Bicycle Mechanics - Cunningham Design Roller Cams
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Can anyone share tips for effectively adjusting the spring balance on brakes like these? Sheldon talks about them as being "Diacomp" style. I get that the bearing surfaces in the bosses need to be clean and greased and that the wheel needs to be centered on the frame, but is there a technique for holding both of the arms/springs in a specific position - at the same time - (centered), so that you can then tighten them down and have them stay put? Some kind of third hand? It seems like even a small adjustment of one ruins the balance of the other.
I try over and over, but the brakes still don't center... One of them always seems to stay off center. Would a small tourque wrench help? The spring adjusters need a cone wrench or a small crescent wrench because there are just the two surfaces that the wrench can grab. But has anyone seen a socket that would fit these adjusters, that could then be snapped on to a 3/8ths inch torque wrench drive? Maybe if the springs were tensioned by the number instead of by eye and feel? It gets to a point where you seem to have to accept a slight imbalance and then compensate for it by mis-adjusting the shoes...
I have these brakes on an 85 Ross Mt. Hood. My winter commuter. The rear brake is mounted on the lower chainstay - where it's hard to reach and gets filthy when riding in the winter... Thanks in advance for comments. :thumb:
01-02-10, 11:57 AM
"I have these brakes on an 85 Ross Mt. Hood. My winter commuter. The rear brake is mounted on the lower chainstay - where it's hard to reach and gets filthy when riding in the winter..."
that is why, aside from them being cheaper, the manufacturers went to cantis on the SS. I think your best tool here is just patience. I have not worked on one of these for sometime but IIRC you loosen the 'arm' with an allen and adjust the spring tension with the cone wrench then tighten yes? it is just a matter of delicately adjusting one and tightening it. then adjusting the other. my U brake is like that and I hate it. if you are only talking 1 - 2 mm of difference I would not worry about it.
01-02-10, 01:46 PM
I have this same bike and had a tough time adjusting the brakes until I read the directions in an insert that was in the original owner's manual. If you don't have the manual, PM me with your email address and I can send you a jpg of the two page insert. As far as keeping the brakes clean, Overland used to make a canvas cover that went over the brake mechanism. Works pretty good. It's basically a triangle-shaped sleeve that slides over the brakes from the top and is held in place by a velcro strap. Would be very easy to sew up if they're no longer available. I can send a photo of that too, if you're interested.
I have a Schwinn with the diacompe version of these brakes. It took lots of playing around including adjusting the pads relative to the rims to get them working. I gave up on having them really close to the rim too.
01-02-10, 05:26 PM
Some people like them, but I don't. I replaced mine with a Campagnolo Euclid U-brake.
A third hand makes adjustment much easier, and like wilber says, so does the proper procedure. It took me a while to get it too - I think I found the procedure online.
Once adjusted properly, I learned to really like this brake (on the Dorado it's on the chainstays only). The mechanical advantage is contoured by the cam giving you good closure and swing early in the stroke and serious muscle at the bottom. This has to be the hardest clamping rim brake I've seen, while remaining 'not grabby' unless you really want it. I wouldn't change it, though I do like the idea of a cover.
wilber, maybe post both procedure and pic of cover in the "Hints and Tricks" thread?
01-04-10, 02:21 PM
Another idea is custom-cut your own cam out of sheet metal. You can change the profile and starting position to be anything you want. What's more if you create a much taller triangle shape for the cam, then the cable would have more mechanical advantage over the slightly irregular horizontal movement of the arms that you are describing.
DMF, Walt sent the info to me as JPEGs I can do the same for you. PM? See, I told Walt I'd pay it forward... And another note for anyone that knows, I just noticed that my Cunninghams have a broken roller. Mine were the original plastic ones. I think they re-called those. Any idea what people are using to replace those?
01-11-10, 08:25 AM
Any idea what people are using to replace those?
Just buy another such brake off ebay, where sometimes you can find just the rollers but not often.
DMF, I'm just going to post these. You are not the only one who might like to see them. These JPEGs are courtesy of Walt @ post number 3 Walt, thanks again friend. My brakes are way better, but now my rollers are beginning to deteriorate!
Please post the full resolution images, or PM them to me. These don't blow up well enough to see detail.
01-12-10, 01:12 AM
Damn, this thread comes along after I spent hours fiddling, trying to get mine to work just right. oh well, the proper set-up has been covered, and damn do they work well when set up right.
the really nifty cunningham bikes have an integrated mud shield to guard these (strangely placed) brakes. I have heard tell that the chain-stay mount is to avoid over-flexing the weaker seat-stays, and I could believe it. I'm not saying I do, but it sounds kinda plausible.
Well, no brake cable on the top tube. And it does look cool. But I can't think of an overwhelming reason either.
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