What's this?
Plain words for the ones I use most. No apology: they are the words the makers use, and you meet them the moment you look at a geometry chart. Every one of them also opens where it is written, so you never have to come here to read one.
- Words
- 12 entries · the makers' own, in the order you meet them
- Pictures
- The measuring guide has the pictures. Open the measuring guide
- BB, or bottom bracket
- The axle your cranks turn on, in the middle of the frame. Every number on this site is measured from it, because it is the one point that sits in the same place on every bike.
- Headset cover
- The little cap on top of the head tube, under your spacers. Most makers do not publish it, so I assume 15 mm and add 6 mm to the band, which on its own is enough to hold an answer at "probably" rather than "fits".
- Stem clamp, and its centre
- The collar on the steerer that your stem bolts to. I need the middle of it. Where a maker gives only the height, I assume halfway up and say so on the answer.
- Steerer
- The tube coming up out of the fork. The cover, the spacers and the stem all sit on it, and it is the thing a mechanic cuts to length.
- Bar reach
- How far forward the hoods sit from the middle of the bar. Two bars on the same stem can put your hands 20 mm apart, which is why I ask.
- Setback
- How far your saddle sits behind the bottom bracket.
- Drop
- How much lower your bar is than your saddle.
- Rails, and the rail centre
- The two rods under your saddle, and the middle of the straight part of them. That midpoint is the point I use, because it is the one you can find with a tape.
- Stack and reach
- How high and how far forward the top of the head tube is, from the bottom bracket. They are the two numbers that decide whether a frame can be set up like yours.
- The band
- How far out I could be, in millimetres, and why. It is a straight sum of everything I had to assume rather than a clever average, so it errs wide on purpose.
- wb, stand, trail
- Wheelbase, standover and trail: how long the bike is, how high the top tube is where you straddle it, and how steady the steering feels. I show them against your bike, and I leave them out when the maker does not publish them.
- est.
- Estimated: a number I worked out rather than read off the maker's table. Anything marked this way can move if the maker publishes the real one.