Originally Posted by
mstateglfr
Why wouldnt it make the most sense to use it on the bike that will see the most bumps?
Trek said it themselves in discussing the omission on the Checkpoint -
“At some point, the volume of the tyre becomes the dominant part of the compliance experience for the bike, especially for front IsoSpeed,” Roessingh explained. “That additional compliance is very subtle, it’s not a lot of travel [10mm], so as we experimented with using front IsoSpeed and taking it out, we found that the rider couldn't really perceive much of a difference when using such a big volume tyre.”