Thursday, September 19, 2019

A world of squish

Once again I spend a couple of hours chasing down weird issues in disc brakes.

The customer came in with his Giant Revolt gravel bike. He said that the brakes needed bleeding, especially the rear, because the lever was pulling right to the bar.

I squeezed it. It was pulling right down. But at the end it didn’t have the telltale squishy feeling of air in the system. It came to a sort of firm stop, as hydraulics go. I told him I thought that it probably just needed new pads.

When I pulled the old pads out, they were only about one-third gone. Because the bike uses Giant’s cable actuated master cylinder, to work with normal brifters, I thought maybe I could snug up the cable part of the system.

No such luck.

I had to root around on the internet for a real service manual. There are little screws all over this unit, so I wanted at least a sketch map to confirm where to attach the syringes full of mineral oil.

As always the configuration of the rear brake line makes it impossible to get a clean, rising line from caliper to master cylinder. I had already taken the bars out of the stem to get access to the cable anchor screws. That made it easy to turn them 90 degrees to the ground to orient the bleed port upwards. But the brake line itself serpentines down and under and around in ways that make the rising line approximate. I hoped it was good enough. Sometimes it is.

After doing the bleed two complete times, the lever feel was still no better. Screw it. I threw a set of pads in, and bingo.

Well, bingo-ish, anyway.  Because I never got to feel this bike in the flower of its youth, I have no way to know how it felt at its showroom best. I can tell you this much: almost every set of hydraulic brakes I have operated has felt squishy, even when the rider was perfectly happy with it. A mountain biker passing through this spring laughed when he felt a set of brakes that a noob complained were too soft. “They all feel like that!” he said. “Get used to it.”

The only hydraulic disc brakes that haven’t felt squishy have been overfilled and rock-like. They’ve needed to be bled down to get the pads to retract at all.

I’m really starting to hate them.

I’m also starting to hate Outside Magazine. Always the rag of egotistical vacationers, their increasing attempts to represent cycling expertise are oriented toward the hobbyist with disposable income and no resistance to technofascist propaganda. Because of all my searching for info on disc brakes, Google fed me this article on “Why you should throw your rim brakes in the trash.”  Hobbyist McMoneybags says that when he’s riding down a mountain pass in the rain, rim brakes don’t work at all on his carbon rims. Dude! I’ve found your problem! Use disc brakes on your tech-weenie wanker hoops. Preach to your well funded hobbyist buddies about what they really must have. But save your pronouncements about what should be the future of a once simple, durable, and highly user serviceable technology.

1 comment:

Rob in VA said...

Regarding Outside Magazine: agree wholeheartedly. What a useless, albeit flashy, publication. It has gotten worse, year after year, though it is evidently still fulfilling the objectives of its advertisers.