Hello there

So I was watching videos on chainsizing for E mountain bikes with rear suspension.
First video with a normal mountain bike: The mechanic disengages the rear shock and compresses the linkage (moves the rear wheel as close as possible to the bike). Then he passes the new chain only through the largest rear and front cogs and not the rear derailleur. He meusures the chain while adding 2 extra links and voila
Second video with a E mountain bike: The mechanic does not disengage the rear shock. He passes the chain through rear derailleur, the smallest rear and front cogs. He measures the chain length while pulling tension on the chain so that the rear derailleur is parralel to the chainstay. And voila.

In the 2nd circumstance you don't have to disengage the rear shock? Is there a difference between E MTBs and normal MTBs when it comes to chainsizing?

Thanks (PS: This forum rocks )

Mechanic A is correct (assuming a 2x or 3x system, 4 links would be correct for most 1x drivetrains). Different suspension designs have differing amounts of chain growth as they move through their travel, but manufacturer recommendations are to do this with the bike at maximum chain growth (usually full compressed). Also SRAM spec for B tension distance on Eagle drivetrains is to do so at sag--also often gets skipped (and actually makes a difference a lot of the time).

I have not seen the videos, but there is sometimes more than one way of coming to the correct conclusion.

If a chain was one link too short, it should work on all except the large sprockets. If a chain was one link too long, it should work on all except the small sprockets. Maybe one is determining the length using the large sprockets, and the other is determining the length using the small sprockets.