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Avon front geometry
Northy - 1/7/09 at 07:59 AM

Mmmmm, is it right if built as standard?

I've been driving mine to work again for the last couple of weeks after about a 3 year lay-up and it doesn't seem right.

I have a feeling it has some nasty bump-steer (it's all over the place on bumpy roads) and when going round corners the outside tyre squeals.

Anyone care to comment? Anyone changed anything to improve it?

Cheers,


omega0684 - 1/7/09 at 08:13 AM

has the car been sat in the same spot for 3 years? you my have flat spotted tyres, this ould make steering and the whole ride quite bad


britishtrident - 1/7/09 at 09:38 AM

The tyre squeal is caused by a basic error in the positioning of the steering rack on the Avon -- if you look down from above the steering rack centre line is a few inches ahead of a imaginary line joining the centres outer track rod ends.

This causes excessive toe-in when cornering made worse by roll steer. This over loads the outside front tyre by putting an excessive slip angle on it and cause the inside front not to contribute to the cornering ----- hence the tyre squeal.

What is actually required is some toe-out when cornering, Ford achieved this on the Mk1/2 Escort and Mk3-5 Cortina by mounting the a couple of inches aft of the imaginary line joining the outer track rod end centres.

Not sure if the layout of the front of the Avon chassis will allow an easy way to rectify this.


Northy - 1/7/09 at 11:04 AM

Re we talking Ackerman here? As in it has the opposite to Ackerman (outside wheel turns tighter than inside?)

G

[Edited on 1/7/09 by Northy]


Northy - 1/7/09 at 11:54 AM

Well, I've just been outside for a look and yes, the outside wheel turns tighter than the inside wheel!

That's BS. Anyone fixed this?

G


Rudy - 3/7/09 at 06:14 AM

I have sierra uprights instead of escort and I had antiacheram, I solved this problem repositioning steering rack please read this : http://www.locostbuilders.co.uk/viewthread.php?tid=53010


Rudy - 3/7/09 at 06:28 AM

In the past I asked some Avon owner if they have akcheram or antiacheram and they say ackerham ... now I have some doubt. So Avon owner what do you car have ?


t.j. - 7/7/09 at 09:02 PM

quote:
Originally posted by britishtrident
The tyre squeal is caused by a basic error in the positioning of the steering rack on the Avon -- if you look down from above the steering rack centre line is a few inches ahead of a imaginary line joining the centres outer track rod ends.

This causes excessive toe-in when cornering made worse by roll steer. This over loads the outside front tyre by putting an excessive slip angle on it and cause the inside front not to contribute to the cornering ----- hence the tyre squeal.

What is actually required is some toe-out when cornering, Ford achieved this on the Mk1/2 Escort and Mk3-5 Cortina by mounting the a couple of inches aft of the imaginary line joining the outer track rod end centres.

Not sure if the layout of the front of the Avon chassis will allow an easy way to rectify this.


Oh, Oh...
I did use the steering-rack position....
Should I worry and leave it, Or should I take the grinder?


front clickie

[Edited on 7/7/09 by t.j.]


JacksAvon - 8/7/09 at 09:44 PM

I raced one for two years and did well with it. It was a standard build, handled great and went like stink


Northy - 23/10/14 at 12:32 PM

Well after a long time I'm hopefully going to find time to look at this over the winter again.

I'd like to fit wide wishbones to the car, but what about everything else? Did anyone figure out how to fix the bump steer and anti-ackerman?

G