Rocker Arm Swift Spring rates?

[tsillay]

Question for the brains trust.
I've recently replaced the splindly rear rockers on an SE3 with the much stiffer US made DB3 item
It has certainly altered the effective spring rate, I'm guessing from a much greater tendency to oversteer I now need a softer rear spring

Does the collective memory still recall roughly what rate rear springs made the DB3's light up?

Many thanks.. Tim

[tlracer]

I have a DB3 here in the UK that I am rebuilding. The springs currently on it are 180lb/in front and 350lb/in rear.

Depending on set-up these - especially the fronts - may be quite soft as it was common in the UK at that time (mid 1980's) to run soft springs with a lot of preload wound on.

Preference in the US seems to be harder springs and less preload, I believe.

[S Lathrop]

I am going to suggest that you take the time to calculate the actual spring rate of the rockers on your car. You have proven to yourself that is makes a big difference and to get back to the handling you had with the original rockers, you will need to use that number.

I have run into similar handling changes when I get different tires that have a significantly different spring rates. I have seen front tires for F2000 that have been as low as 700 pounds per inch and as high as 1200. I use the tire spring rate when ever I calculate wheel rates. Also I use tire pressures as well for my calculations. Each tire type is different but a 1 psi change in tire pressure can change the tire spring rate front 25 to 40 pounds per inch.

To add to your problems that the rocker not only has a spring rate that needs to be calculated but it is also an un-damped spring. If you change the rocker spring rate to stiffer and say you want to soften the road springs, the damping will likely need to change because of the fact that now you have a damped spring verses an un-damped spring. It is something that you will likely have to think about to get back to where you want to be. There is no reason you won't be able to end up with a better handling car.

[tsillay]

Thank you gents.