Front/rear elastic roll stiffness balance

[clausen]

Hi, we are soon to be starting some rough tuning of our car. We're effectively a first year team and don't have much data to go by. Just roughly, what sort of roll stiffness balances are people using to good effect? I understand its reasonably common to have similar front and rear wheel rates. If you're running similar springs front and rear, are you using a lot of rear bar?

Cheers

[clausen]

Hi, we are soon to be starting some rough tuning of our car. We're effectively a first year team and don't have much data to go by. Just roughly, what sort of roll stiffness balances are people using to good effect? I understand its reasonably common to have similar front and rear wheel rates. If you're running similar springs front and rear, are you using a lot of rear bar?

Cheers

[Jarrod]

Paul
it all depends on track ratios, roll center heights, weight bias, front/rear tyres, depending on how stiff your chassis is. With wide rear tyres last year(9") and narrower fronts (7") we had to adjust the car on different surfaces. I think we ended up at about 55% rear with 7" tyres all around. like everything, just make sure you have plenty of scope for adjustment, move through the full ranges(front full stiff, no rear, then rear full stiff no front, and in between), see what effects you get. That will tell you how the car responds as well. Of course your car may behave in a completely different fashion to ours, and i am looking forward to seeing it.

[murpia]

If your tyres are equal width F&R, start with your weight distribution and invert it: e.g. if your car is 45% F weight then try running 55% F roll distribution. Start with equal tyre pressures F&R as they will have a big effect on real vs calculated roll distribution. Also make sure you include roll centre effects when calculating wheel and bar rates to achieve a certain roll distribution.

If your tyres are not equal width, factor in this width distribution also, and any vertical stiffness differences between tyre sizes.

This will give you a starting point for tuning, and then I would expect transient effects to dominate and lead you away from this starting point in a consistent direction.

Ian