I've got a quick release clamp on my seat, but I'd like to replace it with something that is a little less easy to steal (like a hex wrench or something). Is it possible to buy just a hex bolt to fit my existing clamp, or should I get a new clamp with bolt?

I found one on Amazon (https://www.amazon.com/Eleven81-Alloy...eat+post+clamp), but i'm not sure what size I need. The outside of the frame where the seat post inserts measures 31.9 with a digital caliper (when the current clamp is tightly attached). Would a 31.8 mm clamp work, or do I need to go a size up?

Thanks!

I plan on just going down to Ace Hardware with the hardware I want to replace in hand and paw through the bulk hardware bins until I find something that fits.

What I did was disassemble the quick release bolt from the clamp and reused the clamp with a long allen head bolt and matching nut. Sorry can't help with the sizing.

6mm bolt. Get grade 8.
NAPA or similar.

In some areas this won't be sufficient security against theft! I used to live in San Francisco, CA, and had my seat post and seat (and attached blinky) stolen, even after I'd replaced the QR clamp with a bolt-on (hex wrench required). This was not in an obviously-sketchy area, either. The LBS folks I chatted with about this all (at several SF shops) said that this was not uncommon (2008 or so, I believe) in SF and other "major" cities.

I ended up getting a product (maker's name escapes me now, but they're well known for other bike stuff) that allows clamp to be opened only when bike is turned upside-down. Later I discovered that Pinhead (was then being sold under a different name -- big bike-lock co., also can't remember that name!!) sold a set of their well-known locking wheel skewers (to replace wheel QR's) that also has a matching locking seat post clamp. My girlfriend bought that 3-piece set, and has been happy with it for past 2 years or so. (I've been happy with Pinhead wheel skewer locks for 4 years or so.)

-Sean

I threaded an old bike chain through the posts on my seat and under the bars that support the wheel, then wrapped it with an old tire tube to keep it neat. Haven't had a problem in the four years since I did that.