Shimano SG-8R20 Service Instructions Download Page 1

1.

SI-34R0B

SG-8R20

SG-8R25

CJ-8S20

General Safety Information

WARNING

– To avoid serious injuries:

NOTE:

You can shift gears while pedaling, but on rare occasions 

the pawls and ratchet inside the hub may produce some 

noise afterwards as part of normal gear shifting operation.
The CJ-8S20 cassette joint should only be used with 

sprockets from 16T to 23T.
If the wheel becomes stiff and difficult to turn, you should 

lubricate it with grease. 
Do not apply any grease to the inside of the hub, 

otherwise the grease will come out again.
You should periodically wash the sprockets in a neutral 

detergent and then lubricate them again. In addition, 

cleaning the chain with neutral detergent and lubricating it 

can be a effective way of extending the useful life of the 

sprockets and the chain.
If the chain keeps coming off the sprockets during use, 

replace the sprockets and the chain.
Parts are not guaranteed against natural wear or 

deterioration resulting from normal use.
For maximum performance we highly recommend 

Shimano lubricants and maintenance products.
For any questions regarding methods of handling or 

adjustment, please contact the place of purchase.

When securing the brake arm to the frame, be sure to 

securely tighten the clip screw and clip nut to the 

specified tightening torque. Use lock nuts with nylon 

inserts (self-locking nuts) for the clip nut. It is 

recommended that standard Shimano parts be used for 

the clip screw, clip nut and brake arm clip. If the clip nut 

comes off the brake arm, or if the clip screw or brake arm 

clip becomes damaged, the brake arm may rotate on the 

chainstay and cause the handlebars to jerk suddenly, or 

the bicycle wheel may lock and the bicycle may fall over, 

causing serious injury.

When installing the hub to the frame, be sure to install 

the correct non-turn washers to the left and right sides, 

and securely tighten the hub nuts to the specified 

torques. If the non-turn washers are installed to one side 

only, or if the hub nuts are not tightened sufficiently, the 

non-turn washer may fall out, which could cause the hub 

axle to rotate and the cassette joint to turn. This may 

then cause the handlebars to be accidentally pulled by 

the shifting cable, and an extremely serious accident 

could result. 

Obtain and read the service instructions carefully prior to 

installing the parts. Loose, worn, or damaged parts may 

cause serious injury to the rider.

We strongly recommend only using genuine Shimano 

replacement parts.
Check that the wheels are fastened securely before 

riding the bicycle. If the wheels are loose in any way, 

they may come off the bicycle and serious injury may 

result.
Read these Technical Service Instructions carefully, and 

keep them in a safe place for later reference.

Technical Service Instructions

Be sure to read these service instructions in conjunction 

with the service instructions for the Inter-M Brake and the 

Inter-8 shifting lever before use.

Inter-8 Hub

Cassette joint

Install the driver cap to the driver on the right side of the 

hub body.

Driver cap

Driver cap

Driver

Note the 

direction

Installation of the cassette joint to 

the hub

t

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