In October 2011, the Yokohama Rubber Co. Ltd. became the first mid-sized tire company to enter the airless tire space. At the “Good Design Expo” in Tokyo the Japanese tire maker revealed its version of a non-pneumatic tire named “Youmyaku”. The unveiling of Yokohama’s airfree tire was surprisingly low key though as it was simply presented as part of Yokohama’s “nature design” series of concept tires. Unfortunately, little further information emerged following the initial unveiling and none of the company’s English press releases make reference to the development of an airless tire.
The tire, a 225/40R18, is reminiscent of other airless concepts such as the Tweel or the Bridgestone airless tire: its design consists a series of load bearing ribs/spokes which relay the bead area to the tread. However, there are several features which set the Yokohama design apart from other airless designs:
Firstly, the Youmyaku is a very low profile tire. Compared to the Tweel, the Youmyaku’s loading bearing ribs are very short thereby having reduced capacity for deflection. Making this tire absorb road defects and tuning it for ride comfort must be quite an engineering challenge.
Secondly, the tread pattern is not a closed surface since it includes perforations to evacuate water. Here the engineers have taken full advantage of the fact that this tire doesn’t need a closed tire cavity and that water can not only be evacuated through the tread grooves but also upward through the tread which should give it an edge in aquaplaning.
Lastly, the Yokohama airless tire seems to be mounted on a conventional rim. This approach is clearly different from the Tweel which aims to fuse the tire and the wheel (hence the name Tweel). Being able to mount the Youmyaku on conventional rims could give it a huge advantage over other airless designs since the barriers to adoption would be significantly lower.
What is interesting about the Yokohama approach (going by the little information that is available) is their focus on passenger cars. Michelin bravely attempted to put the Tweel on an Audi A4 back in 2005 but has since dialed back to putting its airless tire on skid steer loaders. Bridgestone has made it clear that it is their strategy to go after low speed applications such as personal mobility devices. This makes it all the more astonishing that Yokohama’s focus seems to lie with passenger cars, the most demanding of all possible applications.(Below is the official Yokohama video on the “Nature Design” series of tires; the Youmyaku appears at 1:57)