How much should ST my car weigh?

[titanium]

I have been racing a 1994 Mustang in BP/STO since the classes inception.
One area that has always confused me was the additions and subtractions for the rear suspension.

The GCR says:
"8. STO and STU cars that come with a solid rear axle or trailing
arm suspension are permitted an aftermarket or fabricated rear
suspension. Cars with an altered rear suspension must add 50
lbs. Cars with live axle rear wheel drive may reduce the minimum
weight by 50 lbs in STO and STU."

So my car has the factory live axle with an aftermarket EVM 3-link.
Do I get a 50 lb reduction in my base weight or is my aftermarket rear suspension considered and 'altered' rear suspension?
And if so, why the convoluted wording of the rule?
What qualities in a rear suspension must be changed for it to be 'altered'?

 

[Ron Earp]

I'd assume altered means going to say the Cobra IRS setup. Even IT allows a trilink/watts/panhard as being within the scope of limited prep and not considered different from stock.

What is the EVM trilink? I'm researching rear suspensions for SN95s.

 

[Greg Amy]

I can understand the confusion. These rules are a combo of World Challenge specs and re-writes for the current season...

So, your weight depends on the installed engine. The stock engine was the 5L pushrod, correct? If that's true then your base weight is 2550#.

Keeping in mind the genesis of the class as World Challenge, it is my opinion (<-- please read that again) that "altered" within the context of WC means basically a total re-do of the rear suspension, possibly making it into an IRS. I'm not familiar with "EVM 3-link" but if in concept it's the same thing as what live axle cars can do in Improved Touring (such as what the first-gen RX-7s do) then this does not meet my definition (<--as in, my opinion) of "altered" and thus would be eligible for 50# weight reduction. So, your weight would be 2500#.

BTW, just in case I was unclear, this is my personal opinion. As in, not an official ruling.

I'll ask around, see if I can get more info on my opinion. - GA

 

[titanium]

An Evolution Motorsports Tri-link
Unfortunately, they went out of business about 18 months ago, but loads of information is out there on the intraweb.
The upper control arms are replaced with a single central arm, similar to how a 2005-up Mustang rear suspension.
Lateral location is done with a watt linkage.
Lower control arms are aluminum and have adjustable spring perches.
Here are some pics:

After this year's rules change requiring motors from production vehicles, my current engine setup is no longer legal.
I wrote the CRB, requesting a rules change a while back to allow aftermarket heads on a pushrod Ford 302. Their reply was 'use of a alternate engine is allowed', So I purchased the parts to duplicate a Ford Racing crate engine. Now that's illegal under the new wording of the rule....
Even with over 400 HP at the crank, I was 15 seconds a lap slower than the vettes and vipers at the Sebring Nationals in January.

 

[Greg Amy]

Opinion from another committee member, via email:

"IT mods are legal with no penalty. Alternate means they cut the pick up points out and started over."

So I purchased the parts to duplicate a Ford Racing crate engine. Now that's illegal under the new wording of the rule....
Even with over 400 HP at the crank, I was 15 seconds a lap slower than the vettes and vipers at the Sebring Nationals in January.

Rodney, the philosophy of STO is as an actively-managed big-bore class, limited solely by a power-to-weight ratio. Think A/B Production of yesteryear and/or World Challenge GT of today. If you've truly done everything you can within the STO rules, and you still can't make the power to keep up -- and we're not talking lap times here, we're talking basic power-to-weight -- then I'm pretty confident that the committee would entertain engine allowances to get you closer (heads, etc). But you've got to do your homework first, we won't do it for you.

STO is shaping up to be a truly big-boy, big-bore class. There's some deep pockets building cars there. But if you want to swim in the deep end of Club Racing's big-bore production-based-car pool, that's the place to go... - GA