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Sheldon Brown's Bicycle Crank/Chainring Bolt Circle Diameter Crib Sheet

revised and updated by John Allen

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Bicycle chainrings have between three and six bolt holes to attach them to the crank, spaced around in a circle. The table below gives bolt-circle dimensions for the main brands using each bolt pattern. Aftermarket and less prominent brands tend to use the same bolt-circle patterns as the main brands, for compatibility.

Direct measurement of the bolt-circle diameter is often not possible with a ruler. No two of an odd number of holes are directly opposite another. A protruding part may prevent direct measurement of the bolt-circle diameter of a crank spider. So, this page lists spacings between bolt holes which are not opposite one another, and these identify the bolt-circle diameter.

Many references describe distances between bolt holes as "center to center," but there is only empty space at the center of a hole! D'oh! Measuring from right side to right side or left side to left side is more reliable -- as shown in the photo below.

Measuring between two adjacent bolt holes

Measuring between non-adjacent holes reduces the likelihood of mistakes when differences are small. As an exercise, you may check the dimensions in the table farther down this page to identify the chainring in these photos, and then double-check against the brand-name stamp on the chainring.

Measuring between non-adjacent bolt holes

The bolt-circle diameter doesn't tell the whole story about compatibility if you mix and match parts. Sometimes you can fix the problem by installing a chainring inside-out or using washers to adjust spacing. Check for these issues:

After measuring BCD, you might check Wolf Tooth's Road and MTB chainring entries for details on newer 4- and 5-bolt chainrings; also RaceFace's compatibility table. Wolf Tooth also offers a guide to direct-mount (spiderless) chainrings at the bottom of a page on its Web site..

All bolt-circle patterns used to have bolt holes equally spaced around the bolt circle. Starting around 2010, manufacturers introduced patterns with unevenly-spaced holes. These allow bolt heads of a small-diameter pattern to clear a thick crank, and enforce chainring orientation, important with ramps and pins. Unevenly-spaced bolt holes make it impossible to turn chainrings to increase wear life, and some patterns reflect mere cussedness -- "brand lock". Please see the page at discussing technical, pricing and availability issues for chainrings with unevenly-spaced bolt holes.

Bolt-hole spacing dimensions here for evenly-spaced holes reflect exact (known) angles. We have given dimensions reflecting an integer number of degrees, probably correct, for unevenly-spaced holes. Measured angles for all Shimano unevenly-spaced holes were so near 70 and 110 degrees that our numbers are almost certainly correct. SRAM had to be different, and its angles appear to be 72 degrees (same as with a 5-bolt chainring) and 108 degrees. Wolf Tooth and FSA sell chainrings to fit other manufacturers' cranks but also chainrings that fit only their own cranks and direct-mount spiders.

We are working on a Web page with more observations, and a description of how we generated the numbers in the table below. If you can provide corrections or additional information, please do! A Microsoft Excel workbook with calculations of all the dimensions used on this page is available on this site.

Many thanks to Ulrik Hansen for updates to the 4-bolt crank list.

4-Bolt Cranks/Chainwheels, even spacing:

For uneven spacings, see the next section of this table.
Beware of near-matches! Measure!
The BCD is 1.414, 1/sin 45°, times the spacing between adjacent holes.
BCD (mm) Smallest
Between adjacent holes
146 44 103.2 Shimano XTR M960 Hollowtech 4-arm outer.
145 44 102.5 Campagnolo Super Record, Record, Chorus
120 36 84.9 SRAM 2 x 10 and XX. Threaded.
112 34 79.2 Shimano XTR M950, M952 4-arm middle/outer, Campagnolo inner.
110 34 77.8 FSA K-Force Light, Vero Pro
104 30 73.5 Shimano XT, LX 4-arm outer 12 SPD, Sugino MX350. Some are threaded. See RaceFace compatibility table.
102 32 72.1 Shimano 2003 XTR MX960 4-arm middle,
96 30 67.9 Shimano compact triple cranksets models M782, M672, M622, M612
94 30 66.5 SRAM XO1, X1, GX, NX
90 30 63.6 FSA: K-Force Modular Supercompact, Omega Pro, Powerbox Supercompact Stealth, Road Modular, Vero Pro
88 28 62.2 Shimano M985
68 22 48.1 Shimano XTR M950, M952 4-arm inner, FSA Comet Modular
64 22 45.3 Shimano XTR M960, XT, LX 4-arm inner. See RaceFace compatibility table.
58 20 41.0 Sugino MX350 4-arm inner

4-Bolt Cranks/Chainwheels, uneven spacing:

Measurements between adjacent holes of uneven patterns
are adjusted to nearest whole degree of angle between bolt holes,
reflecting probable correct values.
The first number given is for holes either side of the crank.
If there are three spacings, the last and smallest is for holes opposite the crank.

BCD (mm) Smallest
Between adjacent holes
110 34 90.1, 63.1 Shimano Dura Ace 9000, Ultegra 6800, 105 5800, Tiagra 4703, 4700; Dura Ace with modification
110 34 89.0, 64.7 SRAM Apex 1. 72/108 degree angles. Shimano is 70, 110.
110 34 84.3, 77.8, 70.7 FSA Gossamer ABS, K-Force ABS, Powerbox, SL-K ABS
100 32 92.7, 64.3, 58.8 3T Torno. Must use 3T bolts. Looks like a 5-bolt pattern with one bolt missing.
96 30 78.6, 55.1 Shimano XT M8000, SLX M7000, Deore M6000, 10mm holes; XTR M9000 and M9020, M7 threaded holes.
96 36 73.5, 67.9, 61.7 FSA 96/68 SLK MTB ABS
76 26 65.8, 48.9 FSA Afterburner, Comet, K-Korce, SLK MTB ABS
76 25 62.3, 53.7, 48.9 SRAM XX1 11-speed, Cannondale, Specialized Stout. Threaded for M8 bolts.
68 22 52.1, 48.1, 43.7 FSA Comet MTB Modular, Comet triple, K-Force Modular, SL-K MTB Modular, V-Drive MTB Modular
64 22 52.4, 36.7 Shimano XT, SLX, XTR 11-speed with the "X" shaped bolt pattern.

5-Bolt Cranks/Chainwheels:
The BCD is:
1.701, 1/sin 36°, times the spacing between adjacent holes,
1.052 , 1/sin 72°, times the spacing between non-adjacent holes.

BCD (mm) Smallest
Between adjacent holes
Between non-adjacent holes (mm) Application
151 44 88.8 143.6 Very old Campagnolo standard (pre '67) (Obsolete)
144 41 84.6 137.0 Old Campagnolo standard, still used for track; S-A FCT
135 39 79.4 128.4 Current Campagnolo standard
130 38 76.4 123.6 Standard Road double and triple (outer 2); S-A FCS
128 38 75.2 121.7 Nervar Sport, Star (Obsolete)
122 38 71.7 116.0 Stronglight 93, 101, 103, 104, 105 (Obsolete)
118 36 69.4 112.2 Ofmega, SR (Obsolete)
116 35 68.2 110.3 Old Campagnolo Gran Sport touring, Victory, Triomphe
110, 112 34 64.7, 65.2 104.6, 105.6 Campagnolo CT inner/middle/outer with one bolt at larger diameter behind crank
110 38 84.3, 77.8, 70.7, 46.5 FSA K-Force ABS: uneven pattern, 4 bolt with extra bolt behind crank
110 33 64.7 104.6 Touring double, standard triple outer
102 32 60.0 97.0 Avocet triple inner (obsolete). Note, NOT same as Campagnolo.
100 31; 36 58.8 95.1 Merz adapter; Campagnolo triple inner (Obsolete)
94 29 55.3 89.4 Compact triple outer
93 28 58.5, 52.7, 55.3,
54.0, 52.7
Wolf Tooth "CAMO", barely noticeable uneven spacing, requires Wolf Tooth spider and bolts.
Dimensions are reverse-engineered from photos, may be slightly wrong.
92 30 54.1 87.5 Shimano Dura-Ace triple inner
90 30 52.9 85.6 Edco, Mavic triple inner (old)
86 28 50.5 81.8 Stronglight 80, 99, 100, SR Apex (Obsolete). Chainwheels must be installed back to back, triple shifts poorly.
85 28 50.0 80.8 Old Shimano Deore, Takagi triple inner. (Obsolete)
80 26 47.0 76.1 Tevano (TA Campagnolo clone) triple inner. Bolts not interchangeable with others.
74 24 43.5 70.4 Standard ("full-sized") triple inner, used with 110 mm, 130 mm or 135 mm outer.
58 20 34.1 55.2 Compact granny
56 20 32.9 53.3 Sun Tour Compact granny (Obsolete)
50.4 n/a 29.6 47.9 TA Cyclotouriste, Criterium, Lambert, Shimano Deore, others: attachment for outer chainring; 7 mm holes.
6- and 3-Bolt Cranks/Chainwheels:
The BCD is:
2.000, 1/sin 30°, times the spacing between adjacent holes (6-bolt),
1.154 , 1/sin 60°, times the spacing between adjacent holes (3-bolt)
or non-adjacent holes (6 bolt)
BCD (mm) Smallest
Between holes
60° apart (mm), 6-bolt
Between holes
120° apart (mm)
157   78.5 136.0 Several very old Euro models
152 43 76 131.6 TA Criterium bolts between outer chainwheel and others.
143 42 71.5 123.8 Lambert. Inner ring threaded.
140 40   121.2 Campagnolo Gran Sport inner
116 36   100.4 TA Professional (10 mm holes), many old Euro steel cranks
116 36 58 100.4 TA Randonneur: bolts are between outer chainwheel and others.
112 ?   97.0 Takagi
106 32   91.8 Sugino Maxy, others w/8mm holes, SR Apex w/10mm holes.
95 30   82.3 Shimano 600, 310
88.9 (3.5") 30?   77.0 Nicklin, Cross, Williams (very old)
86 28   74.5 FSA Pro MTB 386, Comet 386 MTB
85 28   73.6 SR Custom 3
80 26 40 69.2 TA Cyclotouriste, Lambert: bolts between outer chainwheel and others.
70 24   60.6 René Herse. 10mm holes.

More cribsheets: Click here!

This page is intended as a quick reference primarily for the benefit of folks in the bicycle business. Feel free to print it out, but please don't reproduce it without proper credit and linkage.

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