[wicked93gs]

I found other issues with the drop spindles I tried...namely that by moving the spindle pin location upward, you also move the steering arm location downward in relation to the wheel....probably not a big deal for most people, but with my setup it became a dealbreaker. It severely limits you in tie-rod placement vertically.

Note: I am not talking about any particular drop spindle, just drop spindles that achieve their drop by moving the spindle pin upward.

 

[wicked93gs]

Does your design do anything in the steering game such as reduce bump steer?

I think I read somewhere that his shortened arm and relocated outer tie rod hole does do this....but I can't remember where I read that now.

As far as camber gain goes....its not only LCA/UCA lengths and angles. As a random example: A shorter spindle will also affect roll center:

A shorter spindle will effectively move the outer pivot points of the spindle...pulling down the outer pivot of the UCA, which to some degree undoes some of the effect of a shelby drop(or looking at it a different way allows for more of a shelby drop than the standard 1"). So without re-doing the shelby drop with only the change of a shorter spindle your roll center would effectively be raised. Of course...there are other ways to get around that, such as using a taller ball joint stud, which would effectively keep your outer pivot points where they were...but everything you change effects something else and has to be considered.

Beyond that, spindle height isn't the only thing that affects camber gain under cornering either. SAI for example does as well, an increased SAI will help high speed stability and return-to-center...but at the same time affects the camber as you turn the car, reducing negative camber on the inside tire and increasing positive camber on the outside tire(good for the outside tire, bad for the inside tire), but that's not the end of the story either, because increasing caster can fight this tendency as well and you end up with a rule of thumb that you want 1/2 the caster as your SAI. IE, 4 degrees of caster for 8 degrees of SAI, 5 degrees of caster for 10 degrees of SAI, etc.

Anyway, the point is that none of this exists in a vacuum, there is always more than one variable acting on a car's suspension so what might work perfectly for one car may be completely different for another leading to 2(or more) wildly different approaches that both work.

I am certainly no suspension expert and I have done a LOT of reading on the various factors included, but I am left with the feeling I know just enough to understand I don't know much of anything regarding suspension design and that if I can think of changes to the roll center, etc, there is certainly something else I am missing on a given design that might counteract such a change....or that such a change might not even be bad.

 

[wicked93gs]

I'm no engineer, butt I've read in a couple of places that for a road race car you want around the same degree for the caster and SAI.

I love this thread.

That would make it impossible to get the required caster in a classic mustang then, since the stock spindle has 8ish degrees SAI, but I don't know...maybe the road racing vintage mustangs are able to get that extreme a caster angle? Its quite possible though what I read with that rule of thumb applied to higher speed curves though. 🤷‍♂️ I figure that if you end up changing your spindles you are going to end up playing around with multiple different alignment settings until you find something that behaves the way you like anyway.

 

[wicked93gs]

I don't doubt that aftermarket suspensions can achieve it, but how about stock suspensions? I know there are some out there who road race on stock control arms and non-adjustable strut rods. I guess its pointless to ask that question though since they probably aren't competitive outside of stock classes.

 

[wicked93gs]

I currently run the upper arm with the standard one inch drop. But I also have it drilled for a two inch drop, which I've also used. It handles great at either location, but the two inch drop requires the steering tie rod to be mounted much lower at the spindle to reduce bump steer. I hate that term for our cars, straight axle cars have true bump steer, ours have bump toe.

How much caster is too much is the $64k question. The more caster you have, the lower the steering tie rod connection at the steering arm of the spindle will go, which affects bump steer, and will need to be adjusted.

You change one thing on these cars and it affects 3 more.

Thanks for that tidbit. Since I have front-steer theoretically the opposite would happen and the steering arm would rise instead, which might actually be helpful to me. It might just give me the push I need to go EPAS w/ a de-powered power rack.