Light weight vs. Weight/Weight Ratio

[110stx]

Get rid of the weight wherever it may be.

Lighter is quicker. Lighter handles better. Lighter stops faster.

Whatever weight balance issues you face can be addressed with suspension tuning.

Seriously ... Lose the lbs.

[Liam]

Get rid of the weight wherever it may be.

Lighter is quicker. Lighter handles better. Lighter stops faster.

Whatever weight balance issues you face can be addressed with suspension tuning.

Seriously ... Lose the lbs.

Only up to a point... Indiscriminate chopping of weight without regard to distribution can cause some fairly shocking results.

[LJ851]

An good example of weight distribution comparison is a early 60's Mini and Austin Healy Sprite. They both use the same engine and weigh about the same.

The Mini has most of its weight on the front (drive) wheels, and the engine sits relatively high on top of the gearbox.

The Sprite has much "better" weight balance as the entire engine is pretty much behind the front axle, the engine sits low in the chassis and it's rear wheel drive, even the driver sits much lower in the chassis.

Which one is faster/quicker? If you go to a vintage race now and watch them both run (they are in the same class) with equal power they will run nose to tail lap after lap with the exception of a track that has a lot of high speed sections where aerodynamics will favor the Sprite.

Very different driving experiences and styles, but similar speed. There is more than one way to skin a cat as they say.

My answer to the original post is less weight on your car is better 99.87% of the time

[110stx]

Only up to a point... Indiscriminate chopping of weight without regard to distribution can cause some fairly shocking results.

Sure sure ... There's really only so much you can lose on a production-based car anyway without compromising the integrity of the vehicle. And we're talking about fairly discriminating weight reduction measures, I'd wager, i.e., realistic stuff.

But if we're talking, just for instance, about using a LTW battery in the trunk or keeping a heavier one for the purposes of achieving more optimal weight balance, then the answer is fairly obvious.

Getting rid of trunk tar? Sure, if class rules allow. Etc.

Ultimately, cross-weighting on an e30 is almost more important as achieving some mythical "perfect" weight balance.

The basic answer remains, like LF851 wrote: Lighter is better.

Now I'm wondering about the curb weights of the Mini vs. the Sprite ... I love this shit. :-)

dh

[DuMa]

this thread needs the mag article where they chopped off body parts of a vette to see how much faster it was.

[Sagaris]

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.

Bingo, well said my friend.

More weight = more traction (static friction equation F=(mu)*N)
Think of an F1 car. The aerodynamics are providing a force which increases the grip of the tires.

BUT an object in motion tends to stay in motion unless acted upon by some external force. Your car does not want to make a turn, it wants to continue going straight. Trying to get the car to turn requires energy and the more mass the car has, the more energy required to get it to change directions. Compounding this is the location of the mass as gearhead mentioned. Think of a hammer . It is MUCH easier to swing a hammer when holding it by the head and swinging it as opposed to holding it properly (by the handle) and swinging it. The polar moment of inertia is much greater when the distance between the center of mass and the center of rotation is large and it requires much more effort.

So this is why removing a 15 lb A/C condenser positioned 2 feet forward of the front axle is more beneficial for your cars ability to rotate more easily than removing 50 lbs of weight from the center of the car.

Light weight and keeping the weight between the front and rear axles will help a car change direction faster
An even weight distribution between front and rear (50/50) with all other things being equal (tire size, etc) will yield a more predictable and balanced car which will be less prone to losing control with abrupt direction changes
Additional downward force on a tire (via. a wing or by preventing side to side weight transfer with sway bars) will increase cornering grip.

[Liam]

Bingo, well said my friend.

More weight = more traction (static friction equation F=(mu)*N)
Think of an F1 car. The aerodynamics are providing a force which increases the grip of the tires.

BUT an object in motion tends to stay in motion unless acted upon by some external force. Your car does not want to turn, it wants to continue going straight and the more mass the car has, the more energy required to get it to change directions. Compounding this is the location of the mass as gearhead mentioned. Think of a hammer . It is MUCH easier to swing a hammer when holding it by the head and swinging it as opposed to holding it properly (by the handle) and swinging it. The polar moment of inertia is much greater when the distance between the center of mass and the center of rotation is greater and it requires much more effort.

So this is why removing a 15 lb A/C condenser positioned 2 feet forward of the front axle is more beneficial for your cars ability to rotate more easily than removing 50 lbs of weight from the center of the car.

QTF...
No "like" button on here...
Another forum I frequent has a like button...
Pretty cool.

[atmobenzin]

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



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"..

Was the tank full? Are you sure that springs provided equal ride height? I mean maybe for example rear springs were replaced at some point while front ones were original - 20 years old and a bit saggy?

[DrJosh]

What about the CTS-V? The wagon is heavier then the coupe, but is also faster around the track.

[petrolhead]

People offer their opinions and beliefs about something that's pretty much a matter of fairly simple math an physics..
Weight distribution is a consideration but it shouldn't stand in the way of lightening , ever. Once you get rid of every last ounce you can, start relocating the stuff that remains: Fuel tank , engine & transmission..

Was the tank full? Are you sure that springs provided equal ride height? I mean maybe for example rear springs were replaced at some point while front ones were original - 20 years old and a bit saggy?

Me in the driver's seat (78kg) plus half a tank.

Does that look saggy :) ?



Ride height is correct in all corners , ie. there was nothing that could screw up the scaling (is that a word?).

[Nsquared97]

I have been a part of a formula SAE team (formula student for you guys in Europe) in which we basically design a formula style race car from the ground up. In designing one of our most recent cars trying to figure out what weight balance we wanted was something we looked into. We decided that between 50/50 and 45/55 was ideal. A slight rear bias is beneficial under braking, because it helps keep the car balanced as weight shifts forward (hence why Porsche 911's are great under braking).

And as mentioned earlier, weight outside of the wheelbase is bad, very bad. Creates polar moments which the car will fight to overcome when your trying to corner, resulting in sluggish response times.

There really is a lot to think about when it comes to the 'weight' of a car. Overall weight, weight distribution, unsprung weight, rotating mass, center of gravity, etc etc. All of it adds up to making a car's handling characteristics what they are.

[Emre]

Here's the simple answer:

• Lower absolute weight is going to be quicker around a track, even if the car ends up more unbalanced.
• Better balanced will "handle" better (i.e., more neutral in corners and transition sharper), even if slightly heavier.

Ideally you want the car to be lighter overall without totally throwing off the weight balance. In RWD applications, you'd prefer to have the weight biased slightly towards the rear if possible.

So, stripping out the rear half of the car and swapping a bigger/longer/heavier engine under the hood (as many E30 folks like to do) is really suboptimal from a handling perspective. Even though the lighter weight and increased power will make the car faster around a track, you definitely take a hit in terms of chassis feel and responsiveness.

[110stx]

This all holds true given constant suspension setup.

But within limits, proper suspension tuning can help the "unbalanced" handle just fine, perhaps even better than the "balanced" car, depending on initial setup.

Here's the simple answer:

• Lower absolute weight is going to be quicker around a track, even if the car ends up more unbalanced.
• Better balanced will "handle" better (i.e., more neutral in corners and transition sharper), even if slightly heavier.

Ideally you want the car to be lighter overall without totally throwing off the weight balance. In RWD applications, you'd prefer to have the weight biased slightly towards the rear if possible.

So, stripping out the rear half of the car and swapping a bigger/longer/heavier engine under the hood (as many E30 folks like to do) is really suboptimal from a handling perspective. Even though the lighter weight and increased power will make the car faster around a track, you definitely take a hit in terms of chassis feel and responsiveness.

[Holland]

Bingo, well said my friend.

More weight = more traction (static friction equation F=(mu)*N)
Think of an F1 car. The aerodynamics are providing a force which increases the grip of the tires.

BUT an object in motion tends to stay in motion unless acted upon by some external force. Your car does not want to make a turn, it wants to continue going straight. Trying to get the car to turn requires energy and the more mass the car has, the more energy required to get it to change directions. Compounding this is the location of the mass as gearhead mentioned. Think of a hammer . It is MUCH easier to swing a hammer when holding it by the head and swinging it as opposed to holding it properly (by the handle) and swinging it. The polar moment of inertia is much greater when the distance between the center of mass and the center of rotation is large and it requires much more effort.

So this is why removing a 15 lb A/C condenser positioned 2 feet forward of the front axle is more beneficial for your cars ability to rotate more easily than removing 50 lbs of weight from the center of the car.

Light weight and keeping the weight between the front and rear axles will help a car change direction faster
An even weight distribution between front and rear (50/50) with all other things being equal (tire size, etc) will yield a more predictable and balanced car which will be less prone to losing control with abrupt direction changes
Additional downward force on a tire (via. a wing or by preventing side to side weight transfer with sway bars) will increase cornering grip.

QFT.

This all holds true given constant suspension setup.

But within limits, proper suspension tuning can help the "unbalanced" handle just fine, perhaps even better than the "balanced" car, depending on initial setup.

Yes but suspension will only aid to an extent. I don't think anyone here is arguing the fact that lighter is faster, but balance is just as important.

Let's look again at the 911. Early cars even had lead in the front end to make them more neutral, as the car evolved and suspension technology improved they no longer had to do such things. In the end though, no matter how much you change the suspension, when driven at the limit it's still effectively a massive pendulum.

[Nsquared97]

Yes but suspension will only aid to an extent. I don't think anyone here is arguing the fact that lighter is faster, but balance is just as important.

Let's look again at the 911. Early cars even had lead in the front end to make them more neutral, as the car evolved and suspension technology improved they no longer had to do such things. In the end though, no matter how much you change the suspension, when driven at the limit it's still effectively a massive pendulum.

I was just going to say the same thing, 911 is a great example of what technology and constant evolution of a car can do. But in the end you still cannot defy physics.