Cal398

650b improved every aspect of my riding experience - speed going up technical climbs, speed going down technical descents, acceleration, physical comfort, mental comfort, bike geometry became more fun - and with some wheel companies offering ride and returns, there’s no reason for you to wait to try.

I rarely see anyone talk about the ability of smaller wheels to more easily accelerate over obstacles at very low speeds. With the big tires on the 700c format, I either stalled out (because I would stop abruptly going uphill when hitting a big rock), or I’d lose traction in the rear wheel trying to accelerate over it.

I do most of my riding in the Bay Area, so it’s basically constantly up or down, with the ability to link a full day of fire roads/trails with <25% road. Class 3 and 4 “gravel” mostly. My biggest issues have been having to go slower than I’d like on rough descents, dusty loose corners, losing traction on sustained steep climbs (>20%), and losing momentum when hitting big rocks on steep climbs. If this sounds familiar to you, move over to 650b.

If you say I should get a mountain bike, I think the vast majority of the trails here are boring even on a hardtail.

For those, with modern gravel frames, I’m on a frame that takes a 45mm tire on a 700c wheel, but it turns the bike into a boat! The 650b gave me back the nimble steering needed to quickly maneuver for the best line.

I’m getting the feeling that 650b was a flash in the pan for the industry, so throwing in my vote for this relatively unpopular category.

DorkDisk

I still ride a lot of 26ers. In the city, I am untouchable for a half block. Then 700c passes me. In the woods, its more nimble and fun, where large wheels are smoother over bumps

KJ43

I'm in the Bay Area too and before I got my Stigmata had been mountain biking exclusively for a long time (25+ years). I wouldn't go back to smaller diameter wheels if you paid me.

With no suspension 700c rolls over the bumps more smoothly, are overall faster, more stable, and don't limit how nimble my bike feels whether I'm going up or down singletrack switchbacks or on the road.

Maybe if I only rode very technical mountain bike trails like some over at Skeggs, Crack or Boy Scout in Pacifica, Demo Forest, or trails by UCSC across the hill. But even then I would pretty much be picking a 29er full squish because of how much better the larger diameter wheels roll.

Rolla

I like 27.5+ on my mountain bike, but mostly because at 5'9", they make the bike fit me better than my old 29er. I have a BMX cruiser with 650B that I like because of the increased rollover capabilities over my 26". But the 26" is super flickable and a great climber. I have 700c on my gravel and CX bikes, and they seem great for those applications.

I guess I'm weird in that I like all the wheel sizes, instead of pledging allegiance to only one.

chaadster

I’m rather agnostic when it comes to best wheel size, too, and for the most part, it’s a “six in one, half dozen in the other” situation.

I have 26”, 700c, 650b and 20” (406) all in the fleet, but admittedly none of the different wheel sizes are set up to do exactly the same thing, so it’s kind of hard to make direct comparisons. For example, although my 650b wheels wear road slicks, the tire size and the bike they’re on are for different types of riding than my 700c wheels.

I love the 650b for the large, 48c rubber which confers a lot of smooth riding comfort on gravel, but for aggressive gravel riding, I prefer the crispness and responsiveness of narrower 700c tires. The 700x35 tires I run suit my summer gravel needs pretty well. Would 650x35 be as good or better? Dunno.

Lazyass

I personally think the 27 inch wheel should come back for gravel bikes for the same reasons 29er took over MTB's. Some modern wide rims with 1.70 inch (43mm) tires or something. The larger diameter would roll so smooth and stable on gravel.

dsaul

I have two gravel bikes. One with 650 x 47 tires and the other with 700 x 40 tires. If the ride is anything other than smooth gravel roads, I pick the 650 x 47 bike every time.

jonathanf2

I wouldn't mind a 650b wheelset. Seems like they're cheaper for new lightweight wheels.

Cal398

Great nuanced discussion here, “different spokes for different folks” 😁. As mentioned, I’m definitely not putting 650bs on my road bike anytime soon. Does anyone know if there is a bike with 700c x 2.1” clearance with a low bottom bracket, no toe overlap, and agile gravel geometry (possibly an impossible combination of features?).

What’s the groups personal anecdotal experience on speed between 650b with fat road slicks vs 700c and narrow road slicks? I don’t trust Jan’s work at all, my personal experience with the Rene Herse knobbies can be blamed for that.

JWK

No one really tries to compare fat 650b with narrow 700c. The usual comparison (of which I wonder a great deal) is between 650b x 47/48 and 700c x 42/44. That's the real debate. I wish I could try both on equal footing. Sadly, I just don't have the funds for that experiment.

mattcalifornia

Same here (almost). I have 1 gravel bike with 2 sets of wheels: 650b x 47 knobbies with a bigger cassette (9-46) and 700 x 42 quasi-slicks with a smaller cassette (9-39). It's hard to compare them directly because they have different shoes and different cassettes. However, I don't think I really notice the size difference much one way or the other for gravel bike purposes. The 650s feel a little lighter, as well (they are more expensive rims though). Also, because the 650s have balloon-ier tires, the difference in outside diameter of the two wheels isn't that great anyway. I wind up leaving the 650s on most of the time unless I know that the ride will be exclusively on pavement and fire roads. The 650s are surprisingly fast on pavement.

Incidentally, Ibis says that the max width for 700c tires on the Hakka is 40mm. I didn't even realize that when I ordered my 42mm Rene Herse tires. Luckily, they fit fine with room to spare. You could probably go even wider. They also say you can run 2.1" (53mm) at 650. The biggest reason most gravel bikers will use 650b's is that you can run wider tires on most gravel frames. I doubt there are too many who would opt for 650s over 700s if they accommodated the same width tires.

chaadster

Breezer Radar X and Radar Pro both clear 700 x 2.5” rubber, have low 75mm of BB drop, are long front-center which helps avoid toe overlap, and relatively short 444mm chainstays suggest agility, though the slack 69° head tube and 51mm of fork offset point to the kind of high speed, off road stability such big rubber recommends.

https://www.breezerbikes.com/bikes/a.../radar/radar-x

tangerineowl

Certain I've come across a european frame or two like that with a tucked-in chainstay but they weren't off-the-shelf carbon. Bit like an Open WI.DE but 29er.

Just talking speed-wise (on road), vs a road 700c, I found the 42mm extralight the easiest to keep up with a roadie. Roll-down fairly quick though.

Been on the 48mm also, but now settled on the 2.2" SpeedKing Racesport as it covers a wider range of conditions when not quite requiring some knob height.
As supple as the extralight. Cheaper, and just as fast in my view.

Have noted Jan's new 27.5x2.2" knobby which i would like to try some time though, in some (limited) conditions.
[as an alt to the Conti RaceKing Racesport].

fourfa

I was drawn to my gravel bike by the dream of having a do-it-all bike with 650B semi-knobs and 700x28 race-rubber wheelsets at the same rolling diameter. It's been pretty great overall (and has covered a third garage spot as a touring bike as well). On the aero GP5000TL wheelset it's a much better road bike than the 90s Ti roadie it replaced. Is a fully modern road bike better yet? - sure. Good enough for me though.

If the question was, do I notice the difference between GP5ks and 650b gravel tires - without question, every 650 I've tried is significantly slower on every paved surface around me (also Bay Area). We don't do winter here, or chipseal, or refuse to fix potholes, so some folks with truly awful pavement might feel differently on a plusher tire. The speed difference is enough that I switched to a 10-tooth cog on my road cassette because I was frequently spinning out the 11-tooth (with a 46 tooth chainring). I never spin out the 11-tooth small cog on the gravel wheels; in fact I seldom use it.

On pavement I'm very happy with the quick-ish geometry enabled by this moderate tire clearance (420mm chainstay, moderate wheelbase), and off-road with a dropper to get my center of mass back and down, I seldom wish I was on a long/low/slack gravity sled. It's good enough for me, I dismount for some rock gardens, and I'm happy to be on basically a road bike for the 99.99% of my miles that are not rock gardens.

RH Clark

I've never tried 650B. I have several 26" wheeled bikes and 700c and 29er. My 700c bikes are 38mm and 35mm. My larger 700c or 29er is a 2.2 XC bike. I'm 6'2 and 185lbs. I've been thinking 29er plus lately, but the bikes I could afford seem very heavy.

pbass

Huh. I don't get that impression at all. In fact, I think perhaps it's going to catch on more and more, for all the reasons you state. Personally, I love it. I'm also a smaller guy, just under 5'7". I have both 700c and 650B gravel bikes, and a 29r mtb. The 650B rig just feels right. I think smaller riders in particular should give it a try.

GhostRider62

Without question, same with my data and that includes the super expensive extra legere Rene Hearse tires

freetors

My gravel bike fits up to 29x2.4 tires. I just don't see the point in 650s if your frame can clear real fat meats.

mattcalifornia

wow - what frame is that?

freetors

Salsa cutthroat.

ThermionicScott 

Wow, really high trail on that bike. Maybe that's the way things are going, given the Breezers recommended by chaadster also have super-high trail.

A really slack headtube is one of many ways to get that front wheel out of the way and free up room for big wheels.

SapInMyBlood

My "gravel" bike fits 29x3" 👌 Salsa Fargo

Cal398

To me, these bikes with high trail numbers make more sense when you can fit these big tires, since they give you the traction to run over more things.

IMHO, a 45mm tire isn't big enough to make-up for the fact that I can't reliably steer around obstacles. Maybe I'm just overly sensitive to trail figures.

Love the variety of "gravel" bikes out there though. What are the typical riding use cases for a Fargo or Cutthroat? How much are you losing (if any) on pavement vs. a more standard gravel bike?

chaadster

Yeah, and I suspect it will continue to be the trend, largely because the desire to get more rubber is a pretty clear indicator that people are riding gravel bikes like MTBs, and if you look at that segment, head angles have been getting really slack for years, and trail numbers are way out there, well over 100mm.

Gravel folks seem kind of satisfied with rigid forks for now, I suspect because a lot of the segment are roadies who are enthralled with the effect of fat, LP rubber compared to skinny, HP tires. It looks to me, though, that the gravel bike market is on a similar development trajectory as MTBs were in the ‘90s— exhibit A is the Redshift stem, a rehash of ‘80s MTB tech now all the rage for gravel bikes— and so proper suspension forks will probably be next. We’ve already have the trick proprietary stuff like Lauf and head tube suspension, just like we had the Lawwill Leader and Headshock.

Had it not been for COVID, I think we’d already have seen widespread placement of SR-Suntour’s RockShox Paris-Roubaix SL rehash, the GVX…and head tube angles frequently dipping below 69°.

ThermionicScott 

I suppose it was only a matter of time before "gravel bikes" mutated away from being road bikes with more tire clearance, to something very different. Do you suppose gravel bikes and MTBs will ultimately converge into the same thing?