Monday, June 14, 2021

650B vs 700c For Gravel

No "Country Views" today- I had a little graduation celebration to attend to.
 Normally I would have a big ride report today, but I had a busy weekend setting up for, attending, and tearing down for my son's graduation celebration for his final High School year. In between doing all those things I did get around to swapping back the Standard Rando v2 to 700c wheels and tires and getting a couple of shorter rides in on it. I wanted to get a feel for the bigger diameter wheel again before giving my assessment on the 650B vs 700c wheel debate for gravel bicycles. 

Also, and obviously if you hang around here for very long, I have been riding other 700c wheeled bicycles on gravel right alongside the Twin Six Standard Rando v2 with 650B wheels for months. So, this post will also draw from all those experiences, plus my past thoughts and experiences with both wheel sizes going back for several years now. So, without further adieu, here are my thoughts on the wheel sizes and why I would choose one over the other. 

So, some of this opinion has been formed over a decade of messing about on 27.5"/650B MTB wheels and tires. I have ridden several bikes with that wheel size on mountains, gravel, single track, and on the road. Of course, at one point a lot of people thought that 650B/27.5, (they are essentially the same thing, so don't get confused), was going to knock 29"er wheels and tires out and take over the MTB world, but as we all know, 27.5"ers have, to a great extent, been relegated to being the size better suited to shorter statured riders off-road. But, as we now know, 29"ers actually gained ground on 27.5"ers over the years, and it is now the established wheel size for many styles of MTB bikes. 

I mention this because as others have formed their own opinions over the years, and market forces naturally selected out which bikes have big wheels and which do not, the findings I have regarding the 650B vs 700c debate for gravel follow roughly the same thoughts as many others have come around to over the years. That said, I have had strongly held opinions about each wheel size for over decade and a half of riding, reading about, and writing about these wheels. So, that's where I am coming from here. 

650B for Gravel: 

The most recent review I wrote for was for a set of 650B tires, so I rode those wheels and tires for the better part of three months most recently. I have ridden 650B gravel wheels and tires before that, most often for all those WTB tires that came out, and last year for some IRC tires, so it isn't like I haven't been on 650B for a long time before this. I feel like I have a pretty good handle on what is going on here. 

In my opinion this wheel size does a couple things for you. One- It gives you more cushion, if you choose the right tires. It is close to what you might get out of a heavier, larger wheel with wide tires. That is- if you are comparing similar quality wheels. A heavy, entry level 650B wheel set will just plain suck compared to a decent set of 700c wheels and tires, and vice versa. If all the 700c wheels were heavy and all you could get were nice 650B wheels, then the choice is obvious. Nice wheels (light, strong, stiff laterally) trump all including diameter, to a degree, and especially for this discussion. More on that in relation to my specific situation in a bit....

But the point is, big air volume = better comfort, theoretically. The truth is, 650B kind of gets you there, but there is something missing, which I will bring up in a bit. 

Secondly, those wider tires can aid in getting over rougher, looser gravel and dirt with more stability. You get maybe a bit better flotation too, so a bit better in mud, loose sand, etc. A wider footprint, if you will, and that is something that, if we are talking running 700 X 43 or 650B X 47-50? In the same bike? That's where it makes a difference. But keep in mind, this debate is mostly about the bikes that claim to fit either wheel size, but have clearance limitations, like my Standard Rando here. 

But the big bummer with these wheels, in my opinion, is that they just do not carry momentum like a larger diameter wheel. And maybe you are not at all in 'tune' with that. Then you will not understand my criticism here. But, as a single speeder first, I crave momentum and use it often. 650B looses that momentum faster than a bigger wheel, like 700c X 45mm, let's say. I can feel this every time I ride 650B. These wheels also do not have that roll over effect, the way a big wheel does, so they seem to feel rougher, and things have more of a 'zing' to the hands when you hit them with 650B wheels. So, remember that air volume thing? Some of that gets lost in the trade-off to a smaller diameter wheel. 

700c for Gravel:

So, if you have a bike that takes both wheel sizes, you likely have the option for wider, 650B X 47/48mm tires or something like 700c X 43-45mm. Which do you choose? Well, I already have told you a few things about why I would choose 700c, but what are the downsides? Well, in this specific situation, 700c looses that 'big-volume' tire thing. So, it doesn't float as well, it is not as stable on looser soils and gravel, and you cannot tease out as much comfort with air pressure settings like you can with 650B. That said, in the case of this Standard Rando v2, I am much happier with the bike in 700c mode. 

These wheels just roll over stuff better and they stay rolling with more ease. Oh, other thing. This has specifically to do with single speed bikes, but a smaller wheel diameter lowers the gear versus everything else being the same but the wheel size getting slightly larger, as it does with 700c. So, now with the 700c wheels, I have a slightly 'taller' gear, but I'll adapt to that quickly. I could approximate similar gearing range by varying the rear cog by one tooth, but I have the same cogs for both wheel sets. 

And speaking of that, I promised I would get back to the wheels. I wanted to point out that in my comparison here, the 650B wheels you see are the same model as the 700c ones. They are both Irwin Cycles Aon Carbon 35's. The only difference is the diameter. So, this is an apples to apples comparison in this case. 

So, while some of the benefits of 650B are worthwhile to pursue, for general purpose gravel riding I choose 700c. I choose the 650B option when flotation and traction are imperative, as in Wintry conditions, or on really soft, early Spring roads, as a for instance. But most of the time I'm going to run 700c and it works better, in my opinion, than 650b for all-around stuff. Again- this only applies to bicycles like my T-6 Standard Rando which cannot clear big 700c rubber. I mean, I have  put 650B on a Fargo, but for most riding I'd do, a 29"er tire would work better on a bike that can clear a 29"er tire. 

Which brings me to bikes like my Black Mountain Cycles MCD, or an Otso Warakin, or several others of that ilk that can clear up to a 29" X 2.0 tire. In some cases even bigger. Here the need to swap in 650B wheels and tires is even less, in my opinion. Maybe if you are 5'4", that's a different story, but for me at 6'1"? I'm never going to want to swap 650B wheels and tires into the MCD, not when I can run a 700c X 47mm tire like the Teravail Rutlands.

So, to my way of thinking 650B is a good option if it makes sense for a specific bike/situation. But again- for most riding and for many bicycles? I am opting for 700c. That's my take on things.


Phillip Cowan said...

I've been riding a pair of the new Humptulips Ridge using my MTB dropbar conversion as a test bed. Despite the hokey assed name I like these tires. I like them a lot. So much so I'm considering having a custom frame built around them to correct the obvious deficiencies of the old bike. My thoughts were that 650Bx47/48 isn't going to do anything on gravel that 26x2.125 isn't going to do better. I haven't noticed the loss of inertia with these wheels. Perhaps I'm just not sensitive to it. More likely it's the chunky Velocity Cliffhanger wheelset they're mounted on that helps hold inertia.

Guitar Ted said...

@Phillip Cowan - That is a weird name! Yeah, I spend tons of time riding so many different combinations of tires and wheels and with the years piling into decades now I guess I have a different perspective than most. That's why I pointed out that many folks may not even notice what I am talking about.

james said...

At 5'8", I choose 700x40ish over 650x48 every time, road or dirt. My main driver is the stability of the bigger wheel. It just tracks better and takes less effort to hold a line.

MG said...

I’m with ya… at 6’1” tall, I have very little interest in 650b wheels & tires for gravel travel.

Nooge said...

Another aspect to wheel size to consider, again depending on your frame. 650b will result in a lower bottom bracket height and affect trail as well vs 700c. That could be a good or bad thing for a given frame and rider preference. This is due to tire diameter differences (not just the rim).

With equally wide tires, you get the expected diameter difference, but if the 650b tire is significantly wider, the difference can be canceled out. This can be used to your advantage.

I have a bike that I use for double duty, road and gravel, with two wheelsets. My 700x30 road wheels are equivalent diameter to my 650x50 gravel wheels. So my geometry (except pneumatic trail) is unchanged when swapping wheelsets. I notice no difference in handling, but obviously benefit from the wide rubber off road.

S Sprague said...

Totally agree! Years ago when my Salsa dealer had a demo day, I rode a Journeyman and Cutthroat back to back and could tell the difference then. The Journeyman did feel a bit slow on the downs by losing momentum faster than the Cutthroat for sure.

Now, as you mentioned the MCD can do both sizes so you're limited on the 700c, what 700c tire size is ideal for those frames that can clear a larger size? It seems 45 is about the max for a lot of frames. On my Mooto-X SS converted to gravel riding, I have been riding Vittoria 2.35's which ride very well on gravel yet a little slow on pavement. They work for my riding.