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The conscience of ClubRSX
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I was reading about the BMW Z4 M Coupe vs the Porsche Cayman S and was confused when they said that the handling was better in the Porsche even though it doesn't have perfect 50/50 like BMW. What I don't und is even though the BMW has a front engine, it has 50/50 split, so how come the handling is not as good (supposedly) as the Porsche's? Is having a bit of a bias on the rear better?
 

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A 50/50 ratio is usually considered the best to have but a car's handling is influenced by more than just the weight distribution so the Porsche must have the advantage in other things,
 

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The conscience of ClubRSX
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Discussion Starter · #5 · (Edited)

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Breast inspector by appt.
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Porsche has been making rear engine/rear wheel drive cars for so many years that they know exactly what they are doing. It also helps that the basic design of cars like the 911 hasn't changed in 40 years. Also, Porsche doesn't mass produce cars for the public at large like BMW.
 

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I was reading about the BMW Z4 M Coupe vs the Porsche Cayman S and was confused when they said that the handling was better in the Porsche even though it doesn't have perfect 50/50 like BMW. What I don't und is even though the BMW has a front engine, it has 50/50 split, so how come the handling is not as good (supposedly) as the Porsche's? Is having a bit of a bias on the rear better?
There are a few misconceptions that say 50/50 weight is ideal..

altho it sounds nice...

Under braking and acceleration those numbers change..

some cars like a 350z have a weight distribution of 53/47..

They choose this because, under braking and turning, the front bias helps the car dig and improve traction, while under acceleration that 3% shifts to the rear, giving the car perfect balance under acceleration...

Whether this is actually helpful or not is not for me to say...but thats one theory of an offset distribution..

Cars like the s2k do have a 50/50...they have been proven to perform...
but based on what i said earlier...you cant be too sure which is better without looking deeper...(and frankly thats over my head haha)

as far as porsche's rear bias...im not sure...im in for answers

I know in the past they had some difficulty with it, because the rear bias would lift the front end under hard acceleration and either oversteer to much or have the front end "lift", reducing front traction and stability..

They have improved on this recently, where this has been virtually eliminated
 

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Mmm, 3rd lobe...
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Where the weight is in relation to the axle lines are makes a big difference too.

Sure its front or back, but is it in front/behind of the front/rear tires.
 

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When you say 50/50 weight distribution, the problem with that is that the location of the weight could be...on the front bumper and on the back bumper. That affects the moment of inertia if all the weight is out on the very front/back ends of the car.

I'll just take a guess, but I'll bet that the porsche has more of its mass closer towards its center, which is more important than say...just a 50/50 distribution.


edit:


Think about it this way. The BMW could be a symmetrical dumbbell, and the Porsche is a ball, sort of. The dumbbell may be split 50/50, but the mass is spread out to the two very ends, so rotating it is more difficult than say...a somewhat unevenly mass distributed ball.
 

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These Colors Might Run
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this is a really complex subject that can't be explained without drawing pictures, but first let me clear up a few misconceptions:

1.) 50-50 is NOT PERFECT. The magazines say that because it sounds good, and that's the truth. They're not automotive engineers, they're not even race car drivers, they're just english majors who like cars.

2.) SilverRSXJesus is on the right track with the dumbbell / ball analogy. The porsche will rotate more easily because the weight is concentrated in the middle, but because of that it will get upset more easily if you hit a bump in the middle of a turn.

3.) race cars have a rear weight bias. This is because at corner exit, more weight is concentrated over the rear tires (so they have more grip) and you can rocket out of the turns much sooner. Combine that with a car that rotates easily (mid-engine) and you get a car that handles beautifully.

4.) the braking argument is valid, but keep in mind that to decrease lap times it's more valuable to increase your speeds in the straights than to shorten braking distances.
 

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These Colors Might Run
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as far as porsche's rear bias...im not sure...im in for answers

I know in the past they had some difficulty with it, because the rear bias would lift the front end under hard acceleration and either oversteer to much or have the front end "lift", reducing front traction and stability..

They have improved on this recently, where this has been virtually eliminated
the old 911's tended to rotate about the front axle (like a pendulum) because there was just so much weight being thrown around in the back. The rear end just had too much momentum for the rear tires to handle.

What you're saying about the front end lifting is partially true. That would create an understeering problem under maximum front line acceleration. Porshes are traditionally very oversteer-prone, though.
 

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I have to disagree. You want to be fastest on the slowest part of the track (turns).
i think i read a calculation for this based on distance covered and the time it takes to cover that distance...

just picture a long straight. Two identical cars. If we leave the corner at the same time, and i'm going 4 mph faster than you, i'll get to the braking point some seconds before you just because i'm going 4mph faster than you for a long period of time.

now here's a different scenario. Let's say you nail a turn perfectly and you average 4 mph faster in that turn. You've been going 4mph faster than me for what, a few seconds? You've gained almost nothing.

This is why formula 1 cars take a weird line at the last bend before a long straight, because they need that corner exit speed to maximize their time at full throttle.
 
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