Bicycle Quarterly advocates fat tires: they consider 28 mm excessively narrow, let alone 26 mm. But by the standards of MDR these tires are fatties: most riders were using 23 mm tires. As the VeloNews test showed, fatter tires smooth out bumps even at the same pressure as thinner tires, but the advantage of fatter tires is you can run them at lower pressure for the same tire deflection (and pressure of the bead on the rim) and so can gain considerable further reduction in shock transmission from the lower pressure. So I was interested in going against my inner racer and running these tires at lower pressure than I've used before: only 80 psi.
So despite the $66 price tag (on which I get a 10% discount as a member of the San Francisco Bike Coalition), fairly pricey for a tire I'd use for anything short of racing, I decided to take the plunge.
As with all thins which go on my bike the first thing I did was weigh them. Fatter tires tend to be overbuilt for puncture resistance, since it's assumed their users aren't interested in either rolling resistance or weight. Partially due to Jan's influence, however, the Grand Bois range is built for speed as well as comfort, however, and so I wasn't surprised when for their width the weight came out to be a very competitive 241.5 grams on this sample:
I then mounted them on some clincher wheels I picked for the tour. Each had Velocity Aerohead rims which I've not found to be particularly tight. Despite this, and despite the fact my front rim had VeloPlugs instead of rim tape (in theory allowing the tire to settle deeper into the rim), it wasn't easy mounting these tires: I had to use my tire iron for the last bit. But once I did so they popped right into place.
I was using a Challenge latex tube for the front wheel, a Ritchey butyl tube for the rear. Latex tubes don't patch quite as easily as latex, so I was hedging my bets with using the single latex tube. The latex tube worked out fine, so next time I'd run the Challenge tubes front and rear.
I gave a quick spin on the road in front of home with my wheels with my 23 mm tires with whatever was left of the 100 psi I'd pumped them to at some point in the undocumented past, then put on the wheels with the 26 mm Grand Bois tires on and repeated the test. The difference was striking. I'm sure Jan would claim the massive shock transmission of the 26 mm tires sapped the strength straight out of his legs, but by my standards the improvement in ride quality was palpable. I wondered if I'd ever want to go back to 23 mm except for when I use tubulars, which is only in races.
Once concern with tires larger than 25 mm is brake clearance. This simply wasn't an issue on my Ritchey Breakaway with Rival brakes. There's plenty of room.
Another concern with fatter tires is sluggish cornering. The profile of the Grand Bois Cerf is what I'd describe as parabolic near the contact point: a relatively tight radius. I've used other tires with flatter profiles and you really feel the width of the tire. However, these tires cornered as well as my 23 tires, from what I could tell.
So I set off on the tour. I wish I could describe the silky smooth ride the tires provided, but the reality is that I quickly took them for granted, and on the relatively rough pavement encountered during parts of the route, I felt not only discomfort in my unpadded saddle (to be expected I suppose) but also through the handlebars. Of course the discomfort would have been worse with high pressure, narrower tires.
The Cerf tires have been said to be prone to puncturing. However, during the 370 mile tour we went over a glass-strewn highway shoulders, through potholes, and I even went "off-menu" for a 7 mile dirt and gravel road. At the end I don't even see a nick on these tires. Maybe I was lucky.
Coastdown contest early finishers, photo taken by winner, Alan Armstrong.
In Bicycle Quarterly Jan likes doing coast-down tests for checking rolling resistance. Our tour had our own version: on a hill outside San Luis Obispo it's traditional to have a coasting contest: one stomp of a pedal then it's into a tuck for the often slow speed ride until momentum runs out. Obviously excessive rolling resistance would be a disadvantage on this test, while body weight is an advantage in overcoming wind resistance. Everyone finishing ahead of me was heavier, and all of the light women finished behind me on this contest, so from this there's no indication my 26 mm tires at 80 psi added any substantial rolling resistance.
There were only a few nontrivial descents on the tour, but even with the cross-winds I had no handling issues on these. I once had serious stability issues riding 28 mm Michelin tires which have a different shape than these tires.
A second highly nonscientific test happened today, where I commuted to work for my first nontrivial ride after MDR. I rode SF2G Bayway, where I traditionally put in a good effort on Cortland Ave to check my fitness. I took 4 seconds off my Strava-best time on the hill, reducing my PR from 57 to 53 seconds. Of course last weekend's tour played a role here, but it's safe to say the wide tires or the 80 psi pressure don't seem to be slowing me down much. And for the rest of the commute the smoother ride on familiar roads was familiar.
So I give them a very positive review. The only disadvantage is they're on the tight side, so I'd not want to have to change a flat on the road with cold fingers, especially if I was under time pressure. But hopefully the wider tires make a pinch flat, at least, less likely. So these tires are a keeper.