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Replacement Dual Pivot Centering Screw

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Replacement Dual Pivot Centering Screw

Old 02-18-15, 11:53 AM
  #1  
Dfrost 
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Replacement Dual Pivot Centering Screw

I have an early Shimano 105 dual pivot brake caliper, and the screw-slotted centering screw has just about lost it slotting, thanks to the very stiff thread locking material that makes it very difficult to turn. I can probably get it out with pliers, but it will be useless afterwards.

Can this screw be replaced with a 4mm (or other size) Allen bolt? Can't see enough of the threads to judge the thread pitch. Or are the allen-headed Ultegra equivalents available as a replacement?
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Old 02-18-15, 12:27 PM
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I have early examples of RX-100 (A-550), 103 (1055), and Ultegra (6400) dual pivot brakes on some of my bikes, and they all use the same same screw in one of the arms (philips), and the same mounting screw/bolts (hex/allen).

If you have a slotted screwdriver head small screw, I'd say that someone already replaced the original one. Go ahead and install a philips head screw from an Ultegra dual pivot caliper, if you have one. It should be the same as the original was.
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Old 02-18-15, 01:26 PM
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IME- this screw is overworked by many people. If all is right, once the brake is properly centered, there shouldn't n]be any need to repeat the process. In fact, the brakes usually come from the factory with this screw in a correct neutral position.

Btakes not staying centered is usually because the entire caliper isn't tight against the frame, and is moving when bumped. Center the brake by rotating the caliper appropriately and tightening, or if you prefer not to have it rigidly tight, recenter by moving the caliper back rather than fussing with the centering screw. In almost 50 years of riding with caliper brakes, both single and dual pivot, I don't remember ever having to fuss with centering once a brake was mounted.
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Old 02-18-15, 03:58 PM
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Originally Posted by FBinNY View Post
IME- this screw is overworked by many people. If all is right, once the brake is properly centered, there shouldn't n]be any need to repeat the process. In fact, the brakes usually come from the factory with this screw in a correct neutral position.

Btakes not staying centered is usually because the entire caliper isn't tight against the frame, and is moving when bumped. Center the brake by rotating the caliper appropriately and tightening, or if you prefer not to have it rigidly tight, recenter by moving the caliper back rather than fussing with the centering screw. In almost 50 years of riding with caliper brakes, both single and dual pivot, I don't remember ever having to fuss with centering once a brake was mounted.
+1
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Old 02-18-15, 04:06 PM
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Originally Posted by FBinNY View Post
IME- this screw is overworked by many people. If all is right, once the brake is properly centered, there shouldn't n]be any need to repeat the process. In fact, the brakes usually come from the factory with this screw in a correct neutral position.

Btakes not staying centered is usually because the entire caliper isn't tight against the frame, and is moving when bumped. Center the brake by rotating the caliper appropriately and tightening, or if you prefer not to have it rigidly tight, recenter by moving the caliper back rather than fussing with the centering screw. In almost 50 years of riding with caliper brakes, both single and dual pivot, I don't remember ever having to fuss with centering once a brake was mounted.
From what I seen it's even more simple than that. The most common reason I see for brakes that were properly centered and then suddenly weren't is that they don't have the axle properly installed in the dropouts. It's more common when the wheel is put in place on a workstand but it happens when the wheel is standing on the ground. Stupid lawyer lips and all the fiddling with the "quick" release skewer is usually the cause.

The brake can get bumped but I always check the wheel in the dropout first...saves time
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Old 02-18-15, 04:11 PM
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The Shimano replacements are hard to find. You can pretty much use any old Allen head bolt, it just won't match perfectly. I had the same problem on my 105 (5500) calipers.
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Old 02-18-15, 06:18 PM
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Thanks everyone for your replies.

I mostly agree with all your statements and opinions, and don't have a problem with the brake staying centered on my own bikes, where I might use that adjuster for a tiny bit of tweaking very rarely. I always make sure that the bike is standing on the ground and the wheel is fully seated in the dropouts when tightening the QR.

Roadguy, I know that the screw has never been replaced, because I bought that 105 caliper new more than 20 years ago, but the Phillips portion of the head has stripped (there's very little engagement), and I can still use the flat blade slot for a small amount of motion if I exert enough force to keep the screwdriver engaged. The later Ultegra allen head version would be much more robust for the few times an adjustment might be made. Unfortunately I don't have a spare Ultegra adjusting bolt, but I do have a variety of Allen head 4mm bolts, hence that part of my question.

Gsa103 noted this problem is not uncommon. The bike in question receives less of my personal attention these days (caliper now on daughter-in-law's Centurion) and I'd just like to make it as functional and serviceable as possible before returning it to her tomorrow following a wide range of upgrades that were my birthday present to her. The brakes are very nicely centered as-is, and firmly bolted as FB suggests.
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Old 02-18-15, 06:31 PM
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Yes you can just use the proper sized allen head bolt replacement. Stainless would be best. An allen head will be much less likely to get feckered up when adjusting than the phillips but you can also make it easier to turn by just closing the calipers slightly. The bolt rests against the brake arm which can make it harder to turn so taking the pressure off by closing the brakes will make it turn easily.
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Old 02-18-15, 06:39 PM
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Originally Posted by Dfrost View Post
Thanks everyone for your replies.


.....but the Phillips portion of the head has stripped (there's very little engagement),.
FWIW - I don't know of a single instance of true Phillips head screws ever being used on bikes. This is why so many people have issues with cross-point screw heads rounding out. The true Phillips screw has a deep socket and properly takes the pointed Phillips head drivers most people own. But the cross point screws used on bikes are not nearly so deep, and the point on Phillips drivers keeps the blades from moving deep enough to engage properly. So you end up trying to drive the screw with poor engagement at the center, and zero engagement farther out where the screw could handle some torque.

If you don't want to strip bke screws, don't buy Phillips head drivers, but look instead for the similar Posi-Drive. Or simply look for a blunter point so the engaged screwdriver bottoms on the driving vanes, not the point. If you already own Phillips drivers, you can improving the engagement by grinding back the point, trial and error, until you find the screwdriver engages solidly.
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Old 02-20-15, 03:37 PM
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Thanks for that information, FB. I did not know that.

FWIW, I replaced the damaged screw with a 4mm Allen head bolt, with blue Locktite on the threads. It will probably never need to be touched.
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Old 02-21-15, 02:55 AM
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I've had a set of 1st-gen Ultegra dual-pivot brakes since 1992 and only recently learned what that screw was for; never used it. I've always centered my brakes by loosening the mounting nut, squeeze calipers together by hand and tighten. Always works perfectly.
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Old 02-21-15, 09:57 AM
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I've used Shimano single and dual pivot brakes from RSX up through Dura Ace and never once touched the centering screws. I center them by hand or, for single pivots, with a "brake spanner" and tighten the mounting bolt to keep them in place. The only centering screws I've ever needed to use were on cantilever and V-brakes.
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