rjberner

Any ideas on what’s wrong with the outboard bearing designs on BB’s? From everything I read, they’re just not holding up, especially (but not limited to) the FSA designs. We’re running FSA Mega Exo carbon cranks with Mega Exo BB’s and I’ve already replaced the Captain’s BB, which failed miserably after about 2300 miles. The stoker’s BB is suspect now. Although the FSA cranks are fine, I’m thinking about going to Phil BB’s and Campy or Sugino square taper cranks this winter because the Phil’s seem to be bulletproof, albeit a step back in time. I would consider the Ultegra (not DA) Octalink design, but I don’t think they will be around much longer due to Shimano’s planned obsolescence programs.

Theories in various forums abound:

1. The BB shells must be perfectly parallel.
2. The bearings on the outboard designs are too small.
3. The cups are too flimsy for the loads imposed.
4. Lousy bearings and seals.
5. They can’t stand up to the sideloads imposed.
6. The integral crank/spindle is slightly off center and “orbits”.

Any thoughts? Who is able to reface tandem eccentrics and would it make any difference if I’m hostage to the other issues? I figure if I can put Phil’s on and be happy for 15,000 miles or more, by then they will have solved the issues with these “modern” designs.

stokessd

I have truvativ cranks on our tandem with outboard bearings (really stupid IMHO). One of the things I notice about the cranks is the fit and finish is the worst I've ever seen. There is minimal effort to clean up the casting marks, and what was done is pretty coarse so you see the grinder marks through the plating. The timing chainrings don't run true so the timing chain changes tension throughout the crank rotation (Yes, I've minimized it with ring rotation and adjustment).


So my guess is that the manufacturing tolerances and care is at an all-time low with these new parts, and this is the result.

Frankly, stepping back to an internal BB with a square taper is a reasonable idea and not necessarily a step backward. I've got campy bottom brackets with 10 of thousands of miles on them and still going strong. Hard to argue with an established track record.

Sheldon

TandemGeek

If you're using Phil Wood's BBs you wouldn't need to reface the eccentric BB as they don't use a fixing cup. Both cups are the adjusting type without a lip.

If you opted to go with a Shimano BB and the right side of the eccentric was "buggered-up" by the FSA BB, minor damage can be repaired by refacing just as it is done on an aluminum frame's bottom bracket shell. In other words, if you can find someone who knows how to reface an aluminum frame, they can reface your eccentric (within limits and only once or twice). If they screw it up, you get a new eccentric from your tandem dealer or the OEM.

As for "the problem" with the newer designs, it's a combination of things including some of the issues you've already discovered.

- Shimano's Octalink, while somewhat more reliable than the ISIS ostensibly due to Shimano's more stringent quality controls, was still plagued by the inherent weaknesses of the smaller bearings to accommodate the larger diameter spindle within the confines of the standard BB shell.

- ISIS struggled with the same design weakness but the two major manufacturers -- FSA and TruVativ -- have also suffered from having less robust control systems on their suppliers than those used by Shimano.

- The outboard designs created a whole new set of problems but, once again, Shimano's outboard bearing systems have faired somewhat better than the design houses that created the ISIS standards did with their newer outboard bearing systems and for the same reasons.

- It will be interesting to see if Campagnolo's approach to new products (be the best, not first) worked with their Ultra-Torque system and its Hirth joint.

Me? I've stuck with square tapers on all of our bikes, even on my most recent single bike project. In fact, it also uses a threaded headset and quill stems. Thankfully, the Shimano UN-72, RaceFace, Phil Wood, and Campagnolo bottom brackets ARE durable... which is a good thing since replacements continue to be somewhat limited to a low-endish Shimano UN-73 model, house-branded cheapies and then the high-end Phil Wood and Campagnolo models.

dfcas

My experience has been that chasing/facing improves the life of all BB types I have installed,including square taper. I had a ST that just seemed tight,so I removed it,chased/faced,and it had less drag.

My experience locally has been that bike shops tend to have battered/abused/dull/worn cutting tools.Untrained kids may use them without oil,overheat them,etc.

I suggest you choose who does this service carefully. I treat my tools with respect-I clean the cutters,leave them oiled,etc. I also charge more and don't do much business

zonatandem

Used Phil stuff since it first came out in the mid-70s through the 90s. It may not be the lightest nor the cheapest nor latest, but it's the most durable.
Had one Phil BB that needed replacement after 30,000 miles back in the early 80s. Phil sent us a new BB with a note: 'after all those miles, no charge.'
All other Phil BBs and hubs lasted for as long as we had the bikes; all well over 50,000 miles each. Phil pedals (yes, there was such a thing) lasted about 90,000 miles (had them on 2 consecutive tandems).
Quality lasts!!!
Perdal on TWOgether!
Rudy and Kay/zonatandem

Redpath

+1 on the square tapers. If it ain't broke don't fix it. Square tapers have been around for what, 100 years or so. They still work and work well. Poor installation-i.e. improper prep, installation and toquing of bolts-has given them their reputation as 'creaky'. See Sheldon Brown!

On your failed BB what exactly failed? Most bearing failures are lube failures from what I have seen. And these from poor seals. Shimano stuff seems to be the best sealed although I have had good luck with Race Face components and of course the benchmark-of-benchmarks-Chris King headsets.

'Sealed' cartridge bearings can be easily repacked (most anyway). Pop the seals with an exacto knife, wash and dry thoroughly, repack with the grease of your choice and pop the seals back in. I do mine once a year. More on my MTB depending on abuse level.

I have the FSA Mega EXO crank and BB on one of my singles and a SRAM Rival Integrated crank and BB on another. Both are holding up OK so far and seem to be working as advertised. I should probably keep a closer eye on them though. The tandem has Shimano square taper components that have not been touched in 5 years other than my yearly inspection. Not flashy; just good, reliable stuff.

You have a couple pretty good bike shops there in Holland if I remember correctly. The owner/manager of VeloCity Cycles is a big tandem enthusiast as well. They should be able to help you out with any of the items you mentioned.

rjberner

The unit loosened up on a ride. I retorqued it, it loosened again. I disassembled it and the left bearing fell out of the cup. The cup would not hold a new pressed-in bearing, so we scrapped it. It appears to me that the cup deformed. The bearing was lubed, not dirty, and the bike has seen no water of any consequence.