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Series "B" RFM

Albervin

Well Known and Active Forum Website User
VOC Member
I am in the process of fitting a Series "B" RFM to my Rapide (why? because it is a "B") and am finding all sorts of little problems. In many ways it is good to go right through the rear as I am replacing a few worn out bits and tidying up others. Fitting the mudguard is a pain; while the previous unit fitted the Series C RFM, I am going to need to use spacers to get a decent fit on the "B" item. The spares company should sell thick-walled alloy tube that can be cut to length as spacers all around the machine (?!). Are there any of you who have been through this exercise who can give pointers and tips? Also, what is the largest (best) tyre to fit to a "B" RFM? I have been using a 4.10 Avon Roadrunner but not sure if it will fit the shorter unit and as it needs replacing I might as well get the best I can. As usual I expect many different answers, all of which will be correct..
Thanks in anticipation.
 

davidd

Well Known and Active Forum Website User
VOC Member
I can see the mudguard fitting as a problem, but surely the rear wheel will fit. I thought the lengthening was to make room for the 3.50 21" tire that was growing at speed. I have not heard of any issues with smaller wheels. I assume that it is a 19"? The rear mudguard can change diameter dramatically if made narrower or wider by squeezing or flattening. This works well until you get to the hinges.

This change will increase the tendency to wheelie considerably!

David
 

Albervin

Well Known and Active Forum Website User
VOC Member
I can see the mudguard fitting as a problem, but surely the rear wheel will fit. I thought the lengthening was to make room for the 3.50 21" tire that was growing at speed. I have not heard of any issues with smaller wheels. I assume that it is a 19"? The rear mudguard can change diameter dramatically if made narrower or wider by squeezing or flattening. This works well until you get to the hinges.

This change will increase the tendency to wheelie considerably!

David
David, thank you for both your input and humour. Yes, I have a 19" rear wheel. I would have thought the change in RFM was more about tyre width than diameter but I admit I know little about the reality of engineering. Surely no-one fitted a 21" rear wheel!!? There was a change of nomenclature when wheels were referred to by overall diameter (wheel + tyre) then wheel only which reduced sizes from 26" to 21" or 20"....
Anyway I reckon I should get by with a 4.10 even if I have to "push it out". Now does anyone have any experience with iwis chains? While we are at it, has anyone used NTN bearings that cost 1/3rd the price of Timken?
 

davidd

Well Known and Active Forum Website User
VOC Member
Dear Albervin,

Sorry, you are correct. I meant 3.50 X 20 rear as the 21" is on the front. However, the 3.50 X 20" rear has considerable clearance with the "C" frame and the "B" is only 1/2" closer. You can see day light between the fender and the tire. I do not think the width will be an issue.

David

FlashRearWheel1.jpg
 

davidd

Well Known and Active Forum Website User
VOC Member
Yes, it is a "C". My point is that there is plenty of space. I run a "B" RFM on the racer, but I am using 18" wheels, so it also looks as generous. I do remember reading somewhere that the "B" RFM was lengthened for additional clearance for the Flash and Lightning size wheels. I have fitted 120 mm width tires and still cleared the chain line, so I do not think there are any unusual issues with the "B" RFM. I am also a fan of skinny tires as the compounds in the worst street tires today are far superior to the best racing tires of the 50's. A modern skinny tire with a racing street tread will handle 75 hp with ease and can be seen at any vintage racing event.

David
 
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