weight distribution

[KnifeEdge_2K1]

why are car manufacturers always saying 50/50 is the ideal weight distribution
im pretty sure it's around 45/55 - 40/60

and another thing ive been thinking about, wouldnt it be better to have a high polar moment of inertia to keep squat and dive to a minimum, and since your car isnt really rotating about the middle of itself how far the weight is distributed from the center shouldnt really matter except for in the tightest of hairpins and since a high polar moment of enertia would slow down rotation of the car about its COG wouldnt this give more time for a driver to recognize and deal with oversteer/understeer ??

and if these implications are true (which im so sure they're not) wouldnt this point to a front engine rear transaxle rear drive car to be teh optimum layout ??

[fpv_gtho]

From what ive heard 50/50 gives neutral handling, whilst everyone who cant achieve that seem to come up with reasons for why theirs is better. I think its Nissan say the350Z achieves 50/50 under acceleration, whilst Porsche might say their rear bias gives superior power down. I guess as far as "useable" performance goes though, 50/50 is probably what you want. If your going for a balls out track car i suppose you want the ability to shift the weight balance as you please

[PerfAdv]

In steady state, no acceleration or deceleration, at-the-limit cornering a 50/50 weight distribution provides the most grip.

[Matra et Alpine]

Your commen on high polar moment havin ginertia and "slowign down" os partly right.
Going in to a corner that "slowign down" is making the car stay in a straight line and so you get more UNDERSteer - bad.
Coming out of a corner that is making it OVERsteer - bad

polar moment doesn't slow down or speed up anythign about a cr. it introduces forces durign cornering, braking and acceleration. THOSE forces affect the ability of the car to deliver optimum performance -- adn hence speed.

The best way for things to happen "slower" for a drive ris to drive slower.
So the fastest lap a driver achieves isnt' made by going faster in every corner. It's achieved by going at the optimnal speed to maintain grip. On some corners that means goign in slower our coming out slower controled BY THE DRIVER usign the throttle properly If a driver can't do that adn keep up with the rest then he/she is not made to be a driver and shoudl seek another profession !!!

[hightower99]

50/50 means that the front and back of the car will react equally to any changes and that these changes will be more reliable.


however I have heard of a system that uses a very heavy compact block wieght (up to 500 lbs in some cases) that is supported under the car with hydraulic rams that push and pull the weight around under the car giving it close to 50/50 weight distribution under most conditions (both front to back and left to right) combine that with BOSE's electro-magnetic linier accelerator suspenion and you would get some pretty mind boggling handling.

[derekthetree]

50/50 means that the front and back of the car will react equally to any changes and that these changes will be more reliable.


however I have heard of a system that uses a very heavy compact block wieght (up to 500 lbs in some cases) that is supported under the car with hydraulic rams that push and pull the weight around under the car giving it close to 50/50 weight distribution under most conditions (both front to back and left to right) combine that with BOSE's electro-magnetic linier accelerator suspenion and you would get some pretty mind boggling handling.

no need for all the complexity just have a fat friend who moves seats depending on the corner

[hightower99]

no need for all the complexity just have a fat friend who moves seats depending on the corner

^^ useless comment...

[derekthetree]

^^ useless comment...

^^ useful comment

[dydzi]

as i suspect 50/50 weight distribution will make the car the easiest to foresee. if it's different it tends to be oversteering or understeering

[Matra et Alpine]

50/50 means that the front and back of the car will react equally to any changes and that these changes will be more reliable.


however I have heard of a system that uses a very heavy compact block wieght (up to 500 lbs in some cases) that is supported under the car with hydraulic rams that push and pull the weight around under the car giving it close to 50/50 weight distribution under most conditions (both front to back and left to right) combine that with BOSE's electro-magnetic linier accelerator suspenion and you would get some pretty mind boggling handling.

eh ?
Any car that carries an EXTRA 500 lbs of weight is NEVER going to handle as well as a car NOT carrying that extra 500 lbs !!!!! MASS is a worse enemy than polar moments

Do you have any links to this car ?
I want to know what the engineers were wanting to achieve with it

[PerfAdv]

50/50 means that the front and back of the car will react equally to any changes and that these changes will be more reliable.


however I have heard of a system that uses a very heavy compact block wieght (up to 500 lbs in some cases) that is supported under the car with hydraulic rams that push and pull the weight around under the car giving it close to 50/50 weight distribution under most conditions (both front to back and left to right) combine that with BOSE's electro-magnetic linier accelerator suspenion and you would get some pretty mind boggling handling.

An active ballast seems to make sense however 500 pounds is a little excessive for a sports car meant to tackle turns. I've liked the idea and envisioned a system with two rail along the sides of the car with 50 or 75 pound weights that runs on along the track at lightning speed to maximize grip potential by placing extra weight where it's needed. Example: Approaching a hairpin left-hander; teh ballasts both move back to weigh down the rear in hard braking and then under acceleration out of the corner, the right ballast stays on the outside drive wheel and the left ballast moves to the front to weigh down to gain some extra traction.

[Matra et Alpine]

An active ballast seems to make sense however 500 pounds is a little excessive for a sports car meant to tackle turns. I've liked the idea and envisioned a system with two rail along the sides of the car with 50 or 75 pound weights that runs on along the track at lightning speed to maximize grip potential by placing extra weight where it's needed. Example: Approaching a hairpin left-hander; teh ballasts both move back to weigh down the rear in hard braking and then under acceleration out of the corner, the right ballast stays on the outside drive wheel and the left ballast moves to the front to weigh down to gain some extra traction.

Please remmeber the dynamics of what you describe.
Newtons law tells us that if you apply a force to move the weight then an equal and opposite force will be applied ot the car itself.
So as you move that weight back to help braking you will actually SPEED THE CAR UP Is that REALLY wha tyou want in a race car as you enter the braking zone ??

You get much more effective results just by adjusting the spring and damping settings in much more close to real time Of course that is banned from most race series

[PerfAdv]

Please remmeber the dynamics of what you describe.
Newtons law tells us that if you apply a force to move the weight then an equal and opposite force will be applied ot the car itself.
So as you move that weight back to help braking you will actually SPEED THE CAR UP Is that REALLY wha tyou want in a race car as you enter the braking zone ??

You get much more effective results just by adjusting the spring and damping settings in much more close to real time Of course that is banned from most race series

I guess that's the problem with trying to build a better mouse trap theoretically. Active suspension can do about the same if not better job of keeping a car level and poised even in race conditions. An over-complicated system to achieve a little extra traction seems irrational. However, I like to see one made just to see how it'd fare.

[KnifeEdge_2K1]

From what ive heard 50/50 gives neutral handling, whilst everyone who cant achieve that seem to come up with reasons for why theirs is better. I think its Nissan say the350Z achieves 50/50 under acceleration, whilst Porsche might say their rear bias gives superior power down. I guess as far as "useable" performance goes though, 50/50 is probably what you want. If your going for a balls out track car i suppose you want the ability to shift the weight balance as you please

have slight rear bias is good because it gives 50/50 distribution under braking when you're entering corners, and superior traction going out

[hightower99]

ok lets take a look at what I meant about the active weight system.

firstly I said the in some cases it would have 500 lbs of weight (I believe it was tested to see the effects on a large racing truck...)
On a car weighing around 1000kg or 2200lbs. the weight would be between 50 and 100 lbs. (depending on how much movement you want to give the weight.)

next point:
I believe the point of the system was to help the vehicle retain 50/50 weight distribution (front to back and left to right) during cornering and to make the change in the distribution much more gradual on the straights, the system is also used to facilitate acceleration and braking in straight lines. this would allow you to use suspension setups that didn't have to take the weight distribution into account as much and you could run more optimal settings.

Next point:
thank you for pointing out the physics part Alpine you see physics are real and the effect you describe is another reason that they developed the system for. You see when you are on a straight coming into a corner you want to do the majority of your braking in a straight line before turning the car. This means that the weight is actually pushed forwards quickly. This force helps slow the car and puts more weight on the front wheels allowing the brakes to do a better job. then after the corner where you want full acceleration the weight is moved quickly to the back of the car aiding acceleration and putting weight on the back wheels to help traction. (This only works on RWD and AWD cars)

unfortunately after all that I am afraid that I do not have any links to a vehicle that uses this sytem I read about it several months ago in a magazine and I can't find it.

any other questions as to how the system works I would be happy to ponder (I have a pretty good understanding of the concept from memory)