grandpaul
VIP MEMBER
- Joined
- Jan 15, 2008
- Messages
- 13,209
It's winter, and you're probably not riding right now, so why not FINALLY fix those lousy drum brakes once and for all?
The best thing to do is to turn the drums using a simple wheel stand (jig). No need to even dismount the tire, as long as everything is reasonably well balanced. Have an assistant do the turning, or rig up a motor with a friction drum on it's spindle to turn it for you. An old style shoe polishing rig is the perfect thing, you can get them on ebay.
Get the drum spinning slowly and check it for a true inner face using a fixed wire pointer (or a dial indicator if you have one); this step is really important, you FIRST want the drum face to be nice and true. Mark high spots with calk on the edge of the drum. Use one mark for slightly high spots, 2 marks for her spots, 3 marks for really high spots.
Take an old brake shoe and line it with emery paper to use as a sander, hit the high spots a little at a time then re-check and see if they've become lower. If so, proceed; if not, sand a bit harder. Make nice sweeping passes at them starting to put pressure on as you arrive at the mark, then press hardest, then ease off. It might take a while, BUT ITS WORTH IT!
Once you've got the drum nice and round, time to fix the shoes. Set them in the drum one at a time, and look for obvious curve shape differences. Mark with chalk on the face of the shoe.
Use double-stick tape or wood glue, and stick a new sheet of emery paper to a disposable piece of plywood or board, long enough that you can kneel on it, or screw it into your workbench top if you use a topper of sacrificial material (or if simply don't mind screw holes in your workbench).
Work the shoe(s) gently, smoothing off the high spot(s), check against the drum to see that you've hit it right.
Gently color the entire surfaces of both shoes with light, even passes from a full stick of chalk laid across. You want the entire surface colored evenly.
Fit the shoes to the brake plate, and fit the plate up to the wheel, and put it back on the bike. Fix the axle in place snugly. Have your assistant turn the wheel at a moderate speed, then apply the brake gently for at least two wheel revolutions.
Remove and inspect: The chalk coloring on the brake pads should be evenly disturbed or gone across the ENTIRE faces. Any remaining chalk indicates a low spot on the shoe that the rest of the shoe needs to be reduced to. Drum should have a uniform appearance as well; if not, address it.
Once trued drums and good quality shoes are all properly arced, grease fittings serviced, good quality brake cable properly adjusted, and all lever pivot points lubed, you should have the best brakes that your particular bike will ever be capable of having.
If you haven't been trying to get them to work better by installing new shoes and cable(s), re-adjusting etc, (in other words, if you are going from really crappy brakes to totally nice ones) You are going to be AMAZED at the difference!
The best thing to do is to turn the drums using a simple wheel stand (jig). No need to even dismount the tire, as long as everything is reasonably well balanced. Have an assistant do the turning, or rig up a motor with a friction drum on it's spindle to turn it for you. An old style shoe polishing rig is the perfect thing, you can get them on ebay.
Get the drum spinning slowly and check it for a true inner face using a fixed wire pointer (or a dial indicator if you have one); this step is really important, you FIRST want the drum face to be nice and true. Mark high spots with calk on the edge of the drum. Use one mark for slightly high spots, 2 marks for her spots, 3 marks for really high spots.
Take an old brake shoe and line it with emery paper to use as a sander, hit the high spots a little at a time then re-check and see if they've become lower. If so, proceed; if not, sand a bit harder. Make nice sweeping passes at them starting to put pressure on as you arrive at the mark, then press hardest, then ease off. It might take a while, BUT ITS WORTH IT!
Once you've got the drum nice and round, time to fix the shoes. Set them in the drum one at a time, and look for obvious curve shape differences. Mark with chalk on the face of the shoe.
Use double-stick tape or wood glue, and stick a new sheet of emery paper to a disposable piece of plywood or board, long enough that you can kneel on it, or screw it into your workbench top if you use a topper of sacrificial material (or if simply don't mind screw holes in your workbench).
Work the shoe(s) gently, smoothing off the high spot(s), check against the drum to see that you've hit it right.
Gently color the entire surfaces of both shoes with light, even passes from a full stick of chalk laid across. You want the entire surface colored evenly.
Fit the shoes to the brake plate, and fit the plate up to the wheel, and put it back on the bike. Fix the axle in place snugly. Have your assistant turn the wheel at a moderate speed, then apply the brake gently for at least two wheel revolutions.
Remove and inspect: The chalk coloring on the brake pads should be evenly disturbed or gone across the ENTIRE faces. Any remaining chalk indicates a low spot on the shoe that the rest of the shoe needs to be reduced to. Drum should have a uniform appearance as well; if not, address it.
Once trued drums and good quality shoes are all properly arced, grease fittings serviced, good quality brake cable properly adjusted, and all lever pivot points lubed, you should have the best brakes that your particular bike will ever be capable of having.
If you haven't been trying to get them to work better by installing new shoes and cable(s), re-adjusting etc, (in other words, if you are going from really crappy brakes to totally nice ones) You are going to be AMAZED at the difference!