One of the first things that you're going to discover with those calipers is that many bike parts that are "supposed" to be round are not: for example, seatposts, stems and handlebars. Also you'll find taper in seatposts and stems.
Try measuring frame tubes too, in several places, side to side and top to bottom. Carefully use the flat section of the blades behind the knife edges so as not to scratch the paint. I've found average paint thicknesses of 0.1mm to 0.2mm on a lot of bikes painted after the mid 70s.
Chas. Colerich Oakland, CA USA
accobra wrote:
> I like to think I'm pretty knowledgeable when it comes to bikes. I've been messing with nice lightweights for 36 years, worked in bike shops when I was younger, etc. But one thing I never had was measuring calipers. Things like handlebar diameters, bottom bracket spindles, rear hub axles, all that stuff, was a hit & miss mystery. Mainly I was able to get by because my parts lasted forever and I just didn't need to switch them out that often. But finally I realized I have more these miscellaneous extra parts laying around than I can shake a Silca pump at, and it became very frustrating guessing the size of this or that.
>
> I finally broke down this week and went shopping for a set of digital measuring calipers. I had no idea what they would cost & I wasn't even sure where to buy them. Lo & behold, I quickly found a decent set at my local Home Depot for only $34. Oh my gosh, this tool has opened up a whole new world for me. I'm running around all over my house checking the diameter of those mysterious 3ttt handlebars, Cinelli stems, seatposts which for some reason Avocet saw fit NOT to stamp the size on most of the time, plus a host of other mystery seatposts and misc parts.
>
> Some of you might be shaking your head at my being so far behind the times, tool-wise. But I'm writing this note to the rest of you that are in the same shoes as I was in -- guessing about what parts you have and screwing up the finish on all sorts of handlebars and buying the wrong parts on eBay trying to guess what you need. Bottom line - go out and buy a set of DIGITAL measuring calipers. Digital is the only way to go because it'll quickly tell you the difference between 26.0mm and 26.4mm. No more guessing. It's been one of the best ways I've ever spent $34.
>
> Mark Winkelman
> Dallas, Texas USA