Is 700c the same as 29"?

Yes for bead seat diameter: both use BSD 622 mm. 700c is the road/French naming tradition, while 29" is the MTB name for the same rim diameter with a wider tire.

What does ETRTO 57-622 mean?

The first number is tire width in millimetres, and the second is rim BSD. 57-622 means a roughly 57 mm tire on a BSD 622 rim.

Can a 29" tire fit a 27.5" rim?

No. BSD must match exactly. 29"/700c is BSD 622, while 27.5"/650b is BSD 584, so the tire will not fit the other rim diameter.

Tools

Reference · ISO 5775

Tire sizes

ETRTO table, inch labels and French names. 700c and 29 inch share BSD 622; 650b and 27.5 inch share BSD 584. The table includes 20 common sizes.

ETRTO / ISO 5775: ETRTO / ISO 5775 is the most precise tire size notation. The format is width-BSD; for example, 61-622 means a 61 mm tire on a BSD 622 rim.

BSD: BSD (Bead Seat Diameter) is the tire bead seat diameter of the rim. This number must match the rim.

700c and 29 inch use BSD 622. 650b and 27.5 inch use BSD 584. The naming difference mostly comes from tradition and tire width.

Inch labels are approximate: a 2.4 inch tire can measure differently across brands. ETRTO is the safer reference.

700c / 29" (BSD 622)

Tire size table for 700c / 29" (BSD 622): ETRTO, inch label, width, outside diameter and use case
ETRTO	Common label	Width	Outside dia.	Use case
23-622	700×23c	23 mm	668 mm	Road race
25-622	700×25c	25 mm	672 mm	Road, classic standard
28-622	700×28c	28 mm	678 mm	Endurance road
32-622	700×32c	32 mm	686 mm	Gravel / endurance
35-622	700×35c / 28×1.4	35 mm	692 mm	Gravel / trekking
40-622	700×40c	40 mm	702 mm	All-round gravel
45-622	700×45c	45 mm	712 mm	Gravel / bikepacking
50-622	29 × 2.0"	50 mm	722 mm	XC / light trail
56-622	29 × 2.2"	56 mm	734 mm	XC / downcountry
61-622	29 × 2.4"	61 mm	744 mm	Trail / all-mountain
64-622	29 × 2.5" WT	64 mm	750 mm	Enduro / DH
66-622	29 × 2.6"	66 mm	754 mm	Plus / bikepacking

27.5" / 650b (BSD 584)

Tire size table for 27.5" / 650b (BSD 584): ETRTO, inch label, width, outside diameter and use case
ETRTO	Common label	Width	Outside dia.	Use case
47-584	27.5 × 1.85" / 650b	47 mm	678 mm	650b trekking
56-584	27.5 × 2.2"	56 mm	696 mm	27.5 XC
61-584	27.5 × 2.4"	61 mm	706 mm	27.5 trail
64-584	27.5 × 2.5" WT	64 mm	712 mm	Enduro / DH, MX rear
66-584	27.5 × 2.6"	66 mm	716 mm	27.5 plus

26" (BSD 559)

Tire size table for 26" (BSD 559): ETRTO, inch label, width, outside diameter and use case
ETRTO	Common label	Width	Outside dia.	Use case
58-559	26 × 2.3"	58 mm	675 mm	Classic 26er MTB
61-559	26 × 2.4"	61 mm	681 mm	26 trail / DH

20" BMX (BSD 406)

Tire size table for 20" BMX (BSD 406): ETRTO, inch label, width, outside diameter and use case
ETRTO	Common label	Width	Outside dia.	Use case
57-406	20 × 2.25"	57 mm	520 mm	BMX / dirt jump

Common traps

700c vs 27" — They are not the same. 700c is BSD 622, while old road 27" is BSD 630.

26" MTB vs 26" cruiser — The same inch label can hide a different BSD. On older wheels, check ETRTO first.

"WT" on MTB tires — Wide Trail is a Maxxis label for wider rims. It does not change BSD, but it affects recommended rim width.

MX / mullet — The bike uses mixed wheels, usually 29" front and 27.5" rear. That means two BSD sizes in one frame.

Plus tires — Wide 2.6-3.0 inch tires can still use a standard BSD, but they need frame clearance and a wider rim.

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