renvagn

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It +1 But you would need to keep the torsion bar!

superloaf

this is a great thread--lots of interesting facts.

is there a chart for effective spring rates with different torsion bars sizes or an equation? i have some 26mm bars which i have yet to install and just wondering what the rate is to match the fronts.

also, does everyone agree that it's better to run equal size tires all around? just wondering why so few people actually do it.

and, finally, how much negative camber does the stock eccentric allow? is it consistent side to side and car to car or are all cars different?

thanks, thanks, & thanks.

Richgreenster

While we are on suspension set ups, what are most of you daily driver cars running on your alignment specs?

IanM

http://www.tech-session.com/kb/index...x_v2&id=22&c=4 (click on "rear spring rates vs effective spring rates" article)

Effective rate for a 26mm torsion bar is 189# That would match well with a 225# front spring (eff. rate 203#).

I personally run -2.5 degrees front camber, maximum postive caster, approx. 10 minutes total toe-in front, -1.75 degrees rear camber, 5 minutes toe-in each side rear.

superloaf

225 fronts was what i was leaning towards so that's good.

ian, with your maximum + caster, do you know how that affects steering feel or more specifically, steering weight? i have a manual steering rack & of course it's quite a bit on the stiff side and was thinking that by changing caster, the steering could be made lighter. i was thinking that by reducing the caster (less positive caster---around +2.5 IIRC) i could lighten the steering. any thoughts or knowledge on this? or any knowledge on which alignment setting affects steering the most?

(sorry for hijacking but this thread has really been enlightening on many suspension topics)

MAGK944

This is a great thread, good info. I am however a bit confused about the effective rate calculations used.

I always though that a coil spring in the vertical plane and directly attached to the hub at one end and the body at the other would have nearly the same effective and actual rate. The effective rate would only change when the mounting points change or the spring is inclined from the vertical. I would think that a rear coil-over setup on a 944 would have an effective/actual ratio very close to 1 and not 0.56 as stated. It sits almost vertical and has mounting points close to the hub. And that torsion bars would have a much lower ratio due to their position.

I could be completely wrong, (it's been 20 years since I studied mechanical engineering), but I always thought of it that way.

Mike

Scootin159

You are correct... but remember that our front struts aren't at a perfectly vertical. In order for this to happen, you would need a front strut that curved around the wheel and connected to the body directly above the ball joint.

MAGK944

Yes, I can understand the front strut ratio being less than 1 (0.96) to compensate for that, but why is the rear 0.56. In my view with coil-overs it should be much closer to 1 like the front.

Scootin159

Because the rear shock is rougly 1/2 the way down the length of the rear control arm. This gives the wheel nearly a 2:1 leverage on the shock. Think of it like a crow bar... the spring only moves 1/2 as much as the wheel.

MAGK944

I see, that makes sense, thanks Scott

Scootin159

Mike,

btw, did you ever get that torque tube?

MAGK944

Got it, thanks Scott. Experimenting with an aluminum tube to replace that heavy steel one. Someone here looked at this before but nothing came of it.

Scootin159

Actually I know that 2 or 3 were actually made, and exist in some member's cars on this board. I'd love to see someone make this a feasible cost-effective replacement, as that would be an easy 50lbs off the car.

MAGK944

Mike, sorry I've gone a bit off topic with this post.

Scott, I have got the bearings into the alu pipe and they fit perfectly. The trans housing was a bi#tch to get off, now attempting to sleeve the pipe to fit the removed housing, then alu weld a flywheel housing mounting square on the opposite end. It's a simple design, I shall start a new post with the details when I get further along with fitting and testing. The only problem is the cost of aluminum, the price of the pipe is around $300! Cheap for a 50lb+ weight saving though.

TonyG

I've run all sorts of coil combos over the years, but for a car that's driven to the track I use a 350/500lbs front/rear setup with Weltmeister sway bars.

This is about as much as I can take on the street.

This setup running R compound tires is very balanced at the limit and typically runs in the top 3 lap times of the day.


TonyG