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Roadholder fork widths

Submitted by gary_trimble on Mon, 13/01/2014
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Heavy Twins

Hello.

Could anybody please inform me of the reason for the change from 7" to 7. 3/8 fork width in 1964. I am building a 650SS cafe racer and have alloy top yokes in both sizes. Since I have to source a bottom yoke I have a choice of which width to go for. Is there an advantage in going for the wider one? Also was there a change in hub geometry along with this change to wider forks in 1964?

Actually just found confirmation of what I suspected. That the change was indeed to fit a wider tyre. But still interested to know whether there was a modification to the hub as well. If all fits together ok I'm supposing that wider is better.

Submitted by gordon_johnston on Tue, 14/01/2014

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Hub is the same. The 7" forks make tyre clearance a bit tight once you move up from a 3.00" tyre. A 3.25" may well not fit (I as have discovered).

Submitted by gary_trimble on Tue, 14/01/2014

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Thanks Gordon. The hub being the same is one thing but have now discovered that the sliders were widened at the base where the spindle goes through to take up the extra space created by the widening of the fork width. Since I have the narrow fork sliders perhaps I could use spacers but beginning to think that if I want the wider forks might end up having to swap mine or buy some. I'll assemble and see how it all measures up.

Submitted by tim_gostling on Tue, 14/01/2014

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Hi Gary,

I have a friend who had much the same problem with his Dommie, he had both types of yokeâs in his box of bitâs, but only the narrow type sliders. For obvious reasons, he decided to go with the narrow set up until it came to fitting his mudguard. He then found that the fork shrouds hit the guard when the suspension dropped. It seems the mudguards changed in width as well & the wide guard will not work with the narrow set up. As he only had the one mudguard, he decided to change to the wider yokes, then made up a 3/16ths spacer to fit between the brake plate & the slider. The pinch bolt side was not a problem as the wheel spindle goes right through & locates on the bearing dust cover & pulls the whole wheel assembly over. Iâm pretty sure he had to get the longer wheel spindle though. Looking at it you would never notice.

Regards, Tim

Submitted by gary_trimble on Tue, 14/01/2014

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Hello Tim

Thanks for this encouraging information. I am set on having the wider forks set up now. For the cost of a new spindle I think it will be well worth it.

Regards,

Gary

Submitted by howard_robinson on Wed, 15/01/2014

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Hiyah Gary - The rh fork slider was indeed wider at the bottom where the spindle passes through but also at the slot where the brake plate spigot locates. From my experience you can fit a suitable alloy washer between the fork slider and the brake-plate but then you will need a longer spigot, which is part of the bolt, at the top of the plate ( 0.25 inches should suffice). It would be better to get a wider slider but remember early Commando ones have different threads. Nuisance.........

Cheers, Howard

Submitted by gary_trimble on Fri, 17/01/2014

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I've just come out the shed. After laying everything out I think I see all the pitfalls and solutions to them.HowardI see exactly what you mean about the slot and the brake plate spigot.Thanks everybody you have been most helpful

 


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