"Flat-free"
tires are as old as the modern wheelchair, itself. But, as
mobility technology flourished over the past three decades, flat-free
tire technology equally evolved, dramatically broadening the definition,
construction, and performance of flat free tires. Whereas
flat-free once meant a solid rubber tire, today' definition can range
from a foam filling to a poly urethane tread to a rubber insert, and
it's important for the consumer to understand which construction and
material best meets his or her performance needs.
Foam-Filled
On today's powerchairs, foam-filled tires, especially on the drive
wheels, are the most popular flat-free solution. The foam-filled
process uses a standard pneumatic tire - minus the tube - and via a
mold-in process, fills the tire's cavity with foam, replicating a fully
inflated tire. The foam may vary in density depending on the
required weight capacity, but most equate to a ride similar to the
maximum PSI rating of the tire -- that is, foam-filled tires provide a
somewhat firm ride. Because foam-filled tires compare to a
forever-inflated tire, a split-rim is required for installation (forget
using a flat-head screwdriver to pry these tires on a one-piece rim!).
The foremost benefits of foam-filled tires are that you receive
the same optimal tread as a rubber pneumatic tire, and because
foam-filled tires bead properly, they won't roll off the rim in
high-speed, high-stress applications. The lifespan of foam-filled
tires equals that of a properly maintained pneumatic tire.
Wheelchair Junkie Tip #16,738: If you're storing a powerchair or
scooter with foam-filled tires for a prolonged period, place it on
blocks, with the tires approximately ?quot; to 1" off the ground,
preventing flat spots on the tires from sitting stationary.
Poly Urethane (PU)
PU tires are the most common flat-free tire on manual wheelchairs, used
on both rear wheels and casters. PU tires are a highly-resilient,
one-piece molding that's fairly lightweight. PU tires come in a
variety of tread patterns, with molded air pockets to soften the ride
characteristics. With such a resiliency, PU tires may pry onto a
one-piece rim, with a secure bead (they're typically flawless on manual
chairs, but may roll off the rim on a high-speed rear-wheel-drive
powerchair caster). The lifespan of a PU tire is often three or
four times that of a traditional rubber tire, never needing replacement
in some cases.
Co-Molded/Over-Molded
Co-molded tires are most commonly found via powerchair casters and
low-end manual wheelchair wheels, where a plastic rim and molded-type
tire are permanently bonded as a single unit. Co-molded tires are
especially useful as anti-tip wheels, where durability is more important
than ride characteristics. A version of this genre is the solid
over-molded foam caster - most common in 8" casters on mid-range
powerchairs - which offers durability with an enhanced ride
characteristic. Co-molded tires have an exceptional lifespan, but
the entire wheel assembly requires replacement when worn.
Solid Inserts
Solid inserts were the predecessor to foam-filled tires, filling the
void within a pneumatic tire, and allow use on one-piece rims (a special
tool is required for installation on one-piece rims). Because
solid inserts are. . . well. . . solid - or, solid rubber - they add
considerable weight to the tire, decreasing performance in manual
wheelchairs. On powerchairs, solid inserts may degrade quite
rapidly, leaving you with somewhat flat, flat-free tires (because the
inserts float between the rim and tire, high-weight and torque
applications can stretch and twist the inserts). On manual
wheelchairs, however, solid inserts allow the use of a standard
pneumatic rubber tire, offering improved traction over a PU tire.
Semi-Pneumatic
Semi-pneumatic tires and inserts feature molded-in air pockets, much
like the air pockets in the soles of athletic shoes, providing a
slightly cushioned ride. Found in forms ranging from poly urethane
tires to inserts, semi-pneumatic tires never need air maintenance, nor
will they become flat when punctured, making them truly flat-free.
The important distinction, however, is that while all
semi-pneumatic tires are flat-free, not all flat-free tires are
semi-pneumatic, as with solid rubber tires.
Indeed, who knew there were so many factors and choices in merely
wishing a flat-free tire? But, by selecting the right tire for the
right application, you can stroll the boulevard, ensured that your chair
is both flat-free and trouble free.
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