Corner weight.

[StephenRae]

I appreciate the problems differing corner weights on the front can cause, but how important is it to get the rear corner weights correct?

[richard_sykes]

Wouldn`t depend on the car and what your doing. For a smaller hatchback on tight circuit it would be it bit more important than a bigger car on a more open track?

[graham bahr]

every little helps as they say, theretically in a rwd car if the rear corner weights are out by a far bit it would effect traction, although it doesn't in my car

[zefarelly]

we're not allowed adjustable spring platforms, I've rewelded mine 6mm higher on the drivers sid to allow for my weight, I can tweak that by packing between the top mounts and inner wing

at the rear I can just shim between the axle and the leaf springs, although I havent bothered as it wasnt far out anyway

[Lukin]

In my opinion (ie the one no one ever listens to!) the rear is a lot less sensitive to slight out of balance than the front.

The rule of thumb for ride heights is that for every 1 mm you change in the front, you can change it 3-5 mm in the rear to maintain a balance. I assume the same would apply with corner weights.

[graham bahr]

Originally Posted by zefarelly

we're not allowed adjustable spring platforms,

why is that, cost saving? origonality?
seems a bit daft to me, as it can be got round so surely the best thing would be allow them, cheaper and easier all round. ok they may not be cheaper if you do all your own setting up, but if you've got to pay someone to do it times money

[Peter Mallett]

App K. You have to run the cars as they ran in period. And adjustable platforms weren't invented then.

[halecmini]

the car's have four wheels, therefore if your corner weights are out at the front this also puts the courner weights at the rear out too, it works diagonally, i'e heavy fleft you will also have a heavy right rear. It is very difficult to get the cars perfect but i generally set the car sthe back is equal, and the front right slightly heavier! because in england tracks are prodominant right hand corners and would preffer the weight on the inside for obvious reasons!

[Kev_205]

Well im converting my car to LHD to help sort the weight distribution amongst many other tweaks. My engine is on the drivers side so the car is really weight biased on that side

[zefarelly]

just looking at my car the rear end is virtually symetrical, including the fuel tank,

App K says no adjustment due to not being original fitment, as Peter says.

the only totally non symetrical thing about the car is the driver . . . .currently hovering around the 87kg mark !

[Al Weyman]

Originally Posted by Kev_205

Well im converting my car to LHD to help sort the weight distribution amongst many other tweaks. My engine is on the drivers side so the car is really weight biased on that side

I have always raced LHD's and I think they have a distinct disadvantage as the majority of corners are right handers so I would think twice about doing that, going into Paddock bend at Brands for example is very daunting in a long nosed RWD LHD car.

[marcush.]

????
corner weights are adjusted ,so as to get the diagonals equal.It is not a good idea to try to have the front left and right the same or the back.

this is the only way to get the left and right percentages of front rear split corresponding to the true front rear weight split which is not adjustable (as long as you don´t have ballast to move around).

[Kev_205]

Originally Posted by Al Weyman

I have always raced LHD's and I think they have a distinct disadvantage as the majority of corners are right handers so I would think twice about doing that, going into Paddock bend at Brands for example is very daunting in a long nosed RWD LHD car.

My car is FWD though. I take it your engine sits longtitudinal so without the driver its pretty balanced car - gearbox and engine sitting in the middle.
My engine is transverse. Off the top of my head the engine weighs 100kg on my car and the gearbox something like 30kg. Thats a big bias to the right. I weigh around 66kg (skinny runt) so thats even more on the RHS.

Arent the BTCC boys all LHD?? Considering those cars are only driven on uk soil there still must be a good reason for FWD cars to be LHD

[maddogf3]

Having equal corner weights gives a balanced car it is likely to behave the same on l/h corners as well as r/h corner any in balance will effect handling any loading up of either side will effect grip . so try if possible with saloon cars to centalize weight ( Sit on the transmission tunnel ) Battery, fire extinguisher on left etc in a single seater any in balance at the front shows itself immediately with brake lock up ( the lightly loaded wheel locks before the other ) any attempt to even them up will give a better more predictable car and yes doing corner weights can be a pain in the Arse and very frustrating at times .Try not to do it on race days do it when you have plenty of time .
To me the answer is can you afford not to do it . If the guy next to you is quicker -- why is he quicker? . If you are winning races why bother with hours of frustration leave it alone. if you are not ,start looking the answer is out there corner weights are part of it . regards Martin

[maddogf3]

Originally Posted by Peter Mallett

App K. You have to run the cars as they ran in period. And adjustable platforms weren't invented then.

Dont think that would of stopped racers from shimming and bending stuff and even rewelding mounting points and disguising what they had done . Read what the works teams did ,to get around regs without scrutineers spotting what they had done . I think you will find they are still at it ...

[maddogf3]

Originally Posted by marcush.

????
corner weights are adjusted ,so as to get the diagonals equal.It is not a good idea to try to have the front left and right the same or the back.

this is the only way to get the left and right percentages of front rear split corresponding to the true front rear weight split which is not adjustable (as long as you don´t have ballast to move around).

Dont understand what you are saying . corner weights are set to give an equal loading on wheels on the same axle. there will be a difference front to rear i.e 60/40 70/30
It should be adjusted with a loaded up car fuel etc.and with front rear anti-roll bar disconnected bags of sand could be substituted for the driver ( arguably a better sub ) or the driver himself . personaly I dont bother . have the car on paper and when you can just slide it out read off the corner weight I find electronic ones hard work prefer to see a needle moving then I dont need glasses to read numbers . Martin

[maddogf3]

Originally Posted by Al Weyman

I have always raced LHD's and I think they have a distinct disadvantage as the majority of corners are right handers so I would think twice about doing that, going into Paddock bend at Brands for example is very daunting in a long nosed RWD LHD car.

Suggest you try Paddock Hill bend on a track day sat next to the driver , as you said on the left of the car at race speed Now that is frightening It gave me Angina . Had to get out . My turn to drive -- Got angina thinking about it . But actualy okay doing it, even locked the brakes going into it got round okay but my passenger wanted to get out .Good fun isn't it I find Craner curves a bit the same
Martin

[marcush.]

think about it .
cars are normally not totally symmetric ,especially touring cars .
the front rear split is a given no you cannot change by adjusting corner weights ,it is a
function of where the actual weight is positioned in the car.
so if you got say a 60/40 split front rear it is only logical that you adjust the corner weights accordingly .
As soon as the diagonals are equal ,you are spot on with those percentages(assuming the cars not hopelessly bent or something)
If you go for the eqal fronts the front rear split is less than the effective split on one side and more so on the other .
more important ,the car will stand more on the diagonal wich is loaded higher and will actually pivot around this diagonal when forces are applied .
Of course ,on a single seater this is more or less academic stuff and of course,if your cars not stiff (the body suspension pickups ) in itself (not the springs and bars !)this is more or less self adjusting.....

[maddogf3]

MR marcush
Still dont understand you !!!!
If you have 600 all up weight say for ease 400 0n rear axle and 200 at front car is level ( floor pan) then you should be trying to get 100 on each front corner and 200 on each rear . End of story -- That gives a car which will handle the same r or l
Admittedly you adjust diagonaly to acheive the correct set up for each corner
Are you saying put 80 kg of weight on one side and try and even them out ??
As for our single seater with its carbon tub not being stiff is rubbish . Formula three cars are extremly stiff lateraly and longitudinaly .we are running with wheel frequencies 300 rear 280 front ( Thats over 1000 lbs springs ) at the rear and our cars all up weight, with driver and 2 lires of fuel is 544 kgs thats 4 kgs overweight
you said adjust to give diagonals to give the same reading I think not
Did you say our car then would be self adjusting ????
( Had a Laugh with that one ) I will tell Mr Reynard to go back to his drawing board. perhaps thats why they went bust , Regards Martin

[graham bahr]

i'm with you maddog, is marcush mixing up the function of how you adjust the corner weights which is quite often on the diag with what your actually trying to achive?

[marcush.]

maybe I´m not clear enough with my words ,sorry.

example : lf 720 lbs, rf 584lbs
lr 644 lbs rr 607lbs

so the left side of the car weighs 1364lbs the right weighs 1191

we cannot change weight distribution ,so the left side will always weigh 1364 as the right side will always weigh 1191 ,correct?
We cannot change the weight distribution front rear either ,so the total front will always be 1304 lbs ,rear 1251 (50.9 /49.1%).
So we can only transfer weight diagonally.
If we adjust the corner weights so as to arrive at this 50.9/49.1 Split on each side
the corner weights are

lf694 rf606
lr670 rr585

the diagonals are :1279/1276 the left side still weighs 1364 the right side 1191lbs

we now have the front rear split of 50.9/49.1 on both sides and that was my point.

If your car is symmetrical (good design) ,this rule still works ,but your rule won´t work on the example above ,as you would have a real issue with the right rear corner and throw around spanners shouting this heap of **** is bent like a banana....

[dtype38]

Hmmmm.... very interesting subject and actually I think maddog and marcrush are both right, but solving different problems. maddog is quite correct that for a given basic front/rear load split, the aim should be to make the same axle wheel loadings as equal as possible. In my case I shoved my battery, extinguisher, fuel tank, header tank, catch tank, fuel pumps and uncle tom cobbly and all, as far to the left as they would fit to counter balance yours truely. Having done that, though, with me in, my car is still some 50kg heavier on the right. So where do I put that load? Front right wheel, back right wheel, or a bit on each? It can't go anywhere else! So that's where marcrush's system comes in. When there is no perfect option, the compromise (according to my text books at least) is made by evening up on the diagonals. This will inevitably give an imbalance at the front and at the back... but it's a compromise! Balancing up on the diagonals means that with the car sitting straight and level there is no tendency for it to "teeter-totter" (American phrase which fits nicely) across one diagonal. Of course, as soon as you brake, accelerate, or corner then the tyres are not loaded as evenly as is ideal, but its supposed to be the best you can do for a car that's got poor weight distribution.....

Having said that, I'm actually considering deliberately unbalancing my diagonals to give slightly more even front tyre loading than rear. Reason being that I have awesome brakes, but not too much power, so I need more stabiliy when I'm standing it on its nose trying to outbrake someone than when trying to get the power down (at the back I have a locked diff so I don't really have a problem with spinning an unloaded wheel).

Interested in more views on this

[grelley]

Think of the car like a chair with one short leg. Although only one leg is short the weight is supported by the other two diagonally opposite wheels, and the chair (car) will rock, when going into a corner. Going in one direction the car will feel firm, going in the other direction the car will feel soft. What you need to do is get the "legs" to support as equal an amount of weight as possible. Because of the cars initial weight distribution it will be impossible in most cases to get these weights equal, although top saloon cars will be built from scratch with weight distribution in mind. At best it may be only possible to get each pair of diagonaly opposite wheels to support the same total amount. If this can be acheived then the car will feel much tauter and easier to drive with confidence. This will also depend a lot on chassis stiffnes as to how well the car will respond to adjustments. By shimming the RF wheel you are increasing the load on what is already the highest loaded wheel on a RHD car thus increasing tyre loadings on that wheel. It may be more appropriate to load the RR wheel. Once the car is close to being properly set up, adjustment of one corneer will affect the other three wheels.

[marcush.]

here we are .sorry for my patchy english ,but the dtype and grelley summed it up perfectly.
I like to comment on the braking,though .As you are braking the rears get unloaded ,so it is very well possible ,that having one wheel more unloaded than the other (at the rear) will 1.reduce the rear brake bias wich is posssible before locking one or eve two wheels and second ,it will reduce the capability of the car to trailbrake into the corner more in one direction than the other.
Of course assymmetrical setups make sense .On ovals this is normal proceedure ,and is done by a hydraulic weight jacker ,compressing the spring (preload)on one corner

[maddogf3]

Marcush . I am still not sure exactly what you said BUT . Did you mean this
If you weigh car on weighbridge with driver in assuming all other weight is distrbuted to be as even as possible and then weigh front loaded axle and then rear loaded axle and divide the two , you can obtain a figure for the front to rear split this can then be split between corners and then you recalculate to get an equal ratio between diagnals not the same reading but the same equal ratio as if you add ( lets say 80 kg ) there will always be a loading difference between left and right that cannot be adjusted drivers side will aways be heavier A symetrical split will never be achieved on a Tin Top with one driver in it .I do have a Formula for doing this and I think that is what you ment ! I just didn't understand what you ment . On our 540 Kg car having corner weight out, has a major influence on handling and braking especialy .I try to get it within 10 lbs at the front on our Flat floor (most Important) whilst keeping ride height at 15mm and yes we do have hard springs and packers under the dampers and NO it doesn't bottom out all the time . I believe the oval racer boys in the states have a term "Corner Jacking " which gives unequal weight transfer and induced skewed roll . but i think this then moves from a scientific approach to motor racing into an "Art form " Your English is extremly good . I only wish "Us " as Brits had the same capacity to be multi lingual like yourself Bye for now regards Martin