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Old 07-05-07, 09:52 AM   #1
DMF 
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Roller cam brakes - how much spring tension?

Suntour XC roller cam rear brakes. In each mounting post there is a captive spring that retracts the arm against the cam. The spring tension is set by a post cap that looks like a hub cone and is adjusted with a cone wrench. How much tension should be on the spring? 1/8 turn? 1/4 turn? Best guess?


Know of a set of instructions for setting these up?

One problem I have is spreading the arms to remove the rear wheel. There's no release per se. At the top of the cam there are detents for the rollers to drop into, opening the arms wider than the normal ramp. But if I set the shoes to clear the tire when the rollers are in the detents, there's not enough travel from the brake levers to close the shoes to the rim. Tires are 26x1.95. Are they that much wider than original tires on 1985 mountain bikes?
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Old 07-05-07, 10:19 AM   #2
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Originally Posted by DMF
How much tension should be on the spring? 1/8 turn? 1/4 turn? Best guess?
That's about right, Enought tension that the brake lever snaps back, but not so much that the brake lever is hard to pull.
That adjustment also centers your brake pads on the rim.

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Originally Posted by DMF
One problem I have is spreading the arms to remove the rear wheel. There's no release per se.
Squeeze the pads to the rim with your hand. Pull the cam out from between the roller wheels.
Now one brake arm can be pivoted away from the rim and the wheel should drop right out.

Ultimately, the roller wheels should be just at the top of the buldge in the cam when the brakepads first make contact with the rim.
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Old 07-05-07, 10:29 AM   #3
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Last year about this time I was working on a bike with my first set of Roller Cam brakes and this reply was posted by MnHPVA Guy to help with adjusting mine. I copied it and kept it filed away. See it below. BTW the advice for adjusting really worked. My Roller Cams can really lock up the rear wheel! But I also like the feel for brakeing that they give As far as spring tension goes I remember just adjusting until it felt right and everything worked correctly, sort of trail and error style. As far as the quick release, I don't believe there is any--- which is a downside of an other wise great braking system. I end up removing at least one brake pad in order to remove a wheel. Best of luck.

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Adjust your cables so that before you pull the brake lever, the centers of the rollers are 33mm apart. Then adjust the rim/pad clearance by moving the pads in or out on their posts. You want a fair amount of clearance. properly adjusted, at rest the rollers are just above the shoulders of the cams. They will move quickly to the rims but when they get to the rim they should be on the the steep, high leverage part of the cam plate.

To simplify doing this I drilled and tapped two 5x 0.8mm threaded holed in a small piece of aluminum bar stock, and threaded 5mm bolts into the holes sticking out on the backside. I stick the bolts into the sockets of the roller pivot bolts. Also useful for a quick check of the roller spacing.

Minor adjusments for wear are taken up at the cable adjusters. When the roller spacing gets out to about 35-36mm its time to reset to 33mm and move the pads in on the posts. Fortunately the Kool Stop pads wear slowly so this doesn't need to be done often.

I assume you have already found out how sweet the spring adjusment/balance system is. Especially compared to the, soft, cheap phillips head screws on most linear pull brakes. I should see what thread is on those cheap screws and buy a box of stainless socket head bolts in that size. Throw the original screws away before installing linear pull brakes. Just like I do with the stock pads.
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Old 07-05-07, 10:44 AM   #4
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Originally Posted by Dr.Deltron
Squeeze the pads to the rim with your hand. Pull the cam out from between the roller wheels. Now one brake arm can be pivoted away from the rim and the wheel should drop right out.
AH HA!

Ironically, I've actually done that for disassembly and re-lube. Apparently I lacked the mental horsepower to have made the connection...
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Old 07-05-07, 11:05 AM   #5
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Thanks for the quote, Pastor Bob. Seems like MnHPVA Guy has done this before. Think I'll go downstairs now and try to translate into 3-D.
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Old 07-05-07, 01:13 PM   #6
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I have always liked my Schwinn's RollerCam front brake, which is paired with an under-the-chainstays Shimano U-brake and 4-finger Shimano handles. As Dr. D. notes, the RollerCam quick release "mechanism" is unique. I set the spring tension just heavy enough to retract consistently without flopping about.
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Old 07-09-07, 11:42 AM   #7
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Finally got these set up well. Yes, it was a painful operation to go through the first time. But I have to say, these are very nice - and effective - brakes! And I agree that the spring-loaded posts are very neat once you figure out how to use them. Adjusting balance is a cinch.

Makes me want to replace the cantis on my tank with roller-cams. (aka "U-brakes"?) These require special posts. Do they all, or are there version that will replace cheepo cantis without frame surgery?
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Old 07-09-07, 12:04 PM   #8
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Makes me want to replace the cantis on my tank with roller-cams. (aka "U-brakes"?) These require special posts. Do they all, or are there version that will replace cheepo cantis without frame surgery?
1st~ Rollercams are NOT U-Brakes! They use the same mounting posts, but are NOT the same brakes.
U-Brakes are like frame mounted center-pull brakes. (old road bike style)
2nd~ Yes, the post for canti's are different than the posts for RC/U-brakes. Canti posts are mounted INSIDE the diameter of the rim, RC/U-B's the post is mounted OUTSIDE the rim diameter.
Frame "surgery" would be needed to switch from canti's to RC/U-b.

YES, rollercam brakes are pretty awesome! One of the reasons I bought my Cannondale MTB back in '86!
That, and they weren't mounted on the CHAINSTAYS!
Just because you CAN, doesn't mean you SHOULD!
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Old 07-09-07, 01:49 PM   #9
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Back in the day we had a small device that fit into the allen key holes on the rollers to automaticaly set the distance to 33. It was easy:

1. insert device into holes
2. pull cable tight
3. remove device
4. set pads
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Old 07-10-07, 08:49 AM   #10
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Back in the day we had a small device that fit into the allen key holes on the rollers to automaticaly set the distance to 33.
I set out to make such a tool, but the heads are so close to the chainstays that no tool mounting pins would fit. Then I though of a flat bar with two holes that would take the whole screw heads, but the heads are conical and it probably wouldn't stay without some type of clamp.

There are two unused threaded holes in the arms near the roller pivots that could be approached from the bottom, but it would take some work to figure out the proper spacing, starting with setting the pivot spacing correctly anyway, so I just went ahead and set it leaving tool creation for later.

To set I used a caliper depth rod set to 33mm and measured between edges of the bolt heads. Tighten the cable hold-down enough to hold under static load, but loose enough to slip under increased load (easier than it sounds). Space the arms too wide then with one hand squeeze the arms to force the cam to slip down the cable, meanwhile holding the caliper with the other hand.
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Old 07-10-07, 10:07 AM   #11
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Here's the Suntour tool for their rollercams. It's 33mm wide (center to center), and the rod diameter is 5mm. I found this one on ebay though I can't recall ever seeing any more.
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Old 07-10-07, 12:19 PM   #12
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Here's the Suntour tool for their rollercams. It's 33mm wide (center to center), and the rod diameter is 5mm. I found this one on ebay though I can't recall ever seeing any more.

I never thought I'd find a picture of one so I never bothered to look. Great find.
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Old 07-10-07, 03:36 PM   #13
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Is there a part number stamped on it?
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Old 07-10-07, 05:27 PM   #14
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Is there a part number stamped on it?
Afraid not.
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