Bicycle Mechanics - brake caliper won't open on its own

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zip22
10-02-07, 04:00 PM
i need to to push it back open. i am using a tektro dual pivot caliper and I am pretty sure the small plastic sleeve on the spring that rubs on the caliper arm is to blame.

is the little plastic piece to blame?
if not, whats the issue?
if so, why did it wear out this quickly (~1.5 years) and is there anything i can do or replace it with to make it last longer?

DannoXYZ
10-02-07, 05:41 PM
The plastic sleeve just makes it easier for the arms to slide over the spring, if it wasn't there, there would be more friction on that joint. If it's worn-out, you can typically twist the plastic on the spring and slide it down slightly so that the arms rub on a fresh portion. Add some teflon/graphite/moly grease to that point.

If the calipers have been taken apart, the pivot-bolts may have been tightened down improperly. Or the incorrect stack of washers was installed, leading to binding. Also make sure to add some long-lasting grease to the pivot-bolts and on the caliper-arm's mating surfaces when re-assembling.

Also, does the calipers expand by themselves with the cable disconnected? If you disconnect the cable and squeeze the calipers and find that they expand by themselves, excessive cable-friction is the problem. I've found that the rolled Diacompe cables to work the smoothest and last the longest (add a little teflon grease to the inner cable when assembling).
cascade168
10-02-07, 05:42 PM
What happens if you disconnect the cable? A lot of times it's the cable that's sticking and not the brake.

If you disconnect the cable and it's still sticking, then remove the wheel so you can squeeze and open the brake easily with your hand. Now douse the pivot bolt with TriFlow, or ExtraDry, or some other light weight lube. Actuate the brake several times and see what's happening. Just some lube will fix a lot of this type of problem. A drop or two of lube, every time you wash your bike (you DO wash your bike, right???) will keep brakes operating smoothly. If it's the cable that's sticking then spend a few bucks and replace the cable and housing. Lube the cable with (again) TriFlow or ExtraDry before you insert it in the housing and it will operate slicker than whalesnot.