Fork sizing

[Mike from BA]

I understand that when selecting a fork for a given frame there are 2 considerations: wheel/rim diameter (e.g. 700mm for a road frame) and the headset´s diameter (e.g.1 inch). Why isn´t the frame´s size taken into consideration? Is it that the bottom part of the headtube is always in the same position because it´s lenght compensates for the different geometry?

 

[Team-Peloton.com]

Hi mate,

Check out fork 'trail' and 'rake'

Very interesting article:

http://davesbikeblog.blogspot.com/2007/05/trail-fork-rake-and-little-bit-of.html

 

[Pietro]

I understand that when selecting a fork for a given frame there are 2 considerations: wheel/rim diameter (e.g. 700mm for a road frame) and the headset´s diameter (e.g.1 inch). Why isn´t the frame´s size taken into consideration? Is it that the bottom part of the headtube is always in the same position because it´s lenght compensates for the different geometry?

yes, the fork crown to front axle distance is generally always the same for any size 700c bicycle. See the above post about rake and trail, also take in consideration threadless or threaded and fork steerer length.

 

[Mike from BA]

Science is everywhere!!!

Thanks! Very interesting.
Mike

 

[frameforum]

Beg to differ...
Most manufacturers have their own fork length dimensions, and most frame layouts are altered when you move from one make to another. Different frame styles also mean different lengths, even though the wheel size is the same.

Fork length, i.e. the distance from fork crown top to the center of the dropout/axle is a very important dimension. If replacing a fork with another and there is a difference, then all of the frame angles will alter as a result.
As the head tube angle is part of the equation when determining trail and 'handling', any change will result in different characteristics. This may also occur if one fork has been built for a particular lower headset stack which differs from that of the replacement fork.

BikeCAD is a handy tool for determining whether or not the difference will be marked or negligible. Find a free-to-use version at Bikeforest.com or in the frameforum.org Club section.

 

[Mike from BA]

Awesome!

Thanks frameforum, I have noticed that fork lenght varies +/- 1 inch depending on the manufacturer, so the bike´s angle should be affected. I´ll study your links during the weekend and hope to fully understand this very ineteresting matter.