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 ② Drive BB Cup & Center Sleeve ③ MW005 Bottom Bracket Spacer x3 ④ MW150 Crushwasher* ⑤ Drive Crankarm
⑥ Non-Drive BB Cup ⑦ MW150 Crushwasher* ⑧ Non-Drive Crankarm ⑨ ML145 Pinchbolts x2 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. Installing a MegaExo Crankset onto a bottom bracket shell that is Table 1: Bottom Bracket Shell Dimensions wider than maximum allowable specification will result in poor BB Shell Minimum Maximum Nominal Size Dimension Dimension bearing rotation, and potentially cause lack of crankset spindle 68mm 67mm 68mm engagement which can cause the non-drive crank arm to loosen 73mm 72mm 73mm while riding creating a crash hazard! 83mm*
Gravity MegaExo Bottom Bracket Installation
*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 â€œNOâ€? in second column of table.
Table 2: MW002 Spacer Orientation MTB BB Size 68 68 73 73 83 83
BB cup mount derailleur or chain-guide no yes no yes no yes
x1 x1 x0 x0 X1 X1
x2 x1 x1 x0 x1 X0
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.
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 â€œXâ€? pattern, turning each bolt a Âź 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. Lip on bearing cover
Note: If bearing covers on MegaExo bottom bracket have a lip on the inside edge (as shown), do NOT use the MW150 crushwashers
Maximum Spindle Engagement
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.
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 ①MW150 Crushwasher (BB-7000) ②MS185 MegaExo Bearing Cover (BB-7000) ②MS159 MegaExo Quad Bearing Cover (BB-7550) ③MS186 O-Ring Seal for Bearing Cover (BB-7000) ③MS149 O-Ring Seal for Quad Bearing Cover (BB-7550) ④MR102 MegaExo Bearing (BB-7000) ④MR092 MegaExo Quad Bearing (BB-7550) Bottom Bracket Compatibility: Crankset Description CK-9555 Gravity MegaExo Quad 68/73mm BB Shell CK-9555 Gravity MegaExo Quad 83mm BB Shell CK-9160 Gravity Light MegaExo 68/73mm BB Shell CK-9160 Gravity Light MegaExo 83mm BB Shell CK-7556 GAP MegaExo 68/73mm BB Shell CK-7556 GAP MegaExo 83mm BB Shell CK-7165 Moto X MegaExo 68/73mm BB Shell
Part Number 230-4000 230-4027 230-4012 230-4028 230-4005 230-4027 230-4017
Description ⑥MW002 MegaExo BB Spacer 2.5mm ⑦ML140 Endbolt Black (All Gravity MegaExo Cranks) ⑦ML140 Endbolt Silver (All Gravity MegaExo Cranks) ⑦ML185 Endbolt (Gravity MegaExo Quad Only) ⑨ML145 Pinchbolts
Bottom Bracket BB-7550 BB-7550/83mm BB-7000 BB-7000/83mm BB-7000 BB-7000/83 BB-7000
Part Number 200-1880 200-1881 200-1883 200-1884 200-1883 200-1884 200-1883
Part Number 230-4030 390-2082 390-2083 390-2085 280-1000