# Bicycle frames **URL:** \ **Category:** Factual Questions\ **Created:** [March 15, 2003, 4:56pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616 "2003-03-15T16:56:33Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Raygun99](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@Raygun99](https://boards.straightdope.com/u/Raygun99)\ **Post date:** [March 15, 2003, 4:56pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/1 "2003-03-15T16:56:33Z")
What’s proper way to measure the size of a bicycle frame? ie. when they say a bike is 18", is that a height? a length? a cross-wise measurement like TVs? ---
**Author:** ![Davebear](https://avatars.discourse-cdn.com/v4/letter/d/bcef8e/32.png) [@Davebear](https://boards.straightdope.com/u/Davebear)\ **Post date:** [March 15, 2003, 4:58pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/2 "2003-03-15T16:58:25Z")
That’s the measurement of the central, vertical tube, from the crank housing to the top opening. ---
**Author:** ![Tapioca\_Dextrin](https://avatars.discourse-cdn.com/v4/letter/t/3d9bf3/32.png) [@Tapioca\_Dextrin](https://boards.straightdope.com/u/Tapioca_Dextrin)\ **Post date:** [March 15, 2003, 6:00pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/3 "2003-03-15T18:00:39Z")
If only life were that simple **Davebear**! Your answer is basically right, but there are plenty of people who meausure things a bit differently. According to [Sheldon Brown](http://www.sheldonbrown.com/frame-sizing.html) > [@](#): > > The old standard system was to measure from the center of the bottom bracket to the very top of the seat tube. > > Some manufacturers have decided that this is too easy, so now many bikes are measured instead to the intersection of the centerline of the top tube with the centerline of the seat tube. > > Some other bikes that have seat tubes that protrude farther than normal above the top tube measure as if they were measuring to the to the top of a seat tube with normal protrusion. > > Some bikes are measured to the top edge of the top tube, even though the seat tube protrudes higher up. > > Some bikes with slanting top tubes are measured as if there were a level top tube, they use the length that the seat tube would be if it was as high as the head tube. The _next_ question is why do you need to know? Because thae answer to that makes a big difference if you are trying to get a bike to fit you. ---
**Author:** ![Raygun99](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@Raygun99](https://boards.straightdope.com/u/Raygun99)\ **Post date:** [March 15, 2003, 6:21pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/4 "2003-03-15T18:21:37Z")
I’m trying to figure out what size my old bike is so that I can a) sell it with the correct info b) buy a new, bigger bike that fits me better. It’s a Minelli, bought in 1995, if that’s any help. ---
**Author:** ![EasyPhil](https://avatars.discourse-cdn.com/v4/letter/e/e47c2d/32.png) [@EasyPhil](https://boards.straightdope.com/u/EasyPhil)\ **Post date:** [March 15, 2003, 6:34pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/5 "2003-03-15T18:34:11Z")
> [@](#): > > \*Originally posted by Raygun99 \* > \*\*I’m trying to figure out what size my old bike is so that I can > a) sell it with the correct info > b) buy a new, bigger bike that fits me better. > > It’s a Minelli, bought in 1995, if that’s any help. \*\* Racing frames usually have the size stamped at the bottom and it’s usually in metric. I would measure the seat tube, from the the center of the bottom bracket to where the top tube meets the seat tube. Often times bike sizes are described by the size of the wheels 26", 27" as opposed to the frame size. ---
**Author:** ![vandal](https://avatars.discourse-cdn.com/v4/letter/v/858c86/32.png) [@vandal](https://boards.straightdope.com/u/vandal)\ **Post date:** [March 15, 2003, 9:13pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/6 "2003-03-15T21:13:00Z")
Yeah, most often, bicycles, when desribed in terms of it’s size, are measured using their wheel diameters - 16", 20", 24", etc. But if you’re just going by the frame, as asked in the OP, I’ve always heard it measured by the length of the top tube. So yeah, as **Tapioca Dextrin** mentioned, I guess it varies. ---
**Author:** ![spinky](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@spinky](https://boards.straightdope.com/u/spinky)\ **Post date:** [March 15, 2003, 11:29pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/7 "2003-03-15T23:29:52Z")
Er, I don’t think I’ve ever seen the length of the top tube used, so I assume **vandal** mistyped (the top tube is the one that is missing/lower on a “girl’s” bike). I’d advise just using the traditional method of measuring from the center of the bottom bracket to the opening of the seat tube, since (in my opinion) the measured frame height just gives you an idea of how big the bike is, and you have to actually get on the bike in order to find out if it’s the right size for you anyway (due to varying frame geometries). It’s also wrong to say that bikes are mostly measured using their wheel diameters. It’s a common way of _classifying_ them, but frame sizes vary so much within a given class that it’s not very useful to advertise that you’re selling a 26 inch mountain bike. ---
**Author:** ![Tapioca\_Dextrin](https://avatars.discourse-cdn.com/v4/letter/t/3d9bf3/32.png) [@Tapioca\_Dextrin](https://boards.straightdope.com/u/Tapioca_Dextrin)\ **Post date:** [March 16, 2003, 12:25pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/8 "2003-03-16T12:25:26Z")
> [@](#): > > \*Originally posted by Raygun99 \* > \*\*I’m trying to figure out what size my old bike is so that I can > a) sell it with the correct info > b) buy a new, bigger bike that fits me better. > \*\* Depending on where you live, one thing to consider is trading in your old bike at a bike shop. They should give you a fair price, plus you can get a new bike that fits you properly. ---
**Author:** ![John\_Harrison](https://avatars.discourse-cdn.com/v4/letter/j/b5ac83/32.png) [@John\_Harrison](https://boards.straightdope.com/u/John_Harrison)\ **Post date:** [March 16, 2003, 7:51pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/9 "2003-03-16T19:51:18Z")
> [@](#): > > buy a new, bigger bike that fits me better. If you really want to get technical on frame fit, try this site: [Bicycle Size/ Proportions Analysis](http://www.bsn.com/cycling/ergobike.html) ---
**Author:** ![Tapioca\_Dextrin](https://avatars.discourse-cdn.com/v4/letter/t/3d9bf3/32.png) [@Tapioca\_Dextrin](https://boards.straightdope.com/u/Tapioca_Dextrin)\ **Post date:** [March 16, 2003, 8:03pm UTC](https://boards.straightdope.com/t/bicycle-frames/161616/10 "2003-03-16T20:03:51Z")
It’s not a bad site, but if you really want to get a frame that fits, nothing beats getting on a [bike-sizing machine](http://serotta.com/pages/size.html). The guy in the second B&W picture with hands on hips is the guy that fitted me. We got a good size after maybe an hour. The only reason it was this quick is that I had my old custom built frame with me to use as a guide. The [bike](http://serotta.com/pages/legend.html) is fit for a God. It isn’t ridden by one, however.