tmizzzle

Hi Everyone,
While responding to ads on Craigslist and FB Marketplace, I find myself going back and forth a lot asking, "what size is the frame?". The majority of people posting used bikes don't know how to properly size frames or don't know what they are talking about. A typical situation is they will say "large" or "about 20", even when the bike manufacturere didn't make a 20" frame in that model. Example: Bridgestone made 49 cm, 52cm, and 55 cms, which correspond to about 19", 20.5 inches, and 22". So naturally I would question the true size of the bike (and the photos sometimes show what looks like a very small 16" frame).

So then I go back and ask them if they were measuring from bottom bracket to center of top bar or to the lip of the seat post. And oftentimes I lose people in the exchange and they or I lose interest. Any advice on how to minimize all this? Ask for photos of stickers on the frame? Ask for the height of the rider? Send them a link to proper sizing technique and ask them to re-measure and confirm? They sometimes say, "just come by and try it out" but I don't want to drive potentially an an hour just to find that the bike isn't the size I was expecting. If anyone has experienced this and has advice on how to best streamline the process and not waste time, I'd be most appreciative. Thanks!

SoCaled 

My best advice is get good at guessing. Asking questions (reasonable as it may be) seems to turn off most sellers, they want the easy buyer. Lots of sellers list the size of the bike incorrectly so it can be hard to trust. Many people here use the size of the headtube as the best way to tell. Others would say use the size of the wheels as a reference point. If you see a bike you really like post a picture here on BF and ask for help, there are a bunch of eagle eyed folks on this site that can give a bikes size, often from one bad picture.

Iride01 

What's the proper way to measure the size of a bike?

Some manufacturers BITD of vintage bikes with a horizontal top tube measured from the BB (center of crank) through the center line of the seat tube to the top of the seat tube. Others measured to the apparent intersection of the top of the top tube with the center line of the seat tube. And yet other measured to the apparent intersection of the centerline of both tubes.

With pictures of those old vintage bikes you many times could get an idea by looking at the length of the head tube. But for bikes of the last twenty to thirty years with slanted top tubes, it's going to be hard to guess.

If the seller doesn't have the accurate spec's listed, then they probably aren't going to be great at measuring anything. You might also get a surprise when many say they don't even have a tape measure, yard stick or ruler.

oldbobcat

Learn how to read a geometry chart and get familiar with the dimensions of your size in the bikes that interest you. And if the bike has a horizontal top tube, you can always ask them to measure it for you.

oldbobcat

Vintage bikes with horizontal top tubes are easy, but with all the combinations of sloping top tubes, extended head tubes, and truncated top tubes, it's anybody's guess. For instance, a 58 cm Trek Emonda has not a single dimension that measures 58 cm. All you can say is that it fits about right for riders who would ride a 58. A small-ish 58, because a 58 from Scott, Cannondale, and Specialized would run larger.