shortening springs myself?

[dougisaacs]

I've got a classic impreza to which I've fitted solid adjustable front top strut mounts. These raise the ride height buy about 10-15mm. Would I be doing something very silly if I trimmed down the front springs a bit to lower the ride height back to normal? I know it will decrease suspension travel a bit but is this a major problem and are there any side effects I should consider?
Thanks

[deeen]

do you mean just cutting down the spring with a grinder, or such-like? having tried this on an old volvo, i would consider 2 points...
1) How will the shortened spring sit in its mount? unless you shorten by a full coil, it may not work, and...
2) Shortening the spring will also incerase the spring rate, i.e. stiffen it. So the dampers may no longer be strong enough. And if you just stiffen the front, relative to the back, you will alter the handling... stiffer front = more understeer, i think?

Edited by deeen on Friday 1st January 11:54

[Avocet]

Also, shortening a standard spring will increase the stresses in the remaining coils. Depending on how close to the limits they already are, you might find it breaks (or sags) after a while. Another thing to consider is how much preload there already is. If there is almost none, could you end up in the situation where the shorter spring jumps out of its seat when the car takes off on a crest?

Edited by Avocet on Saturday 2nd January 23:15

[dougisaacs]

Thanks for the comments. I must say I don't understand why shortening the spring stiffens it? Especially if it is a non-progessive spring?

[flemke]

dougisaacs said:

Thanks for the comments. I must say I don't understand why shortening the spring stiffens it? Especially if it is a non-progessive spring?

A coil spring works like a torsion bar. In both, stiffness is proportional to length. If you double the number of coils, you double the length of the "bar".

[dougisaacs]

Very interesting, thanks again

[Avocet]

Or looking at it another way, if you get two identical springs in respect of diameter, material specification, etc but one has fewer coild, the one with the least number of coils will be the stiffest, because when you compress them both by (say) 1", the one with the smaller number of coils will have to twist each coil by more than the one with the larger number of coils.

[mrmr96]

This is PH, not Barry Boys.

Cutting coils off springs is potentially very dangerous as there is a great risk that the handling of the vehicle would be adversely affected. This may have several consequences including MOT failure, Insurance invalidation and potential dangerous driving charges in the event of an accident. (Remember the fellow with the modified 4x4 which killed one of his kids?)

If you want to lower it, get some lowering springs from Eibach or similar. A full kit of 4 springs will be about £100 to £150. Have a look on Camskill.co.uk

Much better than cutting coils.

HTH

[dougisaacs]

mrmr96 said:

This is PH, not Barry Boys.

Cutting coils off springs is potentially very dangerous as there is a great risk that the handling of the vehicle would be adversely affected. This may have several consequences including MOT failure, Insurance invalidation and potential dangerous driving charges in the event of an accident. (Remember the fellow with the modified 4x4 which killed one of his kids?)

If you want to lower it, get some lowering springs from Eibach or similar. A full kit of 4 springs will be about £100 to £150. Have a look on Camskill.co.uk

Much better than cutting coils.

HTH

Fair shout, these actually are the Prodrive/Eibach set but they don't lower the front much, if at all. However, What you say makes a lot of sense, I think I'll live with the slightly higher ride height.