Gravity MegaExo Crankset Installation & Service Instructions

Revision Date: January 2011

Introduction

Congratulations on your Gravity Crankset. Please read these instructions and follow them for correct use. Failure to follow the warnings and instructions could result in damage to product not covered under warranty, damage to bicycle; or cause an accident resulting in injury or death. Since specific tools and experience are necessary for proper installation, it is recommended that the crankset be installed by a qualified bicycle technician. Gravity assumes no responsibility for damages or injury related to improperly installed components.

Specification

These instructions are for the following Gravity Crankset Models:

Model No. / Model Name: CK-9555 / Gravity MegaExo Quad Crankset

Model No. / Model Name: CK-9160 / Gravity Light MegaExo Crankset

Model No. / Model Name: CK-7556 / GAP MegaExo Crankset

Model No. / Model Name: CK-7165 / Moto X MegaExo Crankset

Crankset Components: Refer to Illustration at left

① Bicycle Frame/ BB Shell ⑥ Non-Drive BB Cup

② Drive BB Cup & Center Sleeve ⑦ MW150 Crushwasher*

③ MW005 Bottom Bracket Spacer x3 ⑧ Non-Drive Crankarm

④ MW150 Crushwasher* ⑨ ML145 Pinchbolts x2

⑤ Drive Crankarm ⑩ Endbolt x1

*MW150 Crushwasher may be preinstalled on Drive Crankarm Spindle. MW150 crushwasher is not needed if bottom bracket bearing covers have lipped bearing cover (see illustration in “Installing Crankset in Bottom Bracket” section).

Prepare the Bottom Bracket Shell (①)

Facing the bottom bracket shell and chasing the threads before installing the MegaExo bottom bracket will ensure proper bearing alignment. If the MegaExo bearing

cups are not in alignment, the bearings could potentially bind and rotate poorly after crankset installation. Never assume a frame has been properly faced and

threads chased. When installing MegaExo crankset on old frames that have had cranks previously installed and used, always chase and clean threads to remove old

grease, dirt, and old bottom bracket material before installing new MegaExo bottom bracket.

1. Measure bottom bracket shell of frame ① with calipers or equally accurate measuring device.

2. If the bottom bracket shell is wider than the accepted specifications listed in Table 1, the shell must be faced to the proper specification before installing

MegaExo bottom bracket and crankset.

Table 1: Bottom Bracket Shell Dimensions BB Shell

Nominal Size

Minimum

Dimension

Maximum

Dimension

68mm 67mm 68mm

73mm 72mm 73mm

83mm* 82mm 83mm

Installing a MegaExo Crankset onto a bottom bracket shell that is wider than maximum allowable specification will result in poor bearing rotation, and potentially cause lack of crankset spindle engagement which can cause the non-drive crank arm to loosen while riding creating a crash hazard!

Gravity MegaExo Bottom Bracket Installation

Table 2: MW002 Spacer Orientation MTB BB Size

BB cup mount derailleur

or chain-guide

Non-Drive Spacers

Drive Spacers

68 no x1 x2

68 yes x1 x1

73 no x0 x1

73 yes x0 x0

83 no X1 x1

83 yes X1 X0

*83mm bottom bracket shells require MegaExo Cranksets and bottom brackets made and designed specifically for 83mm shells. Do not attempt to install a crankset designed for 68/73mm shell onto bicycles with 83mm bottom bracket shell.

1. Choose the MW002 Spacers needed for the Bottom Bracket shell width

and derailleur/ chainguide configuration intended for use on the bicycle. Refer to Table 2. Install the MW002 spacers on the Mega Exo Bottom bracket cups

NOTE: If intending to use chainguide on ISCG tabs, NOT bottom bracket cup mount, use spacer orientation shown in rows with “NO” in second column of table. 2. Lightly grease threads of bottom bracket shell and bottom bracket

cups. 3. With center sleeve attached to drive cup, thread the drive side bearing

cup into the bottom bracket shell by hand. Take care not to cross the thread.

4. Using MegaExo tool E0139 and calibrated torque wrench, tighten drive side cup to 400~500 kgf-cm / 39~49 N-m / 29~36 ft-lbs.

5. Thread non-drive bearing cup into the bottom bracket shell by hand taking care not to cross the threads.

6. Using MegaExo tool E0139 and calibrated torque wrench, tighten drive side cup to 400~500 kgf-cm / 39~49 N-m / 29~36 ft-lbs.

Cups

Center Sleeve

Chainring/ Bashguard Assembly

1. With the Gravity Logos and printed surface facing out, position the larger chainring so that the chain drop

prevention pin (illustration D) is located behind the crank arm. If using a bashguard instead of outer chainring,

assemble with Gravity Logo facing out.

2. With the Gravity Logo and printed surface facing out, position the inner chainring so that the alignment guide

(Illustration E) is located in line with the crank arm. Use the same.

3. Apply grease to the chainring bolt threads and surfaces where they contact the crank arm and chainrings. Using

a calibrated torque wrench, tighten the chainrings bolts to a torque of 12 Nm

Note: Gravity only recommends using steel chainring bolts on Gravity Cranksets.

Note for Single Chainring Use

Some aftermarket Gravity model cranksets have a removable 64bcd inner chainring tab. Removing the inner chainring tab eliminates interference when using the crankset with single chainring type chainguides.

Gravity model cranksets assembled onto bicycles as original equipment (OEM) may not have the inner tabs included. In such cases, the inner tab can be purchased separately at a local Gravity dealer.

64mm BCD Inner Tab Installation Instructions

1. Install middle and outer chainring (or bashguard) before installing inner chainring tabs.

2. The removable inner tab has a flat surface, and a surface with machining around the bolt holes. Apply a thin layer of grease on crankarm surfaces

that will be in contact with the inner tab. Position the inner tab so the machined surface is in contact with the crankarm. The flat surface should

contact the inner chainring, facing inward.

3. The chainring has an alignment guide between two of the bolt holes. The alignment guide should be in line with the crank arm.

4. Apply medium strength thread locking compound to the chainring bolt threads.

5. Using a calibrated torque wrench, tighten the chainring bolts in an “X” pattern, turning each bolt a ¼ turn at a time so all four bolts reach proper

torque uniformly. Tighten the chainring bolts to a torque of 12 Nm

6. Removal is reverse of installation.

Chainring Alignment Tab

Installing Crankset in Bottom Bracket

1. Inspect drive crank arm to ensure the MW150 crushwasher is pre-installed on spindle (please see note below). Lightly grease spindle surface to ease installation into MegaExo bottom bracket

2. Carefully slide drive spindle through bottom bracket. Install MW150 crushwasher on spindle. The MW150 crushwasher has a side that is more heavily coated with rubber than the other. The side more heavily

coated should contact the bearing cover of the MegaExo bottom bracket.

3. Install the left crankarm onto spindle.

4. Apply medium strength thread locker to threads of endbolt.

5. Thread the Endbolt into spindle by hand to ensure the threads are not crossed. Then using calibrated torque wrench tighten endbolt to 0.4-0.7 Nm (Endbolt is used to apply preload pressure to the bearings

much like a headset cap applies preload to the bearings of a headset. Do not over-tighten the endbolt or bearings will not rotate freely).

6. Check Spindle Engagement.

Remove the outer most pinchbolt to view spindle insertion to left arm.

The spindle should extend past the center line of the outer most pinchbolt (see illustration).

If spindle is not inserted pasted the center of the outer-most pinchbolt, the crank can loosen while riding and cause the rider to crash and be injured

If spindle engagement is not sufficient, remove crankset and bottom bracket; check bottom bracket shell dimensions and MW002 spacer

orientation. Also check MW150 crushwasher position. (Note MW150 crushwashers can be removed for minor spindle engagement adjustments).

7. Apply medium strength thread locker to pinchbolt threads and screw into crankarm by hand to ensure threads are not crossed

8. Using a calibrated torque wrench, tighten the pinchbolts by turning each bolt 1/4 turn at a time, alternating between bolts so

they both reach proper torque simultaneously.

9. Do not exceed 13Nm torque on pinchbolts.

Pedal Installation

1. Grease pedal threads.

2. Using a calibrated torque wrench, tighten pedals to 29-34 Nm (note: many pedals can be tightened with a 6 or 8mm hex key which allows accessibility with a torque wrench. For pedals that use a 15mm

flattened end, a torque wrench can be used to tighten the pedal properly with a 15mm crowfoot attachment available at most hardware and auto parts stores).

Note: Pedal washers (#2) are not required for Gravity Cranksets. Gravity does not recommend the use of pedal extenders with Gravity cranksets.

Maintenance

Maximum Spindle Engagement

1 2 3

Note: If bearing covers on MegaExo bottom bracket have a lip

on the inside edge (as shown), do NOT use the MW150

crushwashers

Lip on bearing cover

Inspect your Gravity cranks and bottom brackets for straightness, cracks, deep scratches and gouges, or damage before each ride. If any of the preceding conditions are present, do not use your Gravity cranks or

bottom bracket until they have been replaced.

It is the product user’s responsibility to examine the product on a regular basis to determine the need for service or replacement. Cyclist should inspect their bicycle and parts on a regular basis in order to detect

damage that may have occurred from normal use and abuse. Check all parts for damage and wear before every use. Check all screws periodically for tightness. Do not over-tighten. Periodically re-grease all

screws.

WARNING: In the event of a bicycle accident, all parts should be thoroughly examined by a qualified bicycle mechanic, and any damaged Gravity parts replaced. Do not attempt to

straighten bent cranks, they must be replaced.

All damaged parts should be repaired or replaced by a qualified bicycle mechanic before the bicycle is used again. Continuing to use damaged parts may lead to loss of control of the bicycle and cause injury or

death.

Gravity MegaExo bottom brackets can be serviced using the FSA EE073 bottom bracket

tool (sold separately). Service parts can be ordered through any reputable Bicycle

retailer.

Service Parts:

Description Part Number Description Part Number

①MW150 Crushwasher (BB-7000) 230-4000 ⑥MW002 MegaExo BB Spacer 2.5mm 230-4030

②MS185 MegaExo Bearing Cover (BB-7000) 230-4027 ⑦ML140 Endbolt Black (All Gravity MegaExo Cranks) 390-2082

②MS159 MegaExo Quad Bearing Cover (BB-7550) 230-4012 ⑦ML140 Endbolt Silver (All Gravity MegaExo Cranks) 390-2083

③MS186 O-Ring Seal for Bearing Cover (BB-7000) 230-4028 ⑦ML185 Endbolt (Gravity MegaExo Quad Only) 390-2085

③MS149 O-Ring Seal for Quad Bearing Cover (BB-7550) 230-4005 ⑨ML145 Pinchbolts 280-1000

④MR102 MegaExo Bearing (BB-7000) 230-4027

④MR092 MegaExo Quad Bearing (BB-7550) 230-4017

Bottom Bracket Compatibility:

Crankset Description Bottom Bracket Part Number

CK-9555 Gravity MegaExo Quad 68/73mm BB Shell BB-7550 200-1880

CK-9555 Gravity MegaExo Quad 83mm BB Shell BB-7550/83mm 200-1881

CK-9160 Gravity Light MegaExo 68/73mm BB Shell BB-7000 200-1883

CK-9160 Gravity Light MegaExo 83mm BB Shell BB-7000/83mm 200-1884

CK-7556 GAP MegaExo 68/73mm BB Shell BB-7000 200-1883

CK-7556 GAP MegaExo 83mm BB Shell BB-7000/83 200-1884

CK-7165 Moto X MegaExo 68/73mm BB Shell BB-7000 200-1883