Any Corner weight Experts Out There?

[LuckyP]

Hi chaps,

A couple of weeks ago I stuck the Ult on some corner weight scales and came up with this:

w/o driver

LF 175.5 RF 215.5
LR 363 RR 318.5

with driver

LF 197 RF 249
LR 375.5 RR 346

Now it doesn't take a rocket scientist to work out that the weights are way off optimum for track - and his probably explains why after a recent spring change, whilst rebalencing teh brake bias, I was locking up one front rather than the pair together.

Question is, to get the fronts more even (and bringing the front height down and the rear up a bit (I'm at 120mm front 140mm rear - where I should be at 110mm front and 160mm rear)), with the front weights more balenced, what do I have to do to the spring collars?

Cheers
Pete

[Ross_328i_sport]

I would imagine you will need to rotate the front collars anti clockwise reducing the preload on the spring and for the rears you will need to rotate thm clockwise to increase the preload on the spring.

I hope this helps

Ross

[lanan]

Pete.
YHM

Graham

[GreenV8S]

LuckyP said:

with driver

LF 197 RF 249
LR 375.5 RR 346

If you want to take the torsional preload (weight jacking) out then the weights you're aiming for will be roughly:

LF 219 RF 227
LR 353 RR 368

This gives the same overall front/rear and left/right distribution but without any torsional preload.
If you were aiming for perfection then you would then start shifting components or ballast to move that extra 11 Kgs to the left.

Assuming you have adjustable springs seats on your dampers you would wind them up on the corners you want to make heavier, and down on the other corners. Once you have the torsional preload taken out you can then wind both front or both rear up or down together to sort out your ride height. Remember that changing the ride height will usually have some effect on the geometry so recheck that afterwards.

[stylussprinter]

Weight transfer in cornering is diagonal so to transfer more weight from the front right , for instance , you would wind up the spring seat and lower the rear left spring seat. It's not easy plus a bit of a 'black art' . You'll need to have an equivalent weight guy to yourself sat in the drivers seat OR weights in the seat/up the back rest and some on the floor (matching your weight) to be accurate. It took me an hour and a half to do my own but had another car here to do which took 4 hours !

[GreenV8S]

stylussprinter said:

Weight transfer in cornering is diagonal so to transfer more weight from the front right , for instance , you would wind up the spring seat and lower the rear left spring seat.

I'm having trouble making sense of that. Winding one seat up and the diagonally opposite down by the corresponding amount won't affect corner weights or weight transfer. All it will do is change the attitude of the car by a small amount.

To adjust the corner weights to change/remove torsional preload ("weight jacking") you would wind the spring seats for two diagonally opposite wheels up, and the other pair down.

[stylussprinter]

GreenV8S said:

stylussprinter said:

Weight transfer in cornering is diagonal so to transfer more weight from the front right , for instance , you would wind up the spring seat and lower the rear left spring seat.

I'm having trouble making sense of that. Winding one seat up and the diagonally opposite down by the corresponding amount won't affect corner weights or weight transfer. All it will do is change the attitude of the car by a small amount.

To adjust the corner weights to change/remove torsional preload ("weight jacking") you would wind the spring seats for two diagonally opposite wheels up, and the other pair down.

Do you have your own corner weight gauge ? I've balanced my car and others many times. On one occasion I was fortunate enough to be at Goodwood when a race mechanic had some drive on scales so I got the opportunity to check my settings or rather he did ---- they differed in the front by 0.5kg and the rear were 1.5kgs difference.

[GreenV8S]

stylussprinter said:

Do you have your own corner weight gauge?

Yes, it is made out of some bathroom scales for fat people plus a few bits of 2"x4" and cost me about £20. I used it to find out what the weight distribution is and confirm the chassis and suspension are straight but beyond that I hardly ever need to use it. You don't need a corner weight gauge to set the spring seats to equal heights on both sides, and that's all it takes to achieve the correct weight distribution if your chassis is straight.

[Sam_68]

GreenV8S said:

You don't need a corner weight gauge to set the spring seats to equal heights on both sides, and that's all it takes to achieve the correct weight distribution if your chassis is straight.

Yeah, but you drive a TVR don't you?

Seriously, though, even if the chassis is perfectly straight, trying to set weight distribution by setting equal spring seat heights is pretty iffy at best:

• Spring rates and uncompressed lengths of individual springs can vary by enough to have an influence, so unless you've got the facility to accurately measure and match springs to make sure they're equal...
• Weight distribution within the chassis can be asymmetric (I've usually got 100kg's of fat bd driver sitting over on the right hand side and nothing to balance on the passenger seat, for a start!).
• Particularly if you're using fairly stiff spring rates for track use, you'd need pretty accurate measurements of spring seat distances; even if everything else is perfect, 1mm of difference could easily give 10kg or more difference at the contact patch.

... and joking aside, the chassis on specialist cars, particularly spaceframes, are seldom perfectly straight.

I've always tended to use equal spring seat measurements as the starting point for corner weighting (followed by a check to equalise chassis ride height), but you'd be surprised how far out you can be when you then come to put the car on the scales.

Edited by Sam_68 on Monday 8th September 17:55

[LuckyP]

Now if you recall, after installing the uprated springs I was running high at the front and low at the rear, and the corner weights with me on board were:

LF 197 RF 249
LR 375.5 RR 346

Total 1167.5

Static Weight Dist = 49% L, 51% R

Cross Weight Percentage = 53.5% Wedge (LR,RF)


The factory set the normal ride height for me and with now changes this came in at:

LF 199 RF 246
LR 368 RR 356

Total 1169 (filled up only 1 mile away)

Static Weight Dist = 48.5% L, 51.5% R

Cross Weight Percentage = 52.5% Wedge


After several hours of spinning platforms up or down a turn at a time I finally got to (with 100kg of lead as me)

LF 212.5 RF 235
LR 356.5 RR 371.5

Total 1176.5

Static Weight Dist = 48.4% L, 51.6% R

Cross Weight Percentage = 50.2% Wedge

Ride heights:

LF 110 RF 109

LR 152 RF 151

Towards the end I was just getting confused and was woried that my heights were getting out too much.

Importantly, the differents in the fronts has come down and the cross weight is near perfect.

Don't know if this is interesting to anyone. But I can say it's interesting watching the weights change - and frustrating to see some go out at some come in!!

Lucks

[stylussprinter]

Sam_68 said:

GreenV8S said:

You don't need a corner weight gauge to set the spring seats to equal heights on both sides, and that's all it takes to achieve the correct weight distribution if your chassis is straight.

Yeah, but you drive a TVR don't you?

Seriously, though, even if the chassis is perfectly straight, trying to set weight distribution by setting equal spring seat heights is pretty iffy at best:

• Spring rates and uncompressed lengths of individual springs can vary by enough to have an influence, so unless you've got the facility to accurately measure and match springs to make sure they're equal...
• Weight distribution within the chassis can be asymmetric (I've usually got 100kg's of fat bd driver sitting over on the right hand side and nothing to balance on the passenger seat, for a start!).
• Particularly if you're using fairly stiff spring rates for track use, you'd need pretty accurate measurements of spring seat distances; even if everything else is perfect, 1mm of difference could easily give 10kg or more difference at the contact patch.

... and joking aside, the chassis on specialist cars, particularly spaceframes, are seldom perfectly straight.

I've always tended to use equal spring seat measurements as the starting point for corner weighting (followed by a check to equalise chassis ride height), but you'd be surprised how far out you can be when you then come to put the car on the scales.

Edited by Sam_68 on Monday 8th September 17:55

Thank you for putting him straight !! Corner weighting has nowt to do with equal spring platform settings -- exactly the opposite in fact . The front platforms may be fairly close but the rear will never be close to achieve the optimum. If equalising platforms was all that's required then how did I knock time from my lap time , corner weighting ?

[stylussprinter]

LuckyP said:

Now if you recall, after installing the uprated springs I was running high at the front and low at the rear, and the corner weights with me on board were:

LF 197 RF 249
LR 375.5 RR 346

Total 1167.5

Static Weight Dist = 49% L, 51% R

Cross Weight Percentage = 53.5% Wedge (LR,RF)


The factory set the normal ride height for me and with now changes this came in at:

LF 199 RF 246
LR 368 RR 356

Total 1169 (filled up only 1 mile away)

Static Weight Dist = 48.5% L, 51.5% R

Cross Weight Percentage = 52.5% Wedge


After several hours of spinning platforms up or down a turn at a time I finally got to (with 100kg of lead as me)

LF 212.5 RF 235
LR 356.5 RR 371.5

Total 1176.5

Static Weight Dist = 48.4% L, 51.6% R

Cross Weight Percentage = 50.2% Wedge

Ride heights:

LF 110 RF 109

LR 152 RF 151

Towards the end I was just getting confused and was woried that my heights were getting out too much.

Importantly, the differents in the fronts has come down and the cross weight is near perfect.

Don't know if this is interesting to anyone. But I can say it's interesting watching the weights change - and frustrating to see some go out at some come in!!

Lucks

It's not an exact art but very rewarding when you get it right. It's all about weight transfer in roll/cornering and therefore improved rear grip , even more so when combined with a front anti roll bar. Good on yer for going through the exercise.

[Mr2Mike]

stylussprinter said:

Thank you for putting him straight !!

What you said is still incorrect though; raising the spring seat of one corner of a diagonal and lowering the other will not change corner weights, it will simply tip the car over slightly on a diagonal line!

[s.m.h.]

Mr2Mike said:

stylussprinter said:

Thank you for putting him straight !!

What you said is still incorrect though; raising the spring seat of one corner of a diagonal and lowering the other will not change corner weights, it will simply tip the car over slightly on a diagonal line!

Not if he means up on LR and down on RR. Increase the loading to the FR winding up the rear and unloading LF by winding down.

Look at corner weighting as a wonky four legged stool, by shortening 1 leg it will become stable - its just knowing what one needs adjusting!

Might sound stupid, but are tyres pressures set, roll bars disonnected, 1/2 tank fuel in?

Do you have a ride height to aim for? If so set the front dampers so both front corners are the same height - ignore the fact 1 damper may be a turn or 2 different. Then adjust the rears to bring them in, otherwise youll be running round in circles up at the front, down the rear etc.

Its easy to get anal over cornerweights, it just takes a bit of time!

One thing to add, something I do as well now, a mate of mine worked on ALMS ferrari for a bit and found they were getting good feedback from the driver by aiming for a 50/50 split left to right, and as long as the fronts weren't too far out it worked.

Edited by s.m.h. on Thursday 30th October 08:04

[S6PNJ]

I realise I'm a bit late posting this, but I was searching for info on corner weighting and found this link to a spreadsheet. Might be of some use maybe?
Corner Weight Spreadsheet

[Incorrigible]

s.m.h. said:

One thing to add, something I do as well now, a mate of mine worked on ALMS ferrari for a bit and found they were getting good feedback from the driver by aiming for a 50/50 split left to right, and as long as the fronts weren't too far out it worked.

But you can't sort out a 50/50 L/R balance by corner weighting, you have to do that by ballasting.

Also, depending on the track, you may find that you'll gain more time optimising the braking rather than than getting a 50/50 cross weight split. Even more so in a race situation, if you can out brake the next guy, he's going to be behind in the corner

Worth mentioning too, as no-one else has, it's important to have the ARBs disconnected when you do the corner weights, and you should adjust them to fit without twisting them when re-fitting

[s.m.h.]

Incorrigible said:

s.m.h. said:

One thing to add, something I do as well now, a mate of mine worked on ALMS ferrari for a bit and found they were getting good feedback from the driver by aiming for a 50/50 split left to right, and as long as the fronts weren't too far out it worked.

But you can't sort out a 50/50 L/R balance by corner weighting, you have to do that by ballasting.

Also, depending on the track, you may find that you'll gain more time optimising the braking rather than than getting a 50/50 cross weight split. Even more so in a race situation, if you can out brake the next guy, he's going to be behind in the corner

Worth mentioning too, as no-one else has, it's important to have the ARBs disconnected when you do the corner weights, and you should adjust them to fit without twisting them when re-fitting

Are we talking road or race cars here?
Ive not come across a race car thats been so far out on corner weights at the correct ride height that we needed to move weight around. Unless it was bent!
N24's I do have a 50/50 L/R and a 51/49 F/R. Trade off is 2mm or under difference in spring platform height on the rear.

[Incorrigible]

s.m.h said:

Are we talking road or race cars here?
Ive not come across a race car thats been so far out on corner weights at the correct ride height that we needed to move weight around. Unless it was bent!
N24's I do have a 50/50 L/R and a 51/49 F/R. Trade off is 2mm or under difference in spring platform height on the rear.

Any car shirley, if it's got a 45/55 L/R balance unless you move ballast it's going to stay at 45/55 whatever you do to the corner weights

Unless we're talking at cross purposes and you're talking about L/R balance across one axle ??

[s.m.h.]

Incorrigible said:

s.m.h said:

Are we talking road or race cars here?
Ive not come across a race car thats been so far out on corner weights at the correct ride height that we needed to move weight around. Unless it was bent!
N24's I do have a 50/50 L/R and a 51/49 F/R. Trade off is 2mm or under difference in spring platform height on the rear.

Any car shirley, if it's got a 45/55 L/R balance unless you move ballast it's going to stay at 45/55 whatever you do to the corner weights

Unless we're talking at cross purposes and you're talking about L/R balance across one axle ??

Corner weighting is done across diagonals, so, for example, if you raise the RR, the weight will increase slightly on the LF and decrease on the LR and RF. In doing so some of the weight from the RH / LH split will move to the left.To increase the weight shift the adjustment on one side should be the opposite applied on the other - 1/2 turn up - 1/2 turn down.

For euro GT4 we run 70+ kilos of ballast that is fitted in a specific place - not by choice. Its dialed out with a quick sit on the scales.
I always set the car to the necessary ride first then see where it comes in on corner weights. Plus once the fronts are set at the required height, adjustments are done to the rear to bring it in. The rears can be a bit out across the axle without any noticeable problems. Problems really occur when theres a bent component and no amount of adjustment will compensate! As we say, you can't polish a turd!

[Incorrigible]

I concur,

But you see my point re distribution ??

FWIW, the large majority of cars I set up are hampered by a fat bloke sitting over the RR wheel, so it's always a compromise. Also as it's fairly budget racing (if there is such a thing) they tend to want a set up that works quite well all year rather than endless tinkering on endless test days.

Now that's the sort of work I'd really like