Bicycle Mechanics - TRP 8.4 brakes: spring tension setup question

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i_r_beej
11-26-12, 05:23 PM
Hey all,

I recently installed TRP 8.4 linear pull brakes on my cyclocross bike. They are a vast improvement over the conventional (old-fashioned) cantilevers they replaced.

There is only one little issue that's threatening to drive me crazy: The uneven actuation of the brake arms.

Here's what's going on: When I squeeze the brake lever, the arm with the noodle moves to the rim first, THEN the other arm moves. I've experimented with the spring tension extensively and I've also disassembled the pivot sleeves and lubed them with some Rock-n-Roll Super Slick. Nothing seems to make any difference. (New cables and housing were installed at the same time as the brakes.)

The bottom line is that the braking performance seems unaffected (I can lock up the wheels with just one finger on the brake lever!) and so I suppose that the uneven actuation of the arms is a cosmetic issue. But it still bugs me, especially since I have a few other bikes with various brands of linear pull brakes and none of them exhibit this behavior (both brake arms actuate evenly with a pull on the brake lever).

Has anyone else seen this? Do you have a"fix"? Or should I just relax?

Thanks for reading.

HillRider
11-26-12, 05:29 PM
It's really not a problem as long as both pads retract fully when you release the lever. As you said, the braking performance is good so I view it as an annoyance, not a defect. Symmetry is nice but performance is what counts.
dsbrantjr
11-26-12, 06:14 PM
Is it possible that your new cable housings are slightly longer than necessary and are exerting pressure on the arm with the noodle which is causing it to move before the other one? Maybe shortening the housing an inch or so will help the arms move evenly. Or just don't look at the brakes and just ride the bike.

FBinNY
11-26-12, 09:45 PM
It absolutely doesn't matter if one shoe strikes first. Once one arm makes contact the extra force transfers to the other. There's no side pressure on the rim except for a tiny amount reflecting variation in the springs. Compare to the disc brakes in cars where the piston is only on one side, once it touches the caliper moves across until the brake force is balanced on both sides.

There are spring balance adjustments, but those are only to make sure both sides release evenly.