Pace RC36 elastomer-to-coil swap
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- Опубликовано: 5 сен 2012
- What can I say, I couldn't justify spending 40 quid on a handful of diddy rubber blocks. So I sought out some coil springs and here is the result. For the record they ride alright, a bit of top-out clunk but it's all held together...
Хобби
Gate springs are designed for tension not compression.
With springs in series you divide the spring rate by 6, but then you have two legs so times by 2, so your effective rate is 1 kg/mm. However your springs are actually similar to those used as part of the stack inside older RST, Manitou and Rock Shox.
I've used a 50/50 combo of spring and polyurethane rod in the past but it's a lot of cutting/drilling work and finding soft polyurethane rod is tough.
As a lightweight guy, elastomer forks barely move under my weight so it's great to add some plush travel.
Good point about the spring rates but the odd thing is that I know for certain the overall spring rate is a damn sight more than 1kg/mm, otherwise it would bottom out as soon as I sat on it (the total travel is only 50mm)! So something doesn't add up somewhere. That leaves the individual spring rates to be called into question, but these are actually stated on the manufacturer's website (www.ashfield-springs.com/compression-springs-online.php - Type S.307). However, without pulling the fork apart I can't measure them.
Gate springs differ. The one I used was designed to mount vertically, wrapping round the post in such a way as to be compressed when the gate opened; its resistance to this compression then tended to close the gate. Doesn't matter anyway, cos it didn't work!
The1trueDave
I have got a degree in engineering ;-)
That's the theoretical rate based on their spec and your configuration but in reality the forks have stiction, damping, springs don't have a linear response and most of your weight is on the rear wheel when riding. The cheap eBay springs I bought (similar spec) also became shorter and stiffer once I had bottomed them out.
TBH fitting and experimenting with alternatives for my early 90s Manitou's was so much effort, next time I think I'll just find some cheap used forks for sale locally and pull them apart for springs and elastomers rather than try to make my own.
should show the surclip removal too, but otherwise a good guide
Thinking of doing this myself. How was the ride after the swap, better/worse. Did the spring rate allow you to get full travel.
...characteristic which steel springs lack, so this may need to be compensated for. I did this by experimenting with the oil damper and eventually needed it on maximum. I may try the heavier oil myself so that I am not on maximum damping but that bike is in bits atm for a frame respray... hope this helps anyway...
Hello Dave.
I have the same fork.
I tried springs with 30 N/mm but it seem the fork is not stable enough.
My weight is 85KG and the Bike is about 12KG. I Wonder if I misunderstood anything.
Many thanks in advance for your reply.
cheers,
Stefan
Hi,
Sorry it's taken me so long to get back to you - my desktop PC has been in bits and my phone isn't smart enough for RUclips :-/
Anyway, I wasn't sure what you meant by 'stable' but I'm guessing it might be to do with damping... are your forks bouncing around too much without settling down?
For the record I am 78kg, so not too different from you. Does your fork have an oil damper in one leg? If so perhaps some heavier oil might increase the damping. Elastomers have an inherent damping...
Clearly a guy with no idea how suspension is meant to work! Elastomers provide damping too which now does not exist. Try driving your car with no shock absorbers..... Just pick your ditch, wall, hedge back etc. (Delete as appropriate). Back to the drawing board methinks.
You have a point, but if you'd read the other comments you'd know that these forks have a separate oil damping unit. At the time I thought they were all built that way.
I'm only adding this for the benefit of the 2 other people who might read this and because (a) I subsequently found out some Pace forks don't have additional oil damping and (b) I realised I never mentioned the oil damper in the video!
Finally, take heed of the disclaimer at the end - I absolutely recommend that you get this done properly if you have the money...