Weight Distribution
 

So after being on here for some time lurking around and nosing my way through some threads that I find interesting, I have come across many who question the RX8 and the weight distribution. I find it very hilarious that many feel that if you change the engine or even move the engine further back in the car it will "DRASTICALLY" change the handling of the car. My question for you guys (seeing only guys saying this) is

1: why do you feel this way?
2: Name another sports car that has perfect 50/50 that has amazing handling or that is a 50/50 ratio.
3: Now name sports cars that don't have a 50/50 distribution and have much better handling than a RX8. (Warning you this list is going to be much much much longer than number 2.) Yes I know suspension designs changes from cars to cars.

My example I will use is the Noble M15. It has a 42/58 F/R ratio and is probably one of the best handling cars. Though its a mid mounted engine vs. a front mount but it gets the point across.

Moving the engine back would only add more weight to the back.

Sorry I just wanted to start this cause every time I see somebody saying that if the car doesn't have a perfect 50/50 the car will not handle correctly or it will handle like crap.

There are certainly cars that handle very well without having a 50/50 weight distribution, but obviously if you start with 50/50, and a low center of gravity, the odds are pretty good that you'll have an excellent handling vehicle. It's just good physics.

"All design is compromise."

Name #2 in the price range of the RX-8 please.

I'm not saying that 50/50 is the holy grail of handling - but a car is designed to match it's weight ratio. Finding a car that can do 45/55 or more doesn't mean the RX-8 will handle well at 45/55 or more.

Show us a review where the Noble is said to be one of the best handling cars. We can produce quotes on the RX8. Probably the most famous one is J. Clarkson's Top Gear review in 2004.
And, the RX8 is a mid-engine car. The engine sets completely behind the front axle.

[QUOTE=amo;3604039]

My example I will use is the Noble M15. It has a 42/58 F/R ratio and is probably one of the best handling cars. Though its a mid mounted engine vs. a front mount but it gets the point across.

Moving the engine back would only add more weight to the back.

QUOTE]

That 42/58 is most likly without the driver in the vehicle. The Lotus Elise is quoted something like 40/60 but with the driver in the vehicle is is much closer to 50/50.

Your target weight distribution is not the same for every vehicle. Tire size, power, aero dynamics and driving style are all factors.

pretty much all the BMW 3 & 5 series are 50/50
911 is 47/53 I think
most of the mid engined super cars are 50/50 too

Who is moving the engine? There are a few V8 conversions but they are just trying to get the motor as far back as possible because the larger motor will add more weight to the front.

You will find several threads and a lot of comments about relocating the battery to the trunk to IMPROVE the balance and with a smaller battery loose some weight. Its not a big change but it does help.

I'll go with #4.
Audi TT with the 3.2L is so nose heavy that it understeers. The sad part is its AWD, so it should have the grip and traction to compensate, yet still cant. Just plows through turns all day long. So much so that the new RS version uses a lighter 2.5L Turbo setup to restore the balance it so desperately needs.

Audi knows what were talking about, hopefully now you do to.

In theory, that makes no sense. More weight over a given axle = more grip. Front end gripping more than rear means oversteer, not understeer. If it's so nose heavy and it's understeering, that means that they must have really stiff suspension on the front, really soft suspension on the rear, or both. Saying it is so heavy on the front that is understeers is a paradox.

If a car understeers the front to rear slip ratio is greater. Adding weight over an axle helps add grip to it, not lessen it.

Too much weight in the front for the tire size or a high center of gravity will cause the understeer. Think braking in the middle of a turn. If you lightly apply the brakes it will understeer, apply too much brake and the back end will come loose and the back end will come around at the same time. Yes understeer and oversteer at the same time = 4 wheel spin. I have seen it done, the tire skids start with the front tires and then the rears start and then just the rears. Usually ends with the car into a wall.

Sorry but, you're wrong.

Adding weight over a given axle gives it more grip, I know this coming from a racing background adjusting the car all the time. I think you're confused

What you should be talking about is in terms of grip or slip. Understeer occurs when the front slips or the car is pushed to the limits in the corner and the rear end has more traction than the front. Oversteer when the rear slips, or has less traction than the front when pushed to the limits in a corner. When you add weight, you're adding more loading over an axle to provide more grip.

This is why when you are using a 2WD truck in the winter, you add weight via sandbags to the bed to provide grip to prevent the tires from slipping due to the snow. Same concept in the idea that adding weight helps the tires keep in contact with the road better.

Adding more weight over the front of a car give it more grip contrast to the rear and thus more prone to oversteer or more neutral if it was rear heavy in the first place. I'm not saying he's wrong that from his experience the Audi TT understeers; I'm saying his logic is a paradox. Search and read about handling dynamics and loading, you'll see what I mean. The oversteer is more than likely due to the AWD drivetrain,and the front winds up slipping more when powered than the rear and creates an understeer in the same aspect a FWD goes through when too much power is at the tire than what it can grip trying to keep traction with the road creating slip and thus, understeer.

Your 4 wheel spin is actually really what's called, a 4 wheel slide. In relation to braking, if you have heavier brakes on the front than the rear, it can contribute to understeer. If heavier in the rear, then oversteer.

Have to keep in mind braking and accelerating are two different influences to a car's handling in the corner. Braking should be done before even entering the corner thus why I don't include it in my explanation. As for a higher center of gravity, unless the front and rear are at different heights in quite some measurement, then it influences both equally side to side when going through a corner and loads the front more than the rear under braking to set up a car for oversteer. More roll gives you more traction over the outside tires going through a corner. In another perspective, with a higher front end contrast to rear it will resist oversteering and the opposite is also true There is no one contributor to oversteer and understeer and as you can see there are many factors.

Back to the real argument, my statement simply said that stating a car understeers because it's front end heavy is simply a paradox, that's a fact.

Okay so you dont lime my braking analogy, fine but trust me I have seen it many times on street cars, not race cars. I have seen and investigated more crashes then you can imagine.

Too much weight can cause understeer because you are trying to turn too much weight. With your thought process you could add an extra 1000lbs to a race car and improve the handling soo much that you can fly through the turns. You are forgetting that while you may have more grip, that tire/grip has to work extra hard to turn the extra weight. Why do you think miata's are so fast in the turns? They are very lightweight. Now, exchange vehicle weight for aero downforce and yes handling will improve.

Yes adding sandbags to a truck in the snow will improve the grip on accleration and maybe even in turns but thats because without the sandbags there is too little weight to get any grip. Add 1000-2000lbs and see what happens.

50:50 weight distribution means nothing, it's how far that weight is from the axis of yaw that is the important thing.

300lbs sitting underneath the strut tower tops, or 300lbs sitting above the strut tower tops?

300lbs in a 2'x2' box, or 300lbs in a 3'x3' box?


All relative questions manufacturers must make when designing the drive train and suspension of a vehicle!

300lb two inches from the axis of rotation, or 300lb right up front 6 feet away from it?

'S a big lever...

wow, i see some really funny posts in this thread.

and i see idiots claiming to be experts spreading false gospel or whatchamacallit.

just an input: weekend nights messing around at the drag strip does NOT count as professional racing experience.

Oh, and shifting weight from one axle to another axle decreases the grip compared to the weight carried from the tyres at that end, as tyres are most effiecient with light loads.

The reason shifting/adding weight to the rear helps traction in snow is because even though the overall grip level is lower per unit weight over that axle - so when cornering the car would oversteer more - the tractive force vs the overall vehicle weight is higher. (As acceleration is loading the rear axle vs cornering loading the outside pair)

Which is why our engine is hung out over the back axle...makes it a bit crap on the smooth stuff handling wise, but it's got a whole load of traction when it's stuck in 2ft of clay and mud...

50:50 = perfect handling = perfect theorycraft

This thread is full of ...

and OP is full of failed.

A slight rearward bias is advantageous for performance. Mid-rear engine is better than front engine (even if you want to call it mid-front). That said, for a street car, front engined with the engined pushed way back and low is a pretty good layout. Placement of weight throughout of a car matters due to moment of intertia, etc. Due to this, two cars with 50/50 weight cars may behave differently once the car is in motion and weight transfers around.

I think it's pretty hard to argue that the RX-8's chassis isn't extremely good, particularly in its price range. As eluded to above, the car is a system that works together. The engine weight, size and shape all play a role in this, but obviously if one dropped in a different engine the system could be adjusted to compensate. Would the car be more fun with a LS3 under the hood and slightly lesser handling and poise? Probably.

please explain to me then why all audi's understeer and why 911's oversteer. think of a hammer as you throw it thru the air which end lands first? the heavy end has more momentum and pulls the light end along.

ha ha...Did you know that, if you lower the rear of the car the weight transfer to the front, so you just argue your own argument......LMFAO

The weight distribution without a driver is meaningless

in most of the general cases you numnuts are arguing about it often just depends on many other factors that you're not considering, which is a classic case of general forum expert fail. There is no single correct answer over a broad spectrum of vehicles and setups. It always "just depends", always ....