Shimano DEORE XT M785 front chainwheel Technical Service Instructions

Shimano DEORE XT M785 front chainwheel Technical Service Instructions

The DEORE XT M785 front chainwheel is a durable and high-performance component designed for 10-speed mountain bikes. This chainwheel is compatible with 38-24T, 38-26T, and 40-28T chainring combinations and features a 104 mm bolt circle diameter for the outer gear and 64 mm for the inner gear. It is designed for use with the SM-BB70 bottom bracket and offers a variety of crank arm lengths to fit different rider preferences. It also includes a variety of features that aim to enhance performance and durability, such as a reinforced connecting pin for the chain and a 2-way release mechanism on the shifting lever.

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Shimano DEORE XT M785 Technical Service Instructions | Manualzz

DEORE XT Front Chainwheel

FC-M785

*

14

1

3

4

5

3

2

6

7

9

8

9 7

7

10 12

13

14

5

11

A: Same parts.

B: Parts are usable, but differ in materirals, appearance, finish, size, etc.

Absence of mark indicates non-interchangeability.

Specifications are subject to change without notice.

1ML0000000-6150-001

1ML0000000-6160-001

FC

-M

98

5 5

FC

-M

78

0 0

FC

-M

77

0-

10

INTERCHANGE-

ABILITY

B A A

A B

A B

A B

A B

A B

A B

A B

A B

A B

A A

A A A

B A A

A A A

B A A

A A A

B A A

A B

May-2012-3165A

© Shimano Inc. I

SI-5MZ0A-001-00

General Safety Information

WARNING

“Maintenance interval depends on the usage and riding circumstances. Clean regularly the chain with an appropriate chaincleaner. Never use alkali based or acid based solvents such as rust cleaners. If those solvent be used chain might break and cause serious injury.”

• In order to obtain good gear shifting performance, this chain has a forward side and a reverse side, and the sides are marked so that the chain will face the correct way when installed. The proper design performance will be obtained when the chain is installed so that it faces the correct way. If it is installed so that it faces the opposite way, the chain may come off and the bicycle may fall over and serious injury may occur as a result.

• Use the reinforced connecting pin only for connecting the narrow type of chain.

• 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

Chain

Reinforced connecting pin

Chain tool connection force may not be obtained, which could cause the chain to break or fall off.

• 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

10-speed super narrow chain for

MTB with groove (3) with groove (2) some other place than the place where the chain has been joined using a reinforced connecting pin. The chain will be damaged if it is cut at a place where it has been joined with a reinforced connecting pin.

• Be careful not to let the cuffs of your clothes get caught in the chain while riding, otherwise you may fall off the bicycle.

• Check that the tension of the chain is correct and that the chain is not damaged. If the tension is

TL-CN32

TL-CN23

TL-CN27

Reinforced Connecting Pin too weak or the chain is damaged, the chain should be replaced. If this is not done, the chain may break and cause serious injury.

Link Pin Link Pin

• The two left crank arm mounting bolts should be tightened alternately in stages rather than each bolt being fully tightened all at once. Use a torque wrench to check that the final tightening torques are within the range of 12 - 14 N·m. Furthermore, after riding approximately 100 km (60 miles), use a torque wrench to re-check the tightening torques. It is also important to periodically check the tightening torques. If the tightening torques are too weak or if the mounting bolts are not tightened alternately in stages, the left crank arm may come off and the bicycle may fall over, and serious injury may occur as a result.

• Check that there are no cracks in the crank arms before riding the bicycle. If there are any cracks, the crank arm may break and you may fall off the bicycle.

• If the inner cover is not installed correctly, the axle may rust and become damaged, and the bicycle may fall over and serious injury may occur as a result.

• Obtain and read the service instructions carefully prior to installing the parts. Loose, worn or damaged parts may cause the bicycle to fall over and serious injury may occur as a result. We strongly recommend only using genuine Shimano replacement parts.

• Obtain and read the service instructions carefully prior to installing the parts. If adjustments are not carried out correctly, the chain may come off and this may cause you to fall off the bicycle which could result in serious injury.

• Read these Technical Service Instructions carefully, and keep them in a safe place for later reference.

CAUTION

• If the chain is on the smallest or intermediate chainring, there is the danger of injury from the tips of the teeth on the largest chainring.

Note

• In addition, if pedaling performance does not feel normal, check this once more.

• Before riding the bicycle, check that there is no play or looseness in the connection. Also, be sure to retighten the crank arms and pedals at periodic intervals.

• When installing the pedals, apply a small amount of grease to the threads to prevent the pedals from sticking. Use a torque wrench to securely tighten the pedals. Tightening torque: 35 - 55 N·m {305 - 479 in. lbs.}. The right-hand crank arm has a right-hand thread, and the left-hand crank arm has a left-hand thread.

• If a squeaking noise is heard coming from the bottom bracket axle and the left crank arm connector, apply grease to the connector and then tighten it to the specified torque.

• Use a neutral detergent to clean the crank arm and the bottom bracket. Using alkaline or acidic detergents may cause discoloration.

• Do not wash the bottom bracket with high-pressure jets of water.

• If you feel any looseness in the bearings, the bottom bracket should be replaced.

• If gear shifting operations do not feel smooth, wash the derailleur and lubricate all moving parts.

• If the amount of looseness in the links is so great that adjustment is not possible, you should replace the derailleur.

• You should periodically wash the chainrings in a neutral detergent and then lubricate them again. In addition, cleaning the chain with neutral detergent and lubricating it can be an effective way of extending the useful life of the chainrings and the chain.

• If the chain keeps coming off the chainrings during use, replace the chainrings and the chain.

• When the chain is in the position shown in the illustration, the chain may contact the front chainrings or

Front chainrings

Rear sprockets front derailleur and generate noise. If the noise is a problem, shift the chain onto the next-larger rear sprocket or the one after.

• For frames with suspension, the chain stay angle will vary depending on whether the bicycle is being ridden or not being ridden. When the bicycle is not being ridden and the chain is positioned on the largest/larger chainring and on the smallest sprocket, the chain guide outer plate of the front derailleur may touch the chain.

• The cuffs of your clothing may get dirty from the chain while riding.

• Apply grease to the left and right adapters before installing them.

Outer casing holders

• For smooth operation, use the specified outer casing and the bottom bracket cable guide.

• The front derailleur is for double front chainwheels only. It cannot be used with triple front chainwheels, as the shifting points will not match.

• When installing the top route type, choose a frame that has three outer casing holders as shown in the illustration at right.

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

Furthermore, check that the shifting lever does not touch the bicycle frame when the handlebars are turned all the way.

• A special grease is used for the gear shifting cable. Do not use DURA-ACE grease or other types of grease, otherwise they may cause deterioration in gear shifting performance.

• 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.

• If the brake fluid used in the oil disc brakes is of a type which tends to adhere to the plastic parts of the shifting lever, this may cause the plastic parts to crack or become discolored. Therefore, you should make sure that the brake fluid does not adhere to these plastic parts. The mineral oil which is used in SHIMANO disc brakes does not cause cracking or discoloration if it adheres to plastic parts, but such parts should be cleaned with alcohol beforehand to prevent foreign particles from adhering.

• Do not disassemble the indicator and shifting lever unit, as this may damage them or cause mis-operation.

• Be sure to read the service instructions for the Rear Drive System in conjunction with these service instructions (SL-M780-I).

• 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 installation, adjustment, maintenance or operation, please contact a professional bicycle dealer.

SI-5MZ0A-001

Technical Service Instructions

Front Drive System (2x10)

In order to realize the best performance, we recommend that the following combination be used.

Series

Shifting lever

Outer casing

Front derailleur

Front chainwheel

Chain

Bottom bracket cable guide

XT (2x10)

SL-M780-L / SL-M780-IL

OT-SP41

FD-M785 / FD-M785-E2 / FD-M786 / FD-M786-D

FC-M785

CN-HG94

SM-SP17

Specifications

Front Derailleur

Model number

Normal type

Top route type

Front chainwheel tooth difference

Front derailleur installation band diameter

Chainstay angle (

a

)

Applicable chain line 48.8 mm

Chainwheel

Model number

Chainwheel tooth combination

Bolt circle diameter

Crank arm length

Chain line

Bottom bracket shell width

Thread dimensions

Applicable bottom bracket

TL-FC16

Plate pin

Push up

Stopper plate

Lever (A) initial position

5

* If using a bottom bracket shell having a width of

68 mm which is a band type, an 1.8 mm spacer and a 0.7 mm spacer can be used together instead of a 2.5 mm spacer.

6

4

■ Spacer installation method

(1) Check whether the width of the bottom bracket shell is 68 mm or 73 mm.

(2) Next, install the adapter while referring to the illustrations.

FD-M785

X

X

14T

S, M, L

66° - 69°

44-38T

FD-M785-E2

X

X

12T

66° - 69°

40-38T

FC-M785

38-26T

104 / 64 mm

165, 170, 175, 180 mm

48.8 mm

40-28T

104 / 64 mm

165, 170, 175, 180 mm

48.8 mm

68, 73 mm

BC1.37 (68, 73mm)

68, 73 mm

BC1.37 (68, 73mm)

SM-BB70 / SM-BB71-41A

FD-M786

X

X

14T

S, M, L

66° - 69°

44-38T

X = Available

FD-M786-D

X

X

14T

66° - 69°

44-38T

Installation band diameters:

S (28.6 mm), M (31.8 mm), L (34.9 mm)

When using the S, M size, use an installation band with a diameter of 28.6

mm, 31.8mm and install it to a L size adapter.

Chainstay angle

Gear shifting operation

The INSTANT RELEASE mechanism makes fast releasing possible because cable tension is released immediately when a lever is depressed. This release lever is equipped with a 2-way release mechanism which allows release operations to be carried out by either pushing or pulling the lever.

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.

To shift from the smaller chainring to the larger chainring

(Lever A)

When lever (A) is pressed once, there is a shift of one step from the smaller chainring to the larger chainring.

Example:

From smaller chainring to larger chainring.

To shift from the larger chainring to the smaller chainring

(Lever B)

When lever (B) is pressed once, there is a shift of one step from the larger chainring to the smaller chainring.

Example:

From larger chainring to smaller chainring.

Installation of the Front Chainwheel

Follow the procedure in the figure.

1, 2 Use the special tool TL-FC32/36 to install the right adapter

(counterclockwise thread) and the left adapter (clockwise thread).

Tightening torque: 35 - 50 N·m {305 - 435 in. lbs.}

Note : Spacers may be necessary depending on the bottom bracket shell width. For details, refer to "Spacer installation method”.

3 Insert the right crank unit.

4 Set section A of the left crank into the axle of the right crank unit where the groove is wide.

(A) TL-FC32

Note :

Set the stopper plate in the right direction as shown in illustration.

68 mm

Band Type

68 mm

Bracket Type

BB mount-type bracket

Spacer

2

2.5 mm

73 mm

1

Inner cover

Lever (B)

• 2-WAY RELEASE

5 Use the TL-FC16/18 to tighten the cap.

Tightening torque: 0.7 - 1.5 N·m {6 - 13 in. lbs.}

6 Push in the stopper plate and check that the plate pin is securely in place, and then tighten the bolt of the left crank arm. (5 mm Allen key)

Note : Each of the bolts should be evenly and equally tightened to 12 - 14 N·m {106 - 122 in. lbs.}.

Wide groove area

73 mm

3

Chain length

Add 2 links (with the chain on both the largest sprocket and the large chainring).

Largest sprocket

Installation of the shifting lever

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

Tightening torque :

3 N·m {27 in. lbs.}

• Install the shifting lever in a position where it will not obstruct brake operation and gear shifting operation.

• Do not use in a combination which causes brake operation to be obstructed.

Note:

When installing the components to carbon frame/handle bar surfaces, verify with the manufacturer of the carbon frame/parts for their recommendation on tightening torque in order to prevent over tightening that can cause damage to the carbon material and/or under tightening that can cause lack of fixing strength for the components.

Refer to the FD-M785 / M785-E2 / M786 / M786-D (Front

Derailleur) Service Instructions for details on installing the front derailleur and SIS adjustment.

Connecting and securing the inner cable

Switch the mode converter to the 3x (triple mode) position, and then check the lowest position. Operate lever B two times or more to set the lever to the lowest position. Remove the inner hole cover, and install the cable.

Lever (B)

Inner cable

Inner hole cover

Mode converter

Note:

Do not force the mode select switch to turn. If you force it to turn, it will break.

Operate lever A once to set it to the middle position. Switch the mode converter to the 2x (double mode) position.

Lever (A)

Mode converter

Mode select switch

Note:

The mode converter cannot be switched while the lever is at the lowest position. Be sure to operate lever (A) one or more times before switching. Do not turn the mode converter by force, otherwise it may break.

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 thread on the cover.

Cutting the outer casing

Chain

Mode select switch

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

Large chainring

4 mm Allen key

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.

Replacement and reassembly of the indicator unit and shifting lever unit

Carry out disassembly and reassembly only when replacing the indicator unit and the shifting lever unit.

■ Replacement of the indicator unit b a

Tightening torque:

0.15 N·m {1.3 in. lbs.}

Indicator fixing screw

Fig. 1 Catch

<Disassembly>

1.

Operate lever B two times or more to set the lever to the lowest position.

2.

Remove the indicator fixing screws (a) and (b) which are securing the indicator unit, and then lift up the lens of the indicator unit to disengage the catch as shown in the illustration. Then remove the indicator unit.

* Do not mix up screws (a) and (b).

If they are mixed up, damage may result.

<Assembly>

1.

Operate lever B two times or more to set the lever to the lowest position.

2.

Check that the indicator needle is at the right edge. (Fig. 1)

3.

Install the indicator unit by first engaging the catch, and then secure it by tightening indicator fixing screws (a) and (b).

4.

Check the operation. If the indicator unit does not operate correctly, reassemble while paying particular attention to steps 1 and 2.

■ Replacement and reassembly of the shifting lever unit

<Disassembly>

Unit fixing bolt (M5 x 9.5 mm)

Tightening torque:

2.5 N·m {22 in. lbs.}

A

Shifting lever mounting screw

(Small)

B

Shifting lever mounting screw

(Large)

C

Shifting lever mounting screw

(Large)

M5 bolt spacer

Pin plate

Adjustment barrel

Tightening torque:

0.5 N·m {4 in. lbs.}

A

C

Tightening torque:

0.08 N·m {0.7 in. lbs.}

Tightening torque:

0.15 N·m {1.3 in. lbs.}

B

1.

Loosen the cable fixing bolt (nut) of the front derailleur, and then pull the inner cable out of the shifting lever unit in the same way as when installing the inner cable.

2.

Remove the indicator unit by following the disassembly procedure given in “Replacement of the indicator unit”.

3.

Remove the adjustment barrel.

4.

Remove the unit fixing bolt.

5.

Remove the four shifting lever unit mounting screws, and then remove the shifting lever unit as shown in the illustration.

* Be careful not to mix up screws A, B, and C.

6.

Remove the pin plate from the shifting lever unit.

<Assembly>

1.

Install the pin plate to the newlyassembled shifting lever unit.

* Insert the projections on the pin plate into the holes in the shifting lever unit as shown in the illustration.

2.

Align the shifting lever unit and the bracket, and then secure with the four shifting lever unit mounting screws.

* Install the M5 bolt spacer before securing the screws.

Pin plate

3.

Tighten the unit fixing bolt.

4.

Install the adjustment barrel.

5.

Install the indicator unit by following the assembly procedure given in “Replacement of the indicator unit”.

* There is no pin plate installed to the SL-M780-I.

■ For details on reassembly without the indicator and reassembly of the bracket band (SM-SL78), refer to the

Service Instructions for the rear drive system.

One Holland, Irvine, California 92618, U.S.A. Phone: +1-949-951-5003

Industrieweg 24, 8071 CT Nunspeet, The Netherlands Phone: +31-341-272222

3-77 Oimatsu-cho, Sakai-ku, Sakai-shi, Osaka 590-8577, Japan

* Service Instructions in further languages are available at : http://techdocs.shimano.com

Please note: specifications are subject to change for improvement without notice. (English)

© Jan. 2011 by Shimano Inc. XBC SZK Printed in Japan.

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Key Features

  • 10-speed compatible
  • 3 chainring combinations
  • 104 mm outer gear BCD
  • 64 mm inner gear BCD
  • SM-BB70 bottom bracket compatible
  • 165, 170, 175, 180 mm crank arm lengths
  • reinforced connecting pin
  • 2-way release mechanism

Frequently Answers and Questions

What chainring combinations are compatible with this chainwheel?
The DEORE XT M785 is compatible with 38-24T (AM), 38-26T (AK), and 40-28T (AJ) chainring combinations.
What is the bolt circle diameter (BCD) of this chainwheel?
The bolt circle diameter is 104 mm for the outer gear and 64 mm for the inner gear.
What bottom bracket is compatible with this chainwheel?
This chainwheel is compatible with the SM-BB70 bottom bracket.

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