Corner Weighting

[fastg]

Next Monday is Dyno Day and I am going to corner weight the car after the dyno session. Any insight would be appreciated. Do you set them up at 25% at every corner or is there a better strategy, say 55% on the rear of the car? I did not have any problems with handling before, but I have changed all 4 springs so I am sure it will be way off. 

 

Graham  

[CBuff]

I haven’t yet done it. But have looked into it. Here was a helpful video. It seems to be more about matching the diagonal weights. Since you can’t really change actual weights in the car (short of moving things like the battery etc ). 
 

 

[fastg]

I just finished watching that exact video:) I have a better understanding now. 

 

Graham 

[KnifeySpoony]

Traditionally the goal is to balance cross (diagonal) weights to aid in handling balance/symmetry. However it seems that some of the UK 7 people prefer to balance the front wheels so that they both lock at the same time. Without the advantage of ABS, we will almost always get the passenger front wheel locking first. Balancing fronts in theory will give slightly more braking performance. I haven't bothered with any kind of corner weighting on my car and i don't notice any ill handling. 

[CarlB]

I haven't watched the video but have done a lot of done a lot of setups. Except for single seat cars you always have more weigh on one side or the other. KnifeySpoony is correct about setting the car up for corner entry or even balance in left and right turns. I have scales if you would like to use them.

[dallasdude]

On 3/13/2023 at 12:28 PM, KnifeySpoony said:

Traditionally the goal is to balance cross (diagonal) weights to aid in handling balance/symmetry. However it seems that some of the UK 7 people prefer to balance the front wheels so that they both lock at the same time. Without the advantage of ABS, we will almost always get the passenger front wheel locking first. Balancing fronts in theory will give slightly more braking performance. I haven't bothered with any kind of corner weighting on my car and i don't notice any ill handling. 

This is correct.  Try to get the cross weight close to 50%, but try not to have the LF and RF over 40 pounds difference.  On a LH drive Caterham, the left rear is gonna always be heavy, so the RF is gonna be light.  Bottom line is, try to get to 50% cross, but compromise before you get the RF too light. Or LF in the UK.

[CarlB]

You are correct. The traditional way to scale a car is to get the cross weight to 50%. You can look at it as a bench with four legs. The bench has more weight on one side. If the left rear leg was a little longer than the right rear leg the bench would have cross weight or wedge (the stock car term). If you remove the weight from the bench and the leg is still long, you still have cross weight. If the right front was high, you would have negative cross weight. 

[fastg]

Thinks for everyone's help, we did a quick setup after our dyno fiasco. The car is a little heavier than I hoped at 1430 pounds, I think the cage must be 75 pounds. I had setup the shocks with the same amount of compression as the original springs just as a starting point.  I had screwed the right front up, the new springe are longer so I was aiming for the same compressed length adjusted for the new spring length. Well the maths went wrong somewhere the right front had a lot more preload. Once that was fixed at the very close, more my luck then judgment we got it to 39/51 percent cross weight with me in the car. Off to NJMP on April 8th to see if it makes much difference. The new springs are a lot firmer them the old ones, road driving is not harsh, but I am hoping it will show an worthwhile improvement on the track. 

 

Graham 

[CBuff]

49/51?  Seems great. Interested to hear how njmp goes. 

[dallasdude]

As a point of reference, we weights are with a full cage, a 190 pound driver and and 30 pound of ballas on the passenger side.  Wet sump Zetec and a cast case T9.

[fastg]

Track day at NJMP went well, it was cold on Saturday morning so it was multiple layers to keep warm. My tires are a little past there prime but the spring upgrade has been a success. The harshness felt on the road did not transfer to the track.  I did have more confidence in faster corns and that was the goal. I was planning on getting some data on the last session, but a BMW look out the tire wall after turn 4, once I spotted the trailer with new tire barriers arrive I pack up and went home thinking it would be a while. PittRace in May will be the next big test, a track I like with more varied corner configurations than NJMP. 

 

First track day of the year you always forget something, for me is was the pour spout for the Jerry cans, so use what you have available:)

 

 

 

Graham 

[Croc]

Why didn't you tell me you were there?  I would have stopped by.  I spent the morning doing car tasks between my garage and the airport hangar.  

[fastg]

Sorry, I kept an eye open every time I drove past your unit and did not see any signs of activity or you BMW parked there, so I wrongly thought you were somewhere else.

 

Graham