Corner Balancing

iceracer said:

For road racing I have always understood that cross weights should be as close to 50% as possible and with the driver or equivalent weight in the seat,

What if I told you that's probably rarely true depending on the track configuration?  

And something we wrote about corner weighting that might help. 

100% of competitive oval track guys corner weight the cars for every track. Its how they set the car up. The cars in a lot of series have to meet specific weights side to side to be legal too. Too much left side weight on a circle track car will fail tech. I think the confusion lies in the word "balance". 

AnthonyGS (Forum Supporter) said:

iceracer said:

For road racing I have always understood that cross weights should be as close to 50% as possible and with the driver or equivalent weight in the seat,

What if I told you that's probably rarely true depending on the track configuration?  

If your racing program is serious enough that you run different cross weights on different tracks or only run one track in one direction then you might want to stray from the %50 mark but otherwise %50 is a pretty typical target.  If you are customizing cross weight for the track configuration there are a lot of variables to consider besides the number of left vs right turns and it takes a lot of track test time to optimize.

In reply to APEowner :

The typical way is not necessarily the right way.  While 50% cross weights are conceptually convenient, it's really just 'close enough' (within a few pounds) to LF/LR = RF/RR for most cars in the real world. The further a car deviates from 50% left weight though, the further a 50% cross weight technically causes the left vs right turn lateral load transfer distribution (handling balance) to diverge.

Driven5 said:

In reply to APEowner :

The typical way is not necessarily the right way.  While 50% cross weights are conceptually convenient, it's really just 'close enough' (within a few pounds) to LF/LR = RF/RR for most cars in the real world. The further a car deviates from 50% left weight though, the further a 50% cross weight technically causes the left vs right turn lateral load transfer distribution (handling balance) to diverge.

The %50 cross weight target is a compensation for the left/right mismatch.  If you have to move away from that you're compensating for something else.  That's not to say that it's bad to do that.  Production car chassis, particularly front wheel drive McPherson strut cars, often need settings that would never be considered on a chassis designed from the ground up for racing.

APEowner said:

Driven5 said:

In reply to APEowner :

The typical way is not necessarily the right way.  While 50% cross weights are conceptually convenient, it's really just 'close enough' (within a few pounds) to LF/LR = RF/RR for most cars in the real world. The further a car deviates from 50% left weight though, the further a 50% cross weight technically causes the left vs right turn lateral load transfer distribution (handling balance) to diverge.

The %50 cross weight target is a compensation for the left/right mismatch. 

Let's look at an extreme (albeit simple) example to better illustrate what's fundamentally occurring. First start with a car having 4000 pound sprung weight (including driver) with a 62.5% left weight bias and a 62.5% rear weight bias. Then give it cornering (one wheel bump) wheel rates of 400 lb/in front and 600 lb/in rear.

With 50% cross weights, the left side has the front and rear with equal natural frequencies, while the right side has a 13% higher front natural frequency than rear. This is the basis for considerably more understeer when loading the significantly front biased right suspension while turning left, than when loading the unbiased (neutral) left suspension when turning to the right.

With LF/LR = RF/RR, the left side has a 5% greater front natural frequency than rear, and the right side has an identical 5% greater front natural frequency than rear. As the weight transfers laterally in a turn, it does so proportionally regardless of direction. This is the basis for the oversteer vs understeer characteristic acting the same regardless of which direction the turn is and which side is being loaded.