Rear 3 link set up

[proey]

Hi guys i've been running this three link rear end for quite some time now and have never really played around with it. I'm going back to Bathurst in December to run the speed weekend and would like to set it up to get off the line as good as possible. I can adjust the single upper arm front pivot point up or down. The lower arms go from the front leaf spring mounts to brackets on the diff these I can adjust up or down at the diff. So does anyone have any suggestions on angles to use?

Thanks
Glenn

[Roger Miller]

Pictures ?

[Gary P.]

Here Roger

viewtopic.php?f=25&t=1869

[Roger Miller]

The lower links need to point up to body at ride height.

The diff rotates, pushes body up, increases weight on rear wheels etc.

Watts pivot as low as you go



That top link is just doing my head in thinking about it

[proey]

Thanks guys. I would have thought in a straight line the three link would behave the same as a 4 link. Around corners it would be a different matter though. Are there any books or sites that go into the theory of three and four link suspensions?

Thanks

[tonysesky]

i have been looking for the same info and i came accross this.
This might help.

http://www.raceglides.com.au/files/four ... r-tips.pdf

http://s-86.com/s-5linkrear.html



regards,
tony.

[proey]

Thanks Tony. The More info the better. It seems I was on the right track as the lower arms are angled up to the chassis and the upper arm is level at ride hight. I believe I had the spring rates a bit hard but I have softened it up for the weekend.


Cheers
Glenn

[Momus]

Three links are terrible things compared to well set up 4 links but they can be satisfactory if the housing is stiff enough to resist the diagonal flex they generate.
This years National sports Sedan champion, the Dean Randle owned Saab Chev is fitted with such a setup and a chassis mounted Watts rocker.

On yours it looks like it might have OK drag racing geometry but the link angle would toe out, ie move back the loaded wheel in roll/cornering which would be oversteery.
Cheers Marcus

[proey]

Thanks for the input Marcus. About the link angle, the pictures show the car in full droop. At ride height they are currently level as I realised last night when I finally got the thing back on the ground. Also the upper link is not at the top hole any more. I will try to post pictures tonight of current settings.

Thanks
Glenn

[maxrs]

I would point the trailing arm to where the front tyre lands on the ground.
Good luck getting out of the hole.

[proey]

Some Pictures

[maxrs]

The lower arm could go one hole up at the axle end.

[Momus]

Looks good now.
Your Watts chassis bracketing is pretty sturdy.
Was the slotted down post made from cattle rail RHS?
I see one on the damper lower mount. Have you grease nipples on all your pivots?

Cheers Marcus

[proey]

[proey]

[maxrs]

Pinion angle effects how the power is put though the rear.
Pointing the diff nose down will give you more forward motion faster from a standing start.
Without the suspension soaking up the power to wheelspin when you reach the bumpstops or end of spring travel.

[jsa]

Max,

Glenn doesn't have leaf spring wind up to contend with, so a large preset pinion angle won't do him any good.

The 3 link will allow only very small pinion angle change under power.

It would be best setup so that gearbox output shaft and pinion angle remain nearer parallel throughout suspension travel.

[maxrs]

Not using enough angle at the uni joints will cause vibrations when running at certain speeds. Dan?

[Roger Miller]

[jsa]

Max,

The vibrations occur when uni angles are not close enough to the same at each end.