So I've a 2019 Trek Checkpoint SL5 with the Isospeed in the seat tube. I've stripped out the threads for the seat leveling adjustment at the back. This is the second time I've done this......first time I just got a tap set and recut the threads, (and I was using a torque wrench, just not the snapping kind when you've hit the set torque.) I've looked online for a replacement seat mast. According to the trek specs, the seat mast has a 10 degree offset. Looking around the web, it seems all they offer now is a 5 degree offset, or a 20 degree offset (the new 2021's come with the 20 degree). Can I just get one the same length but with a 20 degree offset? What does the offset affect? My LBS is over an hour away, so I'd rather just order one to be sent to my house.
The offset should be the center of the two sets of saddle rail clamps. Where is your saddle located in the clamps now - slid back, in the middle, slid forward? If you look at the photo linked below, the saddle appears slid most of the way back. Assuming the saddle fore-aft was set correctly for the ride, if this was a 5mm offset seat post I'd say perhaps they should consider the 20mm offset. In other words, the bigger the off set the further back the saddle clamps are positioned atop the post.
