Weight Distribution

[Forrest Gump]

The front to rear weight distribution of a C3 Corvette is known to be one of its good design features. I think I've read it is in the order of 48% front to 52% rear for a small block car.

I'm curious to know what the side to side weight balance might be? There appears to much more clobber on the drivers side - alternator, steering gear and p/s, brake servo + cylinder, pedals, battery. (Why was the battery not put on the passenger side?). Given the car may often only have the driver in it, this weight distribution doesn't look so clever.

It was only recently that I realised the engine and gearbox is not actually positioned in the centre of the car - it is about two inches offset to the passenger side. Was this just "packaging" or an attempt to balance the cars weight side to side, in which case the balance might be quite even.

Has anyone who's had their car on scales got any figures on this?

 

[Vetman]

Aircon, CAT, heater box, jack, tools on passenger side, and engine offset as you mention.

 

[Roscobbc]

And before someone says it - a big block Vette doesn't change the weight distribution figure too much - compare with figure with other American vehicles for a surprise.

 

[Daytona Vette]

The front to rear weight distribution of a C3 Corvette is known to be one of its good design features. I think I've read it is in the order of 48% front to 52% rear for a small block car.

I'm curious to know what the side to side weight balance might be? There appears to much more clobber on the drivers side - alternator, steering gear and p/s, brake servo + cylinder, pedals, battery. (Why was the battery not put on the passenger side?). Given the car may often only have the driver in it, this weight distribution doesn't look so clever.

It was only recently that I realised the engine and gearbox is not actually positioned in the centre of the car - it is about two inches offset to the passenger side. Was this just "packaging" or an attempt to balance the cars weight side to side, in which case the balance might be quite even.

Has anyone who's had their car on scales got any figures on this?

Sorry Andy unable to help with those figures, I know with my personal weight included I have a 49% to 51% F to R weight distribution, but I have no steering box and other parameters are different - I do not have the side to side figures. If it helps in the future, I know when mine was set up, it was set up first with no driver weight included and then re-adjusted from those good datum points to include the drivers weight.

I have always thought the offset position of the engine was strange, obviously could help with the side to side weight distribution, may have a relevance to big block cars and steering shaft / box clearance issues, need to see a standard set up to know.

 

[Nick B]

Is this a serious post?

 

[Chris Sale]

Have found this explanation for the offset engine in a1963 SAE Paper titled 'The 1963 Corvette Sting Ray by Chevrolet'. Authors were Zora Duntov (concept), Kai Hansen (chassis) & Carl Jakust (Body):

'.....the passenger compartment was placed as far back as possible and the engine centerline was offset one inch to the right, taking advantage of the fact that passenger foot room requirements are less than those of the driver. The offset also reduced the width of the driveshaft tunnel, because the crankshaft and the offset rear axle pinion were now on the same centerline,'

I had long though that the offset was adopted to give better side-to-side weight distribution with driver only, i.e. when racing, but there is no mention of this in the document. This may just be a case of Duntov playing it safe, given that Chevrolet was still observing the infamous AMA ban on racing in 1963.

Chris Sale
'64 Coupe

 

[Oneball]

Offset engined cars in racing is almost always done to lower c of g, move weight inside the wheelbase or reduce drag. I can only think of one instance where it’s been stated that it changes left to right weight distribution and that isn’t the reason for the offset only the side chosen.

In Indy roadsters where the driver is almost along side the engine it was to put on the left so the weight at the bottom of the hill. So even then you could say it’s about about keeping weight low again. But it’s big advantage to bring offset is reduced frontal area and keeps the engine inside the wheelbase.

 

[Forrest Gump]

Thanks for the replies guys (and it was a serious post Nick, albeit a bit nerdy, agreed). Its my curious mind wondering why the engine was offset because there had to be a reason. Also thinking about other recent threads mentioning drivers side suspension sag and the possible extra weight of components on drivers side.

As mentioned, the designers did well to get the weight bias to the rear. If I didn’t know otherwise I would have guessed significantly heavier at the front front axle given the engine location.

 

[Forrest Gump]

And before someone says it - a big block Vette doesn't change the weight distribution figure too much - compare with figure with other American vehicles for a surprise.

What you might theoretically lose on corners you make up on the straights. Mind you the early Vettes like yours Ross were light weight compared to the mid year cars loaded with electrics, emissions and safety bits.

 

[Chuffer]

I have been following this thread with interest as I thought weight distribution was asking her indoors to lift one cheek to free up a trapped seat belt !

 

[Fishy Dave]

I can see you're taking this track driving seriously Before they broke a couple of years back I owned a set of corner weight scales, really useful to fine tune handling. I will buy a new set later this year if funds allow, but they are £1000+. You'd welcome to bring the car over to Wiltshire to weigh it.
This was the weight distribution of my C6 (in lbs), with me in it (1562kg), or 1477kg with no driver.
The biggest difference I've found when setting up my race cars and the Vette is setting the rake, how nose down/tail up the car is. Nose down for better turn in/oversteer, nose up for understeer.
I see many Corvette's (of all models) on forums that have been lowered at both ends to appear more flat, and arguably look better for it, but if they ever saw the track they would probably understeer straight on horribly. A little bit of bum in the air is no bad thing sometimes.

 

[Forrest Gump]

I can see you're taking this track driving seriously Before they broke a couple of years back I owned a set of corner weight scales, really useful to fine tune handling. I will buy a new set later this year if funds allow, but they are £1000+. You'd welcome to bring the car over to Wiltshire to weigh it.
This was the weight distribution of my C6 (in lbs), with me in it (1562kg), or 1477kg with no driver.
The biggest difference I've found when setting up my race cars and the Vette is setting the rake, how nose down/tail up the car is. Nose down for better turn in/oversteer, nose up for understeer.
I see many Corvette's (of all models) on forums that have been lowered at both ends to appear more flat, and arguably look better for it, but if they ever saw the track they would probably understeer straight on horribly. A little bit of bum in the air is no bad thing sometimes.

Hi Dave, it was more of a topic for discussion rather than me getting my car track ready!! Thanks for the weighing offer though, that would be very interesting.
So your front left is quite a bit heavier than FR, and the C6 is slightly front weight biased.

 

[Oneball]

I can see you're taking this track driving seriously Before they broke a couple of years back I owned a set of corner weight scales, really useful to fine tune handling. I will buy a new set later this year if funds allow, but they are £1000+. You'd welcome to bring the car over to Wiltshire to weigh it.
This was the weight distribution of my C6 (in lbs), with me in it (1562kg), or 1477kg with no driver.
The biggest difference I've found when setting up my race cars and the Vette is setting the rake, how nose down/tail up the car is. Nose down for better turn in/oversteer, nose up for understeer.
I see many Corvette's (of all models) on forums that have been lowered at both ends to appear more flat, and arguably look better for it, but if they ever saw the track they would probably understeer straight on horribly. A little bit of bum in the air is no bad thing sometimes.

That’s all over the show. Is that with adjustable spring plates?

 

[Fishy Dave]

That’s all over the show. Is that with adjustable spring plates?

This was before I started the adjustments (47.1% cross weight), but the corners will always be unequal by quite a large amount even after corner weighting. I stopped at around 49.5% cross weight before the scales died. This amount of weight variation between corners is common, indeed it's pretty good compared to other cars I've owned like the BMW Z4M, Porsche 911 and even an Elise.
Caterhams were the easiest to set up, even then though, with a perfect set up there was a large difference between both rear wheel weights.

 

[Fishy Dave]

So your front left is quite a bit heavier than FR, and the C6 is slightly front weight biased.

Yes, the drivers weight makes quite a bit of difference, as does the amount of fuel, with the two tanks either side.
The aim of corner weighting is to balance out the load across the diagonals. Best imagined as a four legged bar stool that rocks, in this case two of the legs are taking more of the share of weight, until you wedge a beer mat under the shorter legs, or chop a bit off the two longer legs when the landlady isn't looking. You're not phyically moving weight around the car/stool, just adjusting how much of the share each tyre/leg is taking.

 

[Oneball]

This was before I started the adjustments (47.1% cross weight), but the corners will always be unequal by quite a large amount even after corner weighting. I stopped at around 49.5% cross weight before the scales died. This amount of weight variation between corners is common, indeed it's pretty good compared to other cars I've owned like the BMW Z4M, Porsche 911 and even an Elise.
Caterhams were the easiest to set up, even then though, with a perfect set up there was a large difference between both rear wheel weights.

Youd got one heavy front and the other heavy on the rear, which wouldon’t be good, you want the same balance front to back on each side.

 

[Fishy Dave]

Hi Dave, it was more of a topic for discussion rather than me getting my car track ready!!

Sorry, back on topic, these could be useful:

C3 Corner Weights or Left-Right weight balance? - CorvetteForum - Chevrolet Corvette Forum Discussion

C3 Tech/Performance - C3 Corner Weights or Left-Right weight balance? - 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.

www.corvetteforum.com

c3 weight distribution Q?(Chassis) - CorvetteForum - Chevrolet Corvette Forum Discussion

C3 General - c3 weight distribution Q?(Chassis) - currently, we are finishing up assembly of our rolling chassis. Everything is on the chassis before we drop the body back on. So, we decided for kicks how much it weighed without the body on and where all the weight is being distributed per...

www.corvetteforum.com

I stumbled on a number of threads where owners claimed their local 'shop' had managed to get left and right perfect, 50/50 weight distribution, as well as front/rear. I don't believe this and suspect what they are getting confused with is cross weight.

 

[Fishy Dave]

Youd got one heavy front and the other heavy on the rear, which wouldon’t be good, you want the same balance front to back on each side.

Agreed, these were the before weights, as the car came from the original owner in the States, I don't have a photo of the after as the control panel had sadly broken.

 

[Forrest Gump]

You've made a good improvement on your cross weights Dave. What is the 51.9% reading on the display? (I got 52.9/47.1 cross weight)
Edit. I can see now: 51.9% is the front to rear weight bias.