Am I Understanding 650B?
08-11-16, 02:18 PM
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Am I Understanding 650B?
My first thought was, "Why is everyone going to smaller wheels...Won't that affect rolling efficiency?"
But now I think I'm getting that the 650B tire/wheel package is as tall as a 27" x 1 1/4......The tire is much taller than normal...Is this correct?
The bikes do look good(and comfortable!) with the ballony tires...
But now I think I'm getting that the 650B tire/wheel package is as tall as a 27" x 1 1/4......The tire is much taller than normal...Is this correct?
The bikes do look good(and comfortable!) with the ballony tires...
08-11-16, 02:24 PM
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Sort of, but the intent is to increase the tire width (or volume). Because the tube's cross section is round(ish), making it wider makes it taller. A 38mm 700C has the roughly the same proportions (tire height:width), but a larger diameter.Sheldon explains it best -
And 650B? It's diameter is less. The point of going to it is that you can fit wider tires.
In the French sizing system, tires are designated by a three-digit number, which may be followed by a letter. The number is the nominal outside diameter of the tire the rim was originally designed for.
The absence of a letter indicated a narrow tire; "A", "B" and "C" indicated increasingly wider tires."A" was originally a tire about 30 mm wide, so the 650A rim is pretty large, 590 mm. If you add the top and bottom 30 mm tire thickness to 590, you wind up with the 650 mm tire diameter.
The 650C size was originally intended for a quite wide tire, about 40 mm wide. Top and bottom 40 mm tire plus the 571 mm rim size again bring you to a 650 mm outside diameter, even though the rim was smaller.
The absence of a letter indicated a narrow tire; "A", "B" and "C" indicated increasingly wider tires."A" was originally a tire about 30 mm wide, so the 650A rim is pretty large, 590 mm. If you add the top and bottom 30 mm tire thickness to 590, you wind up with the 650 mm tire diameter.
The 650C size was originally intended for a quite wide tire, about 40 mm wide. Top and bottom 40 mm tire plus the 571 mm rim size again bring you to a 650 mm outside diameter, even though the rim was smaller.
By switching to 650B from 700C, you suddenly gave clearance enough for medium-width tires, say 35-38 mm width, and for fenders, so you don't need to be a "fair-weather" cyclist.
The wider tires will be more durable, more "sure-footed", and give a more comfortable ride on rough pavement or under moderate off-road conditions. Switching to 650B can also reduce front wheel/toe overlap issues.
Switching to 650B will lower the bottom bracket a bit, making for easier mounting/dismounting. (Many newer bikes have excessively high bottom brackets to begin with.)
It also lowers the top tube, possibly making a bike safely usable for a shorter rider than would otherwise fit it, due to lack of standover clearance.
If you are going from a very narrow 622 (700C) tire to a fairly wide 584 (650B), the difference may be minimal. For instance, a 19-622 (700 x 19C) tire would theoretically have exactly the same outside diameter as a 38-584 (650 x 38B).
The wider tires will be more durable, more "sure-footed", and give a more comfortable ride on rough pavement or under moderate off-road conditions. Switching to 650B can also reduce front wheel/toe overlap issues.
Switching to 650B will lower the bottom bracket a bit, making for easier mounting/dismounting. (Many newer bikes have excessively high bottom brackets to begin with.)
It also lowers the top tube, possibly making a bike safely usable for a shorter rider than would otherwise fit it, due to lack of standover clearance.
If you are going from a very narrow 622 (700C) tire to a fairly wide 584 (650B), the difference may be minimal. For instance, a 19-622 (700 x 19C) tire would theoretically have exactly the same outside diameter as a 38-584 (650 x 38B).
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Last edited by SloButWide; 08-11-16 at 02:33 PM. Reason: Clarifying.
08-11-16, 02:28 PM
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My first thought was, "Why is everyone going to smaller wheels...Won't that affect rolling efficiency?"
But now I think I'm getting that the 650B tire/wheel package is as tall as a 27" x 1 1/4......The tire is much taller than normal...Is this correct?
The bikes do look good(and comfortable!) with the ballony tires...
But now I think I'm getting that the 650B tire/wheel package is as tall as a 27" x 1 1/4......The tire is much taller than normal...Is this correct?
The bikes do look good(and comfortable!) with the ballony tires...
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08-11-16, 02:29 PM
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Well, a 650b with a 42mm tire has the same rolling diameter as a 700c/23. Cannondale went with a 650b on the Slate so they could fit a big tire and still keep a racing geometry.
08-11-16, 02:57 PM
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650b randos were the original gravel grinders
Last edited by bulldog1935; 08-11-16 at 03:01 PM.
08-11-16, 03:12 PM
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I can understand a move to a smaller rim if your frame won't let you use the tire width you want on the standard 622 or 630 rims, but if it does, I don't see the need. On bad roads bigger wheels roll better.
08-11-16, 03:24 PM
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So with the 650B you are not sacrificing rolling efficiency, are you? Like you would if you went from a 27" wheel to a 26"...
08-11-16, 04:02 PM
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Yes, you would, only a little less so, as 26" is slightly smaller (559mm) than 650B (584mm). You would have to fit an even bigger tire on a 26" rim to get the same outside diameter.
08-11-16, 04:07 PM
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Why I ask all of this is I had a Voyager SP back in the 80s(I still have it, actually). Although it came with 27 x 1 1/4 tires, I pub Specialized 27 X 1 3/8 tires on because it gave an extremely soft ride. So when I first noticed this trend in 650B, i liked it, but was loath to give up any efficiency of a taller wheel/tire package. But it sounds like the 650B is taller, and quite close to a typical 7ooC.
08-11-16, 04:43 PM
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Yes. This is correct. It keeps the mountain bike tires in inches: 26", 27.5", and 29". A tire labelled as 27.5" is 650B, but fat and knobby for off road use, most of the time. A 29" tire (or 29'er) is similar. In that case, it has the same diameter as 700c but is designed for off road use, most of the time.
08-11-16, 04:43 PM
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Not really. Larger wheels do save energy by being better at rolling over obstacles, but this is a fairly minor issue in road biking since the bumps are so tiny relative to even small wheels. It's not like MTB where huge tree roots and big rocks are just part of your route.
It's worth noting that the outer diameter difference between 650b setups and 700c setups is pretty small anyway. We're not comparing baby stroller wheels and hula hoops.
Even 26ers are reasonable for road cycling, if you're running supple slicks.
It's worth noting that the outer diameter difference between 650b setups and 700c setups is pretty small anyway. We're not comparing baby stroller wheels and hula hoops.
Like you would if you went from a 27" wheel to a 26"...
08-11-16, 05:30 PM
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Why I ask all of this is I had a Voyager SP back in the 80s(I still have it, actually). Although it came with 27 x 1 1/4 tires, I pub Specialized 27 X 1 3/8 tires on because it gave an extremely soft ride. So when I first noticed this trend in 650B, i liked it, but was loath to give up any efficiency of a taller wheel/tire package. But it sounds like the 650B is taller, and quite close to a typical 7ooC.
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