In building up a Surly Long Haul Trucker for a friend, I encountered this problem: The BB we used is a Shimano UN-73, with stock plastic shoulderless left adapter cup. The left cup cracked during installation while at less than final torque. I've eaten through plenty of left cups now on this frame and they keep dying - one did it at very low torque, I think even before the cup bottomed out on the BB. I currently have it set up using a steel adapter cup off some other Shimano BB that seems to work fine. While installing the steel one, it went in somewhat rough, and I removed it and looked at the inside and there are gouges where it was presumably rubbing against the BB. The bearing feels signficantly less than perfect when everything is all tightened down.
What I'm guessing is going on is that the BB shell threads are out of line with each other enough to cause all this. I don't see how a facing error could cause this - could it?
I don't have access to piloted BB taps and am not familiar with using them. My concern with chasing this frame's threads with piloted taps is that if the error in the shell thread alignment is really bad, how would just forcing piloted taps through it all work without ruining the integrity of the threads? It seems like there's a judgement call here that needs to be made with that, but I have no idea how to make it.
We can still warranty the frame but I really don't want to.
In building up a Surly Long Haul Trucker for a friend, I encountered this problem: The BB we used is a Shimano UN-73, with stock plastic shoulderless left adapter cup. The left cup cracked during installation while at less than final torque. I've eaten through plenty of left cups now on this frame and they keep dying - one did it at very low torque, I think even before the cup bottomed out on the BB. I currently have it set up using a steel adapter cup off some other Shimano BB that seems to work fine. While installing the steel one, it went in somewhat rough, and I removed it and looked at the inside and there are gouges where it was presumably rubbing against the BB. The bearing feels signficantly less than perfect when everything is all tightened down.
What I'm guessing is going on is that the BB shell threads are out of line with each other enough to cause all this. I don't see how a facing error could cause this - could it?
I don't have access to piloted BB taps and am not familiar with using them. My concern with chasing this frame's threads with piloted taps is that if the error in the shell thread alignment is really bad, how would just forcing piloted taps through it all work without ruining the integrity of the threads? It seems like there's a judgement call here that needs to be made with that, but I have no idea how to make it.
We can still warranty the frame but I really don't want to.
It sure sounds like threads that aren't lined up properly.
A piloted tap is really easy to use (but outrageously expensive to buy). You simply set both taps in place (the "axle" through the middle will keep them parallel) and start both of them lightly, then start cutting threads, one side at a time. Unless the threads are WAY out, I'm guessing that a piloted tap would clean up the threads just fine.
In building up a Surly Long Haul Trucker for a friend, I encountered this problem: The BB we used is a Shimano UN-73, with stock plastic shoulderless left adapter cup. The left cup cracked during installation while at less than final torque. I've eaten through plenty of left cups now on this frame and they keep dying - one did it at very low torque, I think even before the cup bottomed out on the BB. I currently have it set up using a steel adapter cup off some other Shimano BB that seems to work fine. While installing the steel one, it went in somewhat rough, and I removed it and looked at the inside and there are gouges where it was presumably rubbing against the BB. The bearing feels signficantly less than perfect when everything is all tightened down.
What I'm guessing is going on is that the BB shell threads are out of line with each other enough to cause all this. I don't see how a facing error could cause this - could it?
I don't have access to piloted BB taps and am not familiar with using them. My concern with chasing this frame's threads with piloted taps is that if the error in the shell thread alignment is really bad, how would just forcing piloted taps through it all work without ruining the integrity of the threads? It seems like there's a judgement call here that needs to be made with that, but I have no idea how to make it.
We can still warranty the frame but I really don't want to.
It sure sounds like threads that aren't lined up properly.
A piloted tap is really easy to use (but outrageously expensive to buy). You simply set both taps in place (the "axle" through the middle will keep them parallel) and start both of them lightly, then start cutting threads, one side at a time. Unless the threads are WAY out, I'm guessing that a piloted tap would clean up the threads just fine.
I agree that running a piloted tap through would probably solve the problem unless it's bad enough, but on the other hand the issue is pretty darn bad on this frame, and I have no idea where to draw this particular line - and if I try the taps and it turns out that it cuts away too much material and very bad things happen to the threads or frame there, I'm worried that all I'm probably gonna be left with to try and warranty is a frame that one could argue strongly looks to have been mangled by incorrect use of BB taps.
Also I should mention FWIW that the individual BB parts thread in perfectly smoothly when not interfacing with one another - could that maybe indicate that the misalignment originated when the threads were cut originally, rather than during welding?
On 31 Jul 2006 21:13:12 -0700, "Nate Knutson" <[email hidden]>
Quoted message said:
Mark Hickey said:
Nate Knutson said:
In building up a Surly Long Haul Trucker for a friend, I encountered this problem: The BB we used is a Shimano UN-73, with stock plastic shoulderless left adapter cup. The left cup cracked during installation while at less than final torque. I've eaten through plenty of left cups now on this frame and they keep dying - one did it at very low torque, I think even before the cup bottomed out on the BB. I currently have it set up using a steel adapter cup off some other Shimano BB that seems to work fine. While installing the steel one, it went in somewhat rough, and I removed it and looked at the inside and there are gouges where it was presumably rubbing against the BB. The bearing feels signficantly less than perfect when everything is all tightened down.
What I'm guessing is going on is that the BB shell threads are out of line with each other enough to cause all this. I don't see how a facing error could cause this - could it?
I don't have access to piloted BB taps and am not familiar with using them. My concern with chasing this frame's threads with piloted taps is that if the error in the shell thread alignment is really bad, how would just forcing piloted taps through it all work without ruining the integrity of the threads? It seems like there's a judgement call here that needs to be made with that, but I have no idea how to make it.
We can still warranty the frame but I really don't want to.
It sure sounds like threads that aren't lined up properly.
A piloted tap is really easy to use (but outrageously expensive to buy). You simply set both taps in place (the "axle" through the middle will keep them parallel) and start both of them lightly, then start cutting threads, one side at a time. Unless the threads are WAY out, I'm guessing that a piloted tap would clean up the threads just fine.
I agree that running a piloted tap through would probably solve the problem unless it's bad enough, but on the other hand the issue is pretty darn bad on this frame, and I have no idea where to draw this particular line - and if I try the taps and it turns out that it cuts away too much material and very bad things happen to the threads or frame there, I'm worried that all I'm probably gonna be left with to try and warranty is a frame that one could argue strongly looks to have been mangled by incorrect use of BB taps.
Also I should mention FWIW that the individual BB parts thread in perfectly smoothly when not interfacing with one another - could that maybe indicate that the misalignment originated when the threads were cut originally, rather than during welding?
Try a different BB, any BB, even the wrong length and see what happens.
I agree that running a piloted tap through would probably solve the problem unless it's bad enough, but on the other hand the issue is pretty darn bad on this frame, and I have no idea where to draw this particular line - and if I try the taps and it turns out that it cuts away too much material and very bad things happen to the threads or frame there, I'm worried that all I'm probably gonna be left with to try and warranty is a frame that one could argue strongly looks to have been mangled by incorrect use of BB taps.
If a (quality) piloted tap buggers up the threads so badly the frame is ruined, the BB was buggered to start with. The threads have to be cut in parallel, and if doing so causes them to go out of spec enough to be unusable, it's a moot point... the frame wasn't useful as it was, either.
Quoted message said:
Also I should mention FWIW that the individual BB parts thread in perfectly smoothly when not interfacing with one another - could that maybe indicate that the misalignment originated when the threads were cut originally, rather than during welding?
The misalignment almost certainly had nothing to do with the welding, IMHO, though I suppose it's possible that the shell was warped somehow. I'm just betting the threads were cut wrong somehow - probably by someone short-cutting (no pun intended) the process and using two non-piloted taps.
In building up a Surly Long Haul Trucker for a friend, I encountered this problem: The BB we used is a Shimano UN-73, with stock plastic shoulderless left adapter cup. The left cup cracked during installation while at less than final torque. I've eaten through plenty of left cups now on this frame and they keep dying - one did it at very low torque, I think even before the cup bottomed out on the BB. I currently have it set up using a steel adapter cup off some other Shimano BB that seems to work fine. While installing the steel one, it went in somewhat rough, and I removed it and looked at the inside and there are gouges where it was presumably rubbing against the BB. The bearing feels signficantly less than perfect when everything is all tightened down.
What I'm guessing is going on is that the BB shell threads are out of line with each other enough to cause all this. I don't see how a facing error could cause this - could it?
I don't have access to piloted BB taps and am not familiar with using them. My concern with chasing this frame's threads with piloted taps is that if the error in the shell thread alignment is really bad, how would just forcing piloted taps through it all work without ruining the integrity of the threads? It seems like there's a judgement call here that needs to be made with that, but I have no idea how to make it.
We can still warranty the frame but I really don't want to.
Yes there is a threading error.
BB shells are threaded before frame assembly. After welding there can be significant curvature to the BB shell. That leaves the two sides' threads not on one axis.
Yes a piloted tap set is _exactly_ what you need. The second component is a skilled operator for those taps. And the appropriate (steel? Al? ti? ) cutting fluid.
-- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
