Rear brake drum to disk conversion for a 1974 Ironhead
There seems to be some problems at least with the older Netscape navigators, I'll look into this later.
Okay, here's the story... so far. I'm still planning to modify the
current set-up but the basic stuff is here. I'll also update this page
if/when I have something to add, and more important, some time...
If there's something that you would like to know more about, please feel free to write me at
affe3(at)nic.fi. This page is put up in very short time (as anyone can see) and I'm maybe missing something fundamental here.
I started by buying a new rear wheel. I guess it's originally from an
mid 80's big twin but I'm not sure. Anyway, it was a 16" wheel with two
flanges and that was good enough for me. When I bought it, I wasn't
even sure if it will fit between the swing. Well, it did.
First thing that I found out was that the new wheel needed a 19 mm shaft
and the original shaft was 17 mm. At first I tried to find a new set of
bearings with a 17 mm inner diameter for the new wheel, no luck (well, I
didn't look THAT hard). OK, then I had to get a new shaft. Well, that's
not too bad, I got one from a "local" shop for pennies. I was 19 mm but
much too long but I thought I could get it shortened somehow.
For the caliper I found one that used to be at the back of an 1100 GSXR
Suzuki. It wasn't much of an eye catcher but I thought that it would be
a good device to test this whole idea.
Since the new shaft was couple of millimeters thicker than the
original, the old hardware wasn't useful, at least without some
modification. Also I was a bit worried if the thicker shaft will fit
into swing holes also.
Here's the old hardware. I'll try to get some pictures and measures about the new ones at some point.
Maybe the easiest way would be just open up those holes to 19 mm,
there's enough material for that. The end of that new shaft must be
machined to fit the swing hole, just like the old one. And of course couple of spacers are needed.
The wheel is in "place" for measuring the needed spacers.
When the wheel is positioned then the chain line can be checked. At
this time it seemed that the line would be just right but after
checking the wheel position I found out that I need 3 mm offset
(inside/negative) at the rear sprocket.
Since there was no sprockets with 3 mm offset available, I used the one with 6 mm offset together with an 3 mm spacer.
This is something that I'm going to change at some point. I'll change
into a 0 offset rear sprocket and manufacture a front sprocket with an
appropriate offset. This way I'll get that 3 mm more space between the
rear wheel and the chain.
Since this setup was pretty original I knew that it would be pretty
tough to find the suitable caliper mount. So, in that case I'd have to
make one, or actually have one made. I downloaded a test version of the
TurboCAD and designed a simple mount. Since I would have to use a laser
cutting shop I could at the same time have some more stuff made so I
also designed the brake rotor. Here are the DXF file for the mount and the rotor.
I'm not 100% sure if those are actually the latest ones and since the
testing period of the TurboCAD is elapsed I can't make sure of it.
Anyway you'll get the idea. Well, this is what came out of the shop...
When I saw the disk IRL, I realized that I should have made those
cutouts little bigger. Or actually, make the disk 10" instead of the
11.5" but in that case I'd have to make a new mount also. Well, I might
still do just that...
Here's the new shaft end and the left spacer. In that spacer you can
see the groove into which the caliper mount will go. That groove is
just a bit wider than the caliper mount plate is thick so that the
mount will rotate freely in it's place.
And here's the caliper mount apart...
... and in place.
The right side...
It really needs some support between the shaft and the swing. Easiest
way, as I said above, is to drill out the old spacer, this one:
and use that. Well, I wanted to keep the old stuff intact and machined
a new set of chain adjusters that now include the support for the
shaft. Unfortunately I don't have a picture of those yet, later...
This shows where the anchor bar is going. As I have understood this should be better than anchoring to the swing.
The main cylinder found it's place next to forward controls. The place is just fine but the assembly still needs some work.
For testing I took couple of screws, one for the plunger and the other for pushing that plunger. Doesn't look too solid, huh?
Finally I modified the pedal to get some more reliable and rigid assembly. This works just fine.
Well, that's that for now. Hopefully someone got something out of it.
