Rebuilding TR3 Rear Brakes
How do you know when it's time to rebuild your rear brakes?
I
found out when two puddles appeared under my rear wheels. That left two
possibilities. I stuck my finder in a puddle and sniffed. I could tell
right away that it wasn't 90 weight. The only thing left was brake
fluid. Time to rebuild my rear brakes.
Start
by jacking up the rear end and putting the car on jack stands or sturdy
blocks. Remove the rear wheels. Now take out the two screws that hold
the brake drum to the axle. If you're lucky, they come right out, if
you're like me, they don't. I found an impact screwdriver did a good
job of removing the screws after I cleaned the slots in the screw head.
Slide the drum off the lug bolts exposing the brake shoes. Do the same
thing on the other side. If you have problems removing the drum, turn
the adjusting bolt at the top of the backing plate counter-clockwise,
this will loosen the shoes allowing the drum to slide off. Remember,
only take off one set of shoes at a time so you have a set to compare
with in case you forget how to put them back together.
Next,
using a small prybar or large screwdriver, spread the springs on the
shoes enough to allow them to be removed from the slots on the
adjuster. When the shoes are loose from the top slots they can be
removed from the slots on the slave cylinder. The shoes can now be
removed intact and set aside for the moment.
Please
remember most brake shoes are made from asbestos. There is usually a
lot of dust coating all the parts you are handling. Please don't blow
off the parts with compressed air as used to be the standard practice.
This will result in asbestos fibers being scattered far and wide
increasing your exposure tremendously. Instead use clean Stoddard
solvent to wash all metal parts. This will evaporate leaving a pile of
asbestos dust you can dispose of properly. Don't put solvent on the
pads of the shoes if you are going to reuse them. any oil or solvent on
the pads will require them to be replaced.
Remove
the brake line from the slave cylinder and plug the hose to keep water
and dirt out, a golf tee fits very well. The slave cylinder is held to
the backing plate with three spring clips. Drive the middle clip out
paying attention to how they came apart so you can put them back
together the same way. Remove the pin holding the hand brake cable to
the lever. The lever can now be removed from the backing plate. When
the lever is removed, the two remaining spring clips can be slipped off
allowing the slave cylinder to be moved. Wash the cylinder with solvent
and take it to a clean work area.
Now
remove the dust cover clip and slip the cover off the piston. Remove
the piston from the cylinder and remove the seal from the piston. Pay
close attention to the direction the seal pointed so you can put the
new one on correctly.
Inside
the cylinder there will be lots of dirt and corrosion. Use one of the
specialized brake parts cleaners to remove it. After it is clean there
will be corrosion pits on the cylinder wall. I don't recommend using a
cylinder hone. They are too hard to control on a soft alloy cylinder.
Instead, use some very fine emory cloth wrapped around a screwdriver
till it fits tightly into the bore. Slowly turn while moving in and
out, this will allow you to control how much honing you do.
When
ordering new parts make sure you take the old parts with you. There are
different diameters of cylinders used on TR3s. They are close enough to
confuse you unless you compare them.
By
car uses 10" drums and shoes. These are made from that rare British
alloy called Unobtainium. I got lucky on my shoes. I had a friend who
had a friend who knew someone in the brake reline business who just
happened to have a set somewhere in New York.
They
wouldn't even sell them to me until I gave them my old shoes. It is
possible to get your own shoes relined. A truck brake shop will have
the equipment to do the job. As for drums, the only reason I would ever
do anything at all to them is if they are out of round. Remember, if
your drums are worn beyond a certain limit some shops won't let them
out of their doors unless they are destroyed. I have found that if the
drum is round the new shoes will run in and clean up even the worst of
scratches.
Reassemble
the cylinder by coating the seal and bore with brake fluid. Slip the
seal onto the piston and the dust cover over the other end. Slide the
piston into the cylinder until the dust cover reaches its proper
position. Put on the steel clip then reinstall on the backing plate.
Check the rubber brake lines for damage. You may want to replace them
at this point. They aren't very expensive and replacing them may save
you some trouble later on.
Put
the springs on the new shoes. Look at the other side to make sure they
are on correctly. Slide the assembled shoes over the axle and put the
ends in their proper slots. Refit the pin in the hand brake lever. Back
off the adjuster until it is all the way in. When you finish, leave the
drum off unitl the other side is finished so you can compare if you get
stuck.
When
the other side is finished, refit the drums and bleed your brakes. I
suggest you replace the old fluid with DOT 5 silicon fluid. DOT 5
doesn't absorb water, so corrosion won't be such a problem.
After
bleeding put the tires back on. Turn the adjuster clockwise until the
tire won't turn by hand then loosen the adjuster till the tire can be
turned freely without drag, ususally two or three clicks.
Go
out on a quiet street and try the brakes a few times to seat the new
shoes. You may have to readjust after a few applications.
Enjoy your project.
Tom Hughes
Pasco, WA