Challenge Criterium Nerone Clincher Tires
Our first order of business after taking the Challenge Criterium Nerone Clinchers out of their boxes was throwing them on the scale. Light tires should be light. These look light. They feel light. One came in at 227g, the other at 216g.
We scratched our heads a bit. Advertised weight is 210g for these 700c x23mm tires. Even if tires (even if all manufactured goods) have weight variation due to manufacturing processes, we want to see +- 5%, not +8.4%. We know that Challenge expects +/5%, so the overage wasn't the best start to our test. Of course, since it's a race tire, we expect to ride off some of that tread pretty fast.
When we regained our senses, we knew that a few grams of tire weight isn't everything. Rolling resistance, and the lack thereof, is really important as well. More important, in fact. Would you rather save 17g or 1w? We'd prefer the watt, even on a spinning wheel, even if it is 34g on two spinning wheels.
We downloaded the last CRR (coefficient of rolling resistance) data on Bike Tech Review to see how these Challenge tires roll compared to others. Pretty good, at 13.4w of drag at 25mph with a 100lbs load and latex tubes. But it falls short of amazing. Playing with the paper thin, supple, casing, we hoped for better. We figured it should be close to the Veloflex Record, which uses a similar construction. The Record uses only 12.1w. But then we looked closer and saw the Record measures 21mm and weighed in at 130g. The tread probably disappears after a century. The still-light Veloflex Pavé, which is 180g, with a butyl tube gave a whopping 18.5w of resistance. The Michelin Pro 2 Light with latex tubes came in at 12.5w of resistance for the same parameters. But it's a different construction. Besides a different casing, the Pro 2 Light doesn't have a belt under the tread, which is something the Challenge possesses.
The belt could add to rolling resistance by stiffening the casing under the tread. The Nerone uses a single-ply 300tpi strip of corespun polyester, the same material as the casing, and it is placed on the casing when the casing is inflated to minimize stiffness.
The numbers get fascinating and lead to single-minded thinking. We have to remind ourselves that this data were produced in the world of a smooth roller, not the world of pavement. Maybe it can help you win a roller race, but going farther with less energy on a wide variety of road surfaces can be another story. A 21mm tire should have more resistance on a road due to the size and shape of the contact patch. Roads, possibly more importantly, are uneven, and a tire conforming to the road rather than bouncing off it can make a huge difference in real-world rolling resistance.
The Challenge tire rep told us that we could run the Criterium Nerones at 5-10psi over the pressure we're used to running and get a much better ride yet. Ever since we tested Continental GP 4000 tires , we've been running our tire pressure between 100 and 110psi. His thinking is that with the supple casing of the Challenge, the tire will still have great, comfortable, road-hugging deflection at the higher pressure, and the higher pressure will reduce rolling resistance. Something the BTR study doesn't take into account. Further, if run at the lower pressure we're used to, the grip could be better than other tires at the same pressure.
This is an idea that has been around for a long time. As your casing gets more supple, you can run higher pressures; it has the ring of truth. The tech people we discussed this proposition with believe it is a reasonable assumption. Testing it in a lab is pointless because the road can't be replicated there. If people want to try this out, it has to be done in the field.
And the field has to be extremely specific. Like the road you're going to race on. We're told in order to do a field test, you want to make repeated runs on the race course at different tire pressures. The tire pressure at which your bike seems to start bouncing is the one that is too high. You want to be just under that. We were pointed to Tom Anhalt's test he published on Slowtwitch as an example of how to do such a test. The results of Anhalt's test also seem to demonstrate that a high thread count clincher can indeed roll better at higher pressures. The bad news is that at the point your pressure is too high you'll initially think you're actually going faster.
While .9w on a smooth roller is a measurable difference and one that can add up to something significant over time, we tend to believe that the real-world impact is probably barely measurable; if nothing else, few of us are fastidious enough to always run the ideal tire pressure for the riding conditions.
The impact is negligible especially when the rest of the tire seems so right. The Nerone has a black casing, hence the name, and a carbon-black tread. Everything seems to indicate this rubber grips very well. The 300tpi casing has latex brushed on the sidewalls to lengthen the life of the tire. When the tire is new, the sidewalls look shiny, but they dull to a matte finish after a few weeks of regular riding. The tread is the classic Clement Criterium tread, with diagonal sipes on either side of a slightly raised center section of longitudinal sipes. While we doubt that the tread grips better than a "bald" tread, and we've been told the tread isn't directional, we lined up the tread so that it could be gripping the ground if it is directional. The bead is folding and is easy to stretch over our clincher sidewalls.
After we pumped the tires up and ventured out on our first ride, we saw something we loved. The Challenge logos that are on either side of the tread at one spot are noticeable as they spin past our line of sight on the front wheel. We love this effect. It reminds us of tracer bullets in a flight simulator video game and gives us a visual cue of our speed. It was a fun distraction for our first several rides.
We also noticed the ride right away. It is excellent. That we noticed this so quickly is most likely due to the fact we were riding heavy training tires before the switch. It might be us imagining things, but we seemed to feel the difference most when we stood on the pedals. The bike felt faster underneath. Hard cornering felt really good as well.
We rode the Nerones some in the rain. We didn't ride any differently than we usually do, and noticed no sliding. We also didn't experience any tread or casing cuts or nicks.
Riding high performance tires in winter is not generally our idea of a product of smart thinking. The road conditions around here generally get worse in the winter. They're cleaned less, patches and even good pavement gets ripped up, so the risk to tires increase. This risk goes up as the mercury takes a dive. Flatting on a cold day is never a good thing, and it's mean to force your friends to wait. So we rode somewhat carefully, dreading the day our luck would run out. Even with this care, we did find ourselves riding over glass and sharp gravel on several occasions.
After many weeks of riding on Nerones in deteriorating conditions, we haven't had a flat. It's a great thing as we've done a number of sub-freezing rides. Nor have we seen the tread disappear. While we don't think the Nerone will necessarily work as a high-mileage training tire, we've already ridden several hundred miles on the tires, which says to us it is also not a low-mileage race tire.
It's time for us to clean the Challenge Criterium Nerone Clinchers tires and retire them until spring. But we're hoping for a warm spell so we can ride a few more days on lively tires, before we re-install the ride-deadening qualities of our winter tires.