Head Tube Length - CX vs Road

[campy man]

Can anyone briefly explain the history/reasons for the shorter head tubes on some of the older cx bikes vs roadbikes?

Is there a general rule of thumb when trying to compare the build & contact points going from road to a cx bike?

[thunderworks]

At least some of the answer has to do with the significantly longer "fork crown to dropout" dimension on CX forks. For any given rider position, on CX bikes the longer fork matches to a shorter head tube to achieve a comparable cockpit relationship.

[fa63]

^^ This. CX forks tend to be about 3 cm taller than the road ones.

[tuscanyswe]

As thunderworks stated the fork is longer (approx 2.5cm generally)

+ you also need to account for 1cm extra on top for the brake hanger for the cantis that those bikes were designed for.

Those are the reasons.. but if you are trying to get an identical fit vs your road frame you will also need to compare the bottom bracket drop as cx bikes generally ride with a little less drop.

[e-RICHIE]

When a head tube is shorter because the forks are longer, the length is taken from the bottom, not the top. It doesn't affect the contact points at all. If you need 'bars higher for any reason at all, one way to support that is to lengthen the head tube at its top. It's not related to drop either. You set the saddle height, and then put the handlebars where you want/need them.

[kramnnim]

Is there a general rule of thumb when trying to compare the build & contact points going from road to a cx bike?

Compare stack and reach...and be annoyed when the manufacturer does not supply it.

[David Kirk]

This might be helpful -

http://forums.thepaceline.net/showpost.php?p=1781559&postcount=433

dave

[nooneline]

Compare stack and reach...and be annoyed when the manufacturer does not supply it.

^this.