I've always been curious what the left/right balance of most C3s are. The front/rear weight ratio is discussed quite often, but has anyone done any actual left/right measurements?

Thanks.

 

I had my car weighed a week ago. The weight distribution was very even from side to side:



The weights are in kilos, so the side to side difference is about 22 lb over the rear axle and about 15 over the front.

 

What motor? Any weight loss mods, like alum heads, composite springs, etc?

 

The car has a small block with aluminium heads, intake and waterpump and the spare tire has been removed, other than that there's no mods that affect weight. That weight was measured with half a tank of gas and without driver. It's a no A/C car.

 

Tomi72,

Thanks for the information. It's greatly appreciated.

I always suspected that these cars were left-side heavy, particularly with a driver in the car. (Fine for circle-track racing, but not beneficial for sportscar driving.)
Putting the alternator and battery on the right side would have helped the weight distribution, but I suppose there were issues with the a/c compressor placement with a right-side alternator. The non-placement of the battery on the right side has always perplexed me, though. There's been a couple previous discussions regarding this issue, but none that made any reasonable sense to me.
It's on my list of things to do to swap the battery and alternator over to the right side.

 

While F/R and L/R weights are indeed important, don't overlook cross-weight percentages so as to avoid having "wedge" dialed into the chassis which will cause your car to handle differently in left vs. right turns. Wedge may be great tool for the roundy-rounders, but IMCO it's best eliminated (in as much as may be possible) for road racing, even where a predominance of turns are the same direction. Not speculating here, as I've actually tested both wedge and stagger on such courses and found any benefits cancelled out, if not outweighed, by the drawbacks.

Calculating: Add the RF & LR weights and divide by total vehicle weight to get the percentage. In the case of the example below, that's (365+370)/1467=50.1%, or only 0.1% of [positive] wedge, which is dang close. (Less than 50% would be negative wedge.) If you've got coil-overs, tho 0.5% + of 50% is generally accepted as within tolerance, IMHO there's really no excuse for not dialing out even this small amount if one is serious enough to have 4-corner scales in the first place. (Call it nit-picking if you will.) Suggest dividing any needed adjustments out over the whole chassis where possible rather than cranking it all in our out at one point (such as with a rear spring bolt) a la NASCAR on-the-fly pit stop wedge adjustments.

And, yes, it's entirely possible to have 0% wedge in a car with less than ideal F/R & L/R weight distribution, so you don't necessarily have to worry about somehow getting all four corners exactly the same to get the cross-weights right.


TSW

 

If you can get your crossweights L/R within 40-50LBs of equal, be happy and be done with it. You dealing with a 3000+LB car, thats less than 2% error.

First thing to measure is ride heigth, I take blue tape on the fenders and mark an even measurement at all 4 corners (like 30".) Start at the rear sping bolts, jack them around, go to the front and equalize the front springs by rotating the springs in their pockets, you can nail the spring down by drilling the lower A-arm pocket and putting a 1/4" stop bolt through it to keep it from rotating back. Recheck the rear, re-adjustment will probably be required now that the front has changed. recheck front once more and continue to go back/front until your happy.

If your jacking you springs and ride heigth is changing by more than 3/4" something should probably be moved in the Vette (like the battery from drivers, to passengers side) or you need to add some ballast weights to the light side (as a last resort.) You may also have to roll the Vette back and forth a few times between weighing to unload suspension wedge while making these adjustments.

This job is much easier done on later generation Vettes

 

I definitely agree about crossweight issues. I've got coilovers up front, so it's possible to eventually make sure there's no inadvertent wedge cranked into the suspension. The store-bought vehicle scales are a bit out of my budget, so I'm in the process of making some fixtures (4) to allow me to measure the corner weights using some bathroom scales I've got out in the garage.

Edit: I'm suspecting Tomi72's car is similar to mine in L/R weight distribution (I don't have a/c either). I did some calculations using a typical driver weight (85kg) and came up with a L/R ratio of 53%/47% (827kg/725kg). This has always perplexed me, as most road courses are clockwise and if Corvettes have to be unbalanced it would be nice if they were right side heavy instead.
Moving a 5kg alternator and a 14kg (typical) battery to the right side would give us a 52%/48% ratio. Not perfect, but closer to symmetrical weight than the stock reading.