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Newbie Question - spring rates
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TOPIC: Newbie Question - spring rates

Newbie Question - spring rates 14 years, 7 months ago #2452

Here is a real newbie question for you. Rules say spring rates are free. How come everyone uses such low weight ones (350 - 400 lbs)? I'm used to running much heavier in a similar wieght/power car.

Pls. be nice, as I got a whole slew of newbie q's!


Re:Newbie Question - spring rates 14 years, 7 months ago #2453

  • JerryW
  • Endurance Racer
  • If you feel in control you arent going fast enough
  • Posts: 659
rear Torsion bars are limited. front springs are sized to balance -
Jerry Whitteridge
Norcal #552

Re:Newbie Question - spring rates 14 years, 7 months ago #2454

That makes sense (Torsion bars are new to me too!). Thanks Jerry!

Re:Newbie Question - spring rates 14 years, 7 months ago #2455

also the koni struts will only handle 400#'s

Re:Newbie Question - spring rates 14 years, 7 months ago #2457

Hey, Rob - nice to see you've found the Spec Boards.

Rob is a Midwest guy who has run an M3, but has tasted the 944 Spec Cool-Aide.

Rob - 30mm (or 31mm hollow) rear sway bar (max as per the rules) equates to about a 350lb effective rear spring rate. As the 944 is balanced front to rear (at Nationals, my car was within 30lbs at *each* corner!), most guys run 350lb front springs to balance this. This keeps us able to use low-cost off the shelf Koni yellows, and the cars work well with them.

Welcome aboard!
Eric Kuhns

National Director Emeritus

2007, & 2008 National Champion
2011, 2012 2nd

Re:Newbie Question - spring rates 14 years, 7 months ago #2460

As stated earlier t-bars are limited to 30 mm effective rate. There are two reason the first being it is the largest common off the shelf size. I will get to the second in a moment. So at the wheels it is about 330lbs-in. Stock was 128 lbs-in or something close to it.

Now front rates are free, but given the rear rate limitation and the need to balance the car you can't go above 400-450 else you have an understeering pig.

The other reason we limit spring rates is that the stock koni shock can only support about 400-450lbs-in spring rate. Beyond that and we would need a proper racing shock rather than a performance street shock. So by keeping spring rates moderate we allow for cheaper shocks.

Now this may sound like it makes for a soft car, but considering the cars are only 2600lbs with driver the spring rates do quite well and the cars are stiff and well composed. Sure they might be a bit better with more spring rate, but that will just add alot more cost due to the shocks need to control them.

If you were to run a 944 in non spec class with open springs/shocks our set-up would be good, but not ideal. However it would cost alot less. Our class has always been about good performance, but with an eye torward cost. So most rules have been designed to get 95% of potential performance at 25% of the cost. Going to 100% can double or triple the cost. Since we are a spec class we can just specific or limit to the cheap spec and everyone is still equal.
Joe Paluch
944 Spec #94 Gina Marie Paper Designs
Arizona Regional 944 Spec Director, National Rules Coordinator
2006 Az Champion - 944 Spec Racer Since 2002
Last Edit: 14 years, 7 months ago by joepaluch.
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