What are units in spring rate section of FAQ?

[Guest Anonymous]

I'm being a big dork but.....Something's up with the spring rates as they are expressed in the History/Reference FAQ. First, the rates are expressed in both metric and english units (good) but they are not of consistent dimension (bad). The metric unit used is kp (1 kilogram force = 9.81 N = 2.2 lb force). The english unit is expressed as lb.ft, which would be a torque, not a force. I think the english unit should probably be lbf (pound force). Somebody probably just saw the 'f' and assumed foot instead of force. Second, rates should have dimension of force/displacement...not just force. Are the numbers in the table actually just total load capacity of the various springs? Perhaps they are spring load at some specific spring deflection? Help! I'm trying to figure out the stock rates and rates of common aftermarket springs so I can make an intelligent decision about what to do with my car. Thanks!

[Guest Anonymous]

Would imagine you just need to convert to lbs/inch so divide by 12.

[Guest Anonymous]

I can start getting info together....no promises on timing though. I imagine this information is lurking somewhere in the 'other' board archives. Of course, there are a lot of conflicting answers in there. Ideally, I'd find a set of each spring and test them myself. I have a lot of friends who club race so somebody might have access to a coil spring tester. Does somebody have a list of springs out there that can be used with the stock spring seats...coil overs are a nonissue since you can get 'standard' racing springs in any rate you want. Once a spring tester is found, I'd have to borrow some springs. Perhaps people getting a new set can loan them out before installing them? Any other ideas? I imagine some of the '02 vendors have info for the aftermarket pieces, hmmmm.

[Guest Anonymous]

that would make the stiffest front spring 54.7 lb/in, which I think is a bit low....

[Guest Anonymous]

My fault for confusion. I just pulled the data from the factory shop manual and added(typing error) a "t" where I should have just left it "lb.f". Let's hope Trent will catch this and correct it.

I've never seen the bmw factory nor any of the aftermarket spring marketers specify a rate/deflection value. Have you?

You're volunteering to undertake this study and publish your findings aren't you. Heh, heh, heh.

I look forward to your findings.

[Guest Anonymous]

I saw that the units were wrong when the faq first went up, but have not had the time yet to type a good response. The other thing is, the faq says the manual does not include data for the rear HD, which it does. The rear HD stuff is just listed at the end of the specification section.

I have some some "normal" spring rate figures to offer the faq, that is easier to interpret.

The factory figures are not really spring "rates" in the normal force vs travel sense.

I've never seen a good explanation of them, and while I think I know what's going on there, I want to look closer at it before submitting a faq update. Anyone with insight on this, please speak up or email me direct.

// John