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SERVICE INSTRUCTIONS SI-R920A

Rear Drive System

Before use, read these instructions carefully, and follow them for correct use.

WARNING
• Use neutral detergent to clean the chain. Do not use alkali-based or acid based detergent
such as rust cleaners as it may result in damage and/or failure of the chain.
• Use the reinforced connecting pin only for connecting the narrow type of chain.
• There are two different types of reinforced connecting pin available. Be sure to check the
table below before selecting which pin to use. If connecting pins other than reinforced
connecting pins are used, or if a reinforced connecting pin or tool which is not suitable for
the type of chain is used, sufficient connection force may not be obtained, which could
cause the chain to break or fall off.
Reinforced
Chain Chain tool
connecting pin
9-speed super narrow chain
such as Silver TL-CN31/TL-CN22
CN-7701 / CN-HG93 6.5mm

8- / 7- / 6-speed narrow
Black TL-CN31/TL-CN22 and
chain such as
TL-CN30/TL-CN21
CN-HG50 / CN-IG51 7.1mm

• If it is necessary to adjust the length of the chain due to a change in the number of
sprocket teeth, make the cut at some other place than the place where the chain has been
joined using a reinforced connecting pin or an end pin. The chain will be damaged if it is
cut at a place where it has been joined with a reinforced connecting pin or an end pin.
Reinforced
End Pin Link Pin Connecting Pin

E
C
RA-A

DU

• Obtain, read and carefully service instructions when installing parts. A loose, worn, or
damaged parts may cause injury to the rider.
We strongly recommend that only genuine Shimano replacement parts be used.

Note
• Always be sure to use the sprocket set bearing the same group Group marks
marks. Never use in combination with a sprocket bearing a different
group mark. ag - 18T
• Because the high cable resistance of a frame with internal cable ag -15
T
ag
- 13
routing would impair the SIS function, this type of frame should not T

be used.
• Use an outer casing which still has some length to spare even when
the handlebars are turned all the way to both sides. Furthermore,
SH

check that the shifting lever does not touch the bicycle frame when
IM

AN
O

the handlebars are turned all the way. HYPERGL I DE - C

• Grease the inner cable and the inside of the outer casing before use
to ensure that they slide properly.
• Operation of the levers related to gear shifting should be made only when the front chainwheel
is turning.
• For smooth operation, use the specified outer casing and the bottom bracket cable guide.
• For maximum performance we highly recommend Shimano lubricants and maintenance
products.
• For any questions regarding methods of installation, adjustment, maintenance or operation,
please contact a professional bicycle dealer.
In order to realize the best performance, we recommend that the following combination
be used.
Series ALIVIO
Rapidfire Plus ST-MC20 / SL-MC20
Outer casing SP40
Rear derailleur RD-MC20
Type SGS
Freehub FH-MC18 / FH-RM40-8
Sprockets 8
Cassette sprocket CS-HG50-8I
Chain CN-IG51 / CN-IG31
Bottom bracket cable guide SM-SP17 / SM-BT17 / SM-SP18 / SM-BT18

Specifications
Rear Derailleur
Model number RD-MC20
Sprockets 8
Total capacity 39T
Largest sprocket 30T
Smallest sprocket 11T
Front chainwheel tooth difference 20T
Applicable front chainwheel FC-MC20 / FC-MC19
(chainring tooth configuration) (42T-32T-22T)

Cassette sprocket tooth combination

Sprockets Group name Tooth combination
8 an 11, 13, 15, 17, 20, 23, 26, 30T

Rapidfire Plus
Model number ST-MC20 / SL-MC20
Sprockets 8

Freehub
Model number FH-MC18 / FH-RM40-8
Sprockets 8
No. of spoke holes 36 / 32
 Installation of the sprockets
For each sprocket, the surface that has
the group mark should face outward The groove is wide ac -14T
▲ mark
and be positioned so that the triangle at one place only.
(▲) mark on each sprocket and the A A
part (where the groove width is wide) of
the freewheel body are aligned.

11T
ab
HYP
A NO ER
IM
H G
S

L I
m

DE
4 0 0 kg /c

- C
J AP
CK
LO

AN
9 U
25 .S
. PA
T 4268

The 6 sprockets are secured by Sprocket spacers Lock ring

means of rivets. (1.0mm)

• For installation of the sprockets, Lock ring

use the special tool (TL-HG16) to
Tool (TL-SR20)
tighten the lock ring.
Tightening torque:
30 - 50 Nm {261 - 434 in. lbs.}
TL-HG16
• To replace the sprockets, use the
special tool (TL-HG16) and TL-SR20
to remove the lock ring.
Disassembly

Installation of the rear derailleur

When installing, be careful that deformation is not caused by the B-tension adjustment screw
coming into contact with the dropout tab.

5 mm Allen key Bracket spindle tightening torque:

8 - 10 Nm {70 - 86 in. lbs.}
B-tension
adjustment screw

Dropout tab

Chain length
Add 2 links (with the chain on both the Largest sprocket Largest chainring
largest sprocket and the largest chainring)

Chain

Checking the chain connection Chain gauge

SHIMANO JAPAN
CHAIN GAUGE

TL-CN24
1=2.38mm
TL-CN24

For IG, chains, insert the chain gauge (TL-CN24) into the
inner link which is next to the chain connecting pin to check
that the inner link width is correct.
Check that the connecting pin pro-trudes past the outer link
by the same amount on both sides, and that the amount of 2.38mm
protrusion is 0.2 mm or more. Connecting pin

Inner link
A, B Q 0.2mm A B
TL-CN24
1=2.38mm

CHAIN GAUGE
SHIMANO JAPAN
TL-CN24
1=2.38mm

CHAIN GAUGE
SHIMANO JAPAN

Connecting pin

Outer link Correct Incorrect

 Replacement of the freewheel body
After removing the hub axle, remove FH-MC18 / FH-RM40-8
the freewheel body fixing bolt (inside
Freewheel body Freewheel body fixing bolt
the freewheel body), and then
replace the freewheel body. Disassembly
Note:
Do not attempt to disassemble
the freewheel body, because it
may result in a malfunction. Assembly
Freewheel body washer

Tightening torque: 10 mm Allen key (TL-WR37)

35 - 50 Nm {305 - 434 in. lbs.}

Installation of the brake lever

Use a handlebar grip with a maximum outer diameter of 32 mm.

SL-MC20 ST-MC20

5 mm Allen key

8 8
1 1

5 mm Allen key

Tightening torque : Tightening torque :

5 Nm 6 - 8 Nm
{44 in lbs.} {53 - 69 in. lbs.}
SL-MC20
Install the brake lever in a position where it will not obstruct brake operation. Do
not use in a combination which causes brake operation to be obstructed.

Adjustment
1. Top adjustment Outer line of
smallest sprocket
Turn the top adjustment screw to
adjust so that the guide pulley is in 1 2
line with the outer line of the
smallest sprocket when looking
from the rear. 1 2
After this, install the chain. Guide pulley
Top adjustment
screw

Lever (B)
2. Connecting and securing the inner cable
Operate lever (B) eight times or more,
and check on the indicator that the lever is
at the highest position. Then remove 8
1
the inner hole cover and connect the inner cable.
Tightening torque :
5 - 7 Nm {44 - 60 in. lbs.}
Inner cable
Inner hole cover

Install the inner hole cover by turning it as shown in

the illustration until it stops.
Do not turn it any further than this, otherwise it may
damage the screw thread.
Tightening torque :
0.3 - 0.5 Nm {3 - 4 in. lbs.}
Inner hole cover

Inserting the inner cable

Insert the inner cable into the outer casing from the end with the marking on it.
Apply grease from the end with the marking in order to maintain cable
operating efficiency.

Marking
 Cutting the outer casing
When cutting the outer casing, cut the opposite end to
the end with the marking. After cutting the outer casing,
make the end round so that the inside of the hole has a
uniform diameter.

Attach the same outer end cap to the cut end of the outer casing.

Outer end cap

Connect the cable to the Note: Be sure that the cable is

rear derailleur and, after securely in the groove.
taking up the initial slack
in the cable, re-secure to
the front derailleur as
shown in the illustration.
Pull

Groove

3. Low adjustment Largest

sprocket
While turning the front chainwheel,
operate the lever to shift to the Guide pulley
lowest gear.
Turn the low adjustment screw so
that the guide pulley moves to a 1 2
position directly in line with the Low
largest sprocket. 2 1 adjustment screw

4. How to use the B-tension adjustment screw

Mount the chain on the smallest Largest
sprocket Smallest sprocket
chainring and the largest sprocket,
and turn the crank arm 2
backward. Then turn the 2
B-tension adjustment screw to adjust
the guide pulley as close to the
sprocket as possible but not so close
that it touches. Next, set the chain to 1 2
the smallest sprocket and repeat the 1 B-tension
above to make sure that the pulley ajustment screw
does not touch the sprocket. 1

5. SIS Adjustment 3rd 2nd Top

(1) Operate the shifting lever to move the

chain from the top gear to the 2nd gear. Outer casing
adjustment barrel
* If the chain will not move to the 2nd
gear, turn the outer casing adjustment
barrel to increase the tension ----- ➀
(counter clockwise)
* If the chain moves past the 2nd gear,
decrease the tension ----- ➁
(clockwise)
➀ ➁

(2) Next with the chain on the 2nd

gear, increase the inner cable Counter-
tension ① while turning the crank clockwise ➀
arm forward. Stop turning the outer
casing adjustment barrel just
before the chain makes noise Clockwise ➁
against the 3rd gear.
This completes the adjustment. Outer casing
adjustment barrel

For the best SIS performance, periodically

lubricate all power-transmission parts.
 Gear shifting operation
Both lever (A) and lever (B) always return to the initial position when they are
released after shifting. When operating one of the levers, always be sure to turn
the crank arm at the same time.
Lever (A) initial position
To shift from a small sprocket to a
larger sprocket 1
To shift one step only, press lever (A) to the
(1) position. To shift two steps at one time, 2
press to the (2) position. A maximum three-
step shift can be made in this manner.

To shift from a large sprocket to a

smaller sprocket
Press lever (B) once to shift one step from
a larger to a smaller sprocket.

Lever (B)

This service instruction explains how to use and maintain the Shimano bicycle
parts which have been used on your new bicycle.
For any questions regarding your bicycle or other matters which are not
related to Shimano parts, please contact the place of purchase or the bicycle
manufacturer.
®

One Holland Irvine CA 92618 U.S.A. Phone 949-951-5003

Industrieweg 24 NL-8071 CT Nunspeet Holland Phone 31-341-272222 77 Oimatsu-cho 3-cho Sakai Osaka 590-8577 Japan

Please note: specifications are subject to change for improvement without notice. (English)
© Apr. 2001 by Shimano Inc. XBC SZK Printed in Japan