Tuesday, March 5, 2013

When wrong is worse than none

So, I had two occasions this past weekend to bemoan the woeful state of technical documentation provided with bike parts... sometimes, having *incorrect* information is worse than having none at all.

My two examples:

1) I was installing some new disc brakes on one of Anna's bikes (the old ones were truly a poor excuse for brakes... but that's another story!) The nice little sheet of installation info that came in the box provided a helpful drawing, with an arrow pointing to the cable-binder bolt, and the torque value to be used. Very nice. But what's the torque that should be used on the brake attachment bolts -- the ones that actually hold the brake on to the bike? Well, there's another helpful drawing, and look another arrow... oh wait. It's the *same* drawing. The *same* arrow. Pointing to the wrong bolt. But hey, the torque value's different here. So now, which one is right? And for which bolt(s)?

Without the (dubiously) helpful information provided by the manufacturer, I would simply have resorted to my tried-and-true mechanic's experience (or, as a fallback, engineering degrees) and applied the 'ol two-fingers-on-the-wrench rule, and worried no further.

2) Installing new Speedplay cleats on a new set of road shoes, one must choose and use the right set of shims to match the base of the cleat to the sole of the shoe. I referred to the handy info sheet... ah, there's a column for shoe manufacturer and model, check, there's mine; at least something close -- the shoes are 2013 model, the sheet only has 2012 and earlier, but all the models list the same shims. OK let's check on-line. Yep, Speedplay keeps the latest and most-updated list conveniently downloadable. Checking that, all looks the same. OK here we go, get everything installed with those shims and %^&%$ doesn't look quite right, cleat's bowed in the middle ^%$%^ gotta take it all apart again. Check documentation, yeah I read it right, what the heck's going on here? Try it with the other shims, yeah I know that's not what the manufacturer *said* it should be, but hey whatta know perfect fit.

Without the (not-quite) comprehensive, up-to-date info provided by the manufacturer, I would have test-fit both sets of shims and decided which actually fit best, *before* clamping down and torquing to spec all seven screws.

So I'm now tempted just to disregard any little pieces of paper that come along with my bike parts in the future. Except that the engineer in me is convinced that, if I do so, some critical nugget of info will pass unnoticed, leading to Dire Consequences.

For the future reference of myself and other bike-wrenches, the important but missing or misleading information from above is as follows:

- Avid BB-7 brake caliper CPS bolt torque is 9-10 Nm.
- Speedplay Zero cleats on 2013 Specialized S-Works shoes require the 1-F and 1-R shims, NOT the 4-F and 4-R.