RGS fork spring spacers

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G'day all, replacing my standard fork springs with IKON progressive units. The replacement springs are 40 mm longer than the standard ones, which means that the 90 mm spacer on top of the springs requires shortening.
Has anybody done this conversion (somebody must have) and could they let me know what spacer length they came up with?
Thanks.
Terry
 
Depends how much you weigh and what sag you want Terry. Assemble the forks with whatever spacers you have (or no spacers if the springs are too long to get the caps on with the existing spacers) and measure the sag. Then add or reduce spacer length to give the sag you want. Typical sag is around 35mm with you sitting on the bike. Remember to do it with your feet off the ground, measure at upper and lower limits of stiction and take the average.

I make fork spacers from PVC electrical conduit. It's plenty strong enough, readily available and cheap, especially if you have a mate who's an electrician! It's easy to cut and file the ends square (I trim the ends on the lathe, because I can).

Cheers,
Cam
 
Measured the sag with the old springs and it came to around 40 mm. With the new springs in place and 40 mm shorter, temporary PVC spacers in place the sag is around 40 mm. Looks in the ball park, test ride coming up on Sunday.
Using zip ties, thanks Chris M.
 
Test ride completed; vast improvement but maybe a bit soft, will increase preload by 5 mm.
 
sag should be lower (at 3cm maybe, depends on the full travel). Please also measure what the full travel is once you make a hard stop on the front end (but please with warm tires only, don't drop the bike...!). To measure the full, use the zip-tie, too, but when you measure the length, make sure you unload the front completely and measure then from top of the dust cap to the lower of the zip-tie. That is your full travel. The sag when sitting on the bike should not be more than 20% of the full travel without the rider and between 25 - 35% when Rider is on board.

Preloading doesn't make it less soft btw.. To make it more firm, you either need to add some oil (if it is the last inch of the travel) to reduce the air-gap on top (should be between 150 and 170mm, depending on the rider...) or change the oil viscosity (if it is f.e. through the whole range) or you might need different springs (depending on how much you have to pre-load the spring to get to the right sag).

Oil viscosity influences the compression damping, but also the rebound damping on the RGS fork, so a compromise is needed.... On a warmed up fork (by riding it for some miles, the oil starts to warm up and tends to get a bit thinner...), you can make an easy test: stand aside of the bike, engage front-brake and bump the front of the bike down as much as you can. Without letting the handlebar go, give it free play to reflex up again and watch what happens: the suspension should extend to full and go down to the 2-3cm sag you adjusted with the pre-loading of the spring (sag without rider). If it waves more than that, your rebound damping is to low (and so is your compression damping I suppose, as both sides work the same on the RGS). In that case, you need to go up with the oil viscosity. Personally, I only buy 5 grade and 10 grad and mix it until it works... if it does not extend beyond the adjusted sag-point, your oil-viscosisty grade is to high and you need lighter oil (f.e. if you are at 10, you need to go down to 7,5 etc.).

you can take some nice infos out of the internet, f.e.: http://www.gostar-racing.com/club/motorcycle_suspension_set-up.htm#Setting your bike up

though this talks more about full adjustable suspension, you can also see he has a section for when the suspension is not fully adjustable. In that case, your oil viscosity as said is how you set the way the suspension travels.

 
Thanks Lothar, full fork travel (according to the workshop manual) is 12 cm, going to add a bit of pre-load to bring the sag down to around 3 cm; measured with two zip ties, one at 12 cm and the other measuring travel.
 
Dont confuse yourself now Tezz  :)  Stick to mm, whats this cm stuff  :P

25- 30mm is nice amount sag, 120mm travel ? some of my chook chasers arent that plush  :P  spose ya need to soak up the bumps on those goat tracks over in SA.
 
According to the manual it's 120 mm. I have two cable ties on the fork leg and after my test run on carefully selected 'goat tracks' and heavy braking tests, about 1 cm (10 mm) separated the two. Checked the sag once back in the shed and it was 40 mm (4 cm).
Will add 5 mm (0.5 cm) of preload and ride the some route to see how it goes. Feels much better already :).
 
Hey Terry

If the ICON springs are progressive as on their site then I would suggests you need to factor that in on your set up. Surely ICON would have advised on the correct preload for the springs, if not then would suggest best to speak to them.

When I buy the Racetech springs  Terry always tells me the correct preload to use for the application.

 
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