Cars balance

[JonnyRocket]

Originally Posted by Atticus808

just wondering, if you do minor mods like changing the exhaust or adding carbon fibre bits, would that throw the balance of the car off quite a bit?
I remember doing centre of gravity calculations in school, and it can change it a lot, so I just want to see what everyone else thinks.

The amount of weight saved by these type of parts does not significantly affect the 'balance' of vehicle. "Adding carbon fibre bits" will in fact add weight. Not to mention most carbon pieces are carbon in look only. True, engineered, light weight carbon parts are not the kind where you can see a pretty weave pattern under clear coat. A good aftermarket exhaust will only save you a handful of pounds as well. We're talking about a nearly 3,000 lb vehicle. The weight of the driver, or the fullness of tank has more of an effect than than the weight of most other pieces.

Originally Posted by Atticus808

also, beginner rwd question. I've only had a bit of seat time in a 335i and c63 AMG, so I'm not too familiar with rwd since I daily drive a fwd. I understand that the frs and brz have amazing handling and balance, but what happens if you accelerate in a turn? wouldn't the back end always come loose?

No. The rear wheels will only come loose when they overcome the kinetic friction between the road and tires. In fact, when racing you ideally want to have completed all of your breaking prior to the turn. That way you can be on the power through-and out of the turn. RWD is typically the preferred setup in race cars because then the wheels each have separate jobs. You see, with a RWD car the front wheels steer and the rear wheels provide power (all wheels brake). With a FWD car, the front wheels steer and have to provide power (as well as brake). An AWD car is great for low traction situations because all wheels can provide power, but you're still taxing the front wheels by asking them to do three things at once.

As others have mentioned, FWD typically understeer or "push" through corners with the nose of the vehicle pushing wide through turns. AWD also usually do this because of what I said in the earlier paragraph, as well as the fact that most AWD systems are based on a FWD layout. The beauty of RWD is that they tend to oversteer, where the rear of the vehicle will tend to swing wide. ***Caveat: there are MANY factors beyond FWD/RWD that affect over/understeer characteristics, these are generalizations.*** The tendency to oversteer can help the RWD drive car to steer through a turn by applying a bit more throttle, to break the back loose a bit and turn the car a bit more.

As another poster mentioned, a common mistake people new to RWD make is letting off the throttle in a turn. This can be very bad. This induces "throttle-off-oversteer" in which the rear suspension becomes unloaded (weight is transferred forward) and the rear of the car looses grip. This typically induces a catastrophic spin.

Other factors: tire grip, road surface, weight balance (FWD tends to be front heavy, RWD tends to have a better distribution), camber, caster, mechanical and pneumatic trail, suspension type, roll center, c.o.g., etc!!!

[Atticus808]

great replies! thanks a lot
now I understand rwd way more (in theory)
just have to go get this car now!

and correct me if I'm wrong. from the comments I gather, it seems as though rwd cars have A LOT more room to work with in a turn.

[RaceR]

Originally Posted by Atticus808

and correct me if I'm wrong. from the comments I gather, it seems as though rwd cars have A LOT more room to work with in a turn.

In general I would say a RWD have more room to work with considering it is easier to adjust the balance. But since you have more room to work with its harder to drive on the limit. But when you do its so much more rewarding.
A FWD/AWD is for the average person easier to drive faster. It is easier to utilize most of the grip. But less fun and generally less work.
Many people find less work and just going fast to be more rewarding without having to balance the car that much.

[einzlr]

Originally Posted by Atticus808

great replies! thanks a lot
now I understand rwd way more (in theory)
just have to go get this car now!

and correct me if I'm wrong. from the comments I gather, it seems as though rwd cars have A LOT more room to work with in a turn.

That's not an unreasonable way to look at it. In FWD the car is being pulled by the front wheels, whereas in RWD it's being pushed by the rears. The reason you spin if you decelerate rapidly in a turn (this can be by braking or simply by lifting off the throttle) is that the deceleration causes the mass of the car to be thrown forward (picture what happens to occupants and loose objects inside the car, well the same thing happens to the car itself; animators often way exaggerate the effect so picturing a cartoon car coming to an abrupt stop gives you a good idea of how it works). When this happens, the traction wheels (rears) lose traction and swing around. Conversely, if you accelerate in a turn, mass goes to the rears and away from the steering wheels so they lose grip and the car straightens out. If you go to a car control clinic or other event where a skidpad is available, you can try this out for yourself.

[fatoni]

Originally Posted by RaceR

In general I would say a RWD have more room to work with considering it is easier to adjust the balance. But since you have more room to work with its harder to drive on the limit. But when you do its so much more rewarding.
A FWD/AWD is for the average person easier to drive faster. It is easier to utilize most of the grip. But less fun and generally less work.
Many people find less work and just going fast to be more rewarding without having to balance the car that much.

im not so sure i agree with that. cars like the frs and the miata are easy to drive and thats the reason why spec miata is more popular than spec focus. with these cars that are balanced is is more dangerous to drive at the limits but many inexperienced drivers in fwd cars just drive too hot and end up pushing off so much speed without learning the lesson.

[muffinman]

Originally Posted by FRiSson

Not impressed with carbon fiber. As a structural material, sure it has a lot going for it. As an aesthetic material - not impressed at all.

whhhattt? im curious as to what kind of carbon fiber applications u have seen. the high quality stuff is beautiful i.e pagani & lambo superleggera.

[FRiSson]

Originally Posted by muffinman

whhhattt? im curious as to what kind of carbon fiber applications u have seen. the high quality stuff is beautiful i.e pagani & lambo superleggera.

As I said, it is an impressive structural material, as in the examples you cited. I just don't much like the look of exposed carbon fiber as trim pieces.

[muffinman]

Originally Posted by FRiSson

As I said, it is an impressive structural material, as in the examples you cited. I just don't much like the look of exposed carbon fiber as trim pieces.

you would be in the minority then.

[CaptainSlow]

Let's say the car is 2800lbs, and is a perfect 50:50 split. That means that there's 1400lbs in front, and 1400lbs in back. That means every 50lbs you take out of 1 side will increase that ratio by 1 point to the other side. For example, if you take out 50lbs from the exhaust at the rear, you change the balance to 51:49 F:R

Math:

1400 (rear) - 50 (weight reduction) = 1350 (new rear)

1400 (front) + 1350 (new rear) = 2750 (new total)

1350 (new rear) / 2750 (new total) = 49%

[Atticus808]

Originally Posted by CaptainSlow

Let's say the car is 2800lbs, and is a perfect 50:50 split. That means that there's 1400lbs in front, and 1400lbs in back. That means every 50lbs you take out of 1 side will increase that ratio by 1 point to the other side. For example, if you take out 50lbs from the exhaust at the rear, you change the balance to 51:49 F:R

Math:

1400 (rear) - 50 (weight reduction) = 1350 (new rear)

1400 (front) + 1350 (new rear) = 2750 (new total)

1350 (new rear) / 2750 (new total) = 49%

true to an extent.
based on what I learned in school, the shape of the peices play a big part. I forgot the formulas but it gets a little
complicated. your COG can get put to the left or right side too.

[CaptainSlow]

Right, I was just trying to make it as simple as possible. Basically, any MINOR change will have next to no effect...nothing that any normal driver would ever be able to tell. You'd have to start shifting hundreds of pounds for it to become really noticeable

[root]

OP, do you have anything like SCCA solo II autocross in your area? Great way to learn. You can read all this theory, you need to experience it to truly know.
And then you'll be able to start feeling what difference mods you make do.