Getting custom springs made (for auto or general purposes)

[Shifty]

If anyone needs custom springs made for a general purpose application, I can strongly recommend National Springs in Brisbane. I figured as I had to do a lot of running around to find a place and the whole experience was a little foreign to me, it was worth posting up here in case it helps someone out.

I had some springs custom made for the clutch on my turbo'd bike. As a guide on cost, I paid $140 for a set of six springs about half the length of your thumb. Turnaround is 5-7 days from dropoff/quote.

You will need to give them a sample (or else full details of what you want), and take the following measurements:

* Allowable OD (ie. can the outer diameter be wider than the sample? in my case, could not be increased)
* Allowable ID (ie. can the inner diameter be narrower than the sample? in my case, allowed to decrease by a maximum of 1mm)
* Installed height (eg. in my case when the clutch was assembled, the springs were compressed 7mm)
* Deflection / Travel (eg. in my case when the clutch lever is depressed, the clutch moves out 2mm)
* How much clamp (they can measure the existing spring and you can just say 10%, 50%, 100% more clamp, etc).

They can make basically anything you want, the only limitation is really the space that you have to work with as far as the inner and outer diameter. They can replicate your spring (or make one to order) with a thicker wire, more or less coils, progressive weight, etc.

They have a computer modelling program that allows them to design a spring that meets all your criterion. In my case the spring was replicated with six coils instead of five, and wire that was 0.3mm thicker. As the OD had to remain the same the 0.3mm was kept on the inside, meaning that the total ID reduced by only 0.6mm. The end result was exactly 50% heavier.

[Shifty]

You wouldn't bother with suspension stuff I don't think, but for wastegates, clutches, LSDs, or even valvesprings, that may not be widely available in the desired stiffness/size, then this is the go.