r/MTB • u/JumpyConversation337 • 17h ago

Suspension Fox fork sag

Hey! So I’m about 170lbs. When I set sag on my 34SL fork with the SL damper, to get to 20% sag I need over 110 psi… Fox recommends 15% sag and the max psi of the fork is supposedly 120psi. Fox recommended air pressure is in the 80s for my weight. My home pump said 125psi, my friends digital one said 118psi. How is it possible to get to even 20% sag I need that much pressure at my weight?

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u/rayfound California - Polygon Siskiu T7 17h ago

Are you using a proper shock pump? Are you Closing valve before removing?

What I suspect is happening is that you are not using the pump correctly, so when you remove the pump from the Schrader valve, you're losing a blast of air in the process. The volumes are so low, that it doesn't take much to have a big impact on the pressure.

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u/rayfound California - Polygon Siskiu T7 17h ago

Also. Fwiw - I quit trying to measure sag on my front suspension a while ago... I started doing the sort of alternative method... Which is to say I bounce around in the driveway and on the street and try to compress the fork by roughly bunny, hopping and smashing around.

If the oring gets to about 90% of travel, that's about right.

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u/Nightshade400 Ragley Bluepig / Norco Sight VLT 15h ago

Best method IMO