Most front hubs use 10 3/16" balls on each side; Most rear hubs use 9 1/4" balls on each side. Most bottom brackets use 11 1/4" balls on each side.

Standard bottom bracket bearing assemblies are specified in terms of width of the bottom bracket shell (generally 68, 70 or 73 mm) and the length of the spindle (102 - 130 mm.)

Current usage generally assumes that 68 and 73 mm bottom bracket units are for British/ISO threaded frames, and that 70 mm units are for Italian threaded frames.

Application	Dimension	Notes
Track/Coaster Brake Traditional One-Speed Most internal gear hubs	40.5-42 mm	Older bikes with 110 spacing would be on the smaller end of this range Newer bikes with 120 mm spacing normally use 42 mm
Road Double	43.5 mm	Shimano spec, measured to the midpoint between the rings. with typical 5 mm chainring spacing, this puts the inner at 41 mm, the outer at 46 mm.
Road Triple	45 mm	Shimano spec, measured to the middle ring.
Singlespeed MTB Alternate	47.5 mm	White Industries ENO hubs use this chainline, which lines up with the middle position of a typical MTB triple. It's also fairly close to the outer position of a typical "road" double.
MTB Triple	47.5-50 mm	Shimano spec, measured to the middle ring. 47.5 preferred, but for frames with oversized seat tubes, the longer dimension may be needed, because the fat tube places the front derailer mechanism farther to the right. SRAM standard chainline is 49mm with 142mm OLD and thru axle
Singlespeed and Single-chainwheel MTB, "Boost 148"	52 mm	Wider chainline need for chainstay clearance on newer MTBs, typically with disc brakes and 148 mm OLD spacing This is close to the chainline of the outer ring of a typical MTB triple.
Rohloff Speedhub	54 mm (58 mm w/13 tooth)	Sprockets are proprietary, threaded. All except the 13-tooth may be flipped over to double wear life.
Freeride and Downhill	55 mm	Newer Freeride and Downhill bikes with 150 mm spacing
Tandem	about 60 mm	Tandems with 160 mm spacing
Fatbike	66 mm	Fatbikes with 170 mm spacing
Fatbike	76 mm	Fatbikes with 190 mm spacing -- needed with 4.8" (125 mm) wide tires.

21.15 mm = 13/16" 22.2 mm = 7/8" 23.8 mm = 15/16" 25.4 mm = 1" 1 Newton = .2248 pounds BAR A unit of pressure, equal to the normal air pressure at sea level, 14.5 PSI or 100 KPa (KiloPascals.)

• headset (25 x 1 mm)
• bottom-bracket (35 x 1mm, right-hand thread on both sides--see Swiss)
• pedal (14 x 1.25 mm)
• rear hub/freewheel (34.7 x 1 mm threading
• handlebar (25 mm)
• stem (22mm) diameter
• frame tubing diameters:
  • Top tube (26 mm)
  • Down tube (28 mm)
  • Seat tube (28 mm)
  • Head tube (32mm)
• cotter diameter (9 mm)

The letter "D" means "right" (Droite); "G" means "left" (Gauche).

Newer French bicycles are built to Italian or I.S.O. standards.

13 gauge	2.3 mm
14 gauge	2.0 mm
15 gauge	1.8 mm
16 gauge	1.6 mm

Handlebar dimensions
Stem Clamp Size		Grip Area Size		Application
22.2 mm	7/8"	22.2 mm	7/8"	Steel bars. Mainly BMX, older Mountain bike bars.
23.8 mm	15/16"	22.2 mm	7/8"	Obsolete British size for steel handlebars, common on older 3-speeds. This size was also used for older British steel drop bars.
25 mm		23.5 mm		Obsolete French size.
25.4 mm	1"	22.2 mm	7/8"	Standard I.S.O. size, used on the vast majority of newer bicycles with upright handlebars. This size was formerly common for steel drop bars.
25.4 mm	1"	23.8 mm	15/16"	Standard I.S.O. size, used on most bicycles with drop handlebars. Also used on older British aluminium upright handlebars.
25.8 mm		23.8 mm	15/16"	Unofficial in-between size used by some Italian handlebar makers for handlebars designed to be usable in either ISO (25.4) or Italian (26.0) size stems.
26.0 mm		23.8 mm	15/16"	Italian standard for drop bars, other bars made to fit Italian stems and some high-end aftermarket drop bars. This is sometimes incorrectly called "road" size.
26.4 mm		23.8 mm	15/16"	Older Cinelli and Cinelli copies. Cinelli changed over to 26.0 mm in 1998.
27 mm		23.8 mm	15/16"	Titan (obsolete).
31.8 mm	1 1/4"	23.8 mm	15/16"	Road oversized.

Threaded Headsets/Steerers in order of frame cup outside diameter, crown race inside diameter, threads per inch, and steerer O.D.-- the dimensions which affect headset compatibility with frame and fork. Crown race seat of fork can be milled smaller, frame bearing seats milled larger.
Standard	Frame Cup Outside Diameter	Crown race Inside diameter	Steerer O.D in mm	Threads Per inch	Stem diameter, Steerer I.D.	Notes
1" J.I.S.	30.0 mm	27.0 mm	25.4 mm	24	22.2 mm (7/8")	Older or lower-quality bicycles from Asia. Can be milled to ISO standard. ISO and other 30.2 mm O.D.cups are a very tight fit into the head tube; best mill it to avoid damage.
1" Raleigh	30.0 mm	27.0 mm	25.4 mm	26	22.2 mm (7/8")	Proprietary size used on Raleighs made in Nottingham, England. ISO and other 30.2 mm O.D, frame cups are a very tight fit into the head tube; best mill to avoid damage.
1" ISO Standard	30.2 mm	26.4 mm	25.4 mm	24	22.2 mm (7/8")	This is the standard 1" size.
1" Professional/ Campagnolo	30.2 mm	26.4 mm	25.4 mm	24	22.2 mm (7/8")	Obsolete. Threads are cut at 55 degrees, but an ISO headset can be used.
1" Italian	30.2 mm	26.5 mm, 27.0 mm	25.4 mm	24	22.2 mm (7/8")	Obsolete. Threads are cut at 55 degrees, but an ISO or J.I.S. top headset can be used. Fork can be milled to ISO.
French	30.2 mm	26.5 mm, 27.0 mm	25.0 mm	25.4 (1 mm)	22.0 mm	Obsolete. French steerers usually have a flat filed on the back, rather than a grooved keyway as with other threaded systems. The bottom headset parts wear faster; you can replace them with ISO parts and use the old top headset.
East German (DDR)	30.6 mm	26.8 mm (1 1/8")	26 mm	26	22.0 mm	Very similar to or the same as Austrian. 0.2 mm discrepancy may result from measuring the I.D. of the head tube (press fit). See page on German site.
Austrian	30.8 mm	26.7 mm	26 mm	25.4 (1 mm)	22.0 mm	These are found on bicycles sold by Sears, made by Steyr in Austria. Higher quality Austrian bikes use English/ISO.
BMX/ O.P.C. bikes	32.6 mm (varies)	26.4 mm (varies)	25.4 mm	24	21.15 mm (.833")	Used mainly on bicycles with one-piece cranks, also some early mountain bikes.
French Tandem	Let us know, if you do!	28 mm	Let us now, if you do!	25.4 (1 mm)	22.0 mm	Obsolete and rare.
1 1/8"	34.0 mm	30.0 mm	28.6 mm	26	25.4 mm (1")	"Oversized" (This size is more often used for threadless systems.)
Moulton	30.2 mm top, 36.4 bottom	33.0 mm	25.4 mm	24	22.2 mm (7/8")	Moulton Mark III and earlier. Top headset is standard ISO.
1 1/4"	37.0 mm	33.0 mm	31.8 mm	26	28.6 mm (1 1/8")	Mainly used on tandems

 

Threadless Headsets/Steerers
Stem I.D., Steerer O.D.	SHIS term	Frame Cup/ Cartridge Outside Diameter	Crown race Inside diameter	Notes
21.15 mm (0.833")	EC32	32.7 mm	26.4 mm	Used mainly on bicycles with one-piece cranks. BMX/O.P.C
1" (25.4 mm)	IS38	38.0 mm	26.4 mm	Slip fit, 36° angular contact at bottom of bore.
	EC30	30.2 mm	26.4 mm	This is the ISO standard 1" size.
1 1/8" (28.6 mm)	EC34	34.0 mm	30.0 mm	Most newer mountain bikes with external cups use this size.
	IS41	41.0 mm		Integrated, angular contact, slip fit.
	ZS41	41.3 mm		Low profile, press fit. May have cartridge or cup-and-cone bearings.
		41.6 mm		Integrated, angular contact. Obsolete.
	IS42	41.8 mm		Integrated angular contact; Campagnolo Hiddenset
		41.9-42.0 mm		Microtech integrated, press fit, square-bottomed recesses. Obsolete
	ZS44	44.0 mm		Retainer/loose balls or cartridge, which is slip fit into pressed cup
		44.0 mm		Integrated, 36° angular contact. Obsolete
	IS47	47.0 mm		Integrated lower only, slip fit.
	Various	52-56mm		Use crown race reducer
1 1/4" (31.8 mm)	EC37	37.0 mm	33.0 mm	Mainly used on tandems
1.5" (38.1 mm)	EC49, ZS49	49.7 mm	39.8 mm	OnePointFive standard for downhill and freeride applications. Press fit
52 mm (2.05")	IS52	52 mm	39.8mm	Integrated lower headset. Slip fit.
55 mm (2.165)	ZS55/40	55 mm	39.8mm	Internal, press fit.
56 mm (2.21")	EC56, ZS56	56 mm	39.8mm	Internal or external, press fit.

Most pedals have 9/16" x 20 tpi threads. Pedals for one-piece cranks are 1/2" x 20 tpi. Older French bicycles used a 14 mm x 1.25 mm thread, but these are quite rare.