Axiom Trekk Seat Clamp Collar for Back Rack 31.8 Black

This is the third seat post clamp I bought, the first one didn't work because the attachment holes for the rack extended below the piece and hit my frame, the second one worked but was big, ugly, and not very secure in my opinion, this piece is perfect. Looks good, discrete, simple, and gets the job done.

This is one of 2 different clamps that I bought one to install on my bike so that I could install a rear rack. ( I bought 2 in case one was a better fit, and to have a spare).I expected that it could be clamped underneath the existing quick-release clamp, but found that it can not be used with the existing clamp. It replaces the quick-release clamp, but does not have the quick-release feature.It has a small lip around one edge of the inner opening that rests on the top edge of the tube, and prevents it from sliding down on the tube. Thus the original clamp can not be re-installed. I don't recall reading about this lip in the description of the product. I ended up installing the other one I purchased, but now if the seat post needs to be adjusted or removed, it requires using an allen key to loosen it. Both clamps appear to share this same lip feature.So if you like the convenience of being to easily adjust your seat post with the quick-release clamp, this item is not good.

Listing title says in giant bold text "31.8mm," but I was sent a 29.8mm. I now see there is TINY text saying 29.8mm wide, in complete disagreement with what the title is selling people on!Wrong sizes don't fit on bicycles, people! Fix your listings or stop selling!

So I got my adapter and went to install it, but found that even when tightened as far down as it'll go, it still wobbles up and down! The clamp hole is not quite round, so it doesn't evenly grip around the psot at all. Luckily Once I mounted it underneath my normal seat clamp, and attached the solid metal rails of my rack to it, it doesn't move around anymore, so it works good enough.

An inexpensive, solid collar that does its job well without breaking the bank. Able to take a lot of torque without stripping (of course... don't overdo it). Much more than a Thomson collar and WAY more than any of the carbon fiber options out there. I try and buy these for my builds whether or not I intend to use the rack eyelets.

The attachment points are threaded for metric 5mm x 0.8mm. There's enough gap space (12mm) between sides for a backing lock nut to also be installed. The inside surface has a seating lip to prevent the collar clamp from sliding down from the top of the seat post.

This thing worked great out of the box. My Ibera IB-RA5 attached to this thing with ease! I used this for a Mongoose Dolomite which has no mounting points for a rack. The rods were the perfect length to attach to this clamp. Excessively happy about my decision not to choose a more expensive product.

Works as it should. I filed off the top stop so it would slide down the post father because I still wanted to use the quick lever style seat collar for adjusting the seat. This collar is an inch or two lower and supports the rear rack. Kind of expensive for what it is. But it worked for me.