This is my (very rough drawing) concept for mounting an upper A arm without large permanent alterations to the lower frame rail. I have not fully worked out the details yet I need to get it into CAD

The only permanent and easily repairable modification I hope to have to make is cutting a rectangular section out of the sheet metal above the lower frame rail to fit the suspension points. The suspension would not be attached to the lower frame rail, it would be attached to the vertical "bar"

[This message has been edited by zkhennings (edited 01-28-2015).]

looks to me like you'll run out of room, your coilover doesn't show a spring on it, which means you'll have even less space, and then you have to fit an axle in there too....

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The poor man's version is already found in such places as the Ford Fusion and Dodge Stratus.
As a plus with adapting Stratus parts, they're already 5x100

Tall knuckle suspensions with the upper ball joint above the top of the tire do not have good camber gain. That's not a design to emulate.

I was looking at different spindles on the locost site .The miata rear suspension is very popular for locosts .I think that spindle could be a good starting point , can't use it as is because it is 4X100 .Also , it is designed for a very short upper CA , something I figure we are forced in to because of the lack of space .

In reality everything would exist on separate planes with the shock/spring and "bar" on either side of the axle, that is the only way that I can see everything fitting. I could also mount the shock very low and have it attach to the "bar" around where the upper arm would attach. I am planning on a twin trailing arm setup with two lateral links on the bottom to control toe and a single lateral link tying to the "bar" on top.

If there is not enough space for a twin trailing arm setup then I will most likely have to use two "bars" and run the control arm to the outside of both bars with the shock running in between the two bars.

Kurt, I have seen that style of double wishbone suspension before and considered that idea, but as Will said it does not perform very well, I would rather stay with the strut suspension than do that. Also adds some unsprung weight.


Will you could probably answer this, how does a rear suspension with no passive steering/toe change feel to drive, AKA in your opinion is it beneficial to design in some passive rear steering?

The best systems generate no toe in jounce and rebound, rather, they generate small toe changes through bushing deflection under lateral loads. You'd want the rear outside wheel to toe-in slightly to induce a bit of understeer.

quote Originally posted by zkhennings: Will you could probably answer this, how does a rear suspension with no passive steering/toe change feel to drive, AKA in your opinion is it beneficial to design in some passive rear steering?

I haven't actually heard much about it either way... which tells me it's not a definitive advantage or disadvantage... or even a significant parameter in system trade studies.

I've read about different drivers liking it different ways. It may just be driver preference.

The '88 rear end has toe change built into the geometry, not the bushing deflection, for example. This is set up to toe the outside rear in slightly to promote understeer as the body rolled in a corner. A large majority of modern cars have some sort of passive steering built into the suspension. I think this is primarily for driver confidence and predictability of the car as it approaches the limit. That's NOT to say that it is for the confidence of *good* drivers...

Alternatively, the 308, 328, 348 and 355 Ferraris use dual H-arm rear suspensions which not only are not designed for toe change, the basic dual H-arm architecture is incapable of bump steer. The later models may not have any either, but their geometry is not as easily understood from looking at photos. This is also true of Jaguars, TVR's, older Lamborghinis, etc.

You can also look at the current Lamborghini Aventador rear end and see that it does not have dynamic toe change.either.

[This message has been edited by Will (edited 01-29-2015).]

quote Originally posted by Will: Tall knuckle suspensions with the upper ball joint above the top of the tire do not have good camber gain. That's not a design to emulate.

As compared to the stock strut, I'd still say it's a step in the correct direction.

Why?

I wouldn't, because it's perfectly easy to set it up wrong.