Clearance

Sheldon Brown's Bicycle Glossary · letter C
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"Clearance" is generally involved with three different areas, in bicycle parlance:

1. Tire/Fender Clearance
2. Tire/fender clearance is determined by frame design. Well-designed frames generally have room for tires of reasonable width to be installed, and ideally there should also be room for fenders to be installed without risk of the tire's rubbing on the fender.
   
   The areas of concern are where the front tire fits through under the fork crown, and where the rear tire fits between the seatstays and chainstays. There's also often an issue with the vertical clearance between the tire tread and the underside of the fork crown or the seatstay bridge, or clearance between the tire and the brake caliper.
   
   Historically, track bikes have been made with minimal clearance, since nobody needs anything but skinny tires on the track. Starting in the 1980s, road bikes began to copy this design, and these days most "racing" type bikes have stupidly tight clearance. This is basically a styling fad, and seems to be beginning to run its course. While it was in full swing, it created a vicious cycle: Bikes with super-tight clearance need brake calipers with very short arms. As the tight clearance fad progressed, brake manufacturers shifted most of their production to super-short reach calipers, and calipers with longer reach became unavailable. This forced frame makers to continue making frames/forks with excessively tight clearance, which in turn led to the demise of medium-reach brakes...
   
   Largely thanks to the efforts of Rivendell's Grant Petersen, calipers with longer arms are once again becoming available, and many bike manufacturers are once again making bikes that combine speed with versatility.
   
   If your frame has tight clearance, there's no easy fix. The only way around the problem is to go to a smaller-diameter wheel.
   
   This site has an article on conversions like this.
3. Pedal Cornering Clearance

4. If you pedal through corners, there is a chance of striking one of your pedals on the roadway as you lean into the turn. The risk of this depends on several factors, including:

   • Bottom bracket height
   • 
     
   • Crank length
   • 
     
   • Pedal length
   • 
     

   The combination of these values determines how far you can lean over and still pedal without risk of striking your inside pedal.

   Pedal cornering clearance is a particularly important issue on a fixed gear bike, because the fixed gear forces you to pedal all the time. In addition, if you strike a pedal on a fixed gear bike, it will tend to lift the rear wheel up off the road, and you will spin out and crash.

   Bottom-Bracket Drop Calculation Spreadsheet

5. Toe Clearance
6. The other major area where clearance is an issue is when the rider's toe or toe clip can strike the back edge of the front tire or front fender.
   
   See: "Overlap."

Copyright © 1996, 2008 Sheldon Brown

Original: https://www.sheldonbrown.com/gloss_cl.html#clearance · Reproduced on en.wikipedalia.com with permission, all rights reserved.