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#11
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Which frames have italian thread bottom brackets?
On 17 Apr, 00:42, Andre Jute wrote:
On Apr 17, 12:06*am, Jay Beattie wrote: On Apr 16, 3:21*pm, AMuzi wrote: Jay Beattie wrote: On Apr 16, 8:10 am, wrote: Jay Beattie wrote: Ultimately, I see only that solution for BB attachment with a precision spindle and bearing assembly just as the threadless steer tube has solved the head bearing/bar attachment problem.. What problem was that? The one that was solved with current outboard bearing, two piece cranks. *Except that now we have fretting against the spindle by the bearing cartridge -- except in the Campagnolo design (and maybe others; I haven't done a market survey). Outboard bearings are not directed at the problem of radially loaded fretting threads but rather to accommodate a larger tubular spindle for crank attachment while retaining reasonable bearing ball size, for which there is no space inside the BB shell. *To make up for that, the overhung bearing besides having rotating radial loaded threads, has overhung loads, worsening thread fretting. Both Shimano and Campagnolo are grasping at straws to solve difficult BB problems. *I think their crank attachment schemes are an improvement but the Shimano solution is a tried and a true solution gleaned from prior art. *To make up for that, the overhung bearing worsens the Bearing to BB shell attachment. I thought you were just talking about the crank attachment which was "fixed" with the Shimano pinch bolt approach. And to be honest, I did not know there was a problem with BB thread fretting or obliteration. *I have never had that problem, at least in terms of seeing thread degredation, not even in my aluminum BB bikes. *I currently have one bike with an outboard BB, and it seems to make a lot more noise that prior BBs, even with grease or Teflon on the threads. You must have wondered why BB's have left hand threaded right bearing cups. *As I said, wherever you see left hand thread fastenings, you are looking at faulty design. *At least the ancients that specified the left hand thread recognized the loosening problem and invoked the left hand thread dodge, not having a clear understanding of the mechanics of radial load bearing threads. Even if the threads do not unscrew, they fret and cause failures as right pedals in aluminum cranks do. *I haven't seen steel cranks fail, but they show rouge and fretting damage on contact faces with chrome plating worn off and a countersink formed under pedal spindle faces. Have you seen bottom racket shell threads degrade due to fretting? -- Jay Beattie. Yes. Gee, I must not be trying hard enough. *Even the head on my minumum bell looks pretty sharp. *I had some steel frames with a lot of bust, but nothing to suggest that fretting was destroying the threads. *Live and learn. -- Jay Beattie. Those suffering fretting, (or worried about it), should get bottom rackets with plastic cups both sides. They allow a certain amount of movement and won't stripe your backside red or cause a rude din. Kinsex is a favourite with high-end Europeans, manufacturers of "maintenance-free" bikes among others reason because Kinsex BB (before breakfast) are optionally available to the largest families, the requirement is best fulfilled with plastic cups both sides. The reasons I remember include fretting but in the main that a plastic cup doesn't have to be regreased; the bottom racket is on the shelf for his wife to hit the target. I'm sure that's not right. |
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#12
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Which frames have italian thread bottom brackets?
On Apr 16, 8:00*pm, Still Just Me
wrote: (Jobst): What extreme conditions? *This design change was not made almost universally in the bicycle industry as a whim as you seem to depict it, done for extremists. *My local frame builders can tell you of the many fork/stem rescues they have performed. (SJM): Care to estimate the percentage of frames that have this issue? Something like .000000001% perhaps? Seatposts, too. Many many occurrences. If SJM hasn't seen them, perhaps that's because he's more careful about maintenance ("pull and regrease") than some, including me. I've had a few tough extractions and one solid freeze (stem) over the years. Common enough IME to suggest to bike sellers that one advantage of parting out "vintage" bikes is to show the seatpost and stem will in fact come out and are not corroded in place. I'm not saying it was done for extremists, but the percentage of the population that benefits from it in any way is very, very small. IMHO everyone benefits from being able to adjust headsets with an allen key instead of the old headset wrenches, simply because the tool is much cheaper g. But really, and the process is so much easier, with no slipping wrenches or rounded corners. I think that trumps any personal facility with tools. You mean MTB's as "demanding"? Yeah, they had issues. Bikes were not designed for severe off road use, at least not in the early days. But for road riding? Headsets were not an issue and the stuck quill was not the norm. Yet this method/design also comes with its own set of disadvantages, like any other. *Not to mention, that while a few of us play with handlebar changes, the percentage of those who do is very small; and the small percentage of those who do and then do not actually _want_ to change brake levers as part of the package smaller still. How about not scratching bars while feeding them through old-style clamps? I mean, easily, no spreader needed (improvised or integral as with 3ttt) needed, and a more secure attachment via a "faceplate" with two or four bolts that does less bending than the old style single bolt clamps on stems without removable faceplates? Those "z" scars on Cinelli engraved bars were a pretty common sight, and never pretty. Bars that rotate in my old-style stems (Cinelli and 3ttt) don't in the faceplate style. After some experimentation over the past several years, I've settled on a favorite handlebar. Three bikes, maybe four if you count the FG. I tried several handlebars with different bends and widths. Much easier via removable faceplate. I'm planning on one more swap between bikes because of handlebar tape color/pattern "mixup"-- IOW, I decided I should have put A tape on bike B and B tape on bike A. All Campy brifters, so the swap will be much easier, not much to take apart. Truly rare in your universe, I understand g. But, "me like". --D-y |
#13
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Which frames have italian thread bottom brackets?
On Apr 16, 4:15*pm, wrote:
If an Italian-thread right-side cup is in tight enough to not unscrew, is it still moving and fretting with use? Just as with pedals, you can't make them tight enough that they don't move. That's the answer to my question; thanks. Just look at the faces of your cranks when removing a pedal. Yeah, those wear visibly. But count me with Jay Beattie among those who haven't seen their BB threads deteriorate-- although I have no reason to doubt your and Andy Muzi's reports that they can and do. Left hand thread in that place is not idly chosen. *Manufacturers and most bicycle shops know about this but do not go so far as to recognize it as a design error. *You ask if this cup can be tightened tight enough... tight enough for what? *How can it unscrew if it isn't moving. *I had right hand threads on my old early Cinellis and re-tightened the right hand cup at major maintenance intervals. Tight enough for what? To not come loose in use. I've had an Italian frame for 30 years. Early on, I learned how tight to install the right-hand cup so that it didn't loosen with use. (I can't give a torque value, I only have the simple hand BB tools--but it has to be on notably tighter than I bother to install cups in English BBs.) Since I learned how tight to install it, it has never come loose--I never retighten it in between the times I take it out for cleaning and regreasing-- which made me wonder whether it ceases to move altogether if it's screwed in hard enough. You say no, and I'll take your word for it. Tom Ace |
#14
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Which frames have italian thread bottom brackets?
(Jobst):
What extreme conditions? This design change was not made almost universally in the bicycle industry as a whim as you seem to depict it, done for extremists. My local frame builders can tell you of the many fork/stem rescues they have performed. (SJM): Care to estimate the percentage of frames that have this issue? Something like .000000001% perhaps? --D-y wrote: Seatposts, too. Many many occurrences. If SJM hasn't seen them, perhaps that's because he's more careful about maintenance ("pull and regrease") than some, including me. I've had a few tough extractions and one solid freeze (stem) over the years. Common enough IME to suggest to bike sellers that one advantage of parting out "vintage" bikes is to show the seatpost and stem will in fact come out and are not corroded in place. -snip- Quite common : http://www.yellowjersey.org/goodn.html -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#15
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Which frames have italian thread bottom brackets?
On Apr 16, 8:18*pm, --D-y wrote:
On Apr 16, 8:00*pm, Still Just Me wrote: (Jobst): What extreme conditions? *This design change was not made almost universally in the bicycle industry as a whim as you seem to depict it, done for extremists. *My local frame builders can tell you of the many fork/stem rescues they have performed. (SJM): Care to estimate the percentage of frames that have this issue? Something like .000000001% perhaps? Seatposts, too. Many many occurrences. If SJM hasn't seen them, perhaps that's because he's more careful about maintenance ("pull and regrease") than some, including me. I've had a few tough extractions and one solid freeze (stem) over the years. Common enough IME to suggest to bike sellers that one advantage of parting out "vintage" bikes is to show the seatpost and stem will in fact come out and are not corroded in place. A google search of this newsgroup will find that how to remove a stuck stem or seatpost is a common question (it's also covered at length in Sheldon Brown's webpages), and that quite a few of the regulars have had to deal with it. Sometimes on used bikes with dodgy histories, but occasionally on their own bikes that have been neglected, perhaps, but not abused. It's certainly more than .0 and a lot of zeroes percent. I don't care too much about the threaded/threadless war, and nearly all my bikes have threaded stems. But I have had a nice threaded stem that just wouldn't work in the bike I used it for. It had a conical expansion nut rather than a wedge. Even a mild tightening force would get it super-stuck and I'd have to whale on it with a mallet to remove it. To add insult to injury, when installed, the actual stem shaft was just a tiny bit undersized (as they mostly are) and it would rock and creak a little when pedaling while standing. So the damn thing was stuck fast, but it wasn't even tight. I replaced it with a wedge stem and the bike's fine, but experiences like this make you think the whole stem-threaded steerer interface was really not engineered for the long term, and that its commonness is a legacy issue more than a desirability issue. Ben |
#17
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Which frames have italian thread bottom brackets?
On Apr 16, 4:42*pm, Andre Jute wrote:
On Apr 17, 12:06*am, Jay Beattie wrote: On Apr 16, 3:21*pm, AMuzi wrote: Have you seen bottom bracket shell threads degrade due to fretting? -- Jay Beattie. Yes. Gee, I must not be trying hard enough. *Even the threads in my aluminum shells look pretty sharp. *I had some steel frames with a lot of rust, but nothing to suggest that fretting was destroying the threads. *Live and learn. -- Jay Beattie. Those suffering fretting, or worried about it, should get bottom brackets with plastic cups both sides. They allow a certain amount of movement and won't strip your bike's threads or corrode in. Kinex is a favourite with high-end European manufacturers of "maintenance-free" bikes among other reasons because Kinex BB are optionally available with plastic cups both sides. The reasons I remember include fretting but in the main that a plastic cup doesn't have to be regreased; the bottom bracket is in the shell for its life, fit and forget. For my sins, I have a bike sporting an Italian thread bottom bracket that actually now has a cheap Shimano cartridge BB with a plastic cup. But the plastic cup is _only_ on the non-drive side. It's one of their BBs (maybe an LP-27) where the drive side "cup" and threads are an integral part of the steel cartridge. I am skeptical that one could tighten a plastic cup enough to hold an Italian drive-side plastic cup in place, without destroying the plastic threads and splines and eventually splitting the cup. I had to really reef on the steel cup (and yeah, I did use a long-handled torque wrench) to get the steel BB threads tight enough. Items like this are rare. You can't generally even buy a cheapo BB in Italian thread anymore, and the selection of spindle lengths in decent Italian BBs (aluminum or steel cups) is now limited. A friend gave me the cheapo item as a temporary fix so I could build up the frame. It is, incidentally, not an Italian frame at all, but a ~30 year old US-made custom frame, an Andy Gilmour. Back in the day, custom builders would sometimes use Italian threading. Mr. Gilmour told me he'd used both Italian and English then (I don't know whether it was at his or the customer's whim). Ben |
#18
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Which frames have italian thread bottom brackets?
On Thu, 16 Apr 2009 16:48:38 -0700 (PDT), Nick L Plate wrote:
On 17 Apr, 00:18, AMuzi wrote: wrote: Even if the threads do not unscrew, they fret and cause failures as right pedals in aluminum cranks do. Tom Ace wrote: If an Italian-thread right-side cup is in tight enough to not unscrew, is it still moving and fretting with use? Fretting wear occurs in all crank bearing thread formats with high mileage or high loads. A cup which is "not moving" isn't moving, by definition. In the case of your right side cup, it probably is moving though. The movement from cyclic loading frets the threaded area whether it unscrews or not. Just checked thread forms and whitworth is 55deg while a cycle thread is 60deg. There could lie the problem. No. a) I know of no bottom bracket cups or shells that used Whitworth threads; please supply an example. b) even if you can do a), at the size of the thread in question a five degree difference in thread angle gives a depth difference of just about a thousandth of an inch; which I suspect is not only smaller than the manufacturing tolerances but also smaller than the fit allowances. ....and in passing, if you do manage to do a), could you get to work on your job of supplying that example of spokes worn through by a third at the crossing point? |
#19
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Which frames have italian thread bottom brackets?
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#20
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Which frames have italian thread bottom brackets?
On Apr 17, 10:54*am, Mike wrote:
On 16 Apr 2009 23:04:05 GMT, wrote: How do you explain the nearly universal adoption of the threadless steertube? Sometimes there is really no logic to the widespread adoption of something new, for most practical purposes this is one of them. -- There is great logic behind the adoption of the threadless steerer tube on forks. Cheaper. One fork fits all sizes of a particular frame. 48cm to 62cm, same fork. No need to cut forks to fit the different sizes within a frame range and thread every single one of them. And cut the keyhole slot. That takes time and money and machining and people. Cheaper stems too. I suspect threadless stems are cheaper and easier to make than quill stems. Assembly time is likely reduced. Probably you can tape and assemble the bars before beginning to assemble the bike. Use lower cost labor for this. Maybe contract with a supplier to deliver already taped up bars with brake levers on them to the final assembly plant. Then just bolt the completed bars to the bike with the removable faceplates now used on all stems. And of course the threadless fork/stem configuration allows for the use of aluminum or carbon fork steerers instead of steel. Weight consideration. Only steel for threaded forks. Your claim that there is no logic to the widespread adoption of the threadless fork/stem is illogical. |
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