Corner Weights

[FilW]

I am not sure what is meant by corner weights. Is it the weight at each corner, ie the wheel, as the name suggests or is it something far more sinister? What is the significance of corner weights, how do you measure them and adjust them etc.........Sorry if I sound a bit dense!

[Onlooker]

It is as you suspected the weight of each individual corner and is a very important part of the handleing of the car from these you can find, front/rear bias,side to side bias(partically on ovals) you use it as the basic start point for weight transfer.
It can be adjusted by a variety of means but most common are either physically moving weight in the car items such as batteries,fire bombs,driver,fuel cell etc or by adjusting the hieghts of the spring platforms bu packers under the spring or adjustable spring seats.
You need either a set of scales(longacre etc) if scales are unavailable you can use a public weigh bridge and some time but I would be suspect as to the accuracy of this method

[ultimatebilly]

The total weight of the car is dispersed between the corners. The weight is measured from the bottom of the tyre because that is what is touching the ground. the aim is to get the wiehgt accros the car the same. ie. the front left the same as the front right. and the same goes for the rear, although obviously it will be a higher value at the rear if its a rear engined single seater.

When a driver gets better it is posible to bias the weights so that as he/she brakes into a corner the front right (if its a right hand corner he/she is braking into) will remain a little heavier and avoid locking the wheel.

the way most people do it with a push rod car is to pretty much leave the front pushrods alone (assuming the chassis is level) and just to lengthen the rears or shorten them to adjust the corner weights.

so

say the front left is too heavy and the chassis is level or as level as your going to get it, you want to shorten the right rear to take weight away from the front left. Its an idea not to do all the adjustment on one corner at the back, try and do it in equal measures on both sides so as to minimise the adjustment on each corner.

hope this makes sence

Billy

[boyracer]

As I understand, diagonal weights matching is more important than left/right, as weight moves diagonal across the car. ie left rear to right front ( left hand corner)

[Warwick]

Dont think so,as that would screw up your braking for a start if RF and LF weighed different,we always set front the same and rear the same.

[Onlooker]

On oval and to an extent the "cross weight" is very important at a cars performance will change a lot by going from say 50.5% to 49.7% not as big a deal on road course,and naturaly measured with the driver and fuel in the car.
If you have identical LF & RF and the same at the back you will infact have 50.0% cross weight.Try changing it to a bit heaveir RF ,LR and see the change.
NASCAR do it by the adjusters in the rear window and CART cars have a driver adjustable system,you wouldn't think a that such systems would be in place for nothing now would you?.It does work and can be checked by turning on just two scales at the display and seeing the percentage.

[Jukebox]

Originally posted by Onlooker
On oval and to an extent the "cross weight" is very important at a cars performance will change a lot by going from say 50.5% to 49.7%

When you mentioned this, what pops in my mind would have something to do with the camber positions that contributes quite considerably to the weight of each sides.

Try to view this discussion thread

[JR Ewing]

Originally posted by boyracer
As I understand, diagonal weights matching is more important than left/right, as weight moves diagonal across the car. ie left rear to right front ( left hand corner)

Nope, you adjust diagonally. For example, if your right front is 'light' you may lengthen the left rear w/bone to push more weight down here and on the right front. This will also lighten the left front a touch. There are other ways of adjusting it as well but, on simple cars at least, this si the most common.

[shiny side up!]

Errr, hope you mean 'pushrod' as opposed to w/bone there JR... as stated, you would be creating quite a mess of problems...

[boyracer]

So when setting corner weights, of course you aim for as close as possible, but for tin lidded race cars there are many factors working against you. So what is an acceptable tolerance 3kgs 5 or maybe 10 ??

[FilW]

Thanks for all your help guys!?!
It makes a bit more sense now, next thing is to try it on the car!
I'm sure I'll be back for more advice.

[verglas]

just another nugget of advice.. don't forget to include yourself in the calculations, and either sit in the car when adjusting, or put bags of weight where you would be sitting. Especially important when checking ride height, which is another can of worms!!

[Jumbo240z]

Some info...

http://www.grmotorsports.com/cornerweight.html

[racealign]

just out of interst, how may of you guys have actually done corner weighing and adjustment on your own cars???

[shiny side up!]

I've done it with a Kart and a Formula car, and helped do it with a stock car as well.

[Onlooker]

I have plenty of times on about 6-7 different class of cars and for both oval and flat track over a 15 year period.
The theory is always the same just the numbers change

[Red Dog]

And did you guys drive the cars before and afterwards?

I set my car up badly end of last season and it was driveable in the dry. But when I went to qualify at the next meeting at Snetterton it was cold and wet. I lost it very badly under braking for Russell and I could not work out what was wrong. Brakes locking front then rear.....five spins that day......oh dear, oh dear, much embarassment! I went to set it it up for the next season with a new set of four bathroom scales (it's not a heavy car) and bingo....the left front and right rear were light. Having got the figures to within 3 kgs the car's handling was transformed.
NOTE: if using bathroom scales they need to be cross checked with each other. They are consistent in themselves (test by weighing yourself ten times in a row) but the next set of scales will make you a different weight, so you have to allow for the differences when weighing the car. They were very cheap ones - £4.95 each!! I expect Longacre scales are a bit better.....
And very importantly the tops of the scales must all be level with each other and the car must be in ready to race condition with driver in full kit etc, tyres at normal pressure and all suspension angles set, and anti roll bars disconnected. Record everything you do so that you can revert if it all feels wrong on track.

[shiny side up!]

I have run into all of the things Red Dog talked about... very good points!

[Onlooker]

No driving for me Red dog ( you can always find a driver with $$$$)
PS Do you set it up before every week end? There must have been a reason for the change in handling from dry to wet apart from the cross weight.
True as you say level the scales,calibrat and weigh it as you would race it.

[THR]

we set it all up b4 every event... makes a lot of difference.. and eliminates the "ohh i wonder if the corner wieghts are right" varible at the track!!

[RWC]

"There must have been a reason for the change in handling from dry to wet apart from the cross weight"
That car is more sensitive to that aspect of setup in the wet

[Onlooker]

My point was simply that is you had corect corner weights at both rounds then the problem is else where ie Dry Camber settings or hard spring/anti roll bar combination.Perhaps to get the speed in the wet you must adjust the shocks a certain way and that is no good in the wet?
Just food for thought.

[Red Dog]

Set up was the same for the two rounds but unchecked in between, and definitely wrong! The first track was dry (almost) and grippy. The second track was very, very slippery and cold. As RWC said, it was just a lot more sensitive. I now check the weights more frequently and carefully. Next thing I would like to try is some really sensitive double adjustable dampers....perhaps there might be some in a skip outside the old Penske place in Poole.....?

[FilW]

When setting corner weights the book I've been reading, and Red Dog's earlier post, said to disconnect the anti roll bar before hand but won't the settings be altered again by reattaching it after?

[ultimatebilly]

The roll bars should have Rose joints either end that you can adjust to make sure there is no Pre-load when they are reatatched.

Also if the dampers are adjustable make sure they are all backed off in adjustment to avoid them sticking down and confusing you as you jump on it between adjustments!

Billy