Ironhead Rear Drum on Big Twin Chopper

[LuckyWheelsGarage]

Hey y'all,

Wrapping up a 72 Shovelhead build and tweaking some final issues before completion, and wanted to see if anyone here could offer some advice.

For the rear wheel I'm running an ironhead 18" w/drum brake. Yes, I realize this is meant to run on the opposite side of the bike - but it's what i've got and I'd like to make it work. I've got axle spacing done and fabricated a cable stay and made a custom cable to actuate the drum. With the bike on the stand the rear wheel turns free, brake grabs just fine using the pedal.

However - under load, I apply the slightest amount of pressure to the brake pedal and the drum locks up. I know that this can happen when flipping the arm due to the cam lobes being backwards and not being able to apply gradual pressure, but the way I am running it the brake arm actuates as intended (just on the opposite side of the bike). Any ideas on what could be causing this? And another couple questions that may help me solve the problem.

-Does the brake stay need to be in line with the axle? I currently have it mounted about 20 degrees to the left and above the axle, with the arm opposite. Seems like the position wouldn't matter much but it's not working so this could be it I suppose.

-Do y'all "arc" new shoes prior to installation? Perhaps one edge is grabbing and causing the lockup.

-Are the shoes directional? They don't seem to have a leading edge and look symmetrical

-Is there supposed to be a spacer between the drum and backing plate?


Cheers and thanks in advance for the help. The only threads I could find either basically said "DON'T RUN AN IRONHEAD DRUM ON A BIG TWIN YA DUMMY!" or had more to do with sanding down the cam (which doesn't apply in this situation).

Thanks!


Ty

[Benny74]

The reason this happens is because the brake isn't centered correctly, there is a procedure for centering the shoes in those bikes, which basically comes down to loosen your axle and brake stay, spin the wheel, apply the brake, and with the brake still applied, tighten the brake stay and axle. I had this same problem with my Ironhead when I first got it running and now that everything is centered it works correctly.

The brake stay does not need to be in line horizontally with the axle, many people move the backing plate to their convenience and it works just fine. I would just make sure everything is in good working order and that your brake stay is tight and where its supposed to be, if that is off and has even a little bit of play you can break that bolt from it slamming off the tabs under heavy braking