Most people are familiar with normal cable hand brakes. You have a metal braided cable attached to a handle on the bars. When you squeeze the handle, the cable tightens. On the other end of the cable is a set of calipers. The caliper fingers have rubber pads attached that pinch the sides of the rim as you squeeze the handle.
Raleigh Sports has cable brakes. The black rubber tubes house steel
cables inside. The steel cables move when you squeeze the brake levers
and that silver caliper pinches the wheel. Most everyone who rides
a modern bike has seen this in one form or another.
There are other ways of moving the brakes though, and steel rods are one such way. Instead of using cables, you can use solid metal rods attached to hinges to actuate the brakes.
These pictures show rod brakes. These metal rods attach to the handle
bars. When you squeeze the brake lever this time, it pulls on the rods,
which in turn applies the brakes. The front brakes are pretty straight
forward- the rods get pulled up and apply the brake shoes or brake
drum. If you have brake shoes, a stirrup applies the two pads to the
inside circumference of the rim. If you have brake drums, as this green
Raleigh has, it causes internal brakes in the hub to expand and rub on
the inside of the hub shell.
you need to turn a corner, you cant just bend a rod as you would a
cable. So a hinge is attached to the bike frame. When the front rod goes
up, the hinge pivots and pulls on a cable running down the bike, which
in turn pulls on a second hinge near the wheel, which then pulls on the
brakes and applies them. It's like a series of elbows all bending to
move the bones of the system.
A basic description of adjusting rod brakes:
Rod brakes can be adjusted. In the picture above you see some hex nuts where the small rods pass into the larger ones.
Loosen the nuts so the
small rods leading to the handle bars are loose. With a stirrup model,
you adjust the brake pads to sit closely to the rim without touching it.
You're looking at the gap in the picture above denoted by the red line added to the picture.
If need be, move the rod peg guides. You want the rods
resting close to the rim without touching it. Then, re-tighten the nuts
linking the mechanism to the small handlebar rods.
you're doing the back brakes, there is a second linkage below the
bottom bracket similar to the one you see at the front. When you do the
back brakes, loosen both the handle bar small rod nuts (seen above in
the picture) and the similar adjustment nut under the bottom bracket. Everything in the system should be loose and ready for adjustment.
Then set the back brakes close to the rim at rest. Move the stirrup peg
guides if need be. Once the pads rest closely to the rim without
touching it, re-tighten the adjustment nuts under the bottom bracket and
up at the front of the bike. You can do the job using a wrench
or socket, just be sure that it fits properly so you don't round off parts.
If a nut is frozen, use Kroil or Liquid
Wrench and let it soak into the joint. It is indeed possible to crack
the adjustment parts at the joint where that nut is. Work slowly.
pads are held in place with a nut to the stirrups. When you want to
replace these, remove the pads and replace with new ones. When you
replace and try to mimic the contour of the inside of the rim as best
you can. They will be a little weird until they wear in, if they're the
flat profile pads. The really good pads come with their shapes
pre-contoured to fit the rim. You can use either, and both work
reasonably well once you wear the flat ones in. You will probably have
to re-adjust both the front and back brakes once the new pads are on.
Use the method I describe above.
A final caution:
that because you are using the inside of the rim's surface with
stirrup/rod brakes, if the pads hit the spokes, you're in for trouble.
Your wheel needs to be trued for both hop (radial movement) and wobble
(lateral movement). Hop is more annoying than anything, but wobble can
be dangerous if the pads are going to hit the spokes or nipples. Test
spin your wheel and test your brakes several times before riding them,
to make sure you're ready to roll.
Also, only certain
rims can be used with rod/stirrup brakes. These are the Raleigh/Westrick
and Westwood rims with wide, flat top profiles that feature a ridge in
the middle where the spokes are.