Long Distance Competition/Ultracycling, Randonneuring and Endurance Cycling - Any experience with the Grand Bois "Cerf" 26mm tire?
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04-24-11, 10:10 PM
My new "sportif" frame doesn't quite have room for my favorite Challenge Parigi-Roubaix tires. They fit, but they're a bit closer to the fenders than I like. The 26mm Cerfs should fit perfectly, but after my experience with the Cypres (at least one flat per week) I'm a bit leery of Grand Bois tires in 700c.
Anybody using them?
At a couple hundred grams, they're going to be like the Cypres.
You might want to take a look at the Vittoria Randonneur Pro.
04-24-11, 10:45 PM
I've been using them for several years now. Not sure about your problem with flats. I run the tires 90-95 psi depending on the route and weight I'm carrying, and use Michelin Airstop tubes. I might have one, maybe two flats during the life of a tire. When the rear looks pretty worn, I rotate front to back and put a new one on the front. They feel great and roll as good or better than anything Conti or Vittoria makes. Easy to mount too. So far they are my favorite tires, and I've tried a lot of different tires. One thing I've noticed is that after some time on rough roads, you might see scrapes on the side walls. This appears to be superficial and the casing seems to hold up quite well. Only once have I had a tear in the sidewall, but it still help up well enough that I road on it for a few weeks without any trouble. I haven't kept track, but off the top of my head, I probably get 5000+ miles out of one tire.
04-25-11, 10:01 PM
It's funny: the flat resistance of a particular tire is truly an individual experience. I can say with all certainty that I had one flat every 12 miles for the two weeks that I had the Parigi-Roubiax tires on my bike. Never, never, never again will I pay darn near $70 for a cotton casing road tire.
04-26-11, 09:31 PM
Yeah, that is strange. I've honestly never flatted with one, in thousands of miles of riding. But the GB Cypres I had punctured constantly. One week I had three consecutive punctures; one every day for three days. The rear one eventually exploded; I noted prior to a 200k that the tread was getting pretty flattened, and 100 miles later it had worn through the cords. The front one also exploded after running over something I never even saw. It was cut from one bead all the way around to the other side of the tread. So yeah, I'm a bit leery... but the 650b Hetres have been the most perfect and reliable tires imaginable. So maybe I'll give the Cerfs a try - but I'll be carrying a spare tire with me!
I have to wonder if it's a quality control issue with the Grand Bois tires. I say this based on your experiences as well as mine. I have a set of the 28's, one of which one has been flawless, the other got flats every ride, every tube. All flats happened on the road and none had anything puncturing the tire that I could find. All the flats were happening in the same place so I booted it (glued a patch to the inside wall of the tire) and it's been perfectly reliable ever since. I guess it was the threads in the sidewall were doing the puncturing. Perhaps you got a pair that were similar?
My road rides generally are about 50% dirt road or doubletrack and they've been 100% reliable ever since I booted the front one.
If I'm right that this is a QC issue than you might luck out. I don't know of another 26c skinwall lightweight tire so this may be your only option.
04-30-11, 10:53 AM
That's a very interesting thought. I really to want GB tires to work - when there's air in them, they're fantastic tires.
06-01-11, 02:44 PM
I got a set of these which I used on a 370 mile 4-day bike tour from Los Gatos, CA to Santa Barbara this past weekend. Lots of rough roads, one extended dirt climb (Cypress Mt Drive to Santa Rosa Creek Road), one super-rough descent (Santa Rosa Creek Road). Riding on glass-strewn highway shoulder on 101 approaching Santa Barbara.... I ran 80 psi.
Not a nick on the tires. And even though I had 80 psi to other riders running 110 psi in their 23 mm tires, I did fine in a traditional downhill coasting contest which should be very sensitive to rolling resistance. Everyone who finished ahead of me was significantly heavier.
The difference between these tires and my previous 23 mm tires was remarkable: much smoother as tested right after I mounted them. During the tour I began to take them for granted, however.... obviously they're not going to compete with, for example, 32 mm tires.
But my experience was very positive with the exception that they are fairly tight to mount on my Velocity rims. I prefer tires which are slightly looser to facilitate flat repair on the road, especially in less than ideal weather. But that proved unnecessary.
06-01-11, 07:00 PM
Good to hear. I just fitted a pair to the sportif; but haven't yet tried them out. Thanks for the heads up.
06-02-11, 02:51 PM
Another test: today I rode the 77 km "Bayway" commute into work. There's a hill, Cortland Ave, at the start I like to test myself on. Again I ran 80 psi in my 26 mm Cerfs.... I reduced my Strava PR from 57 to 53 seconds on the climb.
Okay, so I just did a long 4-day bike tour so took some fitness from that. But obviously the tires aren't slowing me down any.
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