POM HB

Yep,

Back ground: In one of the popular car mag a few months back, there is an article about new 612 from Fer. The article stated that Fer had done there research about weight distribution between front and rear. And, the magic number is 45/55 for Fr/Rr.

The claim (from Fer) says w/ more weight at the back, the car will
1. Acceralate better
2. Has less 'understeer'
3. Brake better
than the magic 50/50 number all car people are dying to have.

Now, the claim has left out Oversteer issue, which should be very very important w/ a car like that (big HP.)

Shouldn't the car will generate more oversteer?

I read it and wanted to follow suit, but if the car will be even more tail happy, I wouldn't like that.

David Bael (If I remember the name correctly) says that he's been running 48/52 for very long time and found it the best for FD (when he races).

What do you guys think?

Of cause, we can do 45/55 like Fer and reduce spring rate at the back to complain the oversteer, but isn't that just avoiding problems? I mean avoiding to fix at the problems if there is any. (I still don't completely agree w/ Fer that 45/55 is the best distribution)

Please keep infor coming, but let them be informative.

POM HB

PS. Rynberg, how about the promised reviews on new set of rims, tires, and monsta oil cooler?

Beny

the better acceleration is true, why do you with people but the battiery in the back other than space? and topfuel cars a rear engined

DamonB

Cars with very high horsepower tend to have increased rear weight distribution; 50/50 isn't as magical as people tend to believe and in many cases will be less desireable. By having slightly more rearward weight bias you can load the rear tires more for increased acceleration (assuming you are traction limited) and at the same time you can get the rear tires to contribute more under braking. 50/50 is only true when the car is parked in the garage; once you start driving it and weight transfers all that goes out the window.

As for more oversteer you think that the thing to do with lots of power going to the rear wheels is to make the rear lighter in order to cure it? Think about that one for a moment...

Comparing the weight distribution of two different cars and then declaring one superior to the other based on those numbers is misleading. If weight distribution was king you could always weight the light end of the car and make it whatever the hell you wanted.

In real racing cars you normally have rules as to how wide of a tire you can run front and rear and so you'll see different distributions in different series in order to try and get the most work out of the rubber you're allowed.

rynberg

Those numbers were Ferrari's research results for THAT particular car. But yes, it's better to have slightly "negative" weight distribution. Better traction and more stable braking. 911s have very high capabilities and they are more like 38/62.....with most of the trailing-throttle oversteer eliminated in the current model...


My review are coming damnit!

'98 Type RS

iTrader: (1)

I can't believe you are questioning research done by a multi-milion dollar company. Ferrari has the fastest cars in the world and you think they are wrong? They have accually done the research and you are using your theories. That's pretty funny.

POM HB

My Q about that was because we all know people (most) would love 50/50 distribution because...you know that right?

NOw, I was wondering if Fer will generate more oversteer. Usually, decrease understeer would mean more oversteer, am I correct???

I am not really in doubt what Fer has done about their research. After all, they are polly the best sport car manufacture. I was just trying to make a point about the report and claim about the distribution. It didn't mention about Oversteer. Why???

Yeah, that 45/55 is surely the best for that 612, I agree. How about our FD 50/50 case? Still, our FD has some problem w/ oversteer. Man, I don't know what I'm talking about here I just can't seem to present my own thoughts well.

ptrhahn

iTrader: (9)

Roughly 50/50 weight distribution is desirable from a suspension tuning standpoint because you're starting from an even point... but it isn't like reaching 88 mph and going back in time, nothing magic happens to a car that is weighted this way.

As we all know, cars are suspended, and spring rates, ride heights etc. all contribute to the relative "weight" that any given tire sees.... thats why you still need to corner balance a 50/50 weight distributed racecar.... never mind the fact that under braking, accelerating, cornering, or any combination at any given time, the car isn't in a 50/50 state anyway and the traction available from any wheel will also depend on the tire size, compound, and the effective angle at which it is in contact with the road. Race driving is almost all about weight TRANSFER.... and 50/50 weight distribution, equal spring rates, and same size tires F/R won't guarantee "balance" because the two ends of the car (and indeed each individual corner on any given turn) perform different funtions.

If Ferrari found that the 612 worked best at a distribution other than 50/50, its likely as a result of everything else mechanical and aerodynamic at work in the vehicle, and doesn't mean that they've discovered a new "ultimate" number applicable to all other vehicles.

'98 Type RS

iTrader: (1)

POM HB, at least you're thinking.
great explenation ptrhahn.

POM HB

That's true about more weight at the back would help more traction at the rear wheels, yet it would be more oversteer if gas padel isn't being applied, right?

However, you're right about my assumption that I have thought and applied the fer phylosophy to FD. And, I'm stupid for that

maxcooper

50/50 has good marketing appeal. Also, most other road cars are front heavy (which I don't think anyone would argue for from a dynamics perspective), so "breaking even" is something to be proud of in a road car. There is no magical distribution, but many race cars are 40/60, suggesting that some more weight in the rear is a good thing.

-Max

DamonB

No. Just by the fact that the rear now has more of the car's weight on it means the rear tires have more grip in every condition than they did before.

This is from our stickied link list. Everyone should read:

The Physics of Racing by Brian Beckman Explanation of vehicle and tire dynamics

POM HB

Opss....thanks Damon

Snrub

iTrader: (1)

Lamborghini has said the same thing for the Galardo.

VQracer

This is what Nissan believes....

rynberg

No, that's what the marketing department came up with.....

DamonB

"Which means during heavy braking into a corner, additional weight shifts to the front of the Z® for better steering grip on the front wheels. "

Definitely written by a non-car type person

Weight shifts to the front on anything that is trying to stop. The Z is no different than a Radio Flyer wagon or a brick

All things equal a car with slightly more rear weight bias will outbrake a car with slightly more front weight bias. The weight transfers to the front under braking so if more of the weight is already over the front to start with that means less is over the rears and therefore the rear tires can't contribute as much to braking because they will unload that much sooner.

If you want a car to stop (or do anything else) as quickly as possible you try to make all four tires do the same amount of work. Under braking a car with a slight rear bias will be closer to achieving this than a car with a front bias.

The increase in downforce or weight transfer is not linear to the increase in grip. If it were you would never be able to make a car slide because the tire would always grip harder and hold traction as more weight was placed on it. The tire does offer increased grip with increased load, but the rate of increase in grip occurs at a rate lower than the increase in weight transfer. The dominant feature of grip is not tire load, it's the cF of the static contact patch.

88IntegraLS

Understeer and oversteer can be eliminated over a range of f/r weight distribution ratios with relative spring and anti-sway bar stiffness. Placing more weight toward the rear than a 50/50 setup won't create a permanent oversteering condition, because the designer can spec wider tires for the rear or relatively softer springs up front and stiffer in back.

There is probably some hardcore physics/calculus involved in coming up with a "ideal" weight distribution considering the tunability of a car's understeer/oversteer condition. Considering how the front tires do a lot more work on turn entry under trail braking, having a little more weight on the rear tires might allow the fronts to rotate the car faster at their ultimate grip limit. The rears generally work the most on post apex turn exit, where gripping tires create understeer due to weight transfer and slipping tires just slide (oversteer), so I can see the merit in having more weight in the rear on both turn entry and exit.

I should find more weight to ditch from the front of my FC. The car currently sits at 1200/1220lbs front/rear which works out to 49/51%. I'd like to see how its handling changes with 50-100 fewer pounds yet on the front tires.

88IntegraLS

Reading that made me cringe. That is some serious marketing BS and the sad thing is, it sounds believable to someone not experienced with chassis setup and racing in general.

Gene

iTrader: (1)

This is correct, but misleading. If you increase the weight over the rear wheels, by say 10% (for example) the traction does not increase by 10%, because tire grip does not increase as a direct function of downforce. Cornering load on the rear wheels, however, DOES increase by 10%, which means a reduced maximum cornering load.

DamonB

Agreed. I tried to state that in the last paragraph of my post above without sounding like this thread where nobody believed me

PVerdieck

Yes! That thread lives!

eoph

you know i read that 2 years ago on a game development website while working on a project and he didn't added nething new today. is he going to update????

POM HB

Now,

How about the new Elise's road test from Car & Driver ?

The weight distribution is about 40/60...conner is easier than cake (from my understanding of their review). Yet, the writer says that if you lift the gas during conner, the rear will come out....that's because the 60% rear weight bias.
Is it true?
If so, what would happen if RX7 racers w/ rear bias have to lift the gas to apply the brake?
How can we change that? Less weight bias on the rear?

Well, once the manufacture 'decide' to use their best weight distribution on a particular car model, they will mod the suspension to help better the car handling. So, the actual weight distribution is not really the best thing to tell how the car will perform. That's what I think.

rynberg

Even front-heavy FWD vehicles have drop-throttle oversteer to some extent. It's actually a desirable thing in most circumstances and more to do with suspension geometry/tuning than it does with weight distribution.

Besides, they are talking about adjusting car attitude during maximum steady-state cornering. If you need to hit the brakes in that situation, ANY car is going to want to swap ends.

DamonB

There are no new additions that I know of. If you want to read more stuff like that visit our stickied link list here .