Best of Both Worlds or Complete Hype? My 650b Experience So Far...

Back in September of last year I bought my first new bike since the I built up the Spider in 2008. Our second child was due a couple months later, and with him would come a lifestyle switch to a single-income family with two kids.  So I knew this was probably my last chance to make a major bike-related purchase and pulled the trigger on an Ibis Mojo SL from Competitive Cyclist.

The Special Blend build was within my already diminishing budget, and I planned to swap out some of the shadier components (brakes, wheelset, seatpost, saddle) with high end parts from my Spider.  At the end of the day, I was thrilled with my choice.  Here it is before it ever touched dirt:

And here it is on its first trail ride on my local loop at Black Mountain:

It was love at first ride.  It climbed just as well as the 4" travel Spider, but the extra 1.5" of travel made the rocky downhills of Black Mountain a ton more fun.

In addition to the price and the timing, another motivating factor for buying this particular bike was that I had read online that I could retrofit it at some point to accommodate 650b wheels.  That versatility intrigued me, but for eight months I simply enjoyed riding it with the 26" hoops and had no complaints.

Then early this year 650b-mania began sweeping the nation.  Virtually every major bike manufacturer announced plans to release a 650b bike, and the internet hype began to really build.  Since I already had an interest in the issue, I was far from immune to the growing demand for this purported "best of both worlds" wheel size.

My curiosity was tempered significantly by my extremely tight budget, but that didn't stop me from dreaming (or scheming).  Then in late May a Craigslist alert I had set notified me of a guy selling a brand new 650b wheelset not far from my house.  It was an OEM wheelset from Focus bikes, and included brad new Schwalbe Racing Ralph tires and a 10 speed cassette that just happened to match the drivetrain I was currently running.  The price was very reasonable and it seemed like the perfect opportunity to see what all the excitement was about.

After doing a ton of internet research I confirmed that with the right size tires and a small shim to the rear shock, running the bigger wheels wouldn't be a problem.  I enlisted the help of my buddy Billy ( great guy and wrench extraordinaire) with the shock shim.  He installed a small rubber plumbing washer in the X-Fusion shock, reducing travel about 5 mm to ensure that the larger rear wheel wouldn't rub against the seatstay when the shock was fully compressed.

He also asked permission to spray a thin coating of plastic-like protectant over the back of the lower rear triangle and bottom of the frame to protect the carbon from damage if any rubbing should occur.  I signed off, and I think it was a good idea in the long run.  The protectant itself is underneath and virtually invisible, but provides a great additional layer of protection against scratches and rubbing on the carbon.

Front tire clearance with the X-Fusion Velvet fork was a non-issue.  There was plenty of room.  Rear tire clearance was another story, with only 2-3mm of clearance between the 2.25 Racing Ralph tire and the rear triangle.

As tight as it was, I decided to give it a shot and set about getting some rides in.  My first ride with the new wheelset came after a six-week period of time where I had been completely off the bike because of a spate of family illnesses.  So I wasn't expecting much in terms of improvement in my actual riding times, but was very curious to see if I noticed a significant difference in feel as I rode my local Black Mountain loop.

Here it is before that first ride.  Not noticeably different visually save the larger wheels...

Whether it was psycho-somatic, the result of giving my body some rest, or actually new hoops, my first ride with the 650b's was a PR fiesta. Climbs, descents, flats I set personal bests on virtually all of the important segments of the trails that I had been riding regularly for years.  And I had a blast.

There were a couple of times where I did notice a tangible difference with the larger wheels, both positively and (perceived) negatively.  On the rocky technical climbs and flats of the Knoll loop in Santa Luz it felt like the 650b wheels rolled significantly better through the chunk.  Same thing on the rocky descents of Miner's Loop at Black Mountain.

At the same time, I felt a bit of a penalty as I grinded up the fire road toward the summit of Black Mountain on that first ride, since the gearing of the bike hadn't been changed to accommodate the larger wheels.  With that being said, I posted my third best time on that climb during that first ride, despite having been off the bike for six weeks and having diminished fitness.  (Also, I subsequently set a PR on that climb with the bigger wheels less than a week later, so despite having to work harder I think the 650b's actually helped overall rather than hurt.  I just needed my fitness to fill the gap created by the more difficult gearing caused by the bigger wheels.)

Over the next few weeks I began to really enjoy riding with the 650b's.  Rear tire clearance was never a problem, and I really enjoyed the improved roll-ability in technical situations.  At the same time I couldn't really discern any negatives to the larger hoops.  I'm not a huge jumper, so the oft-mentioned "flickability" concern was a non factor for me.  I still enjoyed getting air off the little drops on Miner's Ridge at Black Mountain and actually felt more confident in my handling overall.  Cornering and accelerating felt the same or better than with 26" tires, in fact I actually felt the 650b's gripped somewhat better than my old wheels.  (That could partly be due to the tires as well, as the Schwalbe Racing Ralphs were a huge improvement over the Kenda Nevegals I was running on the 26" wheels.)

As I examine my Strava times over the last two months of riding with the bigger wheels, they've consistently been better than those with the 26" ones. So the proof is somewhat in the results.  I'm a fan, and don't see myself going back to the smaller wheels anytime soon.

My only real problem with the new wheelset had nothing to do with its size.  The 650b rims I purchased were not tubeless, and I had been accustomed to running tubeless tires for the last five years.  Over those five years I had gotten exactly zero flats.  All hail Stans sealant I guess.  I also ran those tubeless tires at about 22-25 psi most of the time, which I believe gave me a better feel for the trail beneath me and improved traction.

On my first 7 rides with the tube-utilizing 650b wheelset I got five flats.  Two were from goat heads or artichoke spines over near Black Mountain and three were pinch flats from running them at too low a pressure.  It was brutal. So I started running them at 38-40 psi because I was so afraid of more flats and my budget for tubes was shot.  But that made them feel squirrely and resulted in poorer traction which I didn't appreciate.

So about a week or so ago I finally converted the 650b rims to ghetto tubeless with the help and counsel of a new friend, Geoffrey.  Amusingly, I converted the front tire first and then ran out of time and Stans, so I waited a couple days to do the rear.  Before getting around to converting the rear tire I went for a ride, and surprise surprise, pinch flatted. After a dumpster fire of three destroyed tubes, I actually ended up walking about two miles home pushing the stupid bike the whole way.  I converted the rear tire to tubeless the next day.

That little episode also illuminated another potential shortcoming of the 650b wheels, at least in my specific situation.  I don't know whether it was the hard bump that caused the pinch flat or walking the flat tire home over two miles over asphalt and concrete, but when I fixed the tire and put it back on the bike I realized that the wheel was slightly out of true.  Under normal circumstances it wouldn't have been anything to worry about, but since I have such a small amount of rear tire clearance on my converted Mojo, that little bit of wheel wobble was enough to cause the tire to rub slightly against the rear triangle on every rotation.

I had the wheel trued by Chris over at Black Mountain Bicycles, who did it quickly and well, so now there's no more wobble and no more frame contact.  But if that had occurred in the middle of a long ride and the damage had made the wheel even more out of true, I can envision a situation where I could be in a little trouble.  As I mentioned above I have that spray-on protectant on the area of the bike where the contact occurred, so no damage was done to the carbon frame itself.  But it gave me something to think about in any event.

So that's the saga of my 650b conversion.  The bottom line is that I'm a fan and plan to continue running the bigger wheels indefinitely.  The only drawbacks in my case are derived from the fact that I'm riding a converted Mojo SL rather than a bike specifically designed around the 650b wheels, but so far I think I've mitigated those issues as well as I can and am enjoying the advantages enough to keep using them.

Feel free to post any questions or thoughts in the comments.