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Im trying to design my own bike, and Ive run into a few issues with the leverage ratio on the shock. What range is considered to be normal? Ive heard that the older RM7s had problems with the leverage ratio being too high. Does anyone know this number? 3 to 1 seems to be the most common ratio so I guess i'll probably go with that, but I just thought I would ask for assistance. Thanks!
 

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WheelieMan said:
Im trying to design my own bike, and Ive run into a few issues with the leverage ratio on the shock. What range is considered to be normal? Ive heard that the older RM7s had problems with the leverage ratio being too high. Does anyone know this number? 3 to 1 seems to be the most common ratio so I guess i'll probably go with that, but I just thought I would ask for assistance. Thanks!
3 to 1 is about the highest most run... you sacrifice small bump sensitivity with 3:1 ratios... I much prefer my 2.5:1 despite the loss of extra travel. I believe RM uses >3 to 1 on a lot of their bikes which would account for a loss of high speed bump complience, although I have been happy with the RMs I have ridden, but I don't have the same amount of time on them that I have on mine.
 

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Yeah

Typically, running a shock ratio greater than 3:1 is a no no. Asking a damper to do this puts a lot of stress on the internal bits and guts and can lead to early failure. Plus a lower ratio makes the bike feel so much better. I don't know if there is a golden ratio for dampers or not, but check out shock manufacturers info. A manufacturer will build a damper for your frame using your specifications, or you can build a frame around a specific shock. If you're only gonna do one frame, build it around a pre-existing damper. I know fox doesn't recommend anything over 3:1. Call shock manufacturers. I called Progressive for a school project and they were more than happy to help out with TONS of damper info.
 

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3 to 1 is pretty high. The lower the leverage ration, the lower the spring energy can be. I dont know why bike companies dont use 3 inch stroke shocks on freeride and DH models. Its becoming more popular now, but on smaller xc/trail bikes, the shorter shocks r much lighter. If you really wanna impress me, and alot of others, call up Avalanche suspension, and get a 3.5 stroke shock, and wire that in with a 2:1 ration for 7 inches of amazingily smooth and supple travel :D
 

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bighitboy said:
3 to 1 is pretty high. The lower the leverage ration, the lower the spring energy can be. I dont know why bike companies dont use 3 inch stroke shocks on freeride and DH models. Its becoming more popular now, but on smaller xc/trail bikes, the shorter shocks r much lighter. If you really wanna impress me, and alot of others, call up Avalanche suspension, and get a 3.5 stroke shock, and wire that in with a 2:1 ration for 7 inches of amazingily smooth and supple travel :D
heh. My FXR has a 2:1 in the 5" setting, 2.222:1 in the 6" one.

Back when most DH bikes were 8" of travel, 2.75" stroke shocks were pretty much standard. Now that many bikes are 9" of travel, quite a few manufacturers have moved to 3" stroke shocks, 3" progressives can be found on quite a few bikes, as well as 3" romics.
 

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there is such a thing as too low of a ratio, it depens on what the shock design is optimized for. And believe it or not, it can be hard to squeeze in those larger shocks in certain frame designs. 3:1 isnt high, its about the average for bigger travel bikes.
 

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I've always considered 3:1 pretty low. Many mass production bikes have ratios higher then 3:1, the V10 for example (3.3:1). Higher then 3.5:1 is too high in my opinion. I bet why a lot of downhill bikes still use 2.75 in stroke shocks is they are lighter? Plus, 2.75 inch stroke shocks are still adequate to handle 9 inches of travel (3.3:1).
 

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SevenInches said:
I've always considered 3:1 pretty low. Many mass production bikes have ratios higher then 3:1, the V10 for example (3.3:1). Higher then 3.5:1 is too high in my opinion. I bet why a lot of downhill bikes still use 2.75 in stroke shocks is they are lighter? Plus, 2.75 inch stroke shocks are still adequate to handle 9 inches of travel (3.3:1).

3:1 is not "pretty low", while it may be common, there are 2:1 bikes out there, and a lot of 2.something:1 bikes. I'd say that 3:1 is just a "standard" for lack of a better word.

Most 9" bikes use a 3" shock these days...

2.75 was more popular when 8" of travel was standard on most DH bikes.

Our real limiting factor is that no one makes shocks over 3" stroke really (except for avalanche) and that it is difficult to fit that long of a shock into existing frames, so a bike has to be effective designed around the shock (like the foes mono), rather than just putting in a 3" shock into a bike that can accept a few different kinds of shocks.

Not that we need shocks over 3" of stroke, it's pretty good for 10" of travel, and we can't really squeeze out much more travel out of the rear, and pretty much no one will run forks over 8" for a long time anyhow...
 
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