DD GT3 RD

3,137lbs. 2015 GTS No Driver. Half Tank of Gas. 7 Speed Manual. No options besides Spasm and back up camera.
I'm very happy with that. My e92 m3 was around 3550. Also weighed a friends F80 M3 DCT today and it weighed 3,661lbs. Guess Bmw was full of it when they said the new one is lighter?



Updated:
On level ground
With less than 1/4 tank of gas


And with me in the car

chuck911

I wonder why its so far off? L/R .54/.67 seems a bit much to me. But I guess maybe the car drives itself so much they figure nobody'll ever notice.

DD GT3 RD

Not sure. Hoped the left would be lighter so with driver it's more balanced.

Maybe a corner balance can help

Also ground may not have been perfectly flat. Seemed so but didn't use a leveler to check. Was just using scale to check overall weight.

But
L/R is good (1568/1569)
F/R (1185/1952) (38%/62%)

I dont know how to do cross weights which seem off but front to rear and left right make sense, no?
Chuck not sure what #s you wrote or why. What am I missing? Maybe you or someone can elaborate what the 47.6% on the scale is?

GrantG

I'm pretty sure you can only corner-balance the Motorsports GT cars (GT3, GT4, etc.), since they have height-adjustable coilovers and the rest of the 981 and 991 range is fixed, afaik.

SDaddy

Great info.

008

This gives me hope my MT C2S with only Spasm will be close to the quoted 3,070. I'm going to put it on the scales at the COTA event next month.

DD GT3 RD

good point, I forgot about that. Had kw's on the M and the Vette was adjustable from factory… Thanks, Ill find out for sure

GrantG

The cross weights are summed diagonally (LF + RR, RF + LR).

In this case, your smaller diagonal weight is 1,495 pounds which is 47.6% of the total 3,137 pounds. Ideally, the cross weights would each be 50% (with driver).

I'm not sure if these numbers are good, great, or less than good. Next time, have them do it again with you in the driver's seat and see if you get closer to 50% cross (if you care). As I said, not much you can do about it anyways without going aftermarket suspension with threaded coilovers (like GT3 has stock).

DD GT3 RD

^ I did do one with me in it...and it did get closer to 50%

GrantG

Ok, well good that it improved with you in it. Nice car!

Larry Cable

correct!

Larry Cable

Bilstein damptronic is the answer if you want to retain PASM *and* enable adjustment.

sracer

If you are into these things, I regularly scale my road race car; not that I change the setup that much but after some "use" it's nice to know everything is still on the money.
there are some basic rules to scaling:
1. You have to level the scales; I like a rotating laser level, have used water levels in the past. When you figure out the combo of shims (plywood, vinyl floor tiles, hardboard) mark your spots and write it down. Most garage floors slope to the door, or they should. Mine slopes about 3/4" in 92" - the car WB.
2. Roll the car on to the scales if possible, you have to get any bind out of it and if you use a jack to get on the scales that is a challenge.You can bounce it a bit, too, to get the suspension to settle.
3. Set the tire pressures - I set mine to what i want to see when coming off the track.
4. Disconnect the sway bars, can't have the preload on bars (should be none) impacting the weights. That is easy on race cars - just pull the pins, on a 991 probably a little more effort. and if you find preload when you reconnect the bars (on the scales, so you can see it) try to find a way to get it out of there. (adjustable end links)
5. Sit in the driver's seat. I have a hook on the wall to hang the scale readout on so i can see it when behind the wheel and write the numbers down.
now what? you have data, but without a way to move the spring perches (coilovers with threaded seats) you pretty limited. I've seen shims used on flat bottom springs but not many cars have them.
And you can spend a lot of time chasing the scales to get everything where you want it. But on a street or track day car it's not as critical as a race car. I try to keep the weights on the front wheels within .5% on it.
This thread will result in me scaling my 991s, which i had not considered!

DD GT3 RD

^thanks for sharing! Let us know your results

chuck911

The numbers I wrote are the side to side weight balance, only I screwed up and switched them around. Sorry. The Left side F/R 629/939 is .67, Right F/R 556/1013 is .55. The numbers on the meter, the Right Front/Left Rear cross total 1495 is 47% of total weight 3137. I have no idea why they show that cross and not the other one. Crosses only apply to symmetrical cars.

The 991 doesn't have threaded shock mounts for adjusting this anyway. The old 911's with their torsion bar suspensions had a screw on each front torsion bar mount that made this real easy. But things have changed a lot since then.

Here's a pretty good article on corner balancing. http://www.elephantracing.com/techto...nerbalance.htm

I was kind of surprised the 991 wasn't more evenly balanced, but there's a few things to think about that have me a lot less bothered. A big one is the way cars have changed over the years. Back in the day, before ABS and all the rest, it was real important being able to use the brakes to the max. In your car with 105 lbs more weight on the left front vs the right, hard braking would have the right locking up early. So they would balance more to the left rear, which would put more on the right front, balancing it out. That would result in a left/right difference but it was worth it to stop faster. ABS pretty much eliminated this factor.

Then after a while with ABS they realized its more important to have the same front/rear balance on each side. So the car will handle the same turning left or right. But then they kept on developing increasingly sophisticated systems to correct for things like that.

Anyway, like the article says corner balance is a lot less of a big deal in street cars because spring rates are relatively low. Also now things like PTV and PSM are so powerful they pretty much overwhelm whatever benefit might come from corner balancing, especially on a car where it matters less because of the soft springs.

I guess its one of those times where at first glance my old school eyes saw one thing, but then after thinking about it in light of new school reality it looks a lot different now. Dang it sucks getting old!