Danielle

Giant does not have any e-mail addresses on their webpage, so I came here for some answers. What size is the collar on a Giant OCR2 for the seat post? I don't understand why Giant does not have any tech support.

sydney

Measuring is another way to find out.

Mariner Fan

Are you replacing the collar or the seat post? Generally a seat post will be marked with the size on the very bottom (part that's hidden).

aerodave

The OCR 2 uses a 27.2-mm seat post, a 31.6-mm ID seat tube, and a shim to reconcile the difference. I don't know about the clamp itself, but it's going to be about the same as the seat tube diameter. 32-mm is almost certainly the right size to get.

But I wouldn't swear to it right now.

sydney

That's where measuring comes in.Puts the guesswork in the toilet.

aerodave

Actually, you'll want to match the outside diameter of the seat tube. 32 is probably too small come to think of it, unless that aluminum tubing is *really* thin.

See...guesswork does suck. Measure or ask a good wrench.

aerodave

Actually, after some considerable Google-brand research, I feel safe in saying that you need a 34.9-mm clamp. That's the outside diamter of the seat tube.

sydney

^^^^....dollars to donuts that would take a 35mm clamp.

aerodave

I agree...you can find either 34.9 or 35 pretty easily. Since the clamp is open and drawn together with a bolt, the 0.1 mm won't make a bit of difference. Go with whichever is easier to find.