To 700C or 650B, that is the question

A post on the BC Randonneurs forum,  now included in the online newsletter, from the often humourous pen of Kevin Bruce, claims to be the last word on the 650B versus 700C wheel debate. Kevin knows better than to claim the end of any debate on bike parts and this particular argument will have legs (or wheels) long after the most resilient have DNFd on the subject.

I also own both ERTO designations (650B & 700C). I hate to be contrarian (ask anyone!) but I must attempt to diffuse (or add to :-)) the confusion on this issue. I strongly disagree with the presumption that Kevin Bruce’s list is an exhaustive comparison of the virtues and limitations of the two standards.

First, perhaps I was mistaken, correct me if I’m wrong, but I was under the impression that Kevin’s bike (a Rivendell Blériot) had been built with 650A wheels, rather than 650B?

The all-important area on any bike, independent of wheel size, occurs at the point of contact with the road. Next, and in tandem so to speak, the road surface itself comes into play. Here’s where Harold Bridge’s comment about tubulars has relevance because I don’t think there’s argument that a high pressure silk on a smooth wooden track isn’t the ultimate ride … but randonnées don’t include much riding on velodromes.

Those of us who have been riding and comparing the new 650B tyres on real-world roads have been almost universally taken with the virtues built into the tyres modern developers are trying to emulate from  their predecessors—the hand-made “demi-balloon” tyres of pre-paved France. Especially impressive so far has been the 42mm Grand Bois “Hetre,” which have been spotted on several brevets this spring. Acolytes of 650B are now eager to try Kirk Pacenti’s 38mm “Pari-Moto,” built on completely new casings (127tpi for black, 67tpi tan-sidewall).

So, my point in relation to Kevin’s first claim is that 700C doesn’t necessarily hold the high ground on speed. On bad surfaces, the combination of 650B wheel clad with high-quality rubber will roll much more easily. It doesn’t take a scientific degree to understand that on surfaces like chip-seal, a narrow, high pressure tyre will waste energy bouncing, while the larger, lower-pressure tyre will move forward. Hetres on chip-seal have to be experienced—the buzz just disappears, not only without loss of speed, but with a gain.

I won’t go into the minutia of contact patches, tyre pressure and width, but I encourage those who’ve read this far to research the issue, which might dispel some of the more persistent folklore.

Agility is a rather subjective area, but again a narrow tyre bouncing over potholes and bad paving feels rather tentative in my experience. The degree to which one can relax on bad surfaces compared to the danger-dodging necessary with narrow tyres must be experienced first-hand. It just transforms a ride.

I would agree that climbing feels more immediate with a light wheelset and high-pressure tyre, but I don’t know if any real side-by-side comparisons have been done, besides the rolling-resistance tests detailed by Jan Heine in Bicycle Quarterly (Vol. 5, No. 1). For instance, my titanium rando bike with featherweight wheels is my choice for sprinting up hills, but that bike weighs more than 10 pounds less than my 650B bike. On long brevets, I fit the titanium bike with heavier wheels and wider tyres—for comfort, safety and durability.

Again, climbing and descending (not to mention cornering!) are all predicated on road surface.

The 42mm Grand Bois “Hetre” tyre on a 650b rim results in a total circumference around 207cm–within a couple centimetres of a 700c rim fitted with 23mm tyres (210).

But it is the last claim I must refute most strongly. You can’t have it both ways (well you can with 650b) because girls, as Kevin put it, tend to value carrying groceries and generally have more refined aesthetic sensibilities. Witness the explosion of cycling-style websites and magazines. All generalizations, I know. But while us dudes tend toward buffed titanium and the dark mysteries of carbon fibre (as well as arguing over grams and millimetres) I believe that women often relate more closely to the innate sensuality of the bicycle.

At any rate, I can’t ever remember any of my 700C bikes attracting attention from the opposite sex. My 650B Blériot however, is a veritable “chick magnet.”  I am planning a new one. I anticipate it will again be the bike I ride most, because it will incorporate characteristics that most people find most conducive to riding swiftly in comfort … and style.

Confrerie des 650B | Copenhagen Cycle Chic | Cycle & Style | Let’s Go Ride A Bike | Women’s Cycling | Sheldon Brown on Tyres | Inflation Guide | Fix a Flat

Tagged as: 650B, 700C, harold bridge, kevin bruce, tires, tyres, wheel size