What is X-Seam?
X-seam is the distance from your very lower back (backside) to your heel (riding shoes on). Due to the ergonomics of recumbent riding this is a critical measurement when been measured up for a recumbent. Recumbents are not like ordinary bikes to ride and if you don’t want to end up sore and sorrow for yourself at the end of a 50klm ride knowing a little bit about what it is and how it helps really makes riding painless.
Why is it important?
OK, so as a measurement how do we apply it? Recumbent riding is about cadence (spinning the crank). I could get away with about 60 rpms on the crank on a normal bike and when I went up a hill I would get up off the seat and mash away using my body weight to make it less of a chore climbing the hill.
It’s impossible to get off the seat and mash on a recumbent. You can mash away sitting down in a recumbent but at the end of the ride your knees will probable be complaining bitterly. In fact if you did it all the time you could probable sustain a knee injury. The only way to get around this and save your knees is to spin the crank at a quicker rate. When I started riding a recumbent I went from about 65 rpms to 80 rpms and I though that was quick, now my comfort cadence is low 90s. Some recumbent riders like it above 100 although some feel comfortable below 90. It takes a little time to build to a comfort range but once you get there it just feels right and you then can ride in what they call the ‘groove’. It will just feel right when you do achieve it.
Getting back to that X-seam? When you sit in the seat of a recumbent bike it should hold you in place and not allow you to move your backside either forward or backward. This enables you to retain the same distance between where you sit and the pedals. If the correct x-seam is applied (seated distance from pedals) you won’t hyper extend your knees (this occurs when you completely straighten your legs while pedalling) when you ride reducing the likelihood of injury, although it provides the correct distance for optimal pedalling efficiency.