Mountain Bike Reviews Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
53 Posts
Discussion Starter · #1 ·
Hi All,

Does adding/removing tokens affect the PSI required to achieve the same sag point? For example, if 100 PSI is needed to reach 20% sag, would adding a couple of tokens still result in 20% sag at the same pressure? I understand that tokens affect the frequency and later stages of the stroke, but am curious about the initial stages.

Thank you
 

·
Registered
Joined
·
9,754 Posts
To simplify, think about the situation without a negative air spring. When you set pressure, you do it with the fork/shock fully extended. At sag, the pressure in the fork/shock times the effective area of the piston equals the force trying to compress the f/s. If you decrease the volume of the air chamber, the pressure will increase more quickly as f/s is compressed, so starting with the same pressure, the f/s will compress less for a given force, resulting is less sag. If you add tokens, you'll need to decrease pressure a small amount to achieve the same sag.

The negative air spring complicates things a little. The negative spring works against the normal with nearly the same force at full extension, but rapidly decreasing force through compression as its volume is much less than the positive volume. The common self-equalizing neg chamber is not affected by positive tokens since it is cut off from the positive side as soon as the f/s starts to compress. If you put in positive tokens and decrease pressure to achieve the same sag, you're also decreasing the air pressure in the neg chamber the same amount, so it will work less against the positive spring. This is a small affect but works to further the decrease in pressure needed to achieve the same sag.

Some may chime in and suggest sag is irrelevant, or something like that. That's not entirely true. Achieving an exact amount of sag is not that important as long as you have a reasonable amount of sag. Here're a few that agree with that:

https://www.pinkbike.com/news/suspe...up-technicians-leogang-dh-world-cup-2019.html
 
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top