One of the most frequent questions we receive is “What shape clamp do I need for my frame?” in reference to the Dia Compe “Clamp-on” brake kits.
The Dia-Compe Clamp on kit or Keirin Brake kit was made for professional riders who wanted to adapt a brake to their racing bicycle for training on public roads (A front and rear brake are required by law in Japan). The kit is made to fit an un-drilled fork and allow brakes to be used.
For Keirin frames, the three most common fork shapes are Oval (Left), Round (Center) and, Aero (Right).
This is a general guide and each fork’s measurements may be slightly different but to determine which shape you need have a look at the following photos.
This is the most common fork configuration. Round. As you can see below, the side to side measurements and front to back measurements of the fork blade ,where a clamp would be installed, are both about 24mm.
The next configuration is Aero. This fork blade has a rounded front with a slightly pointed rear. The side to side measurement is about 18mm while the front to back measurement is about 29mm.
The last configuration is Oval. As you would expect, the shape is like a slightly squashed ball. The side to side measurement is about 23mm while the front to back measurement is about 27mm.
It is quite easy to tell if you have a round fork but determining if you have an aero or oval fork can be tricky. If you cannot tell whether your fork is oval or aero, you can buy both clamp types since replacement clamps are available on Tracksupermarket: Replacement Clamps
In addition, it must be noted that these clamps are only made to attach to Steel forks (with the exception of Columbus Max forks). Unfortunately, these cannot be used to adapt a brake to a carbon fork. If you have a Carbon fork and need to adapt a brake, your best option is to acquire a road fork that is already drilled for a brake.