• Welcome to the forum website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Online Forum Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this forum website.

    If you have previously registered to use this forum website, you should log in now. CLICK HERE.

    If you have never registered to use this forum website before, please CLICK HERE.

Front Brake Arm

Albervin

Well Known and Active Forum Website User
VOC Member
In the latest edition of "Old Bike Australasia" there is a picture of a Series B Black Shadow being raced (nothing peculiar there). BUT if one looks closely, both front brake arms are reversed! They are pointing backwards! The brake cable is the original one going to the RIGHT hand side of the balance beam. Can anyone shed any light on how, why, good idea, bad, ??
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
No difference. On the Vin the leading shoe remains the leading shoe regardless of direction of cam rotation. The brake shoe doesn't care which way the cam rotates. While most 2LS designs have a linkage so that the brake arms move in the same direction, some use a Vincent-like combination of cable outer push and inner pull to move the two arms in opposition. One is as effective as the other - in fact the scissors pull is a more elegant solution, because it automatically ensures the two shoes bite equally hard (almost) without the cost and complexity of a link. (The downside must be that if the outer compresses more than the inner stretches the push doesn't equal the pull. Let's not go there.)
One way there is slightly more leverage / less mechanical advantage because the cam hits the shoe face at a smaller radius, but the leading shoe servo effect ought to swamp the lever pull.


I would have thought this mod changes the leading/trailing shoes around but to what possible advantage?
 

John Appleton

Well Known and Active Forum Website User
VOC Member
In the latest edition of "Old Bike Australasia" there is a picture of a Series B Black Shadow being raced (nothing peculiar there). BUT if one looks closely, both front brake arms are reversed! They are pointing backwards!

A thing to consider here is the "self servo" effect. The theory being that, with the arms facing forwards, any slight movement of the back plate in the direction of wheel rotation increases the amount of pressure that the rider is applying via the handle bar control. This can give a grabby brake performance, and in extreme conditions can cause the brake to lock and any failure of the torque reaction arrangements results in the brake being "winched "on by it's own cables, even when the handle bar lever has been released. That is the theory anyway. (dont ask how I know this, I still have the scars that prove the theory)

John
 
Warning! This thread is more than 12yrs ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.
Top