'27 JD Cut Down Project - SWAN

[Steve Swan]

My guess is one hard emergency stop with a disc on a J fork and it would be twisted like a pretzel. They were barely strong enough for the miserable drum of the time.

Robbie, thanks for that reminder. Food for thought as to what to do. do you think the later truss type rigid fork could be any better? or is the weak/problem area that the wheel axle, spring fork and rigid fork are all independent of each other and yet all three are connected to each other by the rocker plate and the torsional stress would twist these parts in the area where the caliper (or brake backing plate) attaches to the rigid fork?

probably a later "I" beam type fork would be better suited?

[Steve Swan]

I agree with Robbie on the J fork with a disk brake. Late J front brakes were hill holders at best and never designed to take the stress of modern brakes. If a person really wanted to use a J fork with disk brakes, I think a well thought out (and attached) truss on the rigid leg would be in order.

Eric, thanks for seconding what Robbie said. i will give this some thought. does anyone know of anyone who has fitted a front disc brake to the JD forks?

[Steve Swan]

Steve,
I know you want a disc brake front end, I don't blame you they way other drivers can be.
Have you considered installing a late model Harley springer with a disc brake, or install a disc to an original JD springer.
Cheers,
Mick

Hi Mick,

yes i have thought of fitting a disc to a Samwel 1936 type front fork, but i like the looks of the early "castle" type JD forks. concensus suggest the JD fork will twist if the disc is used in an emergency stop. what to you mean by " install a disc to an original JD springer?"

[exeric]

Excelsior beefed up their standard fork and called it a 'Military Fork', and those forks were quite strong. They used trusses and a wider crown plate assembly. Many J era H-D hill climber forks were trussed, and reinforced in similar ways. I think you could put a truss on the back of a H-D J fork and make it strong enough for a disk brake. If you do the alteration right, the fork could be restored back to original appearance without any damage if you changed your mind.

[Steve Swan]

Excelsior beefed up their standard fork and called it a 'Military Fork', and those forks were quite strong. They used trusses and a wider crown plate assembly. Many J era H-D hill climber forks were trussed, and reinforced in similar ways. I think you could put a truss on the back of a H-D J fork and make it strong enough for a disk brake. If you do the alteration right, the fork could be restored back to original appearance without any damage if you changed your mind.

Eric, when you say truss, are you referring to the stamped bracket the factory already put in place on the back of the left hand rigid fork? or are you talking about additional reinforcement on the back of each leg of the rigid fork, regardless of year model? (in the case of the 28-29 type JD rigid fork, that plate on the back side of the left rigid fork, in original factory form is not secured well enough to withstand the force a disc brake would exert on it; could tear the plate of the leg.)

probably a later "I" beam type fork would be better suited?

[JoJo357]

Hey Steve,
John Cameron & Lance Tidwell ran many 3000-5000 mile trips with those twin 1926 JD Flexi's, with front wheel disc they fabricated.





*M.A.D.*

[Steve Swan]

JoJo357, thank you for sharing those pics of Mr. Cameron and Mr. Tidwell. the drum brake with the 6 black rubber covers clearly appears the front brake fitted to 1970-71 Yamaha XS650's. the other bike, somewhat difficult to tell, but from what i see, appears to be a Honda sohc CB750 front brake. good stuff! Where are those machines today? do they still exist in the same form as seen in the pics? i suppose the engines in their bikes were JDH...? i wonder what work they did to the fork to adapt these brakes to fit and work properly. it can't be rocket science, but it still requires a sound design. i have my buddy's '29 at my shop right now, so i am going spend some time looking at his fork to come up with some ideas.

[aumick10]

Steve,
This is a general arrangement to install discs to a springer.
Cheers,
Mick

[Eric]

Steve, Yes Cameron bike always exist and are in the same family

[Eric]

Steve in this pict JD Cameron rear disc brake installation

[aumick10]

Steve,
I measured the front hub on my 1978 triumph. They are set of for a 6" spacing between forks. This is too wide for JD forks. They also have a 1" axle that clamps to the forks. You could use this hub if you removed the dished disc and put on a flat disc. machine threads on the end of the axle.
A better option my be to go to a cycle salvage place with a tape measure and go shopping.
Something else to be aware of. Without any dampening on the fork springs, when you apply the brakes the front end has a tendancy to rise as it rotates around the axle. Can be disconcerting if you are not used to it.
Cheers,
Mick

[T. Cotten]

Hey Steve,
John Cameron & Lance Tidwell ran many 3000-5000 mile trips with those twin 1926 JD Flexi's, with front wheel disc they fabricated.
*M.A.D.*

I apologize for going off-topic, Folks..

But Mssrs. Cameron and Tidwell had a profound effect upon me...
Can't be sure which because it was pretty informal at Bean Blossom in the 80's.

At least I asked the right question, when the reply was "I made my flywheels."
Then the skies opened up and angels descended as he confirmed my motor balancing instincts.

Without his encouragement, I might have made better career choices.

....Cotten

[Steve Swan]

Steve in this pict JD Cameron rear disc brake installation

[ATTACH=CONFIG]23706[/ATTACH]

Thanks Eric, for that pic of a rear brake setup. until now, i was thinking of running the factory rear brake setup with a front hydraulic disc given 90% of stopping power is on the front brake, but our conversations are making me wonder if mostly relying on the front brake if fork is up to the job. on the other hand, considering the type of riding i would be doing on this custom '27 would begin to be even close to the same as i do on my modern front/rear disc braked bikes; i.e., by comparison much more rapid acceleration to higher speeds and subsequent deceleration via braking on my modern bikes in contrast to the '27. and i would never run errands or go downtown on the '27, only up around Horsetooth Reservoir and otherwise to get out of town for trips along back highways. i think what i want to accomplish with a non-stock front brake is to not have to be ever-mindful that my rear brake only is not up to the job meeting today's traffic patterns. While i really like the idea of a rear disc brake and can certainly see with a side car rig, i am not sure i want to be dependent on a rear brake only set up. i like the idea of having front brake control; depending on which of my 2 modern bikes i am riding, one or other, i infrequently to rarely if ever use a front brake to stop unless it is to control the rear end... however, Mick brings up an interesting consideration i shall reply to next. if i go with a hydraulic front disc, it is going to be off a contemporary motocross/enduro or maybe a larger dual purpose bike, still a ways off, nonetheless things i want to be thinking about and i do appreciate everyone's input.

[Steve Swan]

I apologize for going off-topic, Folks..

But Mssrs. Cameron and Tidwell had a profound effect upon me...
Can't be sure which because it was pretty informal at Bean Blossom in the 80's.

At least I asked the right question, when the reply was "I made my flywheels."
Then the skies opened up and angels descended as he confirmed my motor balancing instincts.

Without his encouragement, I might have made better career choices.

....Cotten

Tom! NOT at all are you going off topic! i welcome this sort of off-topic conversations; as i know i will keep talking about my custom project and i find it ever so interesting to learn about stuff such as you share!

[Steve Swan]

Steve,
I measured the front hub on my 1978 triumph. They are set of for a 6" spacing between forks. This is too wide for JD forks. They also have a 1" axle that clamps to the forks. You could use this hub if you removed the dished disc and put on a flat disc. machine threads on the end of the axle.
A better option my be to go to a cycle salvage place with a tape measure and go shopping.
Something else to be aware of. Without any dampening on the fork springs, when you apply the brakes the front end has a tendancy to rise as it rotates around the axle. Can be disconcerting if you are not used to it.
Cheers,
Mick

Thanks Mick, for your reply. With regards to what front hub/disc setup to use, when/if the time comes, as you suggest, I plan to “go shopping.”
You bring up a welcome observation as to how the factory front end is going to respond/react with a front brake of any sort of actual stopping power. Given there is no dampening of the fork springs and the travel is limited (maybe 3 inches?) it is hard to know how quickly and with what force the spring fork/front wheel will rise in relation to the rigid fork being a fixed point… Not that I want to over-think this, I sure as heck don’t. But on the other hand I want to at least give some prudent consideration of what a disc brake would be like, how it would act and then on the other hand as long as the fixing points for the caliper are solid, it shouldn’t be that big of a deal. As to the front end rising, it couldn’t be much different that the action the linked brakes on my Moto Guzzi give me when I step on the rear brake pedal only; it has a proportioning valve, so when stepping on the rear brake only, the whole bike very slightly rises, which if one has not prior experienced, is somewhat disconcerting until one realizes it is simply how the setup performs. Having the front end of the JD rise, I can’t imagine would alter handling or affect safety, on the other hand the rate that it would rise, how far it would rise, especially if it would “bang out” to the top might be more than annoying. As I replied to Eric, I basically want a front brake so I don’t be ever-mindful of having limited braking power of factory rear brake only. On the other hand, instead of running a factory rear brake as I currently think I will, I suppose I could fit a more modern rear shoe or disc brake, run no front brake, but I am not keen on not having any stopping power on the front. Or have modern brakes front and rear, but then that would take the project even further away from original than I am already taking it away. Riding my restored ’27, having become accustomed to the externally contracting band brake, it really does an admirable job and although I’ve never locked it up (and don’t plan to!) I think it has adequate stopping power for the way I use a rear brake when I have a front brake. Anyway… ! Thank you for your thoughts; I truly welcome them! Hope this conversation isn’t too mundane or elementary blather or drivel for minds with far greater experience than mine. With exception to my stock Indian days of 3 and 4 decades ago, my experience is limited to stock more modern bikes of all makes from the 50’s through the 70’s and of course riding modern bikes from the late 90’s to current. One other consideration is that the esteemed Mssr’s Cameron and Tidwell must have done ok with their front-braked J bikes, so I am sure whatever I decide to come up with will be just fine. And… of course, if anyone sees any error or has any concern about anything I write, please do not hesitate to speak your piece! As well, I like seeing folks write commentary such as Cotton’s memories of Cameron and Tidwell, I want this thread to be fun, entertaining and informative as well as help me along with the project and give ideas to anyone else with similarly goofy ideas for a project such as I am engaging in.