Saturday, March 21, 2009

Suntour Superbe Brake Caliper Rebuild

Just a quick post about the Motobecane.

This morning I installed the replacement Dia-Compe brake springs into the Suntour Superbe brake calipers. Actually, I tore down the brake calipers completely, cleaned all of the pivoting points (including the quick release mechanism), and reassembled everything with fresh grease on all pivoting surfaces. Took only a half hour for the pair, in large part because the original owner, Steve, is nothing if not fanatical about precision and maintenance. And the all of the nuts on the brakes were perfectly adjusted and well lubricated, so all the parts were moving freely and everything came apart without a fuss.

I'd ordered two sets of springs, one for the Dia-Compe 400N and one for the 500N. It was the 500N springs that I needed, as the guy from Loose Screws had suggested would be the case. I'm not sure what the difference between the two models is, but I'm thinking it's just reach. A set of Shimano 600 calipers from the '80's taken from a friend's bike look very much like the Suntour brakes, but have shorter caliper arms, and look like they'd accept the 400N springs -- the Dia-Compes, Shimanos and Suntours were obviously cloned from the same (Italian) gene pool.

The old rusty springs either had a slightly narrower spread when new than the replacement parts, or had taken a slightly more compressed stance over the years. Either way, the new springs had a wider spread to them. I rebuilt the first caliper, then compressed both the rebuilt and the untouched calipers in my hand to compare. The sense I get is that the new springs will give the levers a stiffer feel and a more positive rebound, which is good because the old-style levers have no return springs and depend on the caliper springs' help. Otherwise the springs fit perfectly.

Together with the Campagnolo barrel adjusters (not seen in the picture because they're hanging on the ends of the Motobecane's brake cables out in the barn -- and there's that Italian gene pool again), the parts needing replacement are nearly all now in place, and the brakes are fully functional again. I'll put them back on the Motobecane today, and take them for a little spin to see how they feel.

The only thing left is to find the missing wheel guide on the rear caliper, and that's only if I decide to leave them on. They look cute, but they're not strictly necessary. I need to figure out what to do about pads, too. I really ought to replace them -- they're probably 25 years old, after all. I have a couple of pairs of contemporary pads I can install, but they'll look significantly different, and I'd like to keep the bike's classic looks.

All for now,


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