raising the   spring doesn't change that arc, but puts it in a range more towards negative, with the rest position dependant on load an d spring tension.    My best suggestion is - measure it!  See above for how to!

Rotaflex makes a large difference to changes from bump to droop, but it's far from perfect!

A model renders these results: 

	Bump	Neutral	Droop
Normal position	-1	+2	+8
25mm spacer (l”)	-1	+1	+5
50mm spacer 2”	-0.5	+0.5	+2

 

 

 

 

 

 

Which might be said to offer little advantage, but combine that, in Rotaflex, with a different wishbone bracket on the chassis rail, and you get this:

	Bump	Neutral	Droop
Standard bracket	-1	+2	+8 (as above)
“Racing” bracket	-2	-0.5	+3.5
Eickoff 'A’ bracket	0	+1	+3.5
Eickoff  'B’ bracket	+1	+1	+1.5

 

Differences from standard bracket

“Racing”        =25mm(1”) down. 5mm(0.2”) out

Eickoff ‘A’     = 44mm(1.7”) down

Eickoff ‘B’    = 66mm(2.6”) down

At one time I made a set of all three, to bolt on and try:

The Swedish engineer, C.H.Eikhoff described his two designs in C.H.Eickoff ‘-Rear Suspension Talk”, p9. Turning Circle Feb.1989 . He predicted, from theory and detailed engineering drawings, both the bracket position for the least strain (plunge) on the Rotaflex doughnut (Eikhoff A), and for minimum change in camber (Eikhoff B).
 

In combination, the optimum is this:

 

Wheel camber from bump to droop.

	Bump	Neutral	Droop
25mm spacer under spring PLUS “Racing” bracket	-1	-2	+1

 

Which I hope you will agree is  big improvement!

 John

Edited July 3 by JohnD

[Pete Lewis]

on swing axle if you want to change the rear wheel camber simplest is to fit a lowering block under the spring .

the  tyres shown dont have any major scrub wear 

but do show aging , side wear is low pressures , edge wear is tracking 

camber in road use wont wear the tyre 

Pete

 

[johny]

Yes I didnt fit the block thinking of camber as original spring sat so well but read lowering back helps to reduce oversteer. Seems then that I might not need the increased toe in as well👍

[Pete Lewis]

most small chassis spec for geometry asks fo 150lb on each seat , some later manuals give unladen specs, 

with the car in whats known as static ride height ( ie loaded up) there is zero toe at the rear wheels  

if the rears have toe in/out then you will get bunny hops on bumps etc

if you fit a lowering block or modify the suspension in any way you must reset/check the front and rear toe 

its the worst error for ripping tread and unstable handling setting that will transform the car if set correctly 

you dont need laser or 4 wheel kit to get within the triumph tolerances 

Pete