Tool Time

Tool Time

Most of you likely are familiar with a ritual that motorcycle riders and mechanics have been performing for decades when installing a front wheel, usually after fixing a flat or mounting a new tire. The procedure varies slightly depending upon the design of the axle and fork legs, but the concept is the same:

Before tightening the pinch bolts that clamp one leg or the other to the axle, you sit on the bike, butt the front wheel against something immovable, grab the handgrips and vigorously pump the front end up-and-down. The purpose of this ceremony is to drive the inner fork tubes as far as possible up (on an inverted fork) or down (on a conventional one) inside the outer tubes, thereby ensuring that both legs are perfectly parallel from top to bottom. This is important because if, during wheel removal and reinstallation, the legs somehow have gotten slightly pinched together or spread apart down at axle level, it can cause added station that could hamper the free and easy movement of the front suspension. Theoretically, at least, the pumping action should align the legs by shifting the unclamped one in the right direction.

Should.

But how do you know if it has? In fact, how do you know at any time if the tubes are parallel? Even as the result of a minor tip-over, fork legs can get tweaked just enough to become misaligned.

Motion Pro (www.motionpro.com) has come up with a simple gadget that allows anyone to quickly and accurately verify fork-tube alignment. It’s called the ForkTru (part #08-0412; $35), and it consists of two adjustable, slotted aluminum arms with large “V-cups” on one end. To use it, you loosen the thumbscrews that hold the two pieces together and place the V-cups against the bike’s upper fork tubes as close as possible to the bottom triple-clamp—preferably just above it, though right below also usually suffices. The shape of the V-cups allows them to be self-centering on the tubes; so while holding the ForkTru firmly against the tubes, you make sure each Vcup is in complete contact with its tube, then tighten both thumbscrews and verify that the V-cups are still centered on the tubes.

Without disturbing that adjustment, move the ForkTru down to the lower part of the fork legs, carefully inserting it between the wheel spokes. Placement is usually limited by a brake caliper or rotor, but you should press the tool against the lower legs as low as possible. If the lowers are parallel, the ForkTru’s V-cups will fit just as snugly against them as it did against the upper legs, with no clearance or possible movement between the cups and the legs. If the legs are not aligned, you will see clearance or detect movement between them and the tool.

ForkTru works best on dirtbikes, which tend to have less-cluttered front ends and smaller caliper/rotor arrangements, and on inverted forks, which have machined upper and lower fork legs. Conventional forks have cast lower legs that usually are perfectly round; but on some bikes, the legs have just enough imperfections to throw off the measurement. When I first got a ForkTru, I checked the alignment on quite a few bikes and was shocked at how many had fork tubes that were not parallel, even after being adjusted via the pump-up-and-down method. That’s why the ForkTru has found a permanent home in my toolbox.