reservoir for rear shock

[TonyB]

was reading an old test on the IT490 and the testers mentioned a Yamaha wrench instruction where they moved the piston position in the shock reservoir by 10mm and this helped with square edge bumps, took the harshness out of the system. How would moving the position of the piston make the shock react quicker over sharp bumps? if the pressure behind the piston (I think its 125psi) is the same for one position as for another then the force required to move the piston would be the same?? any ideas maybe Walter?

[brent j]

I'll stick my neck out here............................

Moving the piston away from the air end of the chamber will increase the air volume and reduce the rise in pressure for the same amount of movement. The gas pressure will be the same at rest but there will be more gas and less oil.

Same as effect as lowering the oil level in your forks

Brent

[YSS]

Well said Brent . That theory is correct , but would 10 mm make such a noticable difference ? Thats only 12.5 % increased air chaimber. Probably a better option is to remove the piston alltogether and replace it with a bladder . That eliminates friction and moving parts changing directions . Usually those aluminium bores are already scored or worn. On our dyno that showed a huge improvement .

[Nathan S]

Tell us more Walter!
How much for a bladder to suit an old Yamaha reservoir?

[YSS]

whats the bore size ?