924Board.org

[bruni]

Spent the weekend lowering the car by about 3/4" and increasing front camber to 2deg- big improvement. Reduced the understeer and body roll can see no downside at the moment, although I guess tyre wear may be a problem. Lowered the front by cutting of one complete coil and the rear by the adjustment on the trailing arms, quick and simple.
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1982 931
1975 harley sportster

[flosho]

Have any pictures of it?

I'm debating cutting a coil on my welmiester lowering springs..
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[This Space For Rent]

[bruni]

No sorry, this mod works so well because of the design of the standard spring which incorporates a very shallow helix angle on the top and bottom coils effectively giving a duel rate. At normal ride height the spring rate is relatively soft for the first part of the suspension travel (in bump) and then rapidly becomes stiffer as the top and bottom coils become coil bound. This design means that you can cut a coil of the top or bottom and it will not not make a big change to the overall spring rate. I am not familiar with the welmiester lowering springs so can't comment, however if they are a single rate spring and they have already lowered the car you must check that there is still pre-load on the spring at full droop. trust this helps

[RC]

After making the stupid dodgy mistake of cutting one coil off the stock springs I can now state "DON`T DO IT!"

You may be happy with it Bruni but I certainly was not. The end coils are "flattened" not for progressive spring rate but to sit square in the seats. The angle of the subsequent coils is much steeper and will only make contact at the end point. It caused the upper mount to deform (cup) and behaved similar to stuffed upper mounts, even though these are quite new.

Stock has 8.5 coils. So removing one will increase the spring rate 8.5/7.5 or around 13%.Negligible really and didnt lower much, 15mm IIRC. It did however have a detrimental effect on the handling.

Flosho, i`ve now got the weltmeister springs too but was disappointed that they didn`t lower much either. Have so far resisted the temptation to hack a coil off but these have similar shallow coils for about 3 turns. Should, in theory, be doable. Please cut yours and let us know the result.

[flosho]

[fiat22turbo]

Many people who cut springs will reshape the spring ends with a torch.

Obviously not ideal, but in lieue of custom-wound replacement springs or adaptation of generic racing-style coil springs and adjustable spring perches, it isn't a bad choice.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[bruni]

Having worked in the motorsport business for over 35 years for the most part specializing in suspension systems I resent being called stupid stupid.
The springs and spring seats are for sure designed as a package, and different manufactures will choose various solutions to mount the springs and for the spring design to give the best compromise for the ride and handling they are trying to achieve for any given model. Most manufactures nowadays go for some form of progressive rate by either varying the helix angle, the wire diameter or the circumference of the spring. Further decisions have to be made concerning the mounting of the spring, typically motorsport springs are ground flat, however many road car spring shape the spring platform to fit the spring as is the case with the 931. Having removed one coil I found that even with no preload eg the strut at full extension the spring made contact over about 1/3 of the platform and when under load over 2/3 of the platform. I was also concerned that the top spring platform might deform so fitted the cut end on the bottom which has much better support. I use my car on the road only, so I was not looking to increase the spring rate to much, furthermore I have no intention to change the rear springs which I would have to do if the front spring rate was increased to much. your calculation is to simplistic and makes no allowance for the fact that the top and bottom coils run almost coil bound as can be seen from the marks when you remove the spring. On my car was lowered by 19mm which was perfect for my requirements. I believe that if you go any lower you will have to start adjusting the angle of the track control arms and the steering arms.to bring the roll center back to a sensible height and reduce the camber change and bump steer. For the time being I have compensated by increasing the camber to 2deg. This has worked fine for me, turn-in has improved, under-steer considerably reduced while still maintaining a good ride compromise. Now I know this is a bit of a bodge but it works fine, if you are really concerned don't do it ,I was just passing on my experience which is what I thought this site was about.
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1982 931
1975 harley sportster