650B, Is It For Me?

Background

I've been curious about the 650B wheel size since first learning about it via the iBOB and Kogswell email lists. My initial impression was that a 650B conversion done on an old tight-wheel-clearance racing frame was a neat way to repurpose the bike by giving it clearance for wider tires and fenders which it otherwise lacked. Many folks have offered the opinion that the 650B wheel size represents a "holy grail" of sorts, combining the best attributes from 700C "road" wheels and 26-inch "MTB" wheels. Several 650B-specific models of new bicycles have come on the market in the past couple of years, along with many framebuilders taking orders for custom frames spec'd for the 650B wheel size. I finally decided that enough was enough and -- wanting to see what all the fuss was about for myself -- I recently converted my 1993 Bridgestone RB-1/7 from 700C to 650B. I swapped the original 700C wheels and 23mm Continental tires for a 650B wheelset comprised of Velocity Synergy rims, Shimano 105 hubs, and Rivendell's Nifty Swifty tires. The original Suntour Superbe Pro short-reach brakes were replaced with Rivendell's Silver super-long-reach brake (re-badged Tektro R556 with upgraded KoolStop brake pads). I changed the SKS P35 fenders for a set of wider P45 mudguards. Today I spent 75 miles on the bike, and these are my impressions.

Tires

The 650B tires used in this conversion measure approximately 33mm in width and leave about 3/16-inch of clearance at the RB-1's chainstays. Wider 650B tires exist, but chainstay clearance would be an issue with this frame. This in itself is interesting, since the limiting factor for wider 700C tires with this frame was brake-arch clearance, yet with 650B wheels it is chainstay clearance. In fact, despite installing fenders, there is still excess clearance under both brake arches, implying that taller tires could be fitted (if such a thing existed). The road manners of these tires reminded me very much of a set of 26-inch mountain bike road slicks I've used in the past: Performance Bicycle's Forté City ST MTB tire. The tires don't seem excessively heavy and I didn't notice any large differences in acceleration or rolling resistance between these and the previous 700C Continentals. As expected, road bumps and irregularities were better absorbed with the wider tire. Trackstanding was perhaps slightly more difficult with the wider 650B tires due to the increased pneumatic trail. Overall, the experience of riding a wider tire on the road felt similar to riding my cyclocross bike with its 700x35 hybrid-type tires on pavement -- bump absorption and ride qualities were comparable. I should also mention that neither before nor after the 650B conversion was foot/fender interference (TCO) an issue.

Brakes

The Silver brakes were easy to install and set up. Although I didn't toe the brake pads, no squealing was evident. As others have written, these brakes do seem to flex more than the stock calipers, presumably due to their increased caliper-arm length. Confidence in stopping power is somewhat diminished as a result. The special quick-release mechanism employed on these brakes does allow them to open up enough to facilitate removal of wheels fitted with wide tires.

Handling

The handling qualities of the RB-1 weren't significantly affected by the change in wheel size. Generally speaking, the bike rides the same with 650B wheels as with 700C. The effort required to ride no-handed wasn't significantly changed. With 700C wheels, a full Banana Bag strapped to the handlebars of this bike tended to produce a front-end shimmy at moderate speeds (10-12mph); this was unchanged with 650B wheels as well. Although the BB height dropped by a full centimeter (268mm down to 258mm), the bike's new lower center of gravity was undetectable. Two negative characteristics were introduced: First, the bike felt a bit less stable overall during the first few miles, although this sensation diminished notably during the course of the ride. Second, the bike seemed to want to "turn in" during fast sweeping descending curves -- before the conversion, the bike was less willing to turn, requiring great concentration to maintain a line through a curve; with 650B wheels the bike seemed to want to "fall in" to the curve, requiring focus to keep it from doing so.

Conclusions

I'll admit I've been skeptical of the whole 650B phenomenon. Several people have opined that 650B wheels/tires offer some sort of magical carpet ride, yet I've maintained that good quality, wider tires should offer less rolling resistance and (obviously) a smoother ride (than skinny 700C tires) regardless of their diameter (within limits of course). My experiences with my own 650B bike reinforce this argument, with ride qualities -- at least in the "plump equals smooth" department -- reminiscent of both 26-inch and 700C bikes I've ridden with similar-width tires. Converting this bike offered no mystical revelations for me; the sole pragmatic advantage is that I can now fit wide tires and fenders, the benefits of which are immediately explicit. Would I perform this conversion again? Probably not. The money that I spent on replacement wheels, tires, and brakes equals the cost of a quality used frameset and also approaches the cost of a budget new frame -- in other words, I could've just as easily purchased a different frameset with improved clearance for wide 700C tires. Also, as I mentioned my RB-1 now sits a centimeter lower -- this means that I could actually move up to the next size frame since the standover height has been decreased. In other words, if I was going to 650Bify a bike, it would've been better to start out with a frame that was slightly too tall so that the resulting bike ends up properly sized, post-conversion. That said, I'm going to leave my RB-1 in 650B-mode for the time being...those wide tires come in handy for the potholes, ruts, grooves, and streetcar tracks in the city streets I've got to traverse to get to the good riding in the country!