Setting sag. Measure off shock or rear axle?

nexusfish

El Mariachi
G'day guys, have been playing around with a new bike that has an extremely progressive leverage ratio (YT Capra). Just got to thinking that I never measures sag on the shock on my dirt bike, but we all do it on mtbs. I've found 3% sag difference on the Capra results in a lot of actual sag difference as the leverage ratio starts at 3.6 and ends up at 2.

Does anyone measure sag off the rear axle and does the 25/30% rule stand in that case?
 

Mattyp

Likes Bikes and Dirt
Just got to thinking that I never measures sag on the shock on my dirt bike,
Well you probably should.. Static / free sag is the first thing you should do... And will also determine if you need heavier / lighter springs.
Next you'll tell me you never check your air pressures...:eek:
What would you use as a point of reference above the axle? On the moto it's fairly easy you measure to the mud guard.
 
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The Duckmeister

Has stumpy thumbs, Speciaized are so weird
The saddle or seatpost head would really be your only static reference point if measuring sag at the axle.
 

kten

Likes Fork
Axle is preferable imo. 30% wheel travel is a good starting point. Tape a long pole/something that doesn't flex onto the seat so that it reaches over the rear axle. Some bikes are such a pain in the ass to measure the shock correctly at the shock (V3 Banshee with a coil springs to mind).

Also a lot of people don't take into account the linkages progression and don't realise that 30% at the shock can actually be much more wheel travel putting them way too deep into the stroke. I watched a mtbtelly video (I think it was the Rune test) and he was saying that Banshee had gotten the sag figures incorrect but basically he didn't understand/comprehend the concept of the linkages progression giving what appeared to be too little sag at the shock (eg Titan is 17.8mm sag for 32% sag recommended. 32% of shock stroke is 20.8mm).
 

dirtdad

Likes Dirt
Surely shock is the most accurate way when your wheel moves on an arc though? Just rely on the manufacturer linkage calculated values and find a good starting point in mm on the shock.

But keen to see people's methods for measuring from the wheel.
 

blacksp20

Likes Bikes and Dirt
Axle is preferable imo. 30% wheel travel is a good starting point. Tape a long pole/something that doesn't flex onto the seat so that it reaches over the rear axle. Some bikes are such a pain in the ass to measure the shock correctly at the shock (V3 Banshee with a coil springs to mind).

Also a lot of people don't take into account the linkages progression and don't realise that 30% at the shock can actually be much more wheel travel putting them way too deep into the stroke. I watched a mtbtelly video (I think it was the Rune test) and he was saying that Banshee had gotten the sag figures incorrect but basically he didn't understand/comprehend the concept of the linkages progression giving what appeared to be too little sag at the shock (eg Titan is 17.8mm sag for 32% sag recommended. 32% of shock stroke is 20.8mm).
Was that the Beta Test (previously bible of bikes) video?? They hated the Prime v3 as they said it was too sloppy, probably Because of incorrect sag setting.
 
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