This post explains what kinds of road bicycle handlebar shapes exist. These shapes differ in terms of curvature, height difference between the top and bottom part, width etc. The term “drop bar geometry” refers to all that.
- For road bar hand positions, read this post: Road bike hand positions.
- How to adjust road bars (change height, angle, etc.): Setting up road bike bars.
1. Important bar dimensions
…1.1. Clamp diameter
…1.2. Hand grip tube diameter
2. Bar shapes
…2.3. Standard, traditional, “Merckx” round
1. Important bar dimensions
This chapter explains the important dimensions, which are: clamp diameter, hand grip tube diameter, width, reach and drop.
1.1. Clamp diameter
- 25.4 mm (1″) – older standard
- 26 mm – unofficial Italian standard by which many old road bars have been made
- 31.8 mm, or 31.7 mm, depends on how manufacturers round the nominal 1 1/4″ – modern oversized (OS) standard
This, along with hand grip tube diameter, is a measurement that is always taken in a certain way, by outer diameter. The rest of the dimensions are usually measured from centre of the bar to the centre, but sometimes from end to end. Sometimes producers don’t note on the package the measuring method, so in order to make sure, one must measure themselves. 🙂
1.2. Hand grip tube diameter
Diameter of hand grip tube is mostly standard: 23.8 mm.
It should match riders shoulder width.
Centre to centre grip tube size should match shoulder width. Like measured in the picture above.
Narrower bars make a bit more aero position, make filtering between cars easier (for those who practice it 🙂 ), but can limit breathing.
Wider bars make for a bit more air drag, with no other ill effects (unless going several sizes wider).
This is a size most often measured in different ways. Sometimes from centre to centre, sometimes the outer width. So before buying make sure what the real size is. Also have in mind that some bars are wider in the drops.
Reach is the horizontal distance between the stem clamp and the furthest part of the bars. Below 80 mm is considered a short, 85 mm is middle, over 90 is considered a long reach. 70 mm and 100 mm being extreme values.
Too short reach can be compensated with a longer stem, but can leave too little room for hands on the bar tops – on ramps.
Too long reach can of course be compensated with a shorter stem, but can make holding the lower part of the bars uncomfortable – not always the case, but can happen.
Drop is the vertical distance between the highest and the lowest part of the bars. It is marked in the picture above (with reach). Drop under 125 mm is considered shallow, 130 mm is middle, while over 135 is a deep drop.
The rule of thumb here is that too shallow can never harm (almost always), while too deep can be a problem – if the rider is positioned lower than comfortable.
2. Bar shapes
There are three shapes: compact, “anatomic” and standard.
Short reach and shallow drop. In the era of anatomic brake levers, short reach can often be advantage, since most riders ride holding the tops of brake levers – the hoods. Shallow drop allows comfortable lower grab position (in the drops), while elbows can be bent for even lower, more aero position. Because of shallow drop, this is the most pensioner bar design – good for riders that aren’t very flexible.
It usually has a flat upper part, which makes a comfortable platform, followed by a sharp bend, making brake levers easily reachable when griping bars lower.
Quotation marks are because this is not the most comfortable solution for most. The idea was to make nice straight surfaces for lower grabs, but most people prefer a nice curve, for lots of small hand placement changes. They generally have the deepest drop that suits most riders the least.
2.3. Standard, traditional, “Merckx” round
Longer reach and deeper drop. Not as bad as anatomic bars though. Suits riders that like round upper part of the bars and constant curve radius bar shape. The most sports-like design – good for flexible riders in good shape.