Need Spring Guidance

[cruiksdr]

I'm working on my roller for a body swap with my current car. My current car has 165# progressive springs that I installed new about 5000 miles ago. The roller has a set of springs that appear to be pretty good, and they are plastic coated. Is there a way to determine 1) whether these springs are still good, and 2) what # rating they are? I know that if they are not too worn, I can increase their tension by cutting them down, I just don't know how to tell whether they are worth the time and effort.

Thanks!

[Dave at Pelican Parts]

If you can locate a shop with a spring tester, you can take the springs there and they will tell you what the rate is.

If not, then you can test them yourself with some weights and a ruler. Stack weights on top of the springs and measure how far they compress with each weight. Divide the number of pounds by the inches of compression and you have lbs/in, the spring rate! Try several measurements at different weights to minimize any errors.

If you can measure the spring itself, not the coating, you can come up with a rougher approximation using a formula. It uses wire diameter, coil diameter, and number of coils to figure the rate. I don't recall it offhand, but a search on this BBS will eventually find it because the formula has been posted more than once.

Don't cut springs. The ends of ours are "finished", which means they have been shaped to fit the spring perches. If you cut the springs you will have "unfinished" ends, which will put more stress on the spring perch. You can also weaken the material of the spring near where you cut it.

Similarly, don't heat up springs to lengthen or shorten them or change their rate. This can weaken them to the point where they will fail after a while.

Springs are not that expensive--buy the ones you want rather than trying to make them.

--DD

[Zeke]

This is one calculator: http://www.bluecoilspring.com/rate2.htm

the problem with cutting them down is making the end fit the spring seat. You will ahve to heat it there and I don't know what happens after that. Like DD says, springs are $50 each. If and when you go to adjustable collars and the universal 10" x 2 1/2" (2 1/2 ?) springs, they get very resonable, like under $40.