Bottom bracket wear

[11.4]

What happens if you use a bulletproof cartridge bottom bracket like a BB7710 (basically the old 7700-era Ultra bottom bracket) and a pair of Octalink cranks. I know you lose your power meter, but try it for a month or two and see what happens.

You had mentioned you used the high-end Wheels annular bearing set, yet it also failed on you. If the issue was a skewed bottom bracket, that Wheels bottom bracket should at least have minimized bearing failure.

Is your chainring perfectly planar through a crank rotation? If your bottom bracket shell is forcing the bottom bracket out of alignment, shouldn't it be reflected in an out-of-plane chainring?

Last, SRM has had episodic problems with bottom bracket milling being slightly off kilter -- their Octalink bottom brackets sometimes weren't concentric so one crank would bring the pedal in and out during a crank rotation. The same happened with their later Dura Ace models (hollow shaft) and was almost a chronic problem in tapered square spline days. This has mostly been seen on track cranks, possibly because they are not a high-volume product and cranks were milled more by hand. Long shot that the crank is out of alignment? I'm not sure that it should be killing bottom brackets like this, but looking for issues.

I've worked with track cranks for over forty years, and almost exclusively with track equipment. I might even have been at it longer than Old Potatoe. I'm always discovering new things, but in all that time, with a lot of screwy track frames, haven't seen a failure rate like you describe. It's got me curious and I'd love to know how you diagnose it in the end and how you fix it.

[jc031699]

There is a chance the Hambini BSA 24 design could help with your alignment issues, since the two cups are threaded together on one side.

https://youtu.be/R7PANRqY0oU

[mjf]

Originally Posted by 11.4

What happens if you use a bulletproof cartridge bottom bracket like a BB7710 (basically the old 7700-era Ultra bottom bracket) and a pair of Octalink cranks. I know you lose your power meter, but try it for a month or two and see what happens.

You had mentioned you used the high-end Wheels annular bearing set, yet it also failed on you. If the issue was a skewed bottom bracket, that Wheels bottom bracket should at least have minimized bearing failure.

Is your chainring perfectly planar through a crank rotation? If your bottom bracket shell is forcing the bottom bracket out of alignment, shouldn't it be reflected in an out-of-plane chainring?

Last, SRM has had episodic problems with bottom bracket milling being slightly off kilter -- their Octalink bottom brackets sometimes weren't concentric so one crank would bring the pedal in and out during a crank rotation. The same happened with their later Dura Ace models (hollow shaft) and was almost a chronic problem in tapered square spline days. This has mostly been seen on track cranks, possibly because they are not a high-volume product and cranks were milled more by hand. Long shot that the crank is out of alignment? I'm not sure that it should be killing bottom brackets like this, but looking for issues.

I've worked with track cranks for over forty years, and almost exclusively with track equipment. I might even have been at it longer than Old Potatoe. I'm always discovering new things, but in all that time, with a lot of screwy track frames, haven't seen a failure rate like you describe. It's got me curious and I'd love to know how you diagnose it in the end and how you fix it.

If I'm remembering correctly, same problem existed with Krispy was running a set of 7710's, cooked the BB within a 6-8 months.

He's currently running the SRM Origin track, alloy model as seen here.
https://www.scientific-coaching.com/...srm-track.html

I've been leaning on Krispy for a bit regarding the crankset, although we are pretty confident that it's a lesser issue.

The problem that I've found with the crankset, is the fixing mechanism. Only has one securing pinch bolt, at a low 5nm, torque spec. Krispy initially had some issues with the arms, and spider on the DS loosening up, which was resolved by torquing everything to spec (SRM says to never touch the DS), and then putting threadlocker on all metal connection points. I'm still not convinced that this is applying appropriate preload on the bearing and is allowing for lateral play to exist in the interface.

Second part is because he's using a 24mm spindle, and how SRM accomodates this, is that they only make a 30mm NDS crank arm, and they use a poly adapter to mate it to the 24mm spindle. Should have gone with a 30mm spindle, but I'm sure Krispy is sick of me saying that from the past year.

I'm 99% positive that Krispy, or his teammate has cracked this adapter, and there was a whole bunch of BS getting that from SRM. I think it's a poor choice by SRM to use this as a solution for the 24->30mm change, especially in high power applications like track sprinting.

[slambers3]

Are there any witness marks on the spindle itself that could indicate the bearings are out of concentricity with each other or are migrating around the spindle? How *stiff* is the BB shell itself? Since you’ve indicated it’s a cheap frame, is it possible that under heavy loads the two sides of the BB are flexing independently and subtly moving out of alignment with each other?
Just a thought.

[BdaGhisallo]

Originally Posted by mjf

If I'm remembering correctly, same problem existed with Krispy was running a set of 7710's, cooked the BB within a 6-8 months.

He's currently running the SRM Origin track, alloy model as seen here.
https://www.scientific-coaching.com/...srm-track.html

I've been leaning on Krispy for a bit regarding the crankset, although we are pretty confident that it's a lesser issue.

The problem that I've found with the crankset, is the fixing mechanism. Only has one securing pinch bolt, at a low 5nm, torque spec. Krispy initially had some issues with the arms, and spider on the DS loosening up, which was resolved by torquing everything to spec (SRM says to never touch the DS), and then putting threadlocker on all metal connection points. I'm still not convinced that this is applying appropriate preload on the bearing and is allowing for lateral play to exist in the interface.

Second part is because he's using a 24mm spindle, and how SRM accomodates this, is that they only make a 30mm NDS crank arm, and they use a poly adapter to mate it to the 24mm spindle. Should have gone with a 30mm spindle, but I'm sure Krispy is sick of me saying that from the past year.

I'm 99% positive that Krispy, or his teammate has cracked this adapter, and there was a whole bunch of BS getting that from SRM. I think it's a poor choice by SRM to use this as a solution for the 24->30mm change, especially in high power applications like track sprinting.

I have been considering getting a new SRM when I upgrade to 12sp, and the Origin cranks have had me worried. The issue you describe is just the thing that gave me pause when I first explored the design. After running SRM DA9000 pm's for more almost 20 years, it's hard to consider a downgrade to a lesser crank chassis.

[mjf]

Originally Posted by BdaGhisallo

I have been considering getting a new SRM when I upgrade to 12sp, and the Origin cranks have had me worried. The issue you describe is just the thing that gave me pause when I first explored the design. After running SRM DA9000 pm's for more almost 20 years, it's hard to consider a downgrade to a lesser crank chassis.

I mean, generally for higher end track power cranks, SRM is the gold standard, for good reason. There aren't many other options for a proper 144bcd track crankset.

What you're really considering is the pm's ability to be accurate (SRM <1% error), along with the pick up speed for the meter to read. Super important for sprinters who are putting out massive power for a short time, and you want to see that number on something like a standing start in that first 0.25 sec, as opposed to lag time that happens with something like a stages pm that might take 0.5-1.0 sec to start reading.

If you are looking at the Origin cranks, make sure you're going with the 30mm spindle model. Second to that, dissassemble, thread lock, and torque the crankset back to spec.

The only other option that jumps to mind is infocrank, but I'd rather have a 30mm spindle rather than isis.
https://infocrank.cc/track-infocrank...ue-measurement

https://infocrank.cc/titanium - Second option but reaaaaallllly expensive

[KrispyK]

Originally Posted by 11.4

What happens if you use a bulletproof cartridge bottom bracket like a BB7710 (basically the old 7700-era Ultra bottom bracket) and a pair of Octalink cranks. I know you lose your power meter, but try it for a month or two and see what happens.

You had mentioned you used the high-end Wheels annular bearing set, yet it also failed on you. If the issue was a skewed bottom bracket, that Wheels bottom bracket should at least have minimized bearing failure.

Is your chainring perfectly planar through a crank rotation? If your bottom bracket shell is forcing the bottom bracket out of alignment, shouldn't it be reflected in an out-of-plane chainring?

Last, SRM has had episodic problems with bottom bracket milling being slightly off kilter -- their Octalink bottom brackets sometimes weren't concentric so one crank would bring the pedal in and out during a crank rotation. The same happened with their later Dura Ace models (hollow shaft) and was almost a chronic problem in tapered square spline days. This has mostly been seen on track cranks, possibly because they are not a high-volume product and cranks were milled more by hand. Long shot that the crank is out of alignment? I'm not sure that it should be killing bottom brackets like this, but looking for issues.

I've worked with track cranks for over forty years, and almost exclusively with track equipment. I might even have been at it longer than Old Potatoe. I'm always discovering new things, but in all that time, with a lot of screwy track frames, haven't seen a failure rate like you describe. It's got me curious and I'd love to know how you diagnose it in the end and how you fix it.

Side note. A friend got a SRM at the same time and has it installed on a BT Ultra with a Dura Ace bottom bracket. He rides more miles than I do but at less power(enduro). He is still on the original BB that was installed at the same time as mine.

The chainrings do appear to be planar.

[11.4]

Originally Posted by mjf

I mean, generally for higher end track power cranks, SRM is the gold standard, for good reason. There aren't many other options for a proper 144bcd track crankset.

What you're really considering is the pm's ability to be accurate (SRM <1% error), along with the pick up speed for the meter to read. Super important for sprinters who are putting out massive power for a short time, and you want to see that number on something like a standing start in that first 0.25 sec, as opposed to lag time that happens with something like a stages pm that might take 0.5-1.0 sec to start reading.

If you are looking at the Origin cranks, make sure you're going with the 30mm spindle model. Second to that, dissassemble, thread lock, and torque the crankset back to spec.

The only other option that jumps to mind is infocrank, but I'd rather have a 30mm spindle rather than isis.
https://infocrank.cc/track-infocrank...ue-measurement

https://infocrank.cc/titanium - Second option but reaaaaallllly expensive

I'd concur on all these points. Lots of options on the road but on the track, you do really want the responsiveness of SRMs. There are ways to get close with other systems, but SRM simply works better for this specific application. Honestly, there are times I've recommended going backwards to SRM Octalink track crank arms. They are reliable and do the job. I've had problems with later SRM track cranks at times not recognizing pedal RPM accurately (missing revolutions in the accelerometer chip) and with initial power spikes not being recognized. In the latter case they tend to smooth out an increase in power when you actually will have a brief and much higher power output for 0.25 to 2 seconds (like at the beginning of a standing start or in a powerful sprint acceleration).

[KrispyK]

Pretty late follow up here. Just incase someone in 5 years has the same problem.
long term sequence of frustrating small problems coming to a close. Thanks to MJF for the help along the way

I have since changed frames and power meters. On the Chinese frame I originally posted about I could never get bearings to last a long time. I also had issues with the NDS crank spindle reducer breaking. While waiting for a new reducer I swapped to a set of Sugino 75 arms and a Hatta 9400 bottom bracket. I also tried a set of Dura ace 7710 arms with the cartridge dura ace track bottom bracket. Only the Hatta bottom bracket was tolerant of the frame alignment. Concluding that the frame cups were misaligned.

The frame was replaced with a Argon 18TKO. This frame has a 1 piece insert for the BSA bottom bracket. The SRM with a 24mm spindle has no bearing issues since changing frame.

Other issues with the SRM has occured with the spindles coming loose and having play. SRM USA was very helpful with this and swapped my SRM origin to a SRM science with a octolink bottom bracket. Fingers crossed but so far. (2 months) it has had no issues. with the arms or bottom bracket.