Originally Posted by Mariner Fan
I looked on the Zefal site and for some reason they show sizing for the seat tube.
Possibly because many frames today no longer have a pump peg on the head tube? have not bought a new frame pump in years, just move the ones I have from bike to bike. I run an HPX for my roadie and it fits either as shown or under top tube. Just look at the four sizes and see if one is slightly longer than the distance from your head tube to seat tube under the top tube. The pumps are spring loaded and compress a bit to fit inot frame and then the spring tension holds them in place. The handle end has an indentation for the pump peg and the inflator head end has two braces shaped to fit tight against the seat tube and top tube on my hpx. I reccomended the zefal pumps because you stated that your bike has a pump peg, and I know that my hpx works in that situation. For best results, ride to the LBS and try some out on your frame in both positions. Nice part about this system is that there are no mounts to break, etc.