924Board.org

[924RACR]

An interesting article in the back of RE, latest (May) issue, more or less the final column inside the back cover, "The Consultant," talks about cornerweight setup. It's a very interesting discussion, he's providing direction to an engineering student down under who plays with a Porsche race team. The main point I was looking at was the discussion of how to set up the balancing of the car. Rather than what we typically hear, to set the cross-weights as close to equal as possible, he advocated a different approach.

He labeled it as "unwedged," specifically to set the car up with an equal rear percentage on both sides, and equal left percentage at both ends. The example given was a 2000lb car, with 60% rear weight bias, and 55% right weight bias. The goal is then to have 60% of the right weight on the right rear, and 40% on the right front; likewise for the left, and concurrently on the rear axle to have 55% of the rear axle weight on the right. Specific to this example, we're talking:
FR: 440#
FL: 360#
RR: 660#
RL: 540#

This does not equate to equal cross weights, unless your car is balanced 50/50 both fore/aft and left/right.

This is suggested as a starting point; he then comments about further adjustment from there based on noted on-track performance (if assymetrical handling is noticed).

Thoughts?
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Joes924Racer]

Hey sounds like that would work for us 924s..Id
like to hear more assymetrical handling course though
I really need to stop and lower mine.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

[drivehard]

even with some weight jacking how would you get to those weights on our cars? I had my car weighed last weekend and was at LF 630 RF 657 LR617 RR 635. I dont have coilovers on this car but I could lower the back end with the torsion bar 1-2 inches and might get something like 45/55 balance. My current crossweight to the LF is 1265 and to the RF is 1273. My car turns great to the left and needs improvement to the right, it has very little bite and pushes way hard when on the gas. There is about -2 degree camber in the front and no camber dialed in the back.
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1977 924 daily driver
1977 924 project racer - parting out to be sold
1981 924 - New daily driver

[924RACR]

Suspension Clinic is now open!

OK, you're in fairly decent shape as it is; not bad. You've got a 1% bias weight to the front, whereas mine's 1% to the rear, which is interesting - must be the weight of my cage. I should ask, are those weights with you in the car? Always setup with your body or equivalent weight in the car (I do it at work, and so have shot bags to put in (3x50lbs close enough) since that's how you'll be driving.

Assuming those weights are with you in the car. I'd say that setup looks very good. According to the article, you could make some adjustments to the weights (have the article at work, forgot to bring it home, so you'll have to wait to get that tweak), but I'd be more concerned about other adjustments. Why are you running no camber in the back? Is that to get the car to turn? Cause I'd say you'd be much faster with more camber (what tires are you running, are you racing or just DE?) in the back as well as maybe front too - I run 2.5-2.75 deg with race tires - but maybe you need more rear bar. Also, even the stock alignment settings are about 1-1.5 deg rear camber. OTOH, if you're still on stock suspension components, so many bad things can happen on track with that (suspension settings don't stay put and you can hit bump stops), we need to account for all those factors as well.

Best would be a full run-down on your suspension setup (springs, bars, shocks, bushings, and tires) and we can go from there.

Also keep in mind that, say, if you're running a single-adjustable Koni, you could always just dial the front left shock softer to deal with that push - if it's only when on the gas. That adjustment is the reboud setting, and making it softer will put more weight on the front left when you get on the gas, allowing it more bite and getting the car to continue to turn.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[drivehard]

weights with me in the car are: lf 695 rf 666 lr 687 rr667 crossweight to lf 1362 and to rf 1353. Things didnt change to drastically with me in the car. I run 205 55 14 victor racers at about 32-34 pounds now. My first autocross today with them on and I was very happy with the handling of my car. My push has nearly gone away. I dont think I had full horsepower and was putting down respectable times, but I got killed by a focus by 6 seconds.
I run HS SCCA bone stock 1981 car. Stock springs with Boge front and monroe rear shocks. They will be replaced before next month. I was contemplating getting the Weltmeister 250 pound springs for up front. I need to lower my ride height about two inches. I have the stock front sway bar on it. I have a good helping of body roll but the car is stable and predictable right now. Shocks and struts should help out even more. Rear camber is whatever stock is, I adjusted front camber myself to -2. While I put new struts in and rear shocks I may put in urethane bushings on the front control arms, there is a bit of movement but not bad. I want to stay in H stock and not have to run modified or prepared categories. I will get dusted bad in either of those due to lack of horsepower.
_________________
1977 924 daily driver
1977 924 project racer - parting out to be sold
1981 924 - New daily driver