In a ‘nutshell’….
Are 650b wheels worth putting onto your cyclocross/gravel bike? I don’t know. Maybe. It depends on what you’re after from your riding experience, where you ride, and how you prioritize sheer speed against versatility. Before delving into details, here are my impressions of 650b wheels with Compass 42mm and 48mm tires following a bunch of riding on my Brodie Romax disc cyclocross bike. I’ll refer to the smaller setup simple as ’42s’ and the larger ’48s. Bottom line: I love the 650b x 42mm setup, and see myself spending a lot of time on them in the years to come. A 45mm tire option could end up replacing the 42 as an all-rounder that ticks all the boxes. Read on for the reasons behind the statements I make
650b x 42mm Compass Babyshoe Pass, Extralight, Woven Precision Handbuilts Gravel + Carbon Rims
- Drop ride height a little compared to 700c x 35mm tire/wheel combos (about 12mm), but it doesn’t really matter.
- Feel super agile and sporty on my bike, encouraging playful riding.
- Corner really well on pavement, and reasonably well on loose-over-hard unpaved surfaces
- Feel twitchy compared to any other 700c tire setup I’ve ridden; it’s not a deal-breaker
- Are more fun and seem to roll faster than comparable 38s.
- Feel equivalent to comparable 35s on smooth roads.
- Climb fast enough on pavement to not bother me, provide good grip on loose surfaces.
- Are ok for fast group riding on pavement, but overkill unless the pavement is bad.
- Are excellent for medium-paced group riding, especially if very hilly, and lots of cornering traction is valued.
- Are excellent for mixed-surface riding (typical dirt roads and gravel), from slow to fast-paced.
- Compass 42s sre too light in construction for pounding trails with sharp rocks, but other 42s built with more material would work fairly well.
- Make for an excellent all-rounder size for those looking to ride a broad spectrum of conditions on one bike, albeit conservatively in some situations. Tires can be tailored to local conditions: Compass ELs and Standard casings are fine for rounded rock and roots, other options will be better suited to sharper rock.
- The 42s are my go-to for general gravel riding on my Romax, and will serve all purposes in the fall when I have cyclocross mounted to my 700c wheels.
650b x 48mm Compass Switchback Hill, Extralight, Woven Precision Handbuilts Gravel + Carbon Rims
- Maintain ride height about the same as with 700c x 35mm tire (about 4mm lower), can’t feel this.
- Feel ‘normal’ on the bike, same basic handling characteristics as with 700c x 35mm setup, but with way more volume.
- Corner like crazy on pavement, large contact patch. Don’t corner as well as 42s on loose-over-hard surfaces.
- Don’t feel twitchy whatsoever.
- Don’t feel fast on pavement, but perform fine. The rougher the surface, the better they perform, until getting sharp rocks, mud, etc.
- Feel similar to comparable 700c x 38s on smooth roads in terms of aero and rolling performance.
- Don’t feel fast on paved climbs, but have lots of traction on dirt climbs, so are very effective in that context.
- Are overkill for fully paved routes at any pace.
- Are overkill for medium-paced group rides on pavement, unless you want maximum grip for descents.
- Are excellent for mixed-surface riding at medium pace, and up to high pace if the surfaces are quite chunky (think golf ball to fist-sized gravel).
- Compass 48s are too light in construction for pounding trails with sharp rocks. However, other tires in this size will work better, because they are built with more material, and would be my preference over 42s.
- Make an excellent all-rounder size for those looking to keep a broad spectrum of riding options open on one bike, less conservatively than with 42s. Tires can be tailored to local conditions: Compass ELs and Standard casings are fine for rounded rock and roots, other options will be better suited to sharper rock.
- The 48s are a niche tire for me, only really required for a handful of routes I’ll ride in a given year. The volume is great, but I need more material in the tire for riding rocky trails at my comfortable pace.
Wheels: Woven Precision Handbuilts D25 Gravel + ($1350 CAN)
I’ve had the pleasure of being able to ride a pair of Woven Precision Handbuilts 650b wheels over the last month or so, following a short stint on them last fall. After that we sent them to Bicycle Quarterly for review, where they saw a bunch of miles under Jan Heine in the Pacific Northwest on a few different bikes. That review will come out later this year. The wheels use standard Woven disc hubs, which accommodate all modern axle standards, which include 9mm, 12mm, and 15mm up front, and 135x9mm and 142x12mm on the back. Actually, you can even run the rear as a 132 on the back on an older non-disc 130mm frame, then swap to one of the newer configurations for a new bike; future-proof! The freehub body uses 4 leaf-sprung pawls, rolls on Enduro Abec 3 bearings, like esewhere in both hubs, and is ready for an 11-speed cassette. XD drivers and Campagnolo freehub bodies are also options. Again, future-proof! Oh yeah, centrelock or 6-bolt rotor options too! Centrelock is cool for those looking to share rotors between wheels (you can only ride one bike at a time!), and/or want to remove rotors easily for travel.
The rims are 27mm wide on the outside, 22mm on the inside, and 25mm deep. Internally, they have a tubeless bead-shelf, which has a little bump-up ridge the tire bead has to climb over when mounting, which then helps keep the bead in place, reducing burping (when the bead separates from the rim, blowing out air). The sidewalls forego a bead hook, like a lot of modern mountain bike rims. This provides a little more robustness in the face of impacts, because the sidewall is shorter and thicker than if it had a hook. It also holds the tire on without issue. Believe it or not, all rims were hookless in the early 20th century.
Built to high tension with round, double-butted Sapim Laser spokes and their Polyax alloy nipples (which are surprisingly strong), the rims are 320g each and come stock with tubeless base tape and tubeless valves.
I have two sets of tires, thanks to Compass’s support, to ride on these wheels. The standard pair is their Babyshoe Pass model, which is 650b x 42mm. This tire came into being as a response to demand for a lighter, faster rolling option than the Grand Bois Hetre, a well-loved tire within the randonnee crowd for decades. Available in standard or extralight casings, both are very supple, the EL being pared down to the bare minimum. Neither tire uses a puncture protection belt under the tread, which lends maximum suppleness at the cost of reduced cut protection.
The mitigating factor here, as with all high volume tires, is that lower pressures reduce casing tension, thereby reducing the tendency of the casing to cut rather than deform when rolling over a sharp object. To illustrate, picture trying to puncture a tire at 30psi with an icepick versus the same tire at 80psi. The higher pressure tire will retain its structure as the pick tries to penetrate, and creating a hole will allow the tire to pull itself apart due to its casing tension. So using higher volume tires at lower pressures reduces incidents of puncture from road debris. This is a valuable benefit for those taking on long rides, especially in harsh conditions. See ‘randonneuring.’
I also have a pair of the Compass Switchback Hill 650b x 48mm tires, also in Extralight casing. These are the tires I was really excited about trying, but I wasn’t sure they’d fit my Brodie Romax. In 2016, I was only able to ride both sets of tires on my Niner 29er mtb with drop bars. That wasn’t a great indication of how they ride on a gravel or cyclocross bike. Fortunately, the 48mm tires easily fit my TRP disc fork, and juuuuust fit my frame. How close? About 3mm clearance on either side. Is that enough for real riding? Well, I’m a wheelbuilder, so I know how to work on wheels out in the field, but if I were to break a spoke, the wheel would not clear the frame. That could strand me, unless I was lacking a 42mm spare tire. Having spent a lot of time on Woven wheels, this is a risk I’m willing to take, as I’ve only ever broken a spoke once, and that was from harsh contact with another bike in a cyclocross race.
For both sets of tires I used old 26″ butyl tubes I dug up in the basement. Both can be run tubeless, and the brand new Babyshoe Pass is actually officially tubeless-ready (Compass is rolling out tubeless versions of all their tires larger than 32mm). The beads are the same between formats; all of them require sealant for airtight mounting.
Impressions: 48mm Switchback Hill ($84 USD)
I was eager to get onto these tires, so I mounted them first. As I said, clearance on the back was tight, so I packed a proper spoke wrench for my first big ride, a mixed-surface route north of Ottawa.
My first impression on the wheels was that they felt pretty much ‘normal,’ i.e., like my 700c x 35mm Compass Bon Jons. The large volume didn’t make the bike handle any slower than usual, and it felt like it rolled well. I didn’t feel any difference in terms of wheel flop, and cornering on pavement was pretty awesome. So much rubber! Pretty fun. My ride height wasn’t noticeably different than usual, I wasn’t clipping pedals while turning.
My long ride was the real test. On pavement, with the tires inflated to around 30psi, feedback through the bike was minimal. Guess what that translates in the ol’ mindbrain? ‘Slow.’ This is the principle deception of high volume tires at low pressures. Bike riders have learned that more high frequency feedback transmitted from tires up through the bike and into the body equals more speed. This is true when we keep certain variables constant: tire and wheel specification and all the frame and contact point elements that contribute to ride feel. Here, we’re taking 35mm tires off the bike – with aero rims, 55mm deep – and replacing them with 48mm tires at more than 10psi lower pressure, shallow rims. The tires are absorbing a lot of the vibration and impacts my 35mm tires would normally transmit into my body on the roads I am used to feeling a certain way. So I feel like I’m going slower; this is perception bias. I have to look at my Garmin to see I’m rolling fine, not slow. Without a power metre, however, I can’t know how much power I’m putting in to achieve this speed. More than anything, the aerodynamic hit is probably the greater contributor to any reduction in speed I feel. This would cost me more the faster I go, since the power required to increase speed follow an exponential, not a linear progression curve.
Out of the saddle, on pavement and dirt, the wheels feel good. I don’t get squirm in the tires, which would make me feel slow. I like the handling, it feels natural.
Climbing: This is where the volume really shows its value on dirt roads. Why? When surfaces are loose, volume helps you maintain traction more than knobs can. This is because loose surfaces don’t necessarily have hard surfaces underneath that tire knobs can penetrate and dig into. Think of sand, and beach cruisers: they have fat, non-treaded tires. They float. For steep climbs, the volume puts more rubber on the road (think snowshoe), and this helps one scale the grade, even standing up. For routes like D2R2, this is very valuable, because you climb loose roads all day.
Cornering: This one depends. For deep, loose surfaces, the volume would be great, especially when embedded rocks are in play. However, more common on dirt roads is ‘loose-over-hardpack;’ this is also common on downhill mtb race tracks, btw. Have you noticed downhill racers are not riding huge tires? This is because many tracks, like many dirt roads, are composed of hard substrate covered with loose material. The ability to steer and brake on such terrain depends on the tire penetrating loose material and gripping into the firm substrate below. This is what knobs on tires do when they’re not simply compressing soft material, like loam. If the surface rubble is heavy, the tire needs to either ‘cut’ through to firmer material below in order to find traction while leaning, or displace enough material to effectively receive enough ‘push back’ to hold the lean. When the tire is too wide to either cut into soft material and find traction below or act as a rudder and push against material along its outer surface (this has long been held as a benefit of using deep wheel in cyclocross for sand conditions: steering like a rudder), the tire will drift/slide, setting up a potential loss of control and a crash. Controlled sliding is common pretty much all the time we corner on bikes (believe it or not, bike tires always slide, at least a little, when we corner, no matter the surface). The control bit is key.
Bottom line / When would I use these tires?: The 48s don’t corner on loose-over-hard surfaces as well as 35s. They float more, and this reduces grip. If dealing with really soft surfaces, where the tires will sink in, traction will be good. For trails, the added volume will provide additional resistance to punctures. Running tubes instead of tubeless could provide a bit more structure to the tire’s casing, reducing pinches to the rim. Otherwise, one might have to use more pressure to prevent rapid collapse of the tire when striking square edges at speed. This is more of a trail issue than a dirt road issue.
I need more time on them to really ‘know’ where their niche is, but if we’re looking at this from the persepctive of wanting to have tires that open up all sorts of riding opportunties without costing much in terms of cruising speed, these are a good choice. The thing is, they are really fun when cornering on pavement, and they roll fine on that surface the rest of the time. Yes, high speeds will be harder to maintain than a smaller tire on smooth surfaces, so if you’re looking to keep up on challenging group rides, you probably want to go with something more aerodynamic. If you’d like to ride whatever terrain you can find, especially when travelling, these could be ideal. No, they are not suited to smashing down rocky trails, and they won’t handle mud well, but lots of riding out there features friendlier rounded rock and roots, which are fine. For example, these tires would be really fun on the trails of Cape Cod. If you ride alone, and sheer speed is not important, these could be ideal all-terrain tires. For me, since I am riding fast with friends a lot of the time, and our dirt roads are not really rough, the 48s are overkill most of the time. Where they would excel would be long routes covering expanses of Gatineau Park, paved roads, and dirt roads, ridden at about 80% speed on the descents. This would keep tire damage down, and see lots of benefit from the volume across a long day. The standard casing model might be the best choice for this riding.
Impressions: Babyshoe Pass, 650b x 42mm ($78 USD)
Basically, these tires make my bike feel like a sports car. Why? They are a tad smaller in diameter than a 700c x 25mm tire setup, and the shape of the tire somehow makes them handle quite differently (technically, I believe this is a function of pneumatic trail). The bike feels zippy, and cornering on pavement is cool, because there’s lots of grip, and it’s also possible to actually steer within the turn, rather than simply establish and hold the line. This can be handy.
I took the wheels – with the same tubes – on few big rides, including two big mixed-surface days, and one big paved route. One of the mixed days was the JAM Fund Grand Fundo, which was pretty rad, as Phil Gaimon and Ted King were there. I wound up climbing Kings Highway, a road Gaimon attacked to score the Strava KOM, at a pace that rendered my arms numb, but was good enoug for 13th overall, not far behind Tim Johnson and Ted King. Either I’m really good at climbing (not really, if I was I’d be schooling everyone on our local A-loop, and I’m not), or the tires are not slow. Overall, I found the tires perfectly suited to the conditions, mostly hardpacked dirt roads and pavement.
The long paved route I did on the 42s was 176k, and pretty hilly, totaling about 2,400m climbing. Heading into a pretty strong headwind with about 12 others was a slog that had me doubting the appropriateness of my bike setup. I wanted the low gearing, but nothing was super steep, and I was thinking my Cervelo road bike would have made a lot more sense. I’d been picturing a lot of heavy, coarse pavement from Eganville, but the roads were fine, just a bunch of holes to steer around through one section. The high volume tire wasn’t doing me big favours as I pushed through the air, avaraging about 33kph. Later, when we turned away form the wind and rolled somewhat downhill for the remainder of the route, my bike felt good, and I had no qualms.
Had I been riding alone, or with a slower group I’d probably never have had any qualms about the wheels, but I was definitely not super keen on their performance while the riding was tough. At the same time, they are fairly twitchy at speeds around 30-35kph, so they require a fair bit of attention. I think this is likely a result of my bike not being designed for low trail, which is what 650b bikes tend to use. It could be interesting to have adjustable rake in my fork to increase the front end’s trail, which could calm the handling somewhat. This is possible with a fairly simple design. I would not suggest executing as below, but on the same plane, moving the front wheel forward, horizontally.
For loose-over-hard surfaces, the 42s are a little better than the 48s in the corners, but still not as good as 35s. This requires a little adaptation, but isn’t really hard to deal with. Climbing is proportionally grippier than 35s and less grippy than 48s.
Bottom line / When would I ride these? The 42s make the bike feel really fun and playful, and allow for fast rolling at very comfortable, low pressures. I feel they are well suited to all mixed-surface riding that doesn’t involve a lot of sharp edges (rocks), large impacts at high speeds, or really chunky gravel. For those conditions, the 48s would be better. I also feel they are well suited to pavement when riding below your threshold and for a long time in particular. As the hours pile on, the low pressure will save energy, even on ‘smooth’ roads. If tacking 5, 6, 7 + hours on the bike, reducing suspension losses in your body will count for a lot. If you’re going to ride your own comfortable ‘all-day pace’ I don’t see a downside. Similarly, if you’re doing riding like what we did in South Carolina in March, which involves long climbs at or below tempo, then fast, winding descents, these are probably ideal, and I expect to take them down in the spring. The cornering traction they provide is worth it, ATMO, when climbing at your own pace and not worrying about being dropped. Not feeling beaten up from hours upon hours in the saddle counts for a lot too.
That’s it for now, I’ve captured all my thoughts to date. Moving forward, I’d like to experiment with Compass’s standard casing 650b tires in tubeless format, and determine the pros and cons of that setup. I’d also like to try something in the 45mm size area with a low tread, a format I’m pretty sure doesn’t exist yet. I feel 45mm will hit the sweet spot for many riders, fitting the majority of cyclocross and gravel frames while bumping volume up form the 42 size. There are practical limitations to riding drop bars offroad, and my experimentation in recent years suggests that the hand positions drops afford and up mismatching the performance of tires beyond about 2″. I expect to see 650b becoming a lot more common in the gravel segment in the near future; I’m looking forward to seeing what happens and being part of the format’s development.