The Revolution in Wheels
650B wheels, so it would appear, are the latest thing in the world of “gravel” or “adventure” bikes. It’s a remarkable renaissance, considering that when I first became aware of 650B as a thing (sometime in the 1980s) it was an obscure French utility-bike format on the brink of extinction. Now, everybody seems to want them - including me...
My “Titanium Devil” bike, which I bought in 2018, is explicitly designed for dual use with either 700C or 650B wheels. 700C, as most people reading this will know, has become pretty much the dominant standard for sports / racing / touring bikes. The claimed advantage of the slightly smaller 650B is that, when fitted to a bike frame sized for the larger 700C, it allows enough extra clearance for a wider tyre - more comfortable for long tours, and more capable of dealing with rough roads and heavy loads.
However, when I ordered that bike, I originally decided to stick with what I knew, and opted for 700C - though keeping in the back of my mind the possibility to experiment with 650B at some later date. And that “later date” just arrived, having had to decommission those original 700C wheels due to various problems (spoke breakages on the front, rim cracking on the rear), leaving me with a perfectly good pair of hubs left over, crying out to be built into a shiny new pair of wheels!
It might sound like the tail wagging the dog, but in fact my first step was to decide what tyres I wanted to use. Here, the brief was something that rolls well on tarmac - where, regrettably but realistically, I do at least 70% of my riding - but still provides good grip, durability and comfort on moderate “roughstuff” and also, crucially, on cobblestones (as you'll see when you read on). I chose the oddly named “IRC Boken Plus”, which combines a smooth-rolling centre strip for tarmac with a more grippy pattern on the shoulders to cope with gravel and other loose stuff. The choice of tyres determined two criteria for the rest of the wheel spec: width, and tubeless compatibility.
I then had to decide on - and source - rims, spokes, nipples, valves and tubeless rim tape, as well as various tools (since it was over 20 years since I last built a wheel) and other incidental parts like brake rotors and a new cassette. I ended up placing orders with 7 different suppliers! The whole fusion of different, supposedly compatible, parts from here there & everywhere called to mind a funny Sony hi-fi advert I once saw...
Enough of the geek stuff (which I've covered in a kind of appendix, below, for anyone who is really interested); what were they like to ride on? After my first few rides getting used to the new setup, I took the bike round the same route which I had used last summer for a comparative test of 3 different types of tyres.
I set off in the dark at 6am - official sunrise was just over an hour later - out through Potsdam city, the tyres skipping merrily over the occasional patches of cobblestones on the way, and heading south-west along the cycleway beside Templiner See lake. It was a lovely clear morning and the dawn was just beginning to turn the sky brighter behind the trees on the hillside to my left. I'm generally slower in the dark, and could feel a slight headwind, so I wasn't expecting much in the way of speed on this first tarmac segment, although the bike was rolling nice and smoothly. Looking at the ride stats afterwards, I was quite surprised to have set (by only a few seconds) a new personal best time on this 5km segment; the previous best was in fact on the third of the tyre test runs mentioned in that earlier article. So, no quibbles about the speed with the new tyres, which is not necessarily what you would expect: smaller wheels, wider tyres and lower pressures should all make things slower, according to conventional wisdom.
It was just about getting light enough to see by the time I turned off the lakeside road to tackle the real torture test, a 3km segment which I have christened the "Lienewitz Extreme Cobbles". This is the most gruelling part of my test route, and it's important because in Brandenburg there are still quite a lot of cobbled road surfaces in use - especially on the quieter roads with less traffic, which one would generally prefer to cycle on - and so it's good to have the bike set up to handle them without it being too slow or painful.
My test procedure here is to blast along the cobbled road as fast as I reasonably can, and then to compare the times on the different tyres; not because I really like going that fast, but because it's a good indication of how well the tyres handle that surface, while still giving adequate control and comfort. Therefore, I didn't stop along the way, although the orange-yellow sunrise sky behind the skeletal winter trees was a really beautiful sight which I would usually have wanted to photograph - I had to wait until I had finished the segment, where the view wasn't quite so stunning.
This part of the ride certainly felt tough - especially in the semi-dark where I couldn't see so well to steer a path around the worst of the cobbles - but the segment times tell their own story: head and shoulders faster than those other tyres I tested on this route last year. I also give quite a lot of credit to the wheels, which feel fantastically supple as a consequence (I think) of my eclectic choice of spokes, explained below. It'll be interesting to see if the wheels show any ill-effects after taking such a beasting; both the bikes in my earlier test suffered broken spokes not long afterwards!
After that, the rest of the ride was pretty much plain sailing, and great fun! The south-westerly breeze pushed me along nicely on the return leg up the other side of the lake, and there was at least one more personal best time to be had on the tarmac, as well as on one of the gravel segments along the route. The tyres felt fabulous, too - stable, grippy, smooth and fast. With their flattish tread, they probably wouldn't be great in soft mud or deep sand, but I didn't have any on this test route and that's not really what I bought them for. [Later edit: after a few more rides venturing onto some of the sandy forest trails around here and the odd muddy patch too, the Boken Plus tyres actually handled those surfaces pretty well - not quite as rock steady as the Gravel Kings, but definitely exceeded my expectations.]
I narrowly failed to improve further on my KOM time on the last long gravel segment homeward bound from Bornstedt, but I was still quicker than on any of the three other tyre test runs.
So the verdict on 650B? I'm a convert! OK, so I probably have confirmation bias, as this is the first pair of wheels I have built for a long time and I really want to love them! But, if the Titanium Devil felt perfect before (and I've found it brilliant right from the start), it feels even more perfect now - more poised, smoother and better balanced; I really have the feeling that it's found its spiritual home with these wheels and tyres. And of course I still have the option to swap back to the 700C wheels again if I fancy a change to bigger wheels with slimmer, more road-oriented tyres.
HOW THE WHEELS WERE SPUN
Here are all the geeky details about the wheel build and how I chose the components … mostly written up for my own future reference 😃 but feel free to read on and send comments/questions if interested!
The most interesting thing about these wheels is that they use a different gauge (thickness) of spokes on either side of each wheel - the first time I have done this.
I’d noticed that both my broken spokes in the old front wheel had been “leading” spokes on the side with the brake disc rotor. These are the spokes under the greatest tension during braking. I initially thought about using thicker spokes for just these (¼ of the total number of spokes in the wheel), but a discussion on Reddit, as well as a Sheldon Brown article, convinced me not to mix different spoke gauges on the same side of the wheel.
I’m a fan of thin “double butted” spokes - thinner in the middle and thicker at both ends - which in my opinion and experience give the strongest and most resilient wheels. So I chose DT Swiss Competition spokes (2.0mm at the ends and 1.8mm in the middle) for the more-stressed left side of the front wheel and right side of the rear; and DT Swiss Competition Race (thinner and flexier at 2.0mm / 1.6mm) on the right front and left rear. I also decided that I wanted to use brass nipples on the spokes - marginally heavier than aluminium, but with better electrolytic properties meaning they are less likely to seize to the spokes and thwart any future adjustments; and I was sold on the advantages of the bizarrely-named DT Swiss Squorx nipples, which allow for initial tensioning using a Torx socket driver from the outer side of the wheel rim, much less fiddly than the traditional square nipple wrench which the design nevertheless also supports (“square + torx”, geddit?). The Squorx nipple also has a curved base which can swivel like a ball & socket when matched with a special curved washer on the inside of the rim spoke hole - this allows the whole spoke & nipple assembly to take up the correct alignment and avoid a stressy bend point where the spoke exits the nipple - which happened to be the exact point of failure of the spokes in my old front wheel which I mentioned earlier.
Compared to the spokes, the choice of rim was relatively easy based on my criteria: tough, tubeless, correct width for my preferred tyres, 28 spoke holes, and available from stock in Germany. The DT Swiss RR-481, whose maker boasts that “this extremely durable rim is made for rough off-road rides… or for your next bikepacking trip”, ticked all those boxes. If I hadn't already had those 28-hole hubs to re-use, I'd definitely have gone for more spokes: probably 32 front & 36 rear. My search was slightly obfuscated by the fact that the Germans seem to insist on referring to this same 650B wheel size as "27.5 Zoll" (Zoll = inch), which is odd for a nation where metric units are universal, and doubly confusing when one grew up with 27" wheels which are actually larger than 650B / "27.5-inch".
(I'm deliberately skating around the vexed and confusing subject of bike wheel sizing and nomenclature; if you want to know more, Sheldon Brown also has the definitive article on the subject.)
Usually, the most difficult part of planning a wheel build is working out what length of spokes to order - but DT Swiss has a handy online calculator to make this dead easy nowadays, rather than having to look up various charts or grapple with trigonometry like we used to. I still needed two more parameters to feed in, though: the measurements from my old hubs (as they are not DT Swiss hubs, which would have already had their dimensions pre-programmed in the calculator); and the decision how many spoke crossings to use in the lacing pattern. The old wheels I dismantled were laced “2-cross”, but the hive mind of Reddit confirmed to me that it’s possible to build a 28-spoke wheel as “3-cross”, which once again (along with the choice of spokes) should give a stronger and more resilient wheel at the expense of a tiny amount of weight.
I had an impatient wait for all my tools and parts deliveries to arrive! As luck would have it, the last items arrived on a Friday at the same time as a really big snowfall, which put a stop to thoughts of going cycling that weekend and meant it was perfect for an indoor wheel-building project. I had the wheels finished by Sunday evening, but then had to suffer another agonising 10-day wait before the roads were clear enough again! (I kept myself busy in the meantime riding around on a different bike fitted with spiked tyres - which is another story.)
I invested, this time, in a couple of specialist tools I never bothered with when I used to build wheels before: a spoke tension gauge (I always just went by feel), and a wheel stand (neater and more convenient than mounting the wheel in the bike frame to work on it). The tension gauge was especially useful in the light of the rim cracking problems I’d had with my old wheels - I was keen to avoid a repeat. The rims’ data sheet specified a maximum spoke tension, and I found by using the gauge that I was in danger of exceeding this before the wheel felt quite tight enough according to my gut feeling and past experience. So of course I went by the gauge, not the gut feeling, and it’ll be interesting to see how the wheels stand up.
Another novelty for me was the tubeless rim taping, which I’ve always left to the bike shop until now. The internal rim diameter is 22mm, but the data sheet recommends 25mm rim tape - this means that the tape wraps slightly up the inside of the sidewalls. It had to be lined up carefully, but was no problem in the end, with the help of a 2nd person holding the wheel steady and turning it while I stretched the tape and smoothed it into place. Could be quite awkward for one person working on their own. I couldn't get either genuine DT Swiss rim tape, or Stan's (another market leader), so I bought some branded "Fun Works" which I'd never heard of, but seemed to work perfectly well. I finished this off on each wheel by making a hole with a sharp knife to insert a fancy, iridescent-coloured tubeless valve - I'm a sucker for sparkly things! - from the brand "Muc-Off", better known for their cleaning and lubrication products.
The final job was to install the Boken Plus tyres, which were a good tight fit on the rims - I blistered the skin on my thumbs pushing them on! - and inflated easily “dry” (no sealant) with a normal track pump. I never believed this before when I read in reviews that people had inflated tubeless tyres with just a track pump, as my experience has generally been rather a struggle, often ending up with resorting to a petrol station air compressor, or taking it to the bike shop. Clearly, with the right lucky combination of rims, tyres and rim tapes, it just works! Then I had to take the valve cores out again to introduce sealant - I use Stan’s Race Sealant which says in the instructions not to inject through the valve stem, which I always ignore - and it works brilliantly, including instantly sealing punctures on my very first two rides with these tyres, so I didn’t even have to stop!
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