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Highest possible location of the upper A arms

derf - 17/8/04 at 12:56 AM

I have been working on the front suspension for a few weeks now, and am half ready to give up. My main problem is availability of upper ball joint.

Anyway without explaining it way out and dissccussing the cost of machining the ball joints to fit:

Can I put the top A arm mounts on top of the upper chassis rail?

derf - 17/8/04 at 02:20 AM

OK, discovered the answer on my own, not a good place to locate it, goes from neg to pos camber real fast, not good at all.

I'll keep playing with it, gonna buy a decent sized heim joint tommorrow and try that.

bad suspension pickup points

[Edited on 17/8/04 by derf]

Steve Hnz - 17/8/04 at 05:21 AM

Derf, it begs the question, do you need or indeed will you have that much suspension travel. Why not work out what shocks you`ll be using, their placement to give the standard setup of I think 1/3 bump , 2/3 droop & then see just how much travel you`ll have. You might find that your top ball joint is OK. Try a search on MK cars, They angle the top ball joint mount to take into account this sort of thing. I`m not sure what your uprights are but it could be you can modify your top wishbones to go some way toward meeting this. HTH, Steve.

Cita - 17/8/04 at 06:03 AM

I think i agree with Steve here Derf.The two pictures show a lot of bump (5" ?) which causes the massive camber changes.
I would'nt worry too much untill you get all the proper parts to play with the suspension.

derf - 17/8/04 at 01:30 PM

Thats just over 5 inches of travel. I have the shocks, and I am still working on fabricating the pushrod system (using yamaha r1 shocks. I would have had it done over the weekend, but I ran out of steel supplies, which I will be picking up today. If you look at the photo, I have already located the upper suspension points at the perfect place, gave me perfect suspension movement with no camber change, but the ball joint I had didnt fit right.

I'm expecting 3 1/2 inches of upward movement from the lower arm parralell with the ground with the spring partially compressed from the weight of the car.

leto - 17/8/04 at 04:42 PM

Looks to me like your upper a-arm might be to long even with a hemi joint. Hard to tell from the picture so hopefully I am wrong. The cortina upright, as per book, have very small KPI and take a comparably long upper A-arms. If you use book size A-arms with another upright the upper one will most probably be to long.

derf - 17/8/04 at 05:20 PM

I'm using westfeild A Arms, I Am going to spend the money today on an a heim joint, and also going to buy enough material to make another lower A Arm, If I can make it work with a heim joint I will, but I am not against building a new lower A Arm.

Oh yeh, the spindles came from a chevy s10, same as the stalker v6, which has the same size upper A Arms as me, but longer lower a arms.

pbura - 18/8/04 at 12:40 AM

quote:
Originally posted by derf
If you look at the photo, I have already located the upper suspension points at the perfect place, gave me perfect suspension movement with no camber change

Derf, that's because your wishbones are parallel. Really great for bump, but if you were to roll your chassis, you'd see sharp negative camber on one wheel and positive on the other.

Is the picture on the left full droop? The bottom wishbone looks about where it should be at ride height, i.e., with the centers of the lower ball joint and chassis pivots horizontal.

Is the problem that the upper wishbone's a bit too long? That could be either because of using the Westie lower bone, or the greater inclination of your upright, or both. If anything, I'd suggest putting the chassis brackets slightly below the originals. Your camber change should be in the range of about 1.4-1.7 degrees for the first 2" of bump, and not crazy positive in droop. If you do that, the camber change in roll should be all right.

Hope this makes sense, and helps a bit.

Pete

derf - 18/8/04 at 01:45 AM

The main problem is that the upper is too long, or you can look at it as the lower is too short.

Instead of rebuilding the lower A arm, I am going to extend them. I bought the wrong size tube or it would be done already. I am going to just extend the lowers, and move the top further back.

This friggin sux.

pbura - 18/8/04 at 03:16 AM

It looks like it's the shank on the rod end that's giving all the length. The rod end is female, unless I'm mistaken (you really need to turn them over to be able to tell ).

Can't see your upper wishbone clearly, but is it possible to instead have a male rod end fitted into a tube at that end of the wishbone? I think you'd be able to shorten by almost 2", and would have a camber adjuster, too.

I can probably find a pic if you're interested.

locost_bryan - 18/8/04 at 04:16 AM

Derf,

IIRC the lower arm should be parallel to the ground at static ride height, and the upper arm should slope down towards the chassis at about 10-20 degrees. This should give greater negative camber as the springs compress - perfect for cornering

Try lowering the inner mounts of the upper arm - this will also move them inwards. Might make the arm the right length (or not...)

my NZD0.02 worth

derf - 18/8/04 at 12:15 PM

If I lower it more than the other set of mounts that I made the tie rod will not let the arms twist up any more. In the lower position the upper arm has a 14* slope towards the chassis.