Life of torque-sensing bottom bracket?

christob

Well-Known Member
Hi;
Any thoughts on the typical life of a torque sensing BB? My bike has a TDCM BB. I’ve put about 4,200 miles on this one, and my LBS technician showed me it was “worn out” when I took the bike in for troubleshooting / diagnosing a nearly constant clicky/squeaky sound and “clicks” I could feel through the pedals—as well as a unexpected trio of chain derailings in the last 3 weeks—-having never had one before. He showed me there was a lot of play and wiggle/slop in the BB, and that a worn bracket produces all of my symptoms typically.
So, I’m replacing it—but it seems like 11 months and 4,200 miles of paved surface, 99.8% rain-free riding wouldn’t or shouldn’t be enough time or use to wear this out? That’s just my gut reaction... but I have no prior experience with lifespan of a torque sensing BB...
 

6zfshdb

Well-Known Member
I'm not sure if this is to blame for your problem or not but it caused me a lot of grief. If you transport or store your bike with the seatpost removed, dirt, debris & water can enter the open tube and get down into the bottom bracket. I lost a BB on my Trek for this reason.

I usually carry the bike without the seatpost for weight & security reasons. Having learned my lesson, I now cover the open tube with snug fitting vinyl cap.
 

christob

Well-Known Member
Hi @6zfshdb -- I've never removed the seatpost for anything, outdoors, actually... (no car rack here -- when I move the bike by car, I put the whole bike in the back of my Prius.)
Of course, water could still get into the BB area -- since the TDCM BB has a wire emerging from it (through a pre-drilled hole in the bike frame) -- and while I generally avoid rain riding, I have been caught in perhaps half a dozen showers, and may have hit, once?, a puddle deep enough that the water could have reached up to that pre-drilled hole...
1555593487767.png
 

Jaxx

Active Member
Hi @6zfshdb -- I've never removed the seatpost for anything, outdoors, actually... (no car rack here -- when I move the bike by car, I put the whole bike in the back of my Prius.)
Of course, water could still get into the BB area -- since the TDCM BB has a wire emerging from it (through a pre-drilled hole in the bike frame) -- and while I generally avoid rain riding, I have been caught in perhaps half a dozen showers, and may have hit, once?, a puddle deep enough that the water could have reached up to that pre-drilled hole...
View attachment 32287
It is possible to get water ingress down the seat tube. I have a very expensive Storck carbon road frame. If I've ever had the bad luck of getting caught in a heavy shower? Then the seat would need removing, the bike placing upside down, while the water drained away.
 

christob

Well-Known Member
Setting aside water (let’s assume some likely VERY small amounts probably could have reached the BB over the 11 mos) — does that help answer the question of whether 11 mos/4200 miles would be “reasonable life” for this hardware?
 

rich c

Well-Known Member
Average cyclist cadence is 60rpm, assume 15mph average over 4,200, doesn't that work out to over a million revolutions? Most under load? Doesn't seem bad to me, but with my lack of confidence in my math who knows? Did the bearings fail, or was it the torque sensor? Bearings are cheap!
 

JRA

Well-Known Member
So they are bad, big question is can the bearings be replaced or do you need to replace the entire bb?
 

christob

Well-Known Member
At this point, the BB is being replaced; in the effort to remove it from the frame, the wire was severed ;)
 

christob

Well-Known Member
Average cyclist cadence is 60rpm, assume 15mph average over 4,200, doesn't that work out to over a million revolutions? Most under load? Doesn't seem bad to me, but with my lack of confidence in my math who knows? Did the bearings fail, or was it the torque sensor? Bearings are cheap!
Hi @rich c -- I'd say pretty darned close -- according to tracking the LCD control panel's stats, I've logged 18,631 minutes of riding time on this frame & BB.
(Of course, that is wheels-in-motion total time -- so it would include stretches of coasting without revolutions, too.) So if your "60rpm average" roughly accounts for coasting, then yeah, that's 1.1 million revolutions.

So. Is that kind of riding use reasonable to expect it would wear out this kind of BB?
(That's the part I don't know -- I'm just seeking anyone's gut-check opinion for reasonableness... ie, if I ride 4000-5000 miles a year, will I just need to expect to replace the BB every year?)
 

Jaxx

Active Member
Hi @rich c -- I'd say pretty darned close -- according to tracking the LCD control panel's stats, I've logged 18,631 minutes of riding time on this frame & BB.
(Of course, that is wheels-in-motion total time -- so it would include stretches of coasting without revolutions, too.) So if your "60rpm average" roughly accounts for coasting, then yeah, that's 1.1 million revolutions.

So. Is that kind of riding use reasonable to expect it would wear out this kind of BB?
(That's the part I don't know -- I'm just seeking anyone's gut-check opinion for reasonableness... ie, if I ride 4000-5000 miles a year, will I just need to expect to replace the BB every year?)
Not on a standard bike. At least my experience is gained from using quality components. Shimano, FSA, Campag etc.
 

Ravi Kempaiah

Well-Known Member
Hi @6zfshdb -- I've never removed the seatpost for anything, outdoors, actually... (no car rack here -- when I move the bike by car, I put the whole bike in the back of my Prius.)
Of course, water could still get into the BB area -- since the TDCM BB has a wire emerging from it (through a pre-drilled hole in the bike frame) -- and while I generally avoid rain riding, I have been caught in perhaps half a dozen showers, and may have hit, once?, a puddle deep enough that the water could have reached up to that pre-drilled hole...
View attachment 32287
One of the downsides of BB torque sensor is that the rider needs to keep a close eye on the BB and eliminate any play in the shell.
Older Izip models had this torque sensor and the wiring would get severed routinely and recently, they switched to the Suntour system that is a bit more robust.

if I were you, every 4 months, I would check the BB and make sure there is no play in the BB shell and crank spindle.
 

christob

Well-Known Member
Update: A new TDCM BB was installed Friday at my LBS --- I got in a 30 mile ride yesterday, and all the prior noises and "crunchy" sensations felt through the pedals are blissfully gone.
Overall pedaling seems smoother, as does the gear shifting, which would make sense if the BB was worn enough / had developed enough slop or play to start allowing some left-to-right wiggle through the spindle...

The folks at VEB (bike maker) said that yes, the bearings for this particular BB could be replaced -- though they've never had a customer need to do that. In my case here, that wouldn't have helped this time anyway, as the torque sensor wire was inadvertently severed during the LBS removal process. But if these same symptoms show up in say, another 12 months / 4 - 5k miles, I'll certainly try to remember bearing-replacement first, hopefully a little less pricey than the $149 BB.
 

christob

Well-Known Member
Further update. The TDCM BB that was installed in April began (apparently) acting up... after just 900 miles on it, the assist started intermittently cutting in and out, at any assist level. My worry (only speculation!) is that the LBS may not have installed it "perfectly" -- they don't sell rear-hub motor ebikes, and so (MAYBE?) they aren't as intimately familiar with torque-sensing BB's?
Just a guess on my part -- but if the install was not spot-on, perhaps with the BB movement @Ravi Kempaiah suggested above, the sensor wire could have eventually become pinched/crimped.

{Ravi -- could you expand on your comment above: "the rider needs to keep a close eye on the BB and eliminate any play in the shell." -- ie, how best to monitor / what to do, every few months?}

Anyway - VEB sent a new BB under warranty. Since I bought my Cafe, they have switched to a new BB (by Thun - I believe the X-cell RT2); that's what I'm getting rather than the previous "model" that was stocked on my bike. The Thun BB is not compatible with my existing controller -- so they've sent a new one of those as well. (Apparently, the updated features that come with the new controller will permit things like Bluetooth connectivity for programming updates, etc.)

All the new gear has arrived, and the bike is at the LBS awaiting a calendar slot to do the install...
 
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Ravi Kempaiah

Well-Known Member
but if the install was not spot-on,
Right This is what happens mostly. May be it is good to check the torque numbers and ensure the sensor "clutches" BB strongly and has no room for wiggle.
You are doing something like 5000 miles a year and that is like several years of riding on acoustic bikes for majority of the riders.

Do you see a small wire jetting out of the BB shell?
 
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christob

Well-Known Member
Hi @Ravi Kempaiah -- yes, the BB has a wire that passes from the spindle/body through a small hole in the frame in order to connect with the wiring system of the bike. (Both the original BB's, and the new Thun have this, since the sensor must communicate to the controller to indicate when I'm pedaling and when I'm not.)
I guess my question is, in terms of trying to check/monitor this on my own once the new one is installed... at home as a non-professional bike mechanic ;) -- where do I start? What would I be looking for or checking, routinely? And what kind of tools would I need in order to confirm torque numbers?
I assume you mean to check on the tightness / torque applied to tightening the components of the BB assembly? ie, the tightness of the threaded rings that secure the assembly into the bike frame -- I know the old BB required a 2-pronged BB wrench to unscrew; I'm not sure the Thun has the same mounting hardware -- but either way, I don't know that I've seen a BB wrench with applied-torque-measuring built into the wrench...?

Thun BB:
Thun.jpg
 

Ravi Kempaiah

Well-Known Member
Hi @Ravi Kempaiah -- yes, the BB has a wire that passes from the spindle/body through a small hole in the frame in order to connect with the wiring system of the bike. (Both the original BB's, and the new Thun have this, since the sensor must communicate to the controller to indicate when I'm pedaling and when I'm not.)
I guess my question is, in terms of trying to check/monitor this on my own once the new one is installed... at home as a non-professional bike mechanic ;) -- where do I start? What would I be looking for or checking, routinely? And what kind of tools would I need in order to confirm torque numbers?
I assume you mean to check on the tightness / torque applied to tightening the components of the BB assembly? ie, the tightness of the threaded rings that secure the assembly into the bike frame -- I know the old BB required a 2-pronged BB wrench to unscrew; I'm not sure the Thun has the same mounting hardware -- but either way, I don't know that I've seen a BB wrench with applied-torque-measuring built into the wrench...?

Thun BB:
View attachment 35416

Right!

Each BB sensor may have slightly different mounting hardware but they all need to latch onto the bike frame very firmly without any jiggle whatsoever.
I don't have a lot of time on those bikes equipped with BB sensors but I am aware of them and I do find them a bit more finicky than dropout sensors.

If I were you, I would start with a detailed look into that BB area every 2 weeks and see if there is any sign of cable pull.
Since I am not an expert on this, I am directing you to the experts who know this really well: https://www.ebikes.ca/about-us/contact-grin.html

These guys sell TDCM, THUN and know the stuff inside out.