This tyre is named for Minnesotas own Almanzo 100 (and related events) held in Spring Valley, every May. The Alamanzo 30 and 33 Open tubular is a clincher-style tyre that is fully handmade. This tyre is ideal for maximising speed on dry, relatively firm surfaces. There is no vulcanising to stiffen the rubber compounds; the tires are fast, grippy and supple for a smooth ride with pinpoint steering and maximum traction, even in the climbs. A thin, hand applied flat-protection layer (Challenge PPS) adds some security without sacrificing weight or ride quality. The folding bead makes them easy to carry. Pair this with Challenge's latex tube for the ultimate in gravel racing performance.

Challenge OPEN TUBULAR
The open tubular construction differs from that of a standard clincher. The open tubular is first constructed exactly like a tubular, using the same materials and technology. But instead of its casing being sewn together with an inner tube inside, the open tubular is produced flat and beads are formed by folding the sides of the tubular casing around aramid fiber threads.

The supple ride of an open tubular provides performance and comfort similar to that of a tubular; excellent traction and cornering, low rolling resistance and excellent shock absorption. If combined with a latex (instead of butyl) inner tube the ride becomes even closer to that of a tubular. The open tubular performs like a tubular, but is conveniently mounted as a standard clincher tyre.

Challenge open tubular vs. traditional clincher
Open tubular construction differs from that of a standard clincher. A classic clincher is put through extreme heat and pressure when vulcanized (or cured or hardened) into the U-shape that you see when it is fit on the clincher rim. This system makes the classic clincher tyre stiffer so it bounces when it hits bumps in the road and has a harder feel. This stiffness translates into higher rolling resistance and more road shock passed to the rider. It also tends to corner poorly, as the harder rubber has less grip over imperfections. People, however, may often choose clinchers for their longer lifespan tread due to the harder, more durable rubber.

The open tubular is ‘a whole different animal’ to a standard vulcanized clincher, offering incomparable quality, benefits and construction. Even a simple width-to-width comparison between the two is not easily or comparable. An open tubular is made using the same processes as a tubular. The natural rubbers and latex used in the tread and casings are soft and supple. When the open tubular is finished it has a flat shape (laterally) so the tire only takes a rounded O-shape when it is fit into the two clincher rim hooks. The open tubular is more supple and deforms easily, conforming to the terrain and absorbing and softly rolling over road shocks. The lower rolling resistance means a faster, smoother rolling tire that absorbs vibrations. The softer natural rubber tread will grip road imperfections better, resulting in extremely safe cornering, like a great Formula-1 tire, on either wet or dry road conditions.

Challenge PPS ‘Puncture Protection System’
A special puncture resistant fabric is placed between the tread and casing to increase the tires’ puncture protection. Some tyres receive a second layer of PPS as a lining in the casing and designated as 2xPPS or Double PPS.