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If only we could have a room full of wheelchairs for every occasion, like others have a closet full of shoes, our lives as wheelchair users would be so much more convenient - going from, say, the office to the hiking trail simply by transferring into a different wheelchair, where each technology was optimized for its intended environment, from dress shoes to hiking boots, you might say.

Unfortunately, most wheelchair users don't have such an option, but must rely on a single wheelchair to serve in all environments. This reality is especially difficult for ultralight manual wheelchair users who are intrinsically effected by rear wheel propulsion efficiencies amidst varied environments. For example, high-PSI, 1"-wide, smooth "court"  tires are optimally efficient on hard-paved surfaces, but become utterly inefficient - if not unusable - in off-road terrain. Likewise, low-PSI, 2"-wide, knobby "all-terrain" tires are very efficient off-road, offering tremendous flotation and traction, but prove sluggishly inefficient on hard-paved surfaces. As a result, ultralight wheelchair users who need to propel over both extremes of environmental terrains - hard-paved surfaces and off-road (including snow) - often end up selecting the lesser of the two evils when it comes to tires: Using a large, knobby tire full time because although it's sluggish on hard-paved surfaces, it's a better alternative than using a court tire that keeps one from going off-road or traversing wintry outdoor conditions. As a result, there are many users who have off-road tires mounted on their ultralight manual wheelchairs full time, simply enduring tougher hard-paved surface propulsion in trade-off for easier access to off-road and wintry environments.

Kenda, a leading tire manufacturer, recognized the trade-off that users were making by using all-terrain knobby tires in everyday use, and came out with the Kobra - a revolutionary wheelchair-specific tire that dramatically reduces the trade-offs of choosing between court and all-terrain tires, offering a remarkable hybrid solution.

For starters, the 2"-wide Kobra tire is available in 540mm, the standard 24" wheelchair wheel size that's most common. This is a very important aspect because no other manufacturer makes a 2"-wide 540mm tire that fits a standard 24" wheelchair rim. When wishing a 2"-wide tire, consumers either have had to downsize to a 507mm rim with a corresponding mountain bike tire, or a 559mm rim with a corresponding mountain bike tire - both adding cost and reconfiguring due to the odd-size specialty rim assemblies. However, the Kobra, at 2" wide, is designed with the diameter to fit industry-standard 24" (540mm) wheelchair rims, so it will interchange with any 24" wheelchair wheel, from mags to wire spokes to Spinergy. Put simply, with the Kobra, you merely need to swap the tires on the wheelchair to go to a true all-terrain 2" width, not buy another wheel set. (Note: Based on a particular wheelchair's rear wheel mounting offset, the rear wheel axle sleeves may need to be adjusted outward to accommodate the wider Kobra tire, so that they don't rub on the backrest or side guards.)

Now, where the Kobra is truly innovative is in its tread pattern and structure. Rather, than having a full knobby tread, the Kobra has a crowned, smoother tread down its center, with aggressive knobby tread along the top of its sidewalls. The result is that on hard surfaces, only the smooth center section serves as a very efficient contact patch - especially at the tire's rated maximum 80 PSI (which is double the air pressure of most all-terrain tires). However, off-road, the full 2"-wide tread pattern comes into play, providing maximum flotation, with the sidewards knobby pattern digging in for traction. Therefore, on hard-paved surfaces, the tire efficiently rolls on its 80-PSI, smooth, minimal contact patch, but then equally serves as a knobby tire when off-road, delivering full flotation and traction. The Kobra, then, literally conforms to the surface it's on, albeit a superior roll rate on hard-paved surfaces, or ultimate flotation and traction off-road.

Getting back to the Kobra's unique 540mm rim comparability, this fact, too, contributes to the Kobra's everyday efficiencies. Because the Kobra mounts on high-performance 540 rims, it can be mounted on a super-light-weight rim assembly like a 12-spoke Spinergy Light Extreme wheel, offering an astounding several-pounds weight savings over conventional all-terrain specialty wheels - another benefit toward propulsion in everyday use.

The Kobra tire sells for $39.00 per pair online, has a non-marking gray tread, and is available with blue, red, or yellow sidewalls to color-key to other components on the wheelchair.

As physics proves time after time, the best money toward propulsion efficiencies in ultralight manual wheelchairs is to invest it in the rear wheels. Kenda's Kobra tire builds upon that fact, offering a hybrid tire that optimizes its propulsion efficiencies from one environment to the next, making the world a bit more hospitable no matter which paths one pursues.

Published 7/2010, Copyright 2010,