Manx Front Forks - Garden gate 1946-1950
|Author: Ken McIntosh
The garden gate forks have offset yokes, with the lower yoke having considerably more offset than the top. The steering head angle is 27 degrees, while the fork tubes sit at about 30 degrees. The yokes are also recognisable by the large diameter (1.125") stem, used only with the old style lug frame and that the lower yoke curves forward, when viewed from above. Because the 1946-1950 frame is a pre-war design, it was designed for girder forks. The knowledge of telescopic fork design was limited, but the lack of proper (later style) damping was the worst problem. The design and size of the main working parts was good, and remained unchanged to the last Commando model.
The good news is the 1950-garden gate forks had most of the problems fixed, and the early forks can be updated.
I have found that the handling on my 1948 Manx, while not in the featherbed class, is certainly nowhere near the generally held perception of wobble and wallow'.
The criticism often levelled at the plunger rear suspension is mainly caused by the lack of damping in the front forks
The 1950-type forks, used on the DOHC garden gate models, are the first to have the later piston type dampers. The earlier type were really just hydraulic stops at the extremes of the travel. There was no attempt made to damp the middle fork movement.
To convert to the later type is possible, without changing the original appearance, but requires the replacement of a number of parts. The easiest way is to use later Commando stanchions and dampers. The Commando internal springs are not required, as the original gardengate external springs will work without problems. The Commando stanchions are slightly shorter than standard the gardengate type but this causes no problems, as the ride height is determined by the springs.
The dampers will fit into the early type sliders without modification, but new top fork nuts will be required, because the damper rod screws into them. The standard Commando top nuts are too long, because they originally mount the speedo/tacho housings.
The Commando steel damper rods are often threaded 3/8" UNF, so alloy rods are a good option, threaded 3/8"x 26tpi, to suit the manx top nuts. The 1946-1949 forks had chrome steel top nuts; 1950 and later were alloy. Both types are available.