type="text/css">
Earn-A-Bike
Instructor Training Manual
Chapter 12
Rear Derailleurs
Bikes
Not Bombs
©2000 Bikes Not Bombs
Chapter 12, Page 1 of 9
Contents
Rear Derailleurs ............................................................ 2
Part One - Planning ............................................................................... 2
I. Objectives .............................................................................................................. 2
II. Materials Needed.................................................................................................... 2
III. Setting .................................................................................................................... 2
IV. Evaluation............................................................................................................... 2
Part Two - Activity Instructions ............................................................... 3
I. Tool Check! ............................................................................................................... 3
II. Process .................................................................................................................... 3
Steps to Installing and Adjusting a Rear Derailleur........................................................................... 3
Disassemble ................................................................................................................................. 4
Reassemble .................................................................................................................................. 5
Adjust your Rear Derailleur System ................................................................................................ 5
Adjust Your Shifting ...................................................................................................................... 7
III. Language Skills ....................................................................................................... 8
IV. System Understanding ............................................................................................. 8
V. Problem Solving/Diagnosis ....................................................................................... 9
VI. Review ................................................................................................................... 9 Earn-A-Bike
Instructor Training Manual
Chapter 12
Rear Derailleurs
Bikes
Not Bombs
©2000 Bikes Not Bombs
Chapter 12, Page 2 of 9
Rear Derailleurs
Part One - Planning
I. Objectives
A. Student can identify a rear derailleur in need of adjustment.
B. Student can name the parts of the rear derailleur system and
the tools used on it.
C. Student becomes more familiar with the math concepts of
perpendicular and parallel.
D. Student becomes more familiar with the physics concepts of
friction and force.
E. Student can describe all the major steps of rear derailleur
installation and adjustment.
F. Student can follow all the steps of derailleur assembly and adjustment.
II. Materials Needed
REAR DERAILLEUR
III. Setting Workshop, with tool benches, bike repair stand and bike storage.
IV. Evaluation
A. Teacher Observation During Work Session
Rotate amongst the students as you work. Observe for
general mechanics skills (e.g. body mechanics, tool use), work habits (e.g. keeping part orderly, replacing
tools), and ability to follow the steps of the process in the proper order. Observe for problem solving skills: Is
student using visual observations? Is student able to pose questions whose answers will help her come up
with a solution?
B. Oral Review at end of work session.
1) Language
: How many of the parts and specialty tools can students identify? Passively? Actively?
2) Systems:
Can the student say what components are part of the system worked on? How do they
function as a whole?
3) Process:
How many of the steps of the process can students name? Can they get the steps in the
correct order?
C. Written Evaluation
How well can student narrate what she did that day on her time sheet?
Demonstration Parts
Rear Der. complete w/guts not
attached to bike
Shift Lever
Indexing and Non-Indexing
Cable and Housing
Tools
Allen Wrenches
Fourth Hand
Flat ended screwdriver
Phillips Screwdriver
Box Wrenches
Other Materials
Grease
Penetrating Oil
Rags
Rubber Gloves
Ball Point Pen Earn-A-Bike
Instructor Training Manual
Chapter 12
Rear Derailleurs
Bikes
Not Bombs
©2000 Bikes Not Bombs
Chapter 12, Page 3 of 9
Part Two - Activity Instructions
I. Tool Check! Students & instructors enter the tool area and confirm as a group that all the tools are there.
II. Process
A. Goal
What are we trying to get done when we install and adjust a rear derailleur? Have you ever ridden
a bike where gears were messed up or the bike didnt shift right? What can happen? How does this effect
your riding? How hard it is to pedal? The main purposes of the bikes rear derailleur system are: 1) To
keep proper chain tension at all times, 2) to smoothly and easily change gears while riding without the
chain falling into the spokes or the frame. A well done rear derailleur adjustment makes sure that:
The chain tension is consistent in all of the bicycles gear combinations.
The bicycle shifts easily and smoothly through all of the gears.
The chain does not fall off, into either the frame or the spokes, when shifting gears.
B. Steps to Installing and Adjusting a Rear Derailleur
Go over the names of each step, as a list. Then
describe each step to the students and have them each carry out that step on their bikes before you move the
group onto the next step.
1. Evaluate Condition
of as many parts
as possible before you take anything
apart.
a) Check Adjustment by pedaling the
bike and using the shift lever to
shift the rear derailleur. Does it
shift smoothly? Does the chain fall
off on either side of the rear gear
cluster? Look at the derailleur from
the rear. Is it bent? Can you push
or pull the derailleur into the
spokes or frame?
b) Derailleur hanger In addition to the
derailleur itself, the hanger that the derailleur is attached to also can get bent. This will keep the
derailleur from lining up with the cogs and keep the chain from shifting improperly.
c) Cables and housing OK? are they too short or too long? rusted, cracked or frayed? The proper function
of a derailleur depends on the cable being able to move freely and easily through the housing.
d) Shifters pivot easily and are not too loose? Earn-A-Bike
Instructor Training Manual
Chapter 12
Rear Derailleurs
Bikes
Not Bombs
©2000 Bikes Not Bombs
Chapter 12, Page 4 of 9
1. Evaluate Condition
- continued
e) Is the chain stretched? Twelve links (24 pins) of a new, unstretched chain will measure exactly 12
inches. If when you measure 12 links (lay a ruler along the straight section of the chain while it is
pulled taught) they are less than 12 1/16 inches long, your chain is fine. If its stretched 1/16 of an inch,
replace the chain. A chain stretched more than 1/16th of an inch over 12 links will have begun to wear
down the teeth of the rear gear cogs, and you will have to replace the cogs along with the chain (a new
chain will probably skip on the old, worn down cogs). You can usually use a stretched chain without
its slipping on the cogs up to 1/8th to 3/16ths of an inch of stretch. After that the chain will begin to
slip even over the cogs of the gears its worn out. For instructions on removing the rear gear cluster
(cassette or freewheel) see the Hubs Chapter.
2. Decide if Derailleur System Needs to be Disassembled
If you can get a good adjustment (no grinding,
it shifts well, and the chain doesnt fall into the spokes or the frame), then the derailleur is in good shape
as is the cable and the housing. If your goal is just to get the bike ready, skip to step 7 and try an
adjustment. If you want to teach the disassembly anyway, go on to step 3.
3. Disassemble
a) Unlock the shifter cable from the derailleur On the underneath side of the derailleur find the anchor
bolt that holds the shift cable. Loosen that bolt.
b) Break the chain with a chain tool In order to remove the de-
railleur from the bike its necessary to break the chain, i.e. open
up a link by pushing a pin most of the way out. Just remember,
DONT push the chain pin all the way out!! Thats the pin youll
use to put the chain back together again. Remember which side
of the chain was Up at the point where you break it. Some people
think that because chains wear in conjunction with the rear cogs,
if you put the chain on upside down from how it was on before
you may get a lot of slipping in the gears or chain suck.
c) Remove Derailleur Depending on what kind of derailleur you are dealing with this step may mean that
you use an allen wrench to unscrew the derailleur from the hanger or you may have to use a wrench to
loosen a bolt that holds both the hanger and the derailleur in the rear drop outs of the bike.
d) Remove cable and housing and place all items on a flat, uncluttered surface in the order in which you
removed them.
4. Clean and Inspect
all the surfaces and threads rub them with a rag with some light degreaser or
penetrating oil.
a) Broken or stuck Jockey Wheels? these are the two wheels on the derailleur swing arm.
b) Swing Arm Bent? make sure the derailleur swing arm which holds both jockey wheels isnt bent or out
of line.
c) Springs are all springs on the derailleur still functioning?
d) Cables and Housing Is the cable rusted or frayed? Is the housing rusted or broken? will the cable move
easily through the housing? W