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KerryIrons
Joined: 12 Jan 2004
Posts: 3236
Location: Midland, MI7/21/15 6:39 PM |
BBs and tires
Two items.
My bike has press fit BB with threaded cups to hold the Campy Chorus Ultra-torque bearing cartridges. When I first built up the bike the BB was fairly stiff which I attributed to new bearing seals and perhaps excess grease. Then all of a sudden the excess friction disappeared. I asked this group for ideas but didn't really get a solution. Since the friction was good I didn't chase it further.
Then I notices variable friction as I turned the crank. I decided to disassemble and sort things out and when I put the wrench to the Hirth Joint bolt I found it was not that tight. I tightened the nut and the friction came back only worse. Smooth but too darn tight. So back to the total disassembly approach. Took it all apart, cleaned everything - found nothing - bearings smooth and clean. But then on reassembly I leaned on the screw-in cups and one of them was not all that tight. So leaning on it a little harder and it went in maybe another half turn. And that totally fixed the friction issue. Somehow I thought those cups would go in solid and bottom out but apparently they need more torque than just "snug."
Second item:
I had my first flats on the road with my Velocity A23 rims. When I first pumped the tire up the tire didn't fully seat in the rim (tubless compatible rims with deeper tire bead grooves). I worked the tire by hand and added more pressure and it sorted itself out. With the second flat, I only got the tire "mostly" seated and since I wasn't far from home I decided to ride with a bump in the tire. However, within about a mile of riding, the tire slowly seated itself until there was no bump at all.
So does anybody have any tricks to get the tire seated on these types of rims, or do I just have to pump them up hard. When I pump them with a floor pump you can actually hear the tires pop into place but nothing like that happened on the road with a "large" mini pump.
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dfcas
Joined: 11 Jan 2004
Posts: 2815
Location: hillbilly heaven7/21/15 8:16 PM |
I had to use a soapy water solution on the bead of the tire with my A23 rims to get the bead to seat evenly. It seems that a new tire will seat properly the first time its installed, but the second time I have needed to use soapy water.
I wonder if on the road water from your bottle would help it seat? Maybe carry a small soap packet that is about the size of a ketchup packet?
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walter
Joined: 11 Jan 2004
Posts: 4391
Location: metro-motown-area7/21/15 8:25 PM |
UT BB torque spec must be there for a reason
campy spec for UT cups is 35Nm...quite a bit more than "snug"!
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dddd
Joined: 11 Jan 2004
Posts: 3345
Location: NorCal7/22/15 6:13 PM |
That's 25 ft-lbs, which is a pretty good heave, very much needed to reliably settle a large-diameter threaded interface to sufficient "pre-load" or "tension".
With increases in diameter, added torque is needed to overcome a loss of leverage as the "working" distance from center is increased!
One thing I always do when torqueing to an accurate level is to hold the torque for some period of time, to verify that no polymer threadlocker or detritus is possibly inhibiting full meshing of the threads to full tension. Often the part or fastener will move significantly, given extra time.
For the same sort of reason, I always rotate the adjustable cup
with
the lockring when arriving at a final state of torque and adjustment when securing the adjustment on old-fashioned cup/cone bottom brackets, and I've never had one loosen. Dirt, paint or rust in the many rows of bb threading might otherwise prevent a full settling of the threadings under tension, which might cause loosening later.
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KerryIrons
Joined: 12 Jan 2004
Posts: 3236
Location: Midland, MI7/24/15 5:15 PM |
Thread locker
quote:
One thing I always do when torqueing to an accurate level is to hold the torque for some period of time, to verify that no polymer threadlocker or detritus is possibly inhibiting full meshing of the threads to full tension.
I think this was the problem with the initial install - the thread locker (factory applied) made things bind. Taking it out and applying grease allowed the unit to thread farther in.
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walter
Joined: 11 Jan 2004
Posts: 4391
Location: metro-motown-area7/25/15 9:42 AM |
"the thread locker (factory applied) made things bind"
maybe thats part of the rationale for the factory-specified 35nm torque spec.
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KerryIrons
Joined: 12 Jan 2004
Posts: 3236
Location: Midland, MI7/25/15 5:07 PM |
Torquing
Since the thing that needs to be torqued is a large diameter threaded cup with the standard (Shimano and Campy anyway) splined wrench, the question is how to measure torque on such a device. The Park shop tool is the splined version of the old Campy fixed cup "D" tool with no way to put a torque wrench on anything. I take it there must be a tool that looks like a very large socket
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walter
Joined: 11 Jan 2004
Posts: 4391
Location: metro-motown-area7/25/15 7:50 PM |
yep
mine fits onto a 3/8" socket.
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Dave B
Joined: 10 Jan 2004
Posts: 4511
Location: Pittsburgh, PA7/26/15 7:01 AM |
quote:
I take it there must be a tool that looks like a very large socket.
Yes, the Park BBT-19.2 (steel) and BBT-69 (Aluminum) are both large sockets that take a 3/8" square drive ratchet or torque wrench. They fit Campy, Shimano and lots of other external bearing cups.
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