Reading And Understanding Coilover Spring Numbers

[OLLIE_NZ]

Hey guys,

Thought the Motorsport section would be the best place to ask about how to read the numbers on our coilover springs.

As some of you know our car is a Circuit car and we are wondering if from the rough deciphering of the numbers printed on our springs if they are too stiff for the circuit?

Are we correct with what the numbers mean below (we've emailed Merwede in Holland but have had no reply yet)

Merwede front Springs read - (25 250 59 118) = 250mm length, 59mm ID, 11.8kg/mm (dunno what the first 25 is)

Merwede rear Springs read - (250 49 98) = 250mm length, 49mm ID, 9.8kg/mm

If we're correct with the fronts being 11.8kg/mm and the rears being 9.8kg/mm are these far too stiff?

Who would you guys recommend as a good softer spring to buy and what rates would be ideal for the circuit?

Currently we run HKS Hipermax III coilovers, Dunlop 240/625R17 slicks and Ikeya adjustable arms...

Front springs they read '25 250 59 118' and are Merwede

Rear springs , read 'Merwede Progressive 250 49 98'

[hrd-hr30]

there's no standard, each manuacturer writes whatever they want on their spring. eg my Swift springs have Swift 070 or similar on them. That's a 7kg spring. My King Springs have thier part number and rate in lb written on them.

any decent/proper suspension shop that specialises in race cars (not franchises) will probably have a test rig to measure the rates. or for linear rate springs, there is a formula you can use to calculate the spring rate - google "spring rate formula"

irrespective of what rates they are, you probably don't want a progressive rate spring in a circuit car.

Edited June 29, 2011 by hrd-hr30