Wednesday, August 28, 2019

2 650B Or Not 2 650B: That Is The Question

Last March I thought 650B tires were the bomb on this ride.
The 650B tire/wheel size seems like a bit of an odd man out in the gravel world. I see that size sometimes, but not a lot. I'm not really sure why that is either. I have a guess or two, but I don't know enough to say for sure.

I do know that I vacillate back and forth between thinking these wheels are great, and then back to not even caring if I ever rode another 650B wheel again in my life. Generally speaking, for my tastes, diameter is "king" and unless a smaller wheel is exceptional at something, I don't get too excited. That said, there have been more than a few times I thought the wheel size was rad.

I think there are a few things I need to see out of a 650B wheel before I get too excited. First of all, don't even come around here with a 650B wheel with a tire narrower than the Road Plus standard, which is 47mm. In fact, I am beginning to feel that is too small. Poofy tires, if they must exist, must be exactly that- big, voluminous, and worth their weight. Using a 42mm tire in a 650B format seems......backward, especially when most gravel bikes worth their salt can fit a 43mm tire with ease in a 700c diameter. Remember- diameter is king, and if you are going to go smaller, then you need to make up for that smaller diameter with air volume. Otherwise, why bother? 

For example, when Surly came out with the Extraterrestrial tire in 26" diameter, they did not offer it in a 26" X 2.1....noooo. They went right out to 2.5" and good for them. If you ever ride one, you'll get it. They are awesome at about 20psi tubeless. Almost makes me want to run 26"ers again it does!

Smaller diameter, but super volume and super smooth ride. Make it worthwhile if you drop down a size in diameter and go wide, or go home. I'm not at all interested in 650B X (anything less than) 47mm. Nope. Give me a big, voluminous 650B, and maybe I'll fall in love with that. So then, why not just go wide and keep it 700c? Yes indeed- why not? 

700 X 50? Why yes. Don't mind if I do.
 The trouble is that then you end up with a bike that almost cannot be anything but a Fargo or clone thereof. I was online the other night perusing Kona's line up for 2020 at the suggestion of a reader here. They make the Sutra model which sports 700c X 50mm tires, but it isn't a whole lot different than a Fargo and has limitations which a Fargo does not have regarding the drive train and tire clearances. (Or you could see that the other way around too.) The 700c X 45+ size tires start to get into a territory that road based drive trains were never meant to live in. That and the emasculation of MTB gearing choices down to a single chain ring has really pinched the rider that understands wide range gearing that promotes a straight chain line. Your choices are more limited than ever on the mountain biking side of things.

So, 650B to the rescue. I guess. There you can get that wider tire stuffed into a frame and still get away with a road based, wide range drive train. You lose that diameter component, but the choices are greater when looking at gearing and all. I'll be checking out some more tire choices and running 650B sizes in the future, and I'll probably still be going back and forth about it.

Stay tuned....


bostonbybike said...

I hear ya! What I really regret is that overwhelming majority of tire manufacturers build nice, supple, light and fast-rolling 650b tires but they stop at 47mm width. I understand that that's maximum what most stock bikes can fit, but I wish there were more wider (non-MTB-specific) options available.

My bike rolls on Maxxis Ikons 650b x 2.2" wide (that's close to 56mm) and I love that width. Like you, I wouldn't go with anything narrower. Unfortunately, I don't have many good options should I ever want to try something else. Most 650b tires are either too narrow (because they're supposed to fit gravel bikes) or too aggressive (because are designed for MTBs).

Steve said...

I have the Black Mountain Cycles Road+ shod with Compass Switchback Hill 650b x 48 Extralight tires.
Fast, quiet, comfortable, good on most of the poorly paved and unpaved roads around here. And it exceeds the GT minimum criteria by a full millimeter!

Rydn9ers said...

I always giggle when gravel folks start talking about "wide" tires in the 45mm range, son you ain't wide until you get to 3" and up. The skinniest tire I run is a 2.1 on my "fast" bike and even that gets put away when I know the roads are going to be soft or extra chunky. This is where the 650b makes it's money as you say, smaller diameter but bulbous tires on the same frame all the skinny tired folks want.

youcancallmeAl said...

Why 650 b or even 26inch?? Jan Heine's tests may give an answer for some folks.

Another Bicycle Quarterly test had three people ride three bikes with identical geometries (fit, trail, bottom bracket height, etc.), but with different wheel sizes (26 inch, 650B, 700C). All test riders independently found that they preferred smaller wheels for wider and heavier tires, and larger wheels for narrower, lighter tires.
When we calculated the rotational inertia of the wheels, we found that these preferences all yielded similar values. Based on that test, we concluded that 700C wheels are best for narrow tires up to about 30 mm. For wider tires (30
to 42 millimeters), our testers preferred the somewhat smaller 650B wheels. Tires wider than 42 millimeters handled best on even smaller 26-inch wheels. It is no coincidence that the outer diameter of bicycle wheels has remained relatively constant, somewhere between 26 and 27 inches, since chain-driven bicycles were first were developed 130 years ago, despite much experimentation with other sizes. Motorcyclists have arrived at similar conclusions; they went to smaller wheels when their tires became wider and heavier, so that the rotational inertia remained the same.
This means that you should first decide how wide you want your tires to be. The wheel size will follow from that. If you love narrow tires, you should use a larger wheel. If you prefer wide tires, your wheels should be smaller.

Guitar Ted said...

@youcancallmeAl- It doesn't surprise me that Bicycle Quarterly found three people to agree with them. It also shouldn't surprise you that I (and a lot of other folks) don't agree with Bicycle Quarterly.

And that's okay.

Tall Guy said...

Guitar Ted, I'm guessing you're a tall chap, right? I think a lot of this actually comes down to toe overlap. Maybe not coincidentally, a lot of BQ tests involve short people - Jan is tall but Natsuko is definitely not.

youcancallmeAl said...

Yes but I was merely offering possible answers to two of your questions:

1)if you are going to go smaller, then you need to make up for that smaller diameter with air volume. Otherwise, why bother?

2) So then, why not just go wide and keep it 700c? Yes indeed- why not?

Obviously some people consider them to be valid answers based on more than anecdotal evidence.

Stevenator said...
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