Rolling resistance is the energy that is lost when the tire deforms in contact with the road and the rubbing of the rubber molecules amongst each other. There are several ways to make these losses smaller. Narrow racing tires typically use the most advanced techniques to lower the rolling resistance (RR) like more and thinner threads to make a thinner and more supple tire possible and better rubber compounds. For wider touring tires, the tire producers tend to give more attention to puncture proofness and durability. I think I can safely say that the HPV scene is slowly changing this, because there are a lot of geeks among them that like to push the tire producers towards Speed.
Especially velos do not really need the low aerodynamic drag of a narrow tire, because they usually are embedded in wheel arches where they are almost completely out of the airflow anyway. Since a wide tire deforms less than a narrow tire they can have a lower rolling resistance, but only when the rubber compound and the tire casing shows up similar techniques as the narrow racing tire. However, the narrow tire has a last line of defense! It can be pumped up much harder than a wide tire before bursting. A hard tire deforms less in contact with the road, so less RR.
The following question came to my mind: how practical is it to use narrow racing tires on a velo?
To come up with an answer, I have ridden Schwalbe Durano 28-406 on the front wheels all winter long and for a shorter period the most extreme 20" tire on the market: Schwalbe Ultremo 23-406.
Durano: a racy tire but much more durable than it's predecessor the Stelvio (not in produktion anymore). I managed to wreck the sidewall of a Stelvio in one race, but the Duranos' can handle almost anything I throw at them. Almost, for the one thing that took one of the Duranos' out prematurely was heavy braking to the point that I lock up the wheel. The abrasion was too much and the road simply scrubbed right through the canvas, also destroying the tube inside.
|destroyed Durano, the canvas scrubbed through|
As to the riding experience: the Duranos' are fast tires and they give the Mango the smallest possible turning circle, so agility is also better. The feel in corners is very direct, so I know exactly what is going on. Because of the 9,5 bar of pressure I keep in them, they do not bulge under the heavy load in fast cornering like wide tires do, especially when the pressure is down to a very comfortable level. Especially in roundabouts the velo may become a "Gallopin' Gertie" with the loaded front tire hopping up and down uncontrollably until you slow down. I like to go fast in corners, so this all is a big plus for me.
Not related to RR, but the light weight does also contribute to the riding experience, since I do relatively much riding in town. A lighter tire accelerates easier, since there is less rotational weight to bring into movement. Likewise, braking is a bit quicker but as written before, it is wise to not let the wheel lock up completely.
On a sidenote: I have put on lighter wheels with narrower rims to have even less rotational weight. The narrow rim is also better suited to such a narrow tire.
Comfort is of course less than what I was used to, but since the Mango has good shocks it's not much of an issue. I got used to it soon enough, but I do avoid getting next to the road and ride much slower on cobblestones. High pressure in the tires does make the velo noisier as impacts are simply more intense. Despite the high pressure and ensuing small contact patch, there still is a reasonable amount of grip on the road. I was surprised by that, since I had the idea that the high durability (for a narrow racing tire) must have something to do with a hard, slippery compound. Not so: the grip is not much less than that of the wider Kojak.
To make things more interesting, we had snow for a while this winter and one might think that a narrow tire is not good for that. Sometimes it's completely the other way around then you'd expect: the Durano cuts through fresh snow easily and does not have to displace as much snow as wide tires, so riding takes less effort and you stay in contact with the road. The non-driven front tires do not need to give traction, so that is not an issue either.
Apart from the above mentioned flat because of the abrasion of the tire, I had no flats all winter. The thin Raceguard protection that Schwalbe puts in seems to do a pretty good job.
Maybe you have noticed that I put in 1 bar more pressure than Schwalbe gives as maximum pressure. I do so, because high pressure cuts the RR from narrow tires enormously and I somehow have a lot of confidence that the Durano is strong enough, unlike the old Stelvio.
So overall the Durano is pretty practical, be it that you won't like to do dirt trails with it as it sinks away too easily there.
Ultremo: Given the rather good impression I got from the Duranos' it only seemed logical to take it even further. The even lighter, narrower Ultremo tire. The ultimate in the line-up from Schwalbe.
|Ultremo: best kept on the shelve until racing day?|
In all other respects the Ultremo is a Durano on steroids and so far it also seems to be strong enough. Only the pressure that is needed to keep this tire going good, is enough for me to completely disqualify it as a practical tire. If you seriously want the max in speed however, this is it.
As you may know, I have an enormous collection of YouTube vids. Here is one featuring the Duranos:
Don't forget to alter the setting on the bicycle computer:
circumference Durano @9,5bar=146cm
circumference Ultremo @11bar=144cm