Seat post clamp size Home › Forum › Bike Forum › Seat post clamp size Viewing 7 posts - 1 through 7 (of 7 total) Seat post clamp size seanodavMember It has the same dia post as mine which is 30.9 so im guessing 34.9 Posted 7 years ago bigyinnMember Std 34.9 clamp will be fine! Just tighten it up some more. Pretty much all spesh bikes these days use that size. (Im using a L35 seatclamp off a Spesh on my Marin and they both use 30.9mm seatposts) Posted 7 years ago elaine anneMember has it got the size on the side… mine is 31.8 size (hope model)…. have you got the correct size seatpost…. if it keeps slipping down ?… my specialized bike has a thicker seatpost than my orange bike… 31.6 for specialized and 27.2 for orange… Posted 7 years ago tonyg2003Subscriber 34.9mm. As I found out – wrong size for my Trek! I now have a unused 34.9mm Thomson clamp sitting on my desk waiting for me to get round to ebaying it! Posted 7 years ago hollyMember I have a Specialized Rockhopper and I broke the seat post clamp bolt. Does anyone know the clamp size. Underneath it says L35 so does that mean its a 35mm size or could it be a 34.9mm I have a problem with the post as it keeps slipping back down the tube….grrrrr !!!!! Posted 7 years ago hollyMember Swmbo liked my Spech rockhopper pro so much she bought one too. Tweedle dee and tweedle dum. Her seat post is the same size as mine and at the mo we have to share seat clamps. Thanks guys for your help. Need to go get a 34.9mm clamp Posted 7 years ago bigyinnMember You should have a look on the classifieds, picked one up the other week for £5, pretty much as new too. Posted 7 years ago Viewing 7 posts - 1 through 7 (of 7 total) The topic ‘Seat post clamp size’ is closed to new replies.