The Mythic Third Arm
What does every mechanic want most? New wrench set? A better set of screwdrivers? Nope. In the middle of just about every job, at some point we say "Damn, I need one more hand!"
Well, when it comes to changing tires, it couldn't happen more often. Fortunately, some bright guy came up with a way to add and extra "hand" and a very strong arm, to a tire changer.
The need is pretty simple. To demount or mount a tire, the sidewall needs to be pushed towards the center of the wheel. Some tires make that VERY difficult, particularly, low profile, high performance tires...the sort you might find on large, powerful bikes. With the advent of "helper arms" on tire changers, jobs that are very difficult with conventional tools become far easier...if not downright easy.
The helper arm, the black mechanism shown above, swings an air ram that is attached to a plastic foot, over a wheel and tire that has been clamped to the turntable. With the press of an air valve, the ram presses the foot down onto the sidewall as far as necessary to put the bead into the "drop zone" (the smaller diameter inner section of the wheel) which now gives enough clearance for the tire to be shifted sideways on the wheel, allowing the bead to be lifted over (demount) or pressed past (mount) the opposite side of the wheel. The arm is double jointed and the foot pivots, allowing the air ram to maintain pressure on the tire, even as the wheel is rotated on the turntable. Pretty nifty.
CLICK HERE to see it in action!