Wednesday, February 22, 2012

What's in a millimeter...

One of the things I've enjoyed about my not-so-new life in the bicycle industry is wearing out parts. You see, prior to this gig at the retail level, I was on the industry side which simply means I worked for a bike company in product development. This meant that every year, parts manufacturers released a slew of new product and would send early production samples to me for evaluation. Instead of wearing out parts on my bikes, I replaced them well before their useful life was reached. Component groups, suspension bits, tires, wheels... All were mine with simply a phone call or e-mail.

Living in SoCal where it never rains, I never wore out brake pads, until now, that is. It's hard to wear out brake pads on a road bike here. Virtually all of my rides are in the country where there is no constant stopping for stop lights. Most descents are open and require little braking. Where heavier braking is required, the duration is short. Finally after two years, I wore out the brake pads on my road bike.

I planned a road ride last Sunday, so set about to replacing the pads on Saturday. The pad of choice - Kool Stop Dura Pad in salmon. Before installing these and most of the Kool Stop pads, I perform one task to the pad - file down that "plow tip" that is at the back edge of the pad. What it is supposed to accomplish does make sense - act as a squeegee of sorts and scrape away any grime, water, mud that may be on the rim before the pads activate as speed modulators. I can imagine the squeegee aspect working if one was to gently apply the brakes so the plow edge does clean the rim. However, brakes are usually applied quickly and I just don't see that action overriding what I perceive as the negative of the plow edge.

Negative to the plow edge? How can that be? The negative is that the plow edge makes the brake pad feel soft and squishy. When the pad contacts the rim, the plow edge is supposed to hit first and with more pressure, the rest of the pad makes contact with the rim - after overcoming the material in the plow edge. In that moment, the feel of the pad is too squishy, at least for my tastes. Additionally, the plow edge reduces the pad-to-rim clearance a bit. I always file that extra millimeter off the pad to get a more positive pad to rim feel.

I filed the plow edges down, installed the pads, re-adjusted the cable tension to accommodate for the new, thicker pads and was ready to ride the next day. Or so I thought. I had decided to ride what I call the Bo-Fax loop. Simple loop ride down Highway 1, up Bo-Fax Road down to Alpine Lake and one to Fairfax, back on Sir Francis Drake through the San Geronimo Valley, hit the dirt section of the Cross Marin Trail, and back to Point Reyes via Platform Bridge Road and the Point Reyes-Petaluma Road.

There is very little braking until you hit the descent down to Alpine Lake. That's where I realized I was about a millimeter off in my cable tension adjustment. When you get used to the feel of the brake lever where the pad to rim contact point is, altering that is like riding with an incorrect seat height. It just feels wrong. At the first corner coming down to the lake, I touched the brakes (while in the drops - more on this later) and "whoa!" Too much too soon.

I like the brake lever to travel almost half its travel before the pads make contact with the rim. This lets me hold on to the lever a bit without having the brakes on and then I can make micro adjustments with my index finger (one finger braking) to control my speed. With the pad contacting the rim with very little brake lever travel, it was throwing my ability to descend fast for a loop. I was braking too heavily with too much force. Not easy to re-learn years of braking technique on a technical descent. However, when the road straightened a bit, I was able to reach down and open the brake's QR a bit to a brake position I was comfortable with. About a millimeter more cable release.

The pad on the right with the plow edge removed.

Brake caliper
New pads installed and field tested.

(What's playing: KWMR Hump Day)


bubba said...

The pad on the left with the plow edge removed? Do you mean the OTHER left, Mike? :)

blackmountaincycles said...

Of course! Fixed.

Anonymous said...

We used to file the fins of the koolstop pads to prevent that mushy braking. Now, new koolstop pads have deleted the fin all together at the factory. Still soft, koolstops reduce rim wear unlike shimano.