Caliper Chain Tesioner
Caliper Chain Tesioner
EVALUATION
Phil Cancilla is an oldtime racer, tuner and sponsor, a straightahead builder, the kind of guy who can rummage around in the toolbox or the back of the truck and come up with the three unrelated parts that can be converted into the device you need in time for the race.
His newest idea is a chain tensioner and the inspiration for it, he says, didn’t come from motorcycles.
It came from the basic safety pin.
The problem, though, does come from motorcycles, more specifically bikes built after the discovery of long travel suspension and before the factories cured the problem on the drawing board.
Because the rear wheel moves in an arc. pivoting behind the countershaft sprocket, the distance from the sprocket to the rear axle varies with wheel position. This means chain tension varies as well. When rear suspension first arrived, no big deal. There wasn’t much travel, the distances didn’t vary much.
When rear wheel travel went from three to 12 inches though, chains began to flap and leap oft' the sprockets. The factories and accessory people provided a series of spring-loaded tensioners, usually working on the lower run. They took up slack. Next came guides and guards, usually at the rear sprocket, to keep the chain in line. The add-ons worked, but not perfectly, so the latest motocross machines have the pivot and the front sprocket much closer together; less variation in the distance between sprockets, less change in tension, less trouble from the chain, no need for tensioners.
Except for those of us who own motorcycles built between these two periods, that is, motorcycles that do have more change in tension than the chain can cope with unassisted.
There’s another factor, less important in racing and more important for bikes owned and ridden by people who pay for their parts: Chain life. Powerful motors and improved traction play hell with the middle links.
Cancilla took both problems and designed his own tensioner, using the principle of the safety pin: a free-floating central pivot for a spring working on tw'o points.
The picture tells the story. There’s a mounting arm and two roller arms, one for each run of the chain. The spring pivots freely on the mounting arm and exerts force on both chain arms, squeezing them together. Neoprene rollers ride on the chain, which is thus in constant tension. under power or braking. Because the pivot is free to move, the tension can instantly shift to whichever side of the chain needs it.
The tensioner is a nicely built device. Hell for stout. Comes in three models; a weld-on universal, a bolt-on for Honda XR and XLs, and a bolt-on for Harleys.
Because we have a Honda XR250. that’s what we ordered. Installation was easy. Remove the stock tensioner and upper chain shield, undo the two halves of the clamp, free the spring.
The half with the arms goes onto the swing arm leg and you slide it around until the two rollers are lined up with the chain runs. Pop the top half on. tighten the alienhead bolts, lever the spring into place and it’s ready. Takes maybe half an hour, with no special tools or skill needed.
How does it work? In the short term, it works well. Phil promised the chain wouldn’t de-rail, and it hasn’t in several months of riding through sand and mud. The tensioner is supposed to smooth shifting. as the spring serves as sort of a cush drive, damping the yanks as you whack the throttle on. or lock the back wheel with the brakes. And it seems to do this, although we have no scientific way of measuring the smoothness of a shift.
What we can’t verify here, yet, is chain life. The chain gets lubed generously after each ride, and it’s dunked in the solvent tank, air dried and doused with oil after mud anyway, so we can’t say that the chain hasn’t needed adjustment in 1000 miles due to the tensioner. And we can’t predict extra years of use from the chain.
But it does seem to work.
As for economics. Cancilla mav have invented a cure for a problem that was on its way out anyway. Long travel, short pivot motorcycles probably don’t need this kind of protection. Harleys, yes. The weight and the torque make the 74s and 80s prime candidates for better chain control, but most other bikes, well, the tensioners sell for $69.95. Unless you can’t resist expensive chain, you may not get your money back.
Sounds almost too practical. The Caliper chain tensioner is a good idea, well carried out. and if w'e haven’t been able to test all the claims, well, the ones we can test have been verified. If you’d like to give your reliable old bike a worthy present, here one is. From:
Cancilla Motorcycle Engineering P.O. Box 24506 San Jose, Calif. 95133
