How do you find out the size of road bikes?

Answer 1

There are a couple of different ways to size bicycles.

The crude way is by wheel size.

This really doesn't say much, as it's possible to design small wheel bikes to fit big riders by stretching the frame.

But for kids and short people, it does provide some info in line with "I can't ride that".

It can also give a hint on what the bike is meant to be used for.

A better way is to measure the frame, the (center-to-center) length of the top tube, and/or the (center-to-top) length of the seat tube.

If the frame has a sloping top tube, a "virtual top tube" is used - meaning how long the top tube would have been, if horizontal.

Another way of measuring frames which is gaining popularity is "stack and reach".

Here, you draw an imaginary line vertically through the bottom bracket, add a horizontal line resting at the top of the head tube and measure from the intersection to the center of the BB and the head tube.

This is probably the best method so far, as it is the one that deals most directly with the most important contact points - where the pedals end up and where the bars end up.

Saddles can just about always be brought into range by use of an appropriate seat post(length, setback), and the length range of stems is well known.

Answer 2

The two most important measurements are center-to-center for seat tube and head tube(top tube length), followed by the seat tube height, measured from the center of the bottom bracket.
the frame size is the distance between the seat post clamp and the bottom bracket.

for smaller bikes measure the size of the wheel

Answer 3

There are two basic measurements:

1. center-of-bottom bracket to top of seat tube/center of top tube. The latter version is not that easy these days, as sloping top tube have been the dominating design for years
2. center-of seat tube to center-of-head tube, measured horizontally. A bit easier.

For some strange reason, road bikes usually use top tube length in cm, while MTBs tend to use seat tube measure in inches.

Do note that these measurements won't tell you which size wheels a frame is meant to take.

Then there are several angle measurements, like head tube and seat tube angle, which also affects the character of the bike.

Answer 4

First you check the wheel size. 700C/622 mm/28" is the most common, although there are others. Then you measure seat tube length, top to bottom bracket center, and top tube length between center of seat tube to senter of head tube.

Answer 5

By measuring it.

The two most important measurements are seat tube length and top tube length. Seat tube length can be given either center-to-center, or center-to-top, but they all start at the center of the bottom bracket shell (the piece of pipe that the cranks turn in).

Top tube length is always center-to-center, but may be a bit tricky on frames with sloping top tube designs.

Sometimes a "virtual top tube length" is given, which then refers to how long a top tube would be if the bike had a horizontal top tube.

Answer 6

Follow this link for a full explanation http://www.fullcycle.co.nz/crupiframes.html

Answer 7

First point is to check the wheel size. Once you've determined that you measure the frame; center-to-center for seat tube to head tube, center-to-top from bottom bracket to seat tube end.