Control arms to increase shock travel, autocrossers?

[Shankenstein]

Originally Posted by SomeoneWhoIsntMe

more like this



/completelyserious

also... how does the drop upright save your CV's? distance from the differential to the wheel centerline is the same either way, the axles know about as much about suspension geometry as most of ft86club.

That's a mighty cool upright! Nissans get all the toys.

I see where you're coming from, and most likely I'm just a little slow tonight. Please bear with me while I walk through it from the other direction.

The suspension controls the distance between a point on the sprung mass and a point on the unsprung mass. Sprung mass point = body. Unspring mass point = LCA-to-knuckle connection

Drop spindles simply extend the offset between the wheel center and the LCA-to-knuckle connection. Since the wheel center is connected to the ground, the net effect is a "body drop" equal to the offset.

If you use adjustable spring perches to raise the ride height back to its original value, it will extend (rebound) the neutral position by the offset * motion ratio. As many people above have pointed out... that's not a bad thing.

Now that we're back at the original ride height, we look at the CV angle. Both the differential and the wheel are at the same height as before... so the CV angle doesn't change. High Five, SWIM!

Offsetting points isn't an area that I know much about. I've heard about this on hotrods... but it seems just as welcome on track cars, if the control arms are sufficiently overbuilt (stresses will be different, especially in cornering).

[wheelhaus]

Originally Posted by SomeoneWhoIsntMe

also... how does the drop upright save your CV's? distance from the differential to the wheel centerline is the same either way, the axles know about as much about suspension geometry as most of ft86club.

Here's another way to look at it...

A car being lowered in a typical manner puts the suspension control arms in a somewhat compromised position, ultimately affecting roll center negatively. The "drop upright" simply repositions the control arms of the suspension back to their ideal positions so the suspension's geometry isn't changed, but the car is still lowered. The end result is that you can relocate the wheel's position (to get lower) without ruining the handling.

This is effectively the same thing as the Whiteline roll center correction kit for the front end. Lower the car, but relocate the ball joints back to their original positions.

Also, the axle is still at a slightly different angle using these drop uprights, this won't change unless the diff is relocated. The purpose of these is not to correct the drive axles, but the suspension geometry.

[SomeoneWhoIsntMe]

Originally Posted by wheelhaus

Here's another way to look at it... ....Also, the axle is still at a slightly different angle using these drop uprights, this won't change unless the diff is relocated. The purpose of these is not to correct the drive axles, but the suspension geometry.

if you lower the car 2", all the axle sees is a 2" drop. it doesn't know or care if it got there by coilovers, lowering springs, drop knuckles, or anything else, all it knows is the wheel centerline is 2" above where it used to be in relation to the differential.

[wheelhaus]

Originally Posted by SomeoneWhoIsntMe

if you lower the car 2", all the axle sees is a 2" drop. it doesn't know or care if it got there by coilovers, lowering springs, drop knuckles, or anything else, all it knows is the wheel centerline is 2" above where it used to be in relation to the differential.

Correct, we're saying the same thing...? I was responding to your post where you were asking how it saves the cv joint and I am agreeing it only corrects suspension geometry, it does nothing for the drive axle angles... I misunderstood your post because it appeared you were asking a question.

[SomeoneWhoIsntMe]

@wheelhaus okay, I misread "the axle is still at a slightly different angle using these drop uprights". when you said different angle, it threw me off, my bad.

[Racecomp Engineering]

Originally Posted by SomeoneWhoIsntMe

Andy,

any chance you guys would come out with a speedway / afco eyelet shock mount onto a steel plate that fits the rear shock towers? it'd be nice to just run double eyelet shocks instead of the stock stuff.

I can look into it if you're seriously interested. No in-house CNC but we've got peoples we can talk to and/or work with. Not a bad idea.

- Andy

[SomeoneWhoIsntMe]

Originally Posted by Racecomp Engineering

I can look into it if you're seriously interested. No in-house CNC but we've got peoples we can talk to and/or work with. Not a bad idea.

- Andy

I'm not sure you'd need NC machines to create such a piece, you could probably farm the plate out to a waterjet / laser cutter and have them cut it out of mild steel, then with a simple fixture you could hold the steel clevis shock mount to it and construct the piece as a simple weldment. powdercoat it and pop two studs into it and you've got a cheap, durable mount which is easy to manufacture.

it's sprung weight anyway, and if you're milling it out of aluminum billet there's a lot of material waste and extra setups to chamfer both sides and such, even with a 5-axis machine.

you might even consider running some simple FEA on the plate... if you could decide that strength wouldn't be negatively impacted, it would be nice to add a hole into the plate and include a rubber grommet large enough for a braided hose to pass through so people have the option of running remote compression canisters

and yeah, I'm serious about planning on running such a setup on my own car, if you think it's something worth bringing to market I'd rather buy the part off the shelf than go through the trouble of making them myself.