A few months ago we first heard about the reTyre system for bicycles, in which interchangeable tread "skins" can be zipped on and off of a smooth underlying base tire. Well, its Norwegian designers recently sent us a setup to review, and we think there's definitely some potential to the concept.
Just to recap, reTyre consists of a slick clincher-type tire that stays on the rim full-time, along with different types of treaded rubber casings (known as skins) that can be mounted over top of that tire utilizing integrated zippers along both sidewalls. The idea is that riders could commute on dry roads using just the base tire, but then zip on an all-terrain tread skin when they want to hit the trails, or swap in a studded winter skin when things get icy.
What we received was a set of 700 x 40c base tires along with a pair of the All Terrain skins, which tipped the scales at 1,300 grams (2.8 lb) per tire/skin combo. While the bare tires could fit on either a 700c cyclocross bike or a 29-incher mountain bike, the skins rubbed against the inside of the cyclocross' stays/fork once they were added – we had the same problem with a commuting-oriented road bike.
So, we went with the mountain bike. Getting the tires onto the rims was a bit of a struggle, as they fit quite tight. Subsequently zipping the treads on was pretty quick and easy, although in order to avoid ending up with a big gap between the two ends of each skin, we had to hand-stretch them forward as we were zipping them up.
Once we hit the asphalt, there was an initial squirminess to get used to, as the skins slightly slid sideways against the tires when cornering. And even though we had minimized the gaps on the skins, we could still feel them bump with each wheel revolution – this wasn't detectable on dirt and gravel trails, however.
As compared to conventional fat/soft mountain bike tires, the reTyres are pretty hard (they have to be inflated to a minimum of 45 psi/3 bar) and narrow (the base tire is 1.6 inches wide, with the added skin taking it to 2.0). This made for a relatively harsh ride on the rooty, rocky singletrack, although you'll be glad to know that the skins did stay zipped up.
To that end, we doubt that serious mountain bikers will have much interest in the system in its current form, particularly since they likely never use their bikes for commuting anyway. The company now does offer a wider, knobbier TrailX skin, although the 45 psi issue would still apply. We're told that a lower-pressure tubeless tire is on the way, which may change things – users could then swap between different types of off-road treads, depending on the terrain.
As it is, the system as set up with the All Terrains could appeal to people who use a fairly basic mountain bike to commute during the week, then go out on multi-use gravel trails on the weekends.
The Urban Winter skin, however, could be where the action really is. Featuring 156 carbide studs per skin, it allows commuters to quickly make their tires ice-ready whenever the weather dictates, but then switch back to the smoother-running base tires when the ice melts. And because it has a lower profile than the All Terrain, it'll likely fit non-mountain bikes.
Should that pique your interest, you might be interested in hearing that the second-generation reTyre system is now the subject of a Kickstarter campaign.
Backers can choose between four tire/tread sizes, along with All Terrain, TrailX or Urban Winter skins. A pledge of US$119 will get you a pair of the base tires, with your choice of either of the first two skins – the planned retail price for that package is $261. For a set of tires with the Urban Winter skins, $139 is required (retail $285). Should everything go according to plan, shipping is estimated to take place next March for the former, and in January for the latter.
Source: Kickstarter
The base tire should be the off-road knobby tire and the skin should be the slick road tire. The skin should have an inverse tread pattern on its inner surface that interlocks with the tread on the base tire. This would eliminate the squirming feeling and would also allow a lower psi.