Joshboody

Playing with scales for the first time. Results with me in the car:
883 884
834 793
49.4% cross weight
I weight 190-ish

Since fronts are even, would you jack weight?
I could add some weight to right cargo hole, but already kinda heavy compared to other vettes.

sway bars: my bars are neutral-ish so I didn't disconnect them. Plus unless you will adjust the links (feeling lazy), should keep connected so weights are equal to on track setup, right? Kinda a pain to drive up on ramps, so I may leave this as a future task.

acrace

Are you certain that the links are set up so that they're neutral? I've always scaled my cars with the bars disconnected and have on occasion checked corner weights with the bars connected to check the difference.

Also, I'd suggest scaling with the fuel load that is important to you and be certain that the scales are level.

Joshboody

Scales are level and fuel load close. I installed the links then checked them after driving... prob could get closer to 90deg but can remove easily on ramps. BUT don't you want to measure the track setup?

So would you jack, add, or do nothing?

chpmnsws6

I'd try to take a touch off that LR corner or see if you can shift weight without effecting ride height too much. Also: ride with a passenger much? If so, there is your counter weight. On my turbo Miata, I couldn't get it that close without making it ride 10x kind of funny looking. Without a link released from the sway bar, your kind of peeing in the wind.

rfn026

You need to disconnect the sway bar links.

Here's a guide to corner balancing.



Richard Newton

GSpeed

Cross weight balance trumps front corner weights being even.

Definitely disconnect the sway bars.

rfn026

I never even knew it was possible to get the left and right front equal.

I would also fill the tank to 1/2 full.

Richard Newton

Nokones

You should try for 50% cross weight. Don't be lazy otherwise you are wasting your time. Don't worry about the fronts being even. If you are about 20-30 pound difference from corner to corner to corner you'll be OK. I would try to jack the L/F to see if you can move some weight to the R/R. Hopefully, the cross will be getting closer to 50%.

Watch the front-to-rear weight percentage. Unless you have a totally adjustable suspension, like coilovers, or jacking pads on each corner of your spring, you might be able to adjust the left-to-right weight for 50%. If you can get 51.2 to 51.7% that will work just fine. Good luck with that. The most critical is the cross if you're making left and right turns on a road course or an autocross course.

Since, I am in the composing mode with this response, I don't remember what your other corner weights were. You'll need start jacking and/or unscrewing weight at each corner until you achieve the 50% cross.

Also keep an eye on your ride heights at all 4 corners and no it won't be even.

You do need to disconnect all sway bars and add the fuel that you want to use in race trim. Also, put the tire pressures at race trim pressures. If you are sitting in the car, perfect. If you are adding weights to your seat, make sure that all your weight is not just in the seat. I always check what is my leg weight as the position I am in while I am driving by putting my feet on a scale pad and place that weight on the floor near the pedals. Also, place about a 50 pound weight of the remaining pounds from the seat up against the back of your seat.

Make sure that your weight pads are bubble or laser level. If they are not perfect level, your 50% cross weight will not be accurate. I use a Longacre Adjustable platform to insure that I have a laser level plane. Roll ons/roll Offs will work also.

When you adjust either by adding or subtracting weight on a particular corner jounce the corner you were working on to make sure that you are not binding up. Make sure all the hoods, deck lids, and doors are in their proper position before you check the weight. When you do achieve the 50% cross and it stays there, take the car off the pads and drive it down teh street and back and put the car back on the scales. You shouldn't be more than 3-4 tenths of a percent off. If you were more than the 3-4 tenths off when you put the car back on the scales, you could have been binding the suspension during your jacking and unjacking the weight. That is why it is important to jounce and rejounce every time at every corner.

If your suspension is adjustable, perfect. If you're just adding weight in various places inside the car, you better be able to tie it down for your safety and the accuracy of your corner weight effort.

Joshboody

Thanks for the responses.

Doing this in the garage. First I tried driving up after leveling with water bucket and tiles, but this is fairly tedious since lowest to highest platforms are 18mm diff. Plus scale/tire placement is not very repeatable... have to get creative with ramps. So next I jacked each side onto the scales with salt/tiles and bouncing but after driving around there's still some settling. Basically trying to find the best method.

This session I kept bars connected and jacked 50% cross in the rear... about 1 turn up and down each side. Can do this while on the scales, so very simple. Also since I'm square tires I'd rather adjust rear to keep my rake which put me full down on stock pads.

Next session I will disconnect bars corner weight and neutral the links again if needed.

I'm learning

Racingswh

Thanks for posting this up!!

fmcokc

Now this suggestion brings about another question.

If you fill the car to 1/2 tank from nearly empty, is all the fuel sitting on one side of the car? How does that work as far as the distribution of fuel between the 2 tanks with the jet pump? Does it empty the passenger side tank first and then the driver side or does it pull equally from both tanks?

rfn026

Now that's a really good question. I have no idea.

Help!

Richard Newton

carefulnow

The best way to avoid the pain and suffering of rolling the car back and forth and back and forth is to get a set of hubstands.

Makes everything easy.

If you're just going to dial it in once and forget it, meh..

But, if you're going to play around with settings over time, probably worth while.

GSpeed

Passenger tank is emptied first. Main pump uses fuel to drain the passenger tank at all times via the jet pump. It uses Bernoullis principle to transfer the fuel.

You can rest assured that no matter what amount of fuel you put in, it will be just like on track.(gas pump fills driver tank first, then spills over to the passenger tank.

Joshboody

Good info! So if you use close to whole tank during track day, weighing at 3/4 or 1/4 might be better since spend most time around those side to side weight ratios. Instead of 1/2 tank.

RichieRichZ06

As Luis mentioned above, the passenger side tank empties first and fills last. In my opinion, I would run the car as close to full as possible and corner weight it with that fuel load. The fuel load will be even make corner weighting the car easier. After each session on track, top the fuel off and the car will always be the same.

If you run half tank (or less), virtually all the fuel load will be on the same side as you (the driver) so you'll be starting the corner weight process with huge adjustments and lot's of left side weight.

chpmnsws6

Speaking of which, why did GM put the priority tank on the driver's side? Wouldn't you want the fuel to counterbalance the driver?

Nowanker

Balanced A LOT of cars...
Drivers weight ballasted (and spread approximately to simulate the driver, as Nokones says)
Disconnect sways! Reconnect without preload while still ballasted.
Fuel load ~halfway from beginning of session to end. You'll be closest to on-track situation. (If you start at 3/4 and finish at 1/4, balance at 1/2) Fuel sloshes from tank to tank... oh well, can't really account for that!
Front tires pointed straight ahead, tire pressures set.
Set ride height where you want it, measure from a frame point close to the wheel and not off the body. (Plastic car...)
Level scales. I use an 8ft level and linoleum tiles as shims
Each adjustment affects the diagonally opposite corner most, but also the other 2 corners.
Raise one corner ("adds weight"), diagonal opposite lowers ("adds weight"), other 2 raise slightly ("subtracts weight")
Jounce the car all around after adjustments. If the car has a lot of friction in the suspension, better to drive it (SUCKS!).
My plan, for the track day/club race guy: Don't worry about F to R or L to R balance, we're not actually moving weight around in the car. Aim for 50-50 ratio diagonally. Different situations might call for something different, but barring some really specific things... get the cross weight even.
With enough aggravation, it's usually possible to get 50% diagonally and maintain very close to desired ride height at each corner. Not always... I usually split the difference btwn the 2 in that case.
The best part of all this? it's not a 1000 lb formula Atlantic, and we're not Max Verstappen. It's a 3000+lb production car, and I sorta doubt any of us will feel 20lbs!

Joshboody

Well the theory behind weighing at 1/4 or 3/4 fuel load is due to ratio between sides considering fuel is transferred to the left side. At 1/2 tank this is your largest diff in side to side ratio at 9:0 but 1/4, 4.5:0 and 3/4, 9:4.5... spend more time around the 1/4 and 3/4 ratios.

Off to lowes to attempt another leveling platform idea, which may allow easier drive up.

rfn026

I use a water level to get all 4 scales level.

Richard Newton