It's probably best to stick with a 23mm, and by the way, the 23mm EVO KS is the best tyre I've ever had (I haven't yet tried the other top quality Vittorias) -- I can't believe how much better they are than all the other 2nd or 3rd rung 23mm tyres I've had. They are also rated to 145psi, which is more than most other leading brands (except for Vredestein), just in case you wanna whack a bit more air in
Even though most of the research says that 23mm tyres are the fastest over most road surfaces, the issue is still a little clouded when it comes to time-trialing and track riding. For "normal" racing, 23s are clearly superior.
Some people claim that if you're doing a time-trial on a very smooth road, the weight and aerodynamic advantages with a very light 20mm clincher (tubulars are a different story)
could be a better choice....but I dunno.
Narrower tyres are meant to be inflated more for optimal deformity, so, the theory is, that unless you're riding on the smoothest of smooth roads, the slightest roughness will bounce you upwards when on a very hard tyre, which obviously slows you down. A slightly wider, slightly softer 23mm will absorb more road roughness, and not impeded your forward movement.
So, harder, narrower tyres feel faster because they bounce you all over the road, but they're not.
If you hunt the net, you'll find plenty more info.
Here are some comments from Lennard Zinn from Velo News in the tech Q&A:
"
Dear Lennard,
I'm a light rider who has always used high-pressure 20mm wide clinchers for training due to their low rotating mass and rolling resistance, However, I'm finding that it is becoming increasingly difficult to find anything but 23mm tires. A local bike shop salesman told me that this is due to the current thinking that a 23mm profile and lower pressures (I usually run 140psi) actually result in lower rolling resistance. I've heard similar comments before, possibly even in your column. Is this true?
It seems counter-intuitive; I would think that with a given tire construction and pressure, a wider cross-section would simply mean a wider contact patch, which should determine rolling resistance. Similarly, I would think that with a given tire construction and size, a lower pressure would mean a larger contact patch, and, therefore, increased rolling resistance. Extrapolating the "wider and softer is better" logic, we should be seeing Lance in the Tour riding balloon tires pumped up to 20psi. Am I missing something or is this a fashion trend?
Langley
Dear Langley,
It entirely depends on the road surface. If it is chip sealed and you ride with a 19mm tire at 140psi, there is no question that you will have higher rolling resistance than with a 23mm pumped to 90psi (assuming that both are high quality high-thread-count tires). Every time you deflect the bike and rider up and back, it costs you energy, as opposed to absorbing the gravel hunks into your tire. This is the same reason that suspension makes a mountain bike, car or motorcycle faster on rough terrain. If you are riding on a smooth track, by all means use a 19mm tire and pump it up to super-high pressure.
http://www.velonews.com/tech/report/articles/5537.0.html
"Dear Lennard,
I've been reading some of Zipp's comments on tire pressure and rolling resistance attached below. When you really sit down and talk to them about tire pressure they're recommending pressures of 100-120psi (sometimes less) depending on the tire, casing, and environment. I am including comments from Josh at Zipp on this topic. One thing I quickly noticed was the absence of weight in his recommendations. A larger rider running 120 psi compared to a lighter individual (say 30 pounds difference) would exhibit a larger contact patch (resistance or traction however you look at it) due to weight so I'm really not jiving on his basic psi recommendations.
Leaving road conditions out (rain, etc.) what are your thoughts on tire pressure? The common theme of tubulars is the advantage of both weight and tire pressure. The ability to run pressures of 180-200 psi. I know for myself I feel faster (have never tried to test this with rollouts or anything) when running pressures of 140-160 psi (clincher) and 180-200 psi (tubular). I've ridden a number of tires and prefer the ride of higher psi tires such as Vittorias, Vredestein and Tufos.
Do you know of any numbers or tests that prove these thoughts on tire pressure? I've had a number of lengthy conversations with Biomechanists interms of rolling resistance (friction) and don't know how a general recommendation on lower pressures can be faster especially not taking weight into account. It goes against everything I've read about rolling friction. It's pretty easy to point out that the average pro in the peloton only weighs about 150 lbs., so of course it's common sense that they wouldn't need to run similar pressures as you or I, but 100-120 psi seems a bit low when you're talking tire pressure for the most efficient rolling resistances.
I've also been reading your blurbs about tubulars, Tufo and their clincher tubulars. Taking Zipp's tire pressure recommendations in mind where do you stand in regards to Tufo and their clincher tubies and other high pressure tires?
Tom
Dear Tom,
I agree with Josh, and yes, there are lots of test numbers to back it up. It is the same reason a suspension bike (or car) is faster over rough ground - less mass must be accelerated when bumps are encountered, thus saving energy and reducing momentum loss. Every little bump that gets absorbed into your tire (another reason that supple, handmade casings roll faster than stiffer, low-thread-count casings) is a bump that does not lift the entire weight of you and the bike.
You feel fast on a rock-hard tire for a similar reason that people like the feel of stiff brakes (V-brakes with the levers set on low leverage). The brake feels good and stiff because you are doing more of the work. If you increase the leverage, the brake feels spongy, because the extra mechanical advantage allows a modest pull to squish the pads.
When you ride a tire at 170psi, the bike feels really lively and fast. That is because you are being bounced all over the place by the surface roughness of the road. However, every time you are bounced, energy you applied to the pedals to get you up to speed is lost. Also, you have less control of the bike, so it feels like it is going faster, even though it isn't. Ever notice how driving down the highway at 75mph in an old Jeep feels crazy fast, and you can cruise smoothly along at 100mph in a nice Saab or BMW and feel like you are going maybe 60mph unless you are looking at stationary objects passing by?
There is simply no question about it; rolling resistance tests conducted with bicycle tires rolling over surfaces akin to normal road surfaces always indicate the lowest rolling resistance at pressures a lot closer to 100psi than to 170psi! Years ago, for example, I saw results like this at the Continental tire factory. I was told of similar results at a number of other tire factories I have visited.
http://www.velonews.com/tech/report/articles/7508.0.html[/QUOTE]
