SunTour Micro Drive
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Category:  Bottom Brackets
Name:  SunTour Micro Drive
Brand:  SunTour
Primary Group:  SL
Model:  SL10-E XC Pro MD
Years:  1992 - 1995
Country:  Japan
Weight:  291 grams (Spec)
Added By: onespeedbiker on 05/25/13
Updated By: peterbman on 03/11/14
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SunTour Micro Drive
Bearing Size/Count per side5/32"/ 12x12Spindle MarkingsML-SL68
Fixed Cup MarkingsMicrolite, WTB Suntour Grease Guard, Japan 1.37 x 24T HFAdjustable Cup MarkingsSuntour, Japan, 1.37 x 24T,HF,ML
Spindle StyleSquare Taper (JIS)Axle MaterialSteel
Available ThreadingsEnglish/ISO: 1.370 x 24;
Italian: 36mm x 24
Length(s)115mm - Engish
Tools NeededSpanner, Locknut Wrench and Fixed Cup Wrench  
General Information
From BikePro.com: The Suntour Micro Drive groups require a shorter length bottom bracket spindle to pull the cranks in toward the frame appreciably, to try to reduce the Q-factor. The standard XC Pro spindle is 125.5mm long, but to make the 115mm length they required immediately for the MD group, Suntour chose to use a modified Road Racing bottom bracket. They settled on the SL series bottom brackets, which do come with a 115mm long spindle. For the XC Pro version the SL Microlite model is used, a standard type, fixed cup bottom bracket with aluminum alloy cups. The cups and spindle are modified to accept Suntour's implementation of the WTB Grease Guard principle. The cups are machined from aluminum rod with the inside bored for an opened sealed bearing cartridge to be pressed in. The opened cartridge is seated against the back of the inner face. A thick rubber gasket surrounds the spindle leaving open a tiny hole in the spindle to fill just the bearing cavity with grease. A small recess cut inside the hole where the spindle exits the cup allows a rubber gasket to snap in. The gasket permits grease to leave the bearing, but does not allow outside contaminants to enter. The bearing uses 12 steel ball bearings. The spindle is machined from steel rod. Because the original SL Microlite B/B had a sealed bearing cartridge, the spindle has no bearing races ground into it's surface. Suntour instead manufactures a separate steel race that presses onto the spindle where the cartridge bearing would rest. This race is machined, with a smoothly ground surface where the ball bearings revolve on it. The adjusting cup has six equally spaced holes for pin spanner final adjustments. The lockring for the adjusting cup is made of steel and chrome plated. This B/B comes with chrome plated steel crank bolts that are drilled through with a tiny hole for the injected grease to pass into the spindle and thereby the bearings. Also included are chrome plated crank arm caps that have a 5mm hex head for removal and a tight fitting round rubber gasket pressed into the inside. The gasket has a small hole in it so grease injection to the bearings can be performed with no part removal. In case of interior frame condensation, Suntour provides a tight fitting, plastic sleeve that fits internally between the two bearing cups. The weight of the SL10-E XC Pro MD B/B, including caps, bolts, sleeve is 291 grams. Silver, English thread only for 68mm (with 115mm spindle), or 73mm (with 119mm spindle) wide B/B shells.

What I find so remarkable about this bottom bracket is how Suntour, instead of re-engineering a new Grease Guard Bottom Bracket, took their existing SL-10 sealed cartridge bottom bracket, pressed a steel (open cartridge bearing) race into the aluminum cups and manufactured some steel races the slipped onto the spindles so it would work with caged bearings. Amazing 
Quality:Rarity:
 
 
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Additional Resources
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Resources:Reference & ChartsCatalogsExternal Resources
Component VariationsView Detailed List  Manage Variations
Variations of Component exist (Component is 1 of 2)BrandGroup
SunTour BB-SL00-I, SLSunTourSL
Component Groups
Primary Group NameBrandQuick InfoBrowse Group Components
SLSunTour1991 - 1994, Road RaceView 15 Components
Details:   Early 90's group (found in 92 catalog)
Brand Information(click to expand)

SunTour (Maeda)

SunTour derailleurs have a two-letter date code. On rear derailleurs the code is stamped on the back side of the inner parallel arm. On front derailleurs it is stamped on the back side of the inner cage.

The first letter represents the year. Larry Osborn and I believe O (Oh) is 1972, V is 1979 and A is 1984. As with Shimano, the second letter is the month code, where A is January and L is December.

SunTour Year Code

N
O
P
Q
R
S
T
U
V
W
X
Y
Z
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
 
A
B
C
D
E
F
G
H
I
1984
1985
1986
1987
1988
1989
1990
1991
1992

SunTour Month Code

A
B
C
D
E
F
G
H
I
J
K
L
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

The earliest Suntour derailleur I have found with a code is marked OF. A rear derailleur marked OD (corresponding to April of 72) was reported by Leighton Walter. I have a bike that dates from between 1970 to 1972 that has the original SunTour derailleurs. These derailleurs do not have date codes on them, so I believe the coding started sometime between 1970 and April of 1972.

(source: vintage-trek.com)

 
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