Front brake setup on KTM works bikes

[vmx1963]

G'day again,

I was flicking through Friedrich Ehn's book on KTM history and noticed that several of the mid 70's works bikes (the grainy photo below is of Moiseev) have a front brake setup with the cable running down the front of the fork leg to activate the brake lever clockwise - as opposed to stock with the cable at the back of the fork leg activiating the brake lever anti-clockwise.



Has anyone seen similar?  From other photos in the book, it looks like the front brake arm is longer, positioning the brake plate further anti-clockwise.





VMX1963
Western Australia
//www.vmxktm.net

[Larry Perkins]

To the best of my knowledge I always ran my front brake the way in the photo.  Maybe my memory is bad or I learned it long ago but that is what I remember.

Larry P

[tomale]

ON my 76 which has not been change since it was new, the arm points to the rear. I had always thought that it was a bit strange but I never change it. It seemed to work pretty good. MY 78 on the other had does not, it points forward. There is a bracket that attaches to the brake stay arm that hold the outside of the brake cable. It looks like to me that it would be easy to duplicate. I figured the difference was due to the fact that the hub on the 78 is a conical and the 77 is the older style. but the brake shoes seem to be interchangable and the backing plate would too if it was not for the fact that it mounts to the hub a little differently. I think it could be made to fit but since I do not have an extra to mess with I have not attempted it..... not need as far as I can tell. I wonder if the brake arm in the forward position would not work better. because of how close the brake stay arm is to the brake lever... just a thought I have no idea if there is a difference at all.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
78' 400 MC5

[Speedy]

quote:Originally posted by tomale

ON my 76 which has not been change since it was new, the arm points to the rear. I had always thought that it was a bit strange but I never change it. It seemed to work pretty good. MY 78 on the other had does not, it points forward. There is a bracket that attaches to the brake stay arm that hold the outside of the brake cable. It looks like to me that it would be easy to duplicate. I figured the difference was due to the fact that the hub on the 78 is a conical and the 77 is the older style. but the brake shoes seem to be interchangable and the backing plate would too if it was not for the fact that it mounts to the hub a little differently. I think it could be made to fit but since I do not have an extra to mess with I have not attempted it..... not need as far as I can tell. I wonder if the brake arm in the forward position would not work better. because of how close the brake stay arm is to the brake lever... just a thought I have no idea if there is a difference at all.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
78' 400 MC5

On an ENDURO bike,with a chance that you hit the forward mounted brakearm and it katapults you over the bar,I would rader have the arm pointing to the rear,but,....Speedy--------->>>>>>>>

Helmut Clasen KTM
162 Hillcrest Ave
L9H 4Y3
Dundas Ontario Canada
Ph.905-627-5349
[email protected]
http://speedy_c.tripod.com
Sachs GP-GS 250-7A reeds
Zuendapp 125 GS ISDT repl.73
KTM 450 EXC Auto.03
Duke spec.Edit,1996
Adventurer 02

[Speedy]

quote:Originally posted by tomale

ON my 76 which has not been change since it was new, the arm points to the rear. I had always thought that it was a bit strange but I never change it. It seemed to work pretty good. MY 78 on the other had does not, it points forward. There is a bracket that attaches to the brake stay arm that hold the outside of the brake cable. It looks like to me that it would be easy to duplicate. I figured the difference was due to the fact that the hub on the 78 is a conical and the 77 is the older style. but the brake shoes seem to be interchangable and the backing plate would too if it was not for the fact that it mounts to the hub a little differently. I think it could be made to fit but since I do not have an extra to mess with I have not attempted it..... not need as far as I can tell. I wonder if the brake arm in the forward position would not work better. because of how close the brake stay arm is to the brake lever... just a thought I have no idea if there is a difference at all.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
78' 400 MC5

On an ENDURO bike,with a chance that you hit the forward mounted brakearm and it katapults you over the bar,I would rader have the arm pointing to the rear,but,....Speedy--------->>>>>>>>

Helmut Clasen KTM
162 Hillcrest Ave
L9H 4Y3
Dundas Ontario Canada
Ph.905-627-5349
[email protected]
http://speedy_c.tripod.com
Sachs GP-GS 250-7A reeds
Zuendapp 125 GS ISDT repl.73
KTM 450 EXC Auto.03
Duke spec.Edit,1996
Adventurer 02

[tomale]

Speedy,
I can see how that would or could be a good thing to do if you are going to set it up for Enduros. But I wonder if it would be more of an advantage for Motocross the other way. I took a closer look at the pictures and I think that the first picture has the brake lever turned towards the rear. The cable appears in the front near the top of the slider but you can not see it at the bottom. Mine came routed that way but the cable still rotates around the slider to the rear and connects to the backing plate at that point. A close look at the backing plate and you can see that the large end of the lever is towards the front, and then it extends to the rear. This looks to me like it is set up like my 76 with the brake lever connected to the cable behind the slider rather than the front. The second however looks like it is set up the other way. Like my 78.
I think speedy is right and if you  are going to riding it in deep woods with lots of things to crawl over then having it mount towards the rear would make more sense. I think I for one will leave mine alone. It would be interesting to see other pictures to see how others had set theirs up and why. Is that the 75' style frame?
Very cool pictures

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
78' 400 MC5

[Big Mac]

VMX - that's a real interesting picture of what I think is a '73 250? I'm guessing that was the Euro style for that year? Do you know what the color scheme was for the tank and side plates? thanks, Mac

[vmx1963]

Mac, I'm pretty sure the 73 works KTMs were red tank and sidecovers

VMX1963
Western Australia
//www.vmxktm.net

[Big Mac]

VMX - that's a real interesting picture of what I think is a '73 250? I'm guessing that was the Euro style for that year? Do you know what the color scheme was for the tank and side plates? thanks, Mac

[vmx1963]

Mac, I'm pretty sure the 73 works KTMs were red tank and sidecovers

VMX1963
Western Australia
//www.vmxktm.net

[Mike Lenz]

I set all my race Pentons up this way. All you need is the brake arm ,cam and cable holder off a 79-82 KTM front wheel.

[TGTech]

That drum brake thing is a rather interesting discussion, and one that I never thought of at the time. The bottom line to the situation, is that the direction that the cam is turned, has an effect on how strong the braking force is. The way that KTM always set up the brake arms, was the direction that gave the strongest braking force. When you move the arm to the front (for the front brake assemblies) or above the axle (for the rear brake assemblies, you are then turning the brake cam in the opposite direction, and lessening the braking force that can be achieved with the same braking force at the lever.

This is all provable theory, but I don't know the exact difference between the two directions.

Helmut has a somewhat valid point in regards to guarding the brake arm from brush etc., but then again, if the arm is in the front, the cable pull is straighter, and potentially easier to pull, than if the cable has to snake around to the rear of the fork leg to the arm.

In the rear, on the conical hub set ups found on the later bikes, putting the arm above the axle, kept it out of harms way, better than if it were below the axle assembly. And since not having enough pressure on the rear brake pedal never seemed to be a problem, that was the positioning of choice.

Dane

[tomale]

Hmm very interesting topic. My 78 front brake seems to work easier and brake harder but I was never sure if that was because it was a conical hub or because of the way the brake arm was set up. I guess I could easily set up the 76 with the 78 lever and cable etc to see if I could feel a difference. something to think about. Not that I have time to get bored.

I was thinking about it some more and with the lever pointed toward the front the front brake shoe would have more leverage off the cam than the rear shoe would. about 5/8 ths of an inch and the reverse would be true if the lever was pointed towards the rear. With the lever pointed towards the front the wheel would move across the front shoe from the weak side of the shoe to the strong side of the shoe
(ie from the pivot point'weak' to the cam side 'strong').  this I think would cause more of the shoe to be in contact with the drum. With the lever pointed to the rear the rear shoe would be the strongest shoe but the wheel would move from the strong side of the shoe to the weak side. I could be all wrong about this. Dane was this what you were getting at? but I think I came up with a different conclusion. Like I said I could be all wrong. but this is fun.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
78' 400 MC5

[tlanders]

Mike Lenz told me the '79 setup on the front worked better, so I converted my Mint 400 front. However, the hole in the backing plate for the shaft had to be bored out to fit the larger diameter shaft. The lever is longer and the brakes work better and for motocross the position should not be a hazzard.

Teddy

[tomale]

So did the conical front hub not come out until 79? Is that right? On my 78 it looks to me like the way it is set up is the only way it could be. There is no outercable stay on the backing plate for the brake cable. And it looks like a speedo cable could be hooked up to it as well..with the gearing for the speedo cable being internal in the backing plate. Very interesting.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
78' 400 MC5