Centering the rear axle with 4-link on a MK3 Roadster

[Benchwarmer]

New to me MK3 a month ago. I am upgrading to coilovers and getting rid of the quad shock setup. I am trying adjust the ride height and I notice the rear end isn't centered in the car. It needs to move 1/2" to the driver's side. I don't really see any way to adjust it until I upgrade to the 3-link?

[Dave M]

What are you measuring off of to get the 1/2in? If it’s the fender lips know that the bodies are not perfectly symmetrical. You really need to measure off the frame and even that might not be perfect.

[Benchwarmer]

I measure off the tire horizontal to the lip at the top of the tire.
Body is off 1/4" as per measurement of the top of the fender lip to the frame.

[CraigS]

If you had adjustable upper links you could move it sideways. Otherwise don't worry about it.

[Norm B]

As Craig said, the 4 link is not really adjustable. If you have adjustable upper links and try to force the axle sideways with them you could setup a very undesirable suspension geometry and handling characteristics.
I did the upgrade to coil overs a few years ago. I kept the quad shocks by moving the mount on the frame back. There is no wheel hop and traction for launch is great.

HTH

Norm

[J R Jones]

Your frame may not be perfectly fabricated, but it is more accurate than bodywork.
As a reference find the center of the axle and the center of the suspension mounts. I would use the lower link mounts.
The component that locates and stabilizes the "three link" suspension laterally is the Panhard bar. I have used a Panhard on leaf spring race cars.
You could put a Panhard on your four link and that would improve handling during hard cornering.
If you use the Panhard to "jack" the axle against the (non centered) upper link location, a little is OK but a lot of jacking will cause upper link bind.
jim

[Benchwarmer]

Your frame may not be perfectly fabricated, but it is more accurate than bodywork.
As a reference find the center of the axle and the center of the suspension mounts. I would use the lower link mounts.
The component that locates and stabilizes the "three link" suspension laterally is the Panhard bar. I have used a Panhard on leaf spring race cars.
You could put a Panhard on your four link and that would improve handling during hard cornering.
If you use the Panhard to "jack" the axle against the (non centered) upper link location, a little is OK but a lot of jacking will cause upper link bind.
jim

Jim,

My plan is to upgrade to the 3-link in the future. Just trying to get the bugs worked out of the car prior to me doing it. I would anticipate it being in the fall of this year.

[ProfessorB]

On the subject of panhard bars on a link suspension, wouldn't it be better the longer the panhard bar is? Meaning that instead of the bar being attached to the axle near the center wouldn't be bettar if the attachment point on the axle was as far to the "opposite" side (Example: if it was attached to the right frame rail then shouldn't the bar be as long as possible and attached to the ale as far left as possible? The longer the bar is the less effect the "arc" would have moving the axle sideways...

[michael everson]

ProfessorB Thats exactly how it is on the FFR setup.
Mike

[CraigS]

Professor you have it figured out.
https://www.factoryfive.com/galleries/mk4/3-link-rear-suspension/

[ProfessorB]

Well, I got lucky.... I have just been reading up on things. My first project will be to "fix" my steering....but I can quickly see that I will never be "done". I've got a Mark 1 with 4-link....I wanns
a improve on it at some point.

[J R Jones]

On the subject of panhard bars on a link suspension, wouldn't it be better the longer the panhard bar is? Meaning that instead of the bar being attached to the axle near the center wouldn't be bettar if the attachment point on the axle was as far to the "opposite" side (Example: if it was attached to the right frame rail then shouldn't the bar be as long as possible and attached to the ale as far left as possible? The longer the bar is the less effect the "arc" would have moving the axle sideways...

We built one race car with a panhard bar, and with performance as the priority, we made it as long as possible, about frame width.
The alternative technology is a watts linkage with two lateral rods and a bell crank in the middle. The watts link method has no lateral displacement with suspension travel. We built the second team car with a watts linkage. (My 1983 Mazda RX7 had a production watts link on the live axle)
If one "trigs" the lateral displacement of an axle with a ~30-36 inch long Panhard and typical suspension travel, it is about 0.030in, or a spark plug gap. That is IMO (practically) nothing.
jim