DaveLeeNC

I just (again) replaced the BB on my Lemond Revmaster Sport spin bike. I did this maybe 100 riding hours ago so maybe there is another issue here (I am basically a bike mechanics beginnner with no intention of changing that - too old). The BB is (from what little I know) a conventional threaded bottom bracket (see pic). When I was installing the BB I was doing my best to match the spec'ed threaded cups torque spec of 175 in-pounds. When I got in that range (as best as I could tell without a torque wrench) I noticed that suddenly the spindle would get very hard to turn. So I ended up tightening these things just below that point (which seemed to me to be somewhat below 175 in-pounds, but ...).

Is this normal? This bike is now 11 years old and I am suspicious (based on how often I end up replacing BB's) that there are other problems (possibly ones that I caused somehow).

Now for the IQ measurement part. I would suggest that you measure how long a person like me spends trying to thread the right side cup into the bike by turning it clockwise (time spent cleaning the threads with acetone counts, BTW). Then apply the equation of "IQ = 120 - 3 x Time" (where Time is how long in minutes the subject spent trying to thread the right side cup). In my case this comes out to 75 which seems about right to me (note that not that long before I had removed the old one by turning the BB tool clockwise - maybe that deserves extra deductions).

dave

ClydeClydeson

Based on your description of the problem, the cause might be misaligned bottom bracket faces or threads. There is a process called 'facing' the bottom bracket where a tool is used to create perfectly flat and parallel surfaces on the faces of the bottom bracket, primarily so the bottom bracket is not twisted or pushed out of alignment by out-of-parallel or -flatness runout. It might be that the faces of the BB were cut unevenly, or warped during welding, or it might simply be that there is some paint left over throwing things out of alignment. Or it might be that the threads in the BB shell are not perfectly aligned L-to-R and need 'chasing'. Bike shops used to have tools for this, but I don't know now that there are so many bottom bracket standards. Call and ask if your favourite LBS has a BB facing tool and/or BB taps for chasing the threads, likely for British standard bottom brackets.

Iride01 

How long did the previous and original BB last? Was it replaced for the exact same symptoms?

Sorry, I'm just incredulous at BB issues. I've never had any. Never replaced a BB for wear, though I came close with an old Ashtabula crank that let all sorts of sand and grit get in the BB. But it just needed cleaning and bearing adjustment. Every other BB replacement was just because I was changing cranks and another 7 to 18 bucks for a new BB seemed like good money spent. Maybe not.

SoSmellyAir

DaveLeeNC What bottom bracket did you install as a replacement last time?

Bb Cartridge Assy (sportsmith.com)

This one? Perhaps try a sealed cartridge bottom bracket from a more reputable brand?

DaveLeeNC

ClydeClydeson Thanks for the tip regarding facing tools.

Iride01 The last time I did this was maybe a year ago and (crude guess) 100 hours. Indoor riding is my bad weather alternative. I have done this replacement 3 or 4 times (bike purchased in 2011). It was enough that the last time that I bought a BB I bought 2 of them (used the last one this morning). I rode for 70 minutes today and at the end was already hearing the hint of a squeak. It was a loud squeal (plus a thump) when I replaced it today.

SoSmellyAir I bought this https://www.sportsmith.com/bottom-br...37?serial=3891 (same BB but last time it was purchased from Hoist fitness). I have no idea about sealed cartridge alternatives.

I am not sure what has happened here but I have been mulling over purchasing a smart bike of some kind. The 'hint of a squeak' on my last ride plus the fact that my BB seems to no longer be available has pretty much pushed me over the edge, I think. The Revmaster Sport was notorious for failing BB's, from what I understand.

dave

ps. I am still curious about this bearing cup torque thing that I referenced in the original thread. I don't recall that happening the other times that I did this replacement.

SoSmellyAir

This looks (to me) just like a regular JIS square tapered bottom bracket (others can confirm?) at a tremendously marked up price. While there are no markings to ascertain its specification (so LeMond can maintain a "monopoly" on the replacement parts), you can measure the spindle length and the shell width (usually either 68 mm or 73 mm) and buy a quality replacement (with the same specifications) for $30, e.g.:

Tange LN-3922 Square Taper Bottom Bracket – The Bikesmiths
Tange LN-3922 Bottom Bracket | - Ben's Cycle (benscycle.com)

Worth a $30 bet unless you are set on a smart trainer.

DaveLeeNC

SoSmellyAir Very interesting. I am sure that I could take one of my several failed BB's down to my local LBS and they could give me the info I need. Thanks. dave

SoSmellyAir

You may also want to measure the BB shell width of your stationary bike after removing the cranks and the bottom bracket.

Iride01 

You mentioned you didn't tighten it to spec. You might be certain to do that next time. If the spindle is getting restricted as you tighten the retainer then something is amiss. Maybe the faces or the threading of the shell as someone mentioned. Maybe something else that will be a head slap when found.

Still, can you describe exactly what is wrong with the BB itself? If it is just noise, then that might just have been the body of the BB wobbling around in the retainer cup that had worked itself looser because it wasn't tightened enough.

And if you didn't, I'd put some grease or anti-seize on the threads before you install the next one.

DaveLeeNC

The last BB was definitely not tightened below spec's. And it was quite a chore to get the cups 'unscrewed'. The BB bracket spindle (old BB) no longer turns smoothly (you can feel a bit of vibration when you turn the spindle. This is different than the old BB spindle. When pedaled the old BB squealed enough that my wife had to close the door so that it did not bother her on the other side of the house.

There is a problem here beyond just multiple failed BB's but I am not enough of a mechanic to address it and it is not something that you pack up in your car and haul off to SomePlaceThatIDon'tKnowWhereThatMightBe. 'Cannot tighten the current BB' to spec was the last straw for me.

So I just ordered a Smart Bike and I will probably give away/donate the 11 or 12 year old Revmaster.

Thanks for all the input and help.

dave

Iride01 

Mr. 66

I've run into this before with a Shimano bb, I ended up using a spacer/washer at the cup and bearing interface on the NDS when I installed.