Nc30 springs in Bros forks?

[Jetblack]

I've got a set of aftermarket springs for an nc30 in my 'stores'. They are 8.25lbs linear springs. They are 12 inches long and I have spacers that are around 2 inches long.

Bros springs are 14" long with 8" spacers. 22" total

Can I use these in the Bros forks?

What spring rate are the stock Bros springs?

[JanM]

NC30 and RC31 both use 41mm RWU forks, so diameter should be OK. Then you just need to make spacers so the springs have app. 15mm built in preload (or any other preload you prefer).

Don't know Bros spring rate, but they are two-stage, usually too soft. But you can measure the springrate if you like... In my notes I have Bros as 4.5mm wire, 27 active coils, outer diameter 35.6mm for a initial spring rate of 5 N/mm and a secondary spring rate of 8 N/mm (but would prefer to recalculate as I have changed method since those measurements and calculations were done).

I hope the NC30 springs aren't 8.25lbs, but 8.25 N/mm or similar.

[Jetblack]

Cool. Good info.

Yes, sorry 8.25 n/mm

So how so I work out how to get to the right sag/correct length spacers?

[JanM]

https://traxxion.com/wp-content/uploads/2019/05/Fork-Spring-Installation-Text-photos-and-diagrams.pdf

[Jetblack]

Awesome. Thanks again

[Talon]

https://traxxion.com/wp-content/uplo...d-diagrams.pdf

Whenever I have used this method I wind up with very little sag, as in around 5mm in the forks using .80 kg/mm springs. I think Racetech recommends 15mm of preload on the springs as well.

[Jetblack]

I suppose its easy enough to whip the spacer back out and trim another 10mm off if I find this is the case?

[Talon]

I suppose its easy enough to whip the spacer back out and trim another 10mm off if I find this is the case?

Yep, very easy.

[JanM]

The overall idea is to have control over the process - the Traxxion method is a method, you need to find the preload (and springrate, oil viscosity, oil level, fork position etc) that you like - they are all parameters in setting up the bike to your liking. A too short spacer in a damperrod fork is easily fixed by adding some washers, a too long spacer just needs to be cut down a little (and then have some washers on hand if it gets too short).

But ride the bike before making bigger changes - you might find slightly different preload and oil level values suits you better, so no need to just chase a given value. Set a value and try it, then decide if you want to make changes.