Mustang II front suspension won't "settle" to consistent ride height - cant set toe

[Beagle]

Bumpsteer is what is says - BUMP steer. If it won't track the same way going down a smooth road that doesn't have truck ruts in it, and won't get back to the same height, I can't help but think something is binding...

[squirrel]

The problem is that the tie rod and the lower control arm are not parallel, so the ends of them swing in different arcs when the suspension moves up and down.



Moving the outer tie rod ends down should fix it.

[Bob Holmes]

^^^^^^^^^^^^^^^^^^^^^^


The relationship you need to worry about is between the steering link and the control arm. The problem has nothing to do with the relationship between the control arm and the ground. A control arm with a ball joint lower than the chassis pivot point can have some benefit.

[Beagle]

what I'm hearing is this will cause the front end to not achieve a consistent ride height at rest? (confused)

[squirrel]

this will cause the toe to change as the ride height changes. So, you can't set the toe because as soon as you move the car up or down, it changes. And the "darty" feeling is because the car is steering itself as the suspension travels up and down, such as when the car rolls.

[Beagle]

that makes sense, but I can't figure out why the front end won't settle. Maybe I'm not getting what Milner means by that. If you shove on the fender and let it settle and get a 2" gap, then shove on it again and it settles at an inch? I'd think something was binding. Maybe it needs some time to normalize?

[SuperBuickGuy]

here's mine


I honestly think something is screwy with yours.

[squirrel]

The problem is that the rack is mounted a few inches lower than it should be. Pretty common problem when you're trying to use a Ford V8 engine with a Pinto suspension.

[SuperBuickGuy]

you mounted the rack too low.

I think you can get spacers - then use heim joints to fix it....

[Loren]

I think I'm just saying what everybody else already is, but I'll post it anyhow...

There's really no way to isolate where the friction is coming from, if that's still a problem, other than disassembling to where each point of movement can be checked individually.

On that bump steer and rack location, what ever the c/l of the rack was lowered by as compared to stock, that's about how far the outer tie rods have to drop. Will require switching to Heim joints as noted, or to a spindle w/ a lower steering arm such as '78-up A/G body (or possibly Granada) and it's appropriate ball joints. If you're thinking of using more caster angle than stock (such as 5 degrees, and you might want to) then it has to drop a little more yet. As viewed from the front, the angle of a line drawn between the outer and inner tie-rod pivot c/l's, and the control arm outer and inner pivot (or bushing) c/l's, should be parallel at ride height.

Mustang II (and Pinto) front suspensions were originally designed for tiny 13" wheels and A78-13 tires. The tie rods mount higher on the spindles than other cars, and the thickness of the rack housing in addition to the fact it can't be dropped in the middle like a drag link adds to the clearance problem you get when using taller tires while still keeping the engine low. When Mustang II suspensions were first popularized in the hot-rod world they were being used on race cars where the engine setback was so great that the rack could be mounted in front of the crankshaft damper, or in older body styles where the engine would normally sit high enough that having the rack run under it was not a problem. (Back in those days Jegs had a chassis they were selling that used Vega components with the conventional drag link and lower tie-rod mounting but the much-simpler Mustang II fabrication scheme won out with most other manufacturers.)

My own Challenger uses a Pinto rack positioned under the crankshaft but attached to Gen III Camaro spindles that have that lower tie-rod mounting I'm talking about. The motor still has to sit rather high to clear but that was less of a problem in a custom chassis and I was using the extra space for oil-pan capacity anyhow.

[SuperBuickGuy]

I learned something -thanks Loren - I didn't know that the grenada and M2 spindles had different tie-rod centerlines.... I'm using Grenada rotors, but M2 spindles with adapter bearings to make up the difference.

[milner351]

Hm
using a stock M2 cross member, I thought I would minimize these issues - but I guess not.

So the angle of the lower ball joint stud at ride height is not a problem (I was concerned that it not being closer to perpendicular between the ball joint shaft and lower arm may cause some issues).

Raising the rack would present several issues - Even if I modified the fox double hump oil pan to look more like a typical sbc rear sump pan - I'd still have issues with the steering shaft from the steering column running through the middle of the engine mount. In fact - I had to use the same angle brackets SBG has on his fiat M2 rack to tilt my rack back wards to get the steering shaft to work.

I have Granada spindles - I'm not sure if they are a bolt in to all the rest of the parts - but I will check to see if they have a lower tie rod connection point that would solve this issue sans "Adaptor kit".

Thanks again guys - I'm a little miffed that the alignment shop didn't take one look at this front end and tell me to lower the outter tie rods immediately before spending a bunch of time/money monkeying with it.

[SuperBuickGuy]

seriously - get a refund from them.

$150 and your problem is solved

https://dagostinoracing.com/image/cache/data/MMTR-2-450x450.jpg

and I'll say it again, I'm glad you car didn't shift; you'd have tried to make this work and run the risk of a crash.

[squirrel]

Alignment shops don't know that stuff...hot rodders do.

[Bob Holmes]

To help inform the discussion:

http://www.longacreracing.com/articles/art.asp?ARTID=13

Cheap DIY bump steer gauge:

http://www.swmtscca.org/forum3/viewtopic.php?f=10&t=1640

I would suggest that you use the spindle you have and fix the bump steer. Unless you can guarantee that the new spindle has the same geometry, except for steering arm height, you may introduce new issues.