dude the CF hatch is so expensive!

 

woah, so ferrari "determined" that the weight balance of their mid-engined car just happens to be the ideal balance!! wow how lucky for them!

 

Can you explain how it would decrease the rear weight...it just makes logical sense to me that if you lower the rear more that some weight gets transfered to the rear from the front. But maybe I'm missing something here...

 

Not hardly. They did the research on test mules with different weight distributions in order to study which had the best acceleration, handling, and braking. They then set a goal of 45/55 and achieved 46/54 with the production car.

 

i have owned a set of scales for 25 years and used them to set cornerweight for my racecars.

weight distribution is extremely important as to racecar setup. one of the reasons i haven't been beaten at Brainerd is my 52% rear weight.

weight distribution is so important that i had a hydraulic cockpit adj weight jacker in my last GT3 RX3. it jacked UP the right rear corner of the car to ADD WEIGHT to that corner to replace the 65 pounds of fuel i had used in the race to bring the car back into trim for the last few laps when the track was greasy and traction was at a premium.

suffice it to say raising a corner adds weight.


howard coleman

 

I guess I'm just looking for a scientific explaination...I'm not doubting what you're telling me, just trying to logically understand it.

 

Wouldnt lowering a corner add weight to the corner that was lowered?

Matthew Walsh

 

if you raise the ride height at a given corner the weight on that corner will increase, as will the weight on the diagonally opposite corner. the other 2 corners will lose weight.

if you lower the ride height at a given corner, that corner will lose weight as will the diagonally opposite corner. the other 2 corners will gain weight.

as you can see, it is impossible to gain, say, rear weight by raising r and l rear ride height.......... the only way you can effect rear weight is by redistributing static weight.

since ride height effects corner weight running alot of front caster jacks the ride height and corner weights as caster changes ride height.

turn the wheel of a car w alot of caster while at rest and watch the left front fender rise while the right front fender drops. strut cars run alot of caster. A arm cars like the fd do not.

howard coleman

 

No. Think of it in terms of crossweight; diagonally across the car.

If we raise the right rear corner of the car slightly we are removing some weight from the left rear and right front corners while adding some to the right rear and left front.

If we were to lower the right front corner of the car slightly we are adding some weight to the left front and right rear while taking some from the right front and left rear.

The total weight of the car is of course the same but to some extent we can control how that weight is distributed to each tire. This is the purpose in life of adjustable coilovers but of course you need a set of scales to set them up correctly.

 

I'm sorry I guess that I am still confused. Take for example a solid piece of flat rectangular metal. If you were to angle down the piece towards one side lets say the front left corner. Wouldnt more of the weight then, focus on said corner because the weight it is then not evenly balanced between all four corners.

Thanks,

Matthew Walsh

 

I too am totally confused as well...what if you take the FD and raise the front 6 inches up and lower the rear 6 inches down...wouldn't the rear have more weight? Damn this seems sooo weird to me...

 

In your example that's true because you are picturing the center of gravity moving ever so slightly. A car sits on springs however and that makes it completely different.

Think of the tires on the car like the legs on a chair. If we very slightly lift the right rear leg of the chair from the floor it will also lift the left rear and right front legs of the chair and all the weight would now be on the left front. Now imagine we had springs on all the chair legs. If we lift the right rear leg of the chair very slightly such that the leg won't come off the ground but it will compress that leg's spring slightly as well as the left front diagonally across from it and at the same time raise the springs of the left rear and right front. If the springs are raising then weight is being taken from them, if they are dropping weight is being added to them.

 

No. The weight distribution of the car from front to rear doesn't alter just because you raise or lower one end of the car.

If you wanted to get down to a knat's *** then yes dropping the rear of the car removes a very, very, very, teeny tiny amount of weight from the front and places it on the rear because the center of gravity will rock back towards the rear of the car ever so slightly. It isn't anything that makes a difference though until you get obscene: Raise the front a couple feet for instance.

Again picture the legs on a chair. If one of the four legs were longer than the other three then the chair will rock on the long one and the leg diagonally across from it. The car works the same way but because it is on springs the tires don't actually leave the ground. It does however still force more weight onto the diagonal pair that was raised.

 

"If the springs are raising then weight is being taken from them, if they are dropping weight is being added to them."

Isnt this exactly what I have been saying all along?

Matt Walsh.

 

Oh and BTW thanks for taking the time to answer my questions:-)


Matthew Walsh.

 

No. You said above "Wouldn't lowering a corner add weight to the corner that was lowered?" and the answer to that is no; it subtracts weight.

If the corner is lowering than that means you made the spring softer so to speak (or else the corner wouldn't lower). Since the spring is softer it is supporting less weight at that corner. If it's supporting less weight at that corner than that means the other diagonal pair has more weight on it.

 

Would the same be true if you kept the same stifness of spring but instead just "cut" it shorter.

Thanks,

Matthew Walsh

 

If the springs were all the same but one were shorter than the shorter one would have less weight on it and the other 3 more. The reason is the three long ones have to compress more than the short one. The force a spring presents is directly proportional to how much you compress it. Since the three long ones have to compress more they will carry more weight than the short one.

This is what happens when you raise and lower the spring perches on a coilover. When you raise the perch you compress the spring and add weight there. When you lower the perch you extend the spring and remove weight. The weight that is added or lost will show at the diagonal pair you didn't adjust. However this is only true when adjusting one spring at a time. If we have the car at some static height but adjust both fronts or both rears the same amount we get no net change in corner weight, only a change in ride height at that end.

 

By the way...thanks guys for being so patient with us. This has been driving me crazy all day.

The reason this thread was brought to my attention to begin with was because I have the spring perch in the rears on the lowest setting on my Koni yellow's. I don't like the way the rears have always been a little higher than the fronts...

So what happened when I did this is soften the springs(H&R's) in the rear a bit, but slightly changed the weight to a little lighter right? Anyway, I'm sure it's not a huge difference...but considering that I was gonna install a roll cage, I was wondering about it.

 

No. All you did was lower the rear. When you adjust both springs at one end of the car an equal amount you do not change corner weight at all. You only change ride height.

 

And softened the spring a bit...right?

Sorry, trying to FULLY understand...

 

No. The spring still has the same rate. The spring's rate is an inherent property of the spring. Whether you squish it more or less, turn it right side up or upside down or sideways its rate is always the same.

When you drop both spring perches on the rear to lower the car all you're doing is lowering the car. The springs support the weight of the chassis and if you move them closer to the ground the chassis moves closer to the ground. The spring rate does not change.

 

Gotcha!

Makes total sense now...Thanks.

 

howard coleman & DemonB,

Thanks a bunch! Great explaination and patient for us. We, other than PandazRX-7 and SkEltAh, really appriciate your help!

Thanks again.

POM HB

 

"btw, lowering the rear decreases rear weight. since you are talking a small amount it isn't an issue."

this is the point of confusion from Howard C. It is a very slight effect that really has noting to do with cornerweighting. It has to do with cg of car, pivoting from a fixed point over the fromt wheels. in fact, if car was highly jacked in back, lowering rear would slightly increase rear wheel weight. assumes no wheelbase change.

stiff plate example .... same spring at each corner, each compressed 2" by plate weight (W). assume 1" thk slab of wood reside between bottom of each spring and ground. remove RF and LR slabs, and use them to double up the slabs under LF and RR springs.

The plate will still be flat and a it's same 'ride height', but with terrible corner weights. all corners started at W/4 load with 2" compression. But now weight at LF and RR springs, compressed extra 1" when raised by slabs, will have 3"/2" x W/4 = 3W/8 load at each of those 2 diagonal corners, 50% more load than before. At each corner with no slabs, springs were 'lowered' ... now at 1" compression vs 2" original, for 50% less load (1"/2" x W/4 = W/8 load). So one diagonal wheel pair carries 75% of plate weight, other diagonal pair carries 25% of plate weight. Same level ride height as when a slab was under eacjh wheel.

magic of corner weighting.