Gt40 suspension configuration and setup

[Mike Pass]

Now my brain has started up again. The issue of too much camber gain at the rear can be sorted by moving the inner top suspension mounting point. This can be done by making up some suitable strong brackets. If my brain keeps on working I will ask it to find some pics of these tweeks.
Cheers
Mike

 

[EGLITOM]

A couple of things popped into the remains of my brain.
I was always under the impression that spring preload was when you put a longer spring on the shock that there was space for. i.e. putting a 10" spring onto a shock which had 9" between the perches. In this way the spring was preloaded. This was done so that a soft spring would take the weight of the car at a sensible ride height. The spring would need to be compressed by spring compressors so that they could be installed.

Dear Mike

Its correct what you say, but only for the uncompressed shock. as soon you mount the shock and put the cars weight on it, the spring will be compressed by the cars weight and the shock(idealy) will move in. If that happens the length of the spring is the same independend from the position of the lower spring perch. The car will just sit higher if you wind up the lower perch or lower if you wind it down. but the absolute compressed length of the spring will not change. ONly if you wind it up that far, that the shock will be fully extended with the cars weight on it, you will be able to further compress the spring and put a real preload on it.

TOM

 

[Mike Pass]

That is true Tom. I was only trying to define what people actually mean by "preload".
A 10" spring preloaded onto a 9" shock will give a higher ride height than a 9"" spring of the same rating as it will reach the balance load in less distance.
Cheers
Mike

 

[Howard Jones]

Mike you are correct. The main issues with the original GTD suspension geometry at the front is kingpin angle. This in itself really doesn't effect overall grip levels all that much but it just make the steering heavy. The front does need to have some better adjustability however. Making new upper a arms with rod ends will allow a good camber/ caster adjustment. Unless the uprights are replaced then you will have to live with the heavy steering.

At the rear I did just what you are suggesting. I made some new mounts that move the top inboard link pickup point upward and use a rod end link instead of the original bush link. I am getting about 2 degrees of camber gain now whereas before it was about 8 if I remember correctly. The car really is balanced now on street tires at .5 neg front and .75 neg rear. I am using 5 degrees of caster at the front and just about straight up and down at the rear. Toe is set to 1/16th of an inch on both sides.

 

[Mike Pass]

Pics of rear pickup modification on Roy Smart/ Paul Thomson GTD. Very quick car.
Cheers
Mike

 

[Mike Pass]

Same pics as jpeg
Cheers
Mike

 

[Mike Pass]

Pics of GTD front suspension using Mk3 Granada/Scorpio upright and the the "mushroom" adaptors which fit where the Macpherson strut normally goes.Mick Sollis at Southern GT can supply wishbones etc.
Cheers
Mike

 

[Howard Jones]

Ya, that's my car and those are the rear transverse link brackets I made, I had lost those pictures with a computer crash a while back. They are based on the geometry change suggested on D Bell's old web-page.

 

[Mike Pass]

Hi Howard,
Sorry, I thought they were of Roy Smarts GTD. I have got thousands of pics so I lose track. A very good mod especially with a soft suspension setup which has a lot of movement.
Cheers
Mike

 

[Howard Jones]

No harm, I forget where I put/get things all the time.

 

[Howard Jones]

Here's the front anti roll bar mod I spoke about, along with the rear one I made with it's adjustment tab.