Light weight vs. Weight/Weight Ratio

[Mr. Tasty]

Exactly as the title states. Is it better to be lighter, or have a better weight/weight ratio. Example: Removing weight from the rear of a car. It has always been a question on my mind. Strictly track purposes. This question was brought up when I was reading Sport Compact (back when they ran), and then also recently with the magazine, Modified, I am not talking about my car, just a general question. Long answers or short answers are greatly accepted.

[Holland]

I would say that weight balance is more important. With that said, a 2000lb car with poor distribution will probably out handle a 3500lb car with good distribution.

[Conki]

I was wondering about this not too long ago, and wasn't even sure why a 50/50 weight distribution would be good. Just because it sounds good doesn't mean it's actually superior.

Check this out:
"In steady-state cornering, front-heavy cars tend to understeer and rear-heavy cars to oversteer, all other things being equal. The mid-engine design seeks to achieve the ideal center of mass, though front-engine design has the advantage of permitting a more practical engine-passenger-baggage layout. All other parameters being equal, at the hands of an expert driver a neutrally balanced mid-engine car can corner faster, but a FR layout car is easier to drive at the limit.

The rearward weight bias preferred by sports and racing cars results from handling effects during the transition from straight-ahead to cornering. During corner entry the front tires, in addition to generating part of the lateral force required to accelerate the car's center of mass into the turn, also generate a torque about the car's vertical axis that starts the car rotating into the turn. However, the lateral force being generated by the rear tires is acting in the opposite torsional sense, trying to rotate the car out of the turn. For this reason, a car with "50/50" weight distribution will understeer on initial corner entry. To avoid this problem, sports and racing cars often have a more rearward weight distribution. In the case of pure racing cars, this is typically between "40/60" and "35/65".[citation needed] This gives the front tires an advantage in overcoming the car's moment of inertia (yaw angular inertia), thus reducing corner-entry understeer.

Using wheels and tires of different sizes (proportional to the weight carried by each end) is a lever automakers can use to fine tune the resulting over/understeer characteristics."
From http://en.wikipedia.org/wiki/Automobile_handling

Another important factor would be the vertical position of the CG. A heavier car with proportionally more hp, appropriate traction, the same weight distribution, and lower CG would probably out handle a lighter car with a higher CG.

Advice: Put your boxer engine in your trunk.

[petrolhead]

to quote Gordon Murray: "Weight is the car desingner's enemy. It's works against you in every aspect of the design."

I was wondering about this not too long ago, and wasn't even sure why a 50/50 weight distribution would be good.

Ferraris and Porsches are tail-heavy. BTW I had my E30 on scales with 78kg of me in the driver's seat and half a tank. bone stock original 1984 euro 316 (so , lightest nose E30 ever came with) , and it's 54/46 front heavy. So much for the marketing department's "50/50"..

Saving weight has a peculiar side effect : It helps you save even more weight :)

Exactly as the title states. Is it better to be lighter, or have a better weight/weight ratio. Example: Removing weight from the rear of a car. It has always been a question on my mind. Strictly track purposes. This question was brought up when I was reading Sport Compact (back when they ran), and then also recently with the magazine, Modified, I am not talking about my car, just a general question. Long answers or short answers are greatly accepted.

Move your engine as far back as possible (transmission moves back just as much so every inch helps). Better weight distribution. Plus now you'll have to shorten the prop shaft=> weight saved yay! :P :D

[Jaxx_]

less weight will always be better. you can always tune suspension to get your unbalanced chassis on your side. there's a reason FWD cars can still be quick around a course.

[gearheadE30]

That's where you start getting into polar moments of inertia and such. If you have a 50/50 balance but all the weight is out on the ends of the car, it's going to be very, very sluggish in transitions. This, combined with wheelbase, is why longer cars feel more stable at high speed or on the highway. The problem with such a comparison is the wide range of suspension geometry options, spring rates, wheel and tire sizes, damping, swaybars, and everything else. It's really more of a tuning tool for carmakers and racers rather than something that you can use to pick the best car out of a lineup.

fwiw the 'ideal balance' is apparently somewhere more like 46/54 for a front engine rear drive layout, according to some study Ferrari conducted awhile back.

[RickSloan]

This is very interesting stuff. I hope this turns into a debate I am very curious.

[Holland]

It is very interesting. And yes weight itself will always be the more important thing. I think two cars that are within a couple hundred pounds of each other, the better balanced car will be quicker, even if it's the heavier car. That's what I think anyway.

[kalib0y]

I believe good weight balance leads to great drivability and control but I noticed I'm always chasing down the lighter, less hp cars on smaller tracks.

[Jaxx_]

It is very interesting. And yes weight itself will always be the more important thing. I think two cars that are within a couple hundred pounds of each other, the better balanced car will be quicker, even if it's the heavier car. That's what I think anyway.

define quicker? pull more Gs on a skid pad? or be faster around a course? Maybe around a course, but I'm no so sure a heavier car could perform as well as a lighter car given that all other things are the same besides weight distribution.

[pharow]

I am no racer. (I want to try it out tho) I think the lighter a car is, the better it will/can be. Take two of the same car, but start removing weight from one of them. The lighter one will start to be quicker, and easier to handle. Then you can work on and adding performance.

That's just what I think.

[ak-]

Aren't some Porsche's like 30/70 or something?

[tjts1]

Front/rear weight distribution is just one of many factors when considering handling potential. But it makes for good marketing speak.

[Holland]

define quicker? pull more Gs on a skid pad? or be faster around a course? Maybe around a course, but I'm no so sure a heavier car could perform as well as a lighter car given that all other things are the same besides weight distribution.

I would say quicker in general since weight effects nearly every performance aspect, given weight and distribution are the only variables.

[Jaxx_]

I would say quicker in general since weight effects nearly every performance aspect, given weight and distribution are the only variables.

let's do this as an exercise...

a car with 50/50 weight distribution weighs 2500 lbs.

You take that car and do a lap around a course. then you remove 100lbs from the trunk of the car, causing it to become more front-heavy. You do another lap.

What's faster?


edit: i don't know the answer, but I think that the lighter car is faster... I'd hope that the laws of physics work that way.