700C vs 650B: Pros and Cons

Posted at: Jul 19, 2022

With the popularity of gravel road bikes and the spread of disc brakes, the choice of road bike wheel size has become not only the standard 700C, but also 650B. In this issue, we will look at the differences between 700C and 650B, and the advantages and disadvantages of each.

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Difference between 700C and 650B

650B wheels have been gaining attention along with the popularity of gravel road bikes in the past few years.

The difference between the standard road bike 700C wheels and 650B wheels is the diameter of the wheel rim: 700C is 622 mm and 650B is 584 mm, with 650B having a smaller wheel rim diameter.

Although 650B wheels are smaller when compared only in terms of wheel rim circumference, there is no significant difference in tire circumference because gravel roads are equipped with thicker tires such as 44C.

Advantages and Disadvantages of 650B

The advantage of 650B is the smaller diameter of the wheel rim. One advantage of the smaller diameter is that larger tires, such as 43C, can be installed.

Installing a larger tire increases the air volume inside the tire, which increases the cushioning of the tire and improves vibration absorption performance, resulting in a more comfortable ride.

Another advantage of the 650B is that the same frame can be fitted with larger tires.

For example, since 700-25C and 650-45C are said to have roughly the same tire circumference, a frame with no clearance of about 700-28C maximum can be fitted with a larger 43C tire on a 650B wheel (if tire width is not a problem).

650B = 27.5 inches?

Although described as 650B in road circles, it is actually the same size as a 27.5" MTB. Therefore, 650B wheels can be used on 27.5-inch MTBs.

MTBs use thicker tires, so 700C (29er) wheels are taller and require more maneuverability, so the 27.5 size has become the standard for MTBs for city riding and entry-level models.

Why can a 650B wheel be mounted on a 700C frame?

The conventional wisdom is that 650B wheels cannot be installed on a 700C bike. This was because the conventional brake was a type of brake that sandwiches the rim, and “smaller rim = brake arm cannot reach = another size cannot be installed”.

However, with the spread of disc brakes that sandwich the rotor, the distance from the frame to the rim is no longer relevant to braking, and 650B wheels can now be installed on a 700C bike.

Conversely, 650B wheels cannot be installed on 700C wheel models on rim-brake or V-brake sport bikes.

Advantages and disadvantages of 700C

The advantage of a 700C wheel would be the higher turning performance due to the larger circumference; there is little weight difference between a 700C and a 650B wheel, so for the same weight, the larger circumference will go better. Also, for the same tire circumference, the 700C tire is narrower, so the tire itself is lighter.

The disadvantage of 700C is that the larger wheel rim circumference requires more clearance on the frame side to accommodate a larger tire.

Road bikes that are designed to accommodate large tires, such as gravel road bikes, have a wide clearance geometry, but normal racer-type road bikes are designed to have as little clearance between the tire and frame as possible, taking aerodynamic effects into consideration.

Therefore, a road bike designed for 700-28C or so will not fit a larger tire such as 700-44C in terms of clearance.

Let’s compare the circumference of 700C and 650B tires

Let’s compare the circumference of 700C and 650B tires to see how much difference there is between them.

Size 700C 650B
25 2111mm 1991mm
28 2130mm 2010mm
30 2142mm 2023mm
32 2173mm 2035mm
35 2168mm 2054mm
37 2186mm 2067mm
38 2192mm 2073mm
40 2205mm 2086mm
42 2217mm 2098mm
44 2230mm 2111mm

※May differ from ETRTO’s specified circumference size

Reference: A Chart of Wheel Sizes with an explanation of BikeCalc’s math

700C or 650B?

So, which is better, 700C or 650B? It depends on “how fat tires you want to run”.

If you are fine with “a moderately fat tire” of about 30C, the latest disc brake road bikes have clearance up to about 28-30C, so you will have a lighter ride if you choose a 700C, which has higher running performance. However, at around 30C, stability when riding on gravel or dirt is not very high.

If you want MTB level stability on gravel and dirt, you can choose 650B because 700-25C and 650-45C have the same tire circumference, which solves the clearance problem, and 650-42C is almost the same size as 27.5 x 1.75, which is considered a little narrow for MTB. The 650-42C is almost the same as the 27.5 x 1.75 size, which is a bit narrower than the 27.5 x 1.75 size for MTB.

What you should pay attention to is “where you want to ride mainly.” A tire as large as 43C will give you stability on unpaved mountain roads, but the feeling of riding on paved roads will be lower than a 28C or 30C narrow tire.

If you mainly ride in town or on mountain roads, you can choose a 650B for a relaxed ride, or a 700C if you want to ride at a certain speed on main roads or bike paths.

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