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Hello great bikng minds, i hope you can help??!!!
I've just bought some used Fox Vanilla 140s n a bike and serviced them myself. I've put a green firm spring in (heaviest they do rated 85-95kg, I am 100kg). Instead of using Fox green suspension fluid I bought Silkolene 10W suspension fluid on the advice of some threads on here.
The forks run very nicely and smooth. The sag is near enough 20% which is right I think.
However, I've only had air forks before. With air forks I found that realistically only about 2/3 of the travel was ever used and i only got near the end of the travel on really big hits. With these forks whilst sat on the bike when i bounce up and down on the front with my own body weight i use about 80% of the travel. If I bounce really hard they don't bottom out, but look close. Don't get me wrong, the travel feels good and smooth but i'm concerned that i will bottom out too easily on big hits. If i bounced on my old air forks I never got close to the end of the travel.
So, am i jut not used to the smoother travel of a coil or is something else wrong? I realise that i'm a little over the recommendation of the green spring but i'd suprised if thats the issue.
My other thought is that the suspnsion fluid i bought is wrong and the damper isnt doing it's job properly. On the website I bought it from it says it's 10W, but it doesnt actually say the viscosity on the bottle.
Any ideas?
Thanks!
Whats your rebound like, are you using all or part of your available adjustment ? If you have plenty of clicks left, then viscosity can't be far off. If you have used all of you rebound adjustment then a heavier weight oil is needed. You could also increase the lube oil level in the none damping leg, eg. in my Rev's I have increased lube oil level from 5cc to 20cc. This gives less air volume in that leg, so ramps up pressure when compressed quicker and prevents diving into the travel as much. Also helps lubing the bushes, as more oil is splashing around.
when oil flows through an orifice the force on it is proprtional to the velocity of the oil (an hence how fast the fork moves through it's travel), so moving it up and down at hand speeds and trying to relate that to trail speeds is just crazy. At 10 miles an hour if you go over a hemisphere that is 120mm in radius it will take 1/36th of a second to push your fork from 0 to 120mm compressed. Or twice that (1/18th of a second) to pass over the rock completly. The damping force will be massive compared to what you can produce bouncing by hand.
I would test by repeating the same bit of trail with varying settings and see how it performs.
(note the damping force can be much higher as the linear relationship only holds for small displacements really, so the force is more likely to be related the square or even cube of velocity over 120mm)
😯
Great advice guys. My rebound adjustment is set 3 clicks from the fastest rebound, and feels fine. I guess the viscosity is ok - it is the recommended one after all....
The science almost baffled me toys19 but it's a good point! I tried pushing the forks very quickly and they don't travel as far. What you're saying makes total sense.
As I say the travel feels good, but just different to previous fork. I'm just concerned about bottoming out, but perhaps i'm worrying too much.
I'll stick with the current set up and see how it goes. I can always play around later.
Really helpful replys though thanks.