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Misc: Everything Else Series B versus Series C Machines


Texas John

Well Known and Active Website User
Non-VOC Member
I have always operated under the belief that the differentiator between Series B and C machines was whether it came from the factory with Brampton or Girdraulic Forks. Even when looking through a number of Vincent books, there is frequent mention of Series B and C, yet the difference is never explained.
But is that correct - Brampton versus Girdraulic Forks? Were there other items that marked the difference between Series B and C machines?
A secret that everyone knows, apparently.
Thanks!
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
In the factory records the only difference between series B & C is series B machines had frame number R#### and Bramptons fitted where as series C had frame number RC#### and Girdraulics fitted.

All other changes like gearlever design, RFM length & design, HRD & Vincent crankcases and transfers were general changes that were subjected to both series B & C at the same time as there was an 18 month overlap where both B & C machines were made at the same time.

So basically yes its all down to the forks that were fitted when new and the frame number.

Simon
Machine registrar - VOC
 

Texas John

Well Known and Active Website User
Non-VOC Member
Hi Simon,
Thank you. I forgot about the Frame Number change. I am glad I asked.
It being a very manual process, would you know if they ever sent out an RC stamped Frame with a Brampton front fork, or vice-versa, by accident?
 

TouringComet

Well Known and Active Website User
VOC Member
VOC Forum Administrator
I recall a story that Indian Sales special ordered a number of bikes to be fitted with Bramptons, some amount of time after Series B production had otherwise stopped. The factory supplied bikes with Bramptons. I don’t know how the frame number is stamped, but perhaps those were stamped RC?
 

Albervin

Well Known and Active Website User
VOC Member
When Girdraulic forks were introduced quite a few riders had their forks "updated" by the factory, There were some notable machines that raced in the clubman TT that had this "upgrade". If you had a bike with such history it would be a moot point to "restore" the bike back to original. Personally I would not as it would detract from the very personal history of the machine.
 

vibrac

Well Known and Active Website User
VOC Member
The new models were launched under the generic name ‘Series ‘C’’, when they were
announced at the 1948 autumn Motorcycle Show. Care should be exercised with the
word launched, as it should not be viewed in the mindset of the twenty-first century.
While at the show a new model was shown and announced, a complete new model
did not really supersede the old one. There was no new production line to be started.
Wholesale re-tooling did not occur. As explained, changes in specification continued
before and after that date, but the announcement of the Series ‘C’ does give a convenient
point to note the changes that had been made to the original Series ‘B’ specifications.

(The Vincent black Shadow)
 

greg brillus

Well Known and Active Website User
VOC Member
Aside all the smaller changes, of which there were many, the significant change was to the suspension. And most notably the upgrade to hydraulic shock absorbers over friction dampers. This would have been the major factor in the specification from a "B" to a "C" model. As great as they are the Brampton forks were very outdated by then, and the factory would have been busy trying to improve on them, especially as most other makes were using telescopic forks. Although not as ridged and strong as the Girder forks, their action and behavior has proven itself pretty hard to beat, and still the norm to this day.
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I recall a story that Indian Sales special ordered a number of bikes to be fitted with Bramptons, some amount of time after Series B production had otherwise stopped. The factory supplied bikes with Bramptons. I don’t know how the frame number is stamped, but perhaps those were stamped RC?
As per every rule, there is the odd exception. Yes there are a couple of bikes that went to ISC that started as series C and the frame were numbered as such but it appears at the last minute altered to series B spec by fitting Bramptons.
The factory would grab any sale as they were constantly needing money so they would sell whatever you ordered.
 

Glenliman

Well Known and Active Website User
VOC Member
I can imagine that riding at speed on imperfect roads would be quite an experience with original Bramptons, friction damping only.
The Girdraulics, with a decent shock fitted, aren't awful even after getting off modern bike such as the Thrux R with its anti-dive Showa big piston forks.
The Girdraulics will bottom now and then when pushed hard on a patchy road. Best to avoid that, however it does sometimes occur when fun is the goal.
The Girdraulics seem to take the abuse without a complaint.

Glen
 

passenger0_0

Well Known and Active Website User
VOC Member
I can imagine that riding at speed on imperfect roads would be quite an experience with original Bramptons, friction damping only.
The Girdraulics, with a decent shock fitted, aren't awful even after getting off modern bike such as the Thrux R with its anti-dive Showa big piston forks.
The Girdraulics will bottom now and then when pushed hard on a patchy road. Best to avoid that, however it does sometimes occur when fun is the goal.
The Girdraulics seem to take the abuse without a complaint.

Glen
Completely agree with Glenliman, I frequently have to stand my bike up and roll off the throttle after encountering corogations on corners. We have some rough roads in NZ and losing all steering with the front wheel bouncing frantically up and down is no fun. Dangerous infact. While I want to keep my Series B with Bramptons as standard as possible I need to either slow down or buy one of those nice coil over shocks.
 

Nulli Secundus

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Completely agree with Glenliman, I frequently have to stand my bike up and roll off the throttle after encountering corogations on corners. We have some rough roads in NZ and losing all steering with the front wheel bouncing frantically up and down is no fun. Dangerous infact. While I want to keep my Series B with Bramptons as standard as possible I need to either slow down or buy one of those nice coil over shocks.
I have a coil over shock on my Rudge race bike and even on the relatively smooth race tracks the forks bounce up and down a lot. I have only recently found out, after receiving some advice from experienced racer Mervyn Stratford, who was watching me recently at Lydden, that reducing the front tyre pressure quite significantly and increasing the suspension friction damping, has calmed the front end down, which has made the bike more rideable. Strangely my lap times did not improve much.
 

Bill Thomas

Well Known and Active Website User
VOC Member
That's what I have found, I can't get on with too high a tyre pressure, Cheers Bill.
 

passenger0_0

Well Known and Active Website User
VOC Member
I have a coil over shock on my Rudge race bike and even on the relatively smooth race tracks the forks bounce up and down a lot. I have only recently found out, after receiving some advice from experienced racer Mervyn Stratford, who was watching me recently at Lydden, that reducing the front tyre pressure quite significantly and increasing the suspension friction damping, has calmed the front end down, which has made the bike more rideable. Strangely my lap times did not improve much.
Now that's a thought Nulli Secundus. I currently run 32 psi in the front 20" Avon Speedmaster ribbed tyres. Maybe a bit too high. I'll try dropping it down to 30 or even lower in my next ride.
What doesn't help is the grease that's got into the side friction damper so I've got no dampening to speak of.
 

Nulli Secundus

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Now that's a thought Nulli Secundus. I currently run 32 psi in the front 20" Avon Speedmaster ribbed tyres. Maybe a bit too high. I'll try dropping it down to 30 or even lower in my next ride.
What doesn't help is the grease that's got into the side friction damper so I've got no dampening to speak of.
My Rudge is light compared to a Vincent twin. I have a narrow 21" and was using a tad over 25 psi. I dropped eventually to 21 psi. Mervyn suggested 20 psi. These figures will be much lower than what you need, so I would gradually reduce and go for a test ride, which is what I did through a series of races. Good luck.
 

peter holmes

Well Known and Active Website User
VOC Member
At what point do you start to risk tyre to rim slippage, if you are not using security bolts that is.
 

Nulli Secundus

Well Known and Active Website User
VOC Member
VOC Forum Moderator
At what point do you start to risk tyre to rim slippage, if you are not using security bolts that is.
Good point. I haven't yet measured the pressure when the tyres are hot and being race compound they warm up a fair bit, so the pressure does increase. So if I had 26 psi when cold the pressure might be over 30 when hot and that would cause the tyre to bounce significantly.
 

vibrac

Well Known and Active Website User
VOC Member
Its not just weight or tyre pressure its also wheel base and tyre size at least thats my conclusion my rigid teles trophy about the same weight as my KSS velo with girders both with single seats is much more uncomfortable.
mind you the Triumph is on knoblies that may affect things but sizes are similar
For track use we found the 18" wheels and tyres of the Comet that Ben suggested much more controllable than standard Vincent which supprised me as I always raced it with 20 & 19 and still do with the Flash
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
My Rudge is light compared to a Vincent twin. I have a narrow 21" and was using a tad over 25 psi. I dropped eventually to 21 psi. Mervyn suggested 20 psi. These figures will be much lower than what you need, so I would gradually reduce and go for a test ride, which is what I did through a series of races. Good luck.
When my brother John was racing my rigid Sunbeam we ran 19" wheels with Avon GP tyres with pressures at 18-19 psi, far lower than any tyre manufacturer would recommend. The friction dampers on the Druid girders were tightened so that they would only just move on a large bump. The suspension then came mostly from the tyres themselves. On most UK tracks there are not many sharp bumps. I'm not suggesting that this will work for every rigid bike but it worked for us and could be a guide for others using similar old machinery. Lots of suspension travel is great but only if you can control it with adequate (i.e. modern hydraulic technology) damping, preferably two way. I think I may have posted something similar before and although it not really specific to this "Series B Versus Series C" it bears repeating with relation to Mervy's suggestion.
 

Albervin

Well Known and Active Website User
VOC Member
Aside all the smaller changes, of which there were many, the significant change was to the suspension. And most notably the upgrade to hydraulic shock absorbers over friction dampers. This would have been the major factor in the specification from a "B" to a "C" model. As great as they are the Brampton forks were very outdated by then, and the factory would have been busy trying to improve on them, especially as most other makes were using telescopic forks. Although not as ridged and strong as the Girder forks, their action and behavior has proven itself pretty hard to beat, and still the norm to this day.
Don't forget that the change to Series C also brought rear hydraulic damping as well. Combining the two made a huge difference in handling. Now that many people (including me) have incorporated front and rear hydraulic damping on our Bs plus added the benefits of a 21" front wheel there are some Series C owners who will admit (in a quiet corner) they are superior to a C in handling.
 

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