Suspension question..., ...probably for the racers amoung us Options

[BMXerror]

Anybody know the equivalent spring rates for some of the larger hollow torsion bars? 21-24 mm. I don't know what, say, '23mm' means in terms of spring rate at the wheel. Any help on where to find, or how to calculate such information would be great! Thanks.
Mark D.

[pcar916]

Long ago I measured the coil-spring equivalent rate for mine (solid 23mm bars) but I don't recall the lever-arm measurement. That's the distance from the middle of the torsion bar to the center-line of the wheel. Whip out your tape-measure and find that one!

Here's a site with a calculator and the terms included.

http://www.alternativecarparts.com/utiliti...orsionbars.html

The assumption with this calculator is the torsional resistance of our T-bars. If any of us knows the right number here please give it up. (IMG:style_emoticons/default/piratenanner.gif)

Don't include the splined portion of the T-bars in the length of the torsion bar.

Here's another one...

http://www.circletrack.com/car_racing_calc...r/photo_01.html

Here's another site with more general information.

http://www.spring-makers-resource.net/torsion-springs.html

Have fun!

[BMXerror]

Hey, thanks for the idea. I found another one, btw.
http://www.proshocks.com/calcs/torsionrate.htm
Basically I'm gonna need 21mm hollow bars in the front on 410lb springs in the rear. (IMG:style_emoticons/default/idea.gif)
.... Although, that calculator is also telling me that my 1" Speedway Engineering bar set at 5-1/2" is a 1203lb swaybar! Could that possibly be right? (IMG:style_emoticons/default/screwy.gif) Whatever it is, it works well!
Mark D.

[jd74914]

Is that 1203# at the wheel? Remember that there is another distance to the wheel center from the bottom sway bar mount.

[pcar916]

(IMG:style_emoticons/default/agree.gif) The sway bar is spring after all and has to be factored into the equation. That'll take car of the static calculation for it. But it's dynamics are harder to quantify since it's attached to the other side... which is moving constantly.

Note: A 1" bar (~25.4mm) with a 5 1/2" lever arm would likely be in that >1000lb range. Out at the wheel (longer lever arm) it'll be a lower number.

Depending on the weight of your car and where you've put things like fuel cells, batteries, and other heavy stuff (like which motor you have) there are lots of empirical threads on this board about how our cars are set up.

I like mine to handle like a cart. It's a 993 motor and heavier than some other engines. So so I put as many things in the front trunk as possible. Briefly...

Front:
23mm torsions
22mm anti-sway bar
Bilstein sport inserts

Fuel cell, battery, BIG oil cooler, fire system in the front trunk

Rear:
200 # adjustable height coil springs
Koni gas-adjustable shocks
no anti-sway bar

I dial in handling with a combination of tire pressures, rear shock settings and sway bar adjustments, in that order.

All of that said, good bushings and solid attachment points for the suspension will transform the car. I use Elephant polybronze bushings with great results.

You didn't say what you want to do with the car but 410# for your rears sounds a bit high. It depends on the rest of your car. On the street that will make you skip over the top of bumps rather than keep your tires planted. That's not really good on high speed turns.

Good Luck