GTD Top Link Mounting Point

Calling all engineers…..after some advice please!

Having finally found the time to fit some brackets I’ve had made to raise the inboard mounting point of the top link,( many thanks to Howard for his help), I now have a few questions…..

1. Brackets - these are made from 4mm steel and raise the top link inboard mounting point by 40mm level with the webbing. They fit in exactly the same place as the original brackets with just a small slot needed in the webbing. Is this strong enough from an engineering point of view?

2. New top link spacers - 1/2” rod ends with steel ‘misalignment spacers’ each side. I need to make additional spacers to fill the remaining gaps…what material should be used - does it need to be steel or is aluminium ok….grades?

3. Top link orientation ( warning, this could be a silly question!)….does it matter where this is placed within the bracket or should it be inline with the lower reverse A arm?…the reason I ask is that on the GTD the lower arm and top link are spaced with washers to change rear toe…I have all the washers on the front lower arm and had the same on the old top link….do I need to somehow replicate this?

Hopefully I can upload some photos.

Thanks in advance.
Cheers
Dave

 

[Mike Pass]

I would think that 4mm steel is strong enough.
The tapered spacers should prevent any binding of the ball joint. Thetapered spacers and any washers should completely fill the gap so that when the bolt is tightened it clamps the centre ball of the ball joint. I would use stainless steel fot washers as it won't crush and also won't corrode.
The idea of raising the inner end of the top link is to improve the action of the rear suspension which has too much camber gain in bump as standard. The basic idea is that when the car rolls due to weighr transfer the camber gain due to suspension geometry keeps the tyre flat to the road. The amout of roll is governed by the weight of that corner, the weight transfer due to cornering, the strength of the sway bar and the spring rate (and initially by the damper rating). The trick is to equalise the the camber change rate to the car roll rate so as to keep the tyre flat to the road in cornering.
To achieve this balance I have used 2 simple methods,
Corner the car hard, stop quickly and feel or measure the temperature across the tyre - an assistant will be needed because by the time you get out of a 40 it will be cool again!
Find a corner with a flat surface and corner hard. Get somone to take a pic of the car showing the rear wheel at a slight angle to the side of the car which just about shows the top and bottom of the wheel. Print the pic in the largest format. Put the pic on a blank sheet of paper and prick through with a pin at the top and bottom of the wheel and at two points on the horizontal road surface. Draw a line through the pin pricks and measure the angle between the wheel line and the road line. Now you know the actual angle of the wheel to the road under hard cornering. I did this many years ago on a race Ginetta G4R and found the same problem of too much canber gain in roll. We couldn't change the suspension design at the track so just altered the static camber. It ran with 1.5 degrees of positive camber down the straight but kept the wide slick flat to the road in the corners. Result was 2 seconds quicker per lap.
Cheers
Mike

 

[Bart Dirkx]

My two cents on the slot in the webbing. This might work, but mechanically it is not pretty. Stresses will concentrate around the slot increasing the odds of rupture. Now the bracket and bar become more important as they have to bear the load.
I would have expected a recess in the bracket instead such that it would remain just under de webbing. One of the options to reinforce the webbing is by welding a small plate on top covering the slot.