[stapfam]

The rear bottom bracket on the Cannondale is on the way out. Normally I would replace it with a Shimano UN72, but is there a stronger unit to use? The Dale is used offroad, and aggressively and does take a fair bit of punishment with 4 powerful legs grinding away uphill on the Off road trails we have.
Any suggestions for a replacement, or is the UN72 strong enough?

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[TandemGeek]

Unless you're willing to shell out some big $$ for the very chi-chi Phil Wood or Specialties TA bottom brackets, Shimano is just about the only game in town. We've tried the Race Face, American Classic, and WTB grease guard BBs and haven't been impressed. It's not so much that the Shimano BB's have been indestructable; rather, they seem to last as long or longer and when they do go replacement cost is only $18 - $25 instead of $50 - $60.

Also, UN72's (XT grade) were the top shelf in taper Shimano BBs but are becoming scarce as I believe they've been replaced by the UN73. The UN73 strikes me as a cross betwen the UN72 and the UN52/3's where the adjusting cup is one of the nylon/plastic jobs instead of being aluminum.
http://www.wiggle.co.uk/images/shimano%20un73.jpg

[SDS]

Mark, did you find the UN72's to be noisy? In my C'dale singles they creaked and groaned and popped constantly under load, and neither Teflon tape nor Loctite would shut mine up. They also maybe had too much runout, and couldn't keep the big ring out of the FD cage. A Phil Wood BB ended the problem for good. Peace, quiet, and speed.

[TandemGeek]

Mark, did you find the UN72's to be noisy? In my C'dale singles they creaked and groaned and popped constantly under load, and neither Teflon tape nor Loctite would shut mine up. They also maybe had too much runout, and couldn't keep the big ring out of the FD cage. A Phil Wood BB ended the problem for good. Peace, quiet, and speed.

No, not really. But then again, I probably don't generate nearly as many watts as you do given our disparate body size/weight. No question that the Phil Wood BB is a fine piece of hardware: I've got a +5 custom off-set on my Erickson single with compact drive and it almost seemed like a crime to hide it in the BB shell.

I should also volunteer that 3 of the 4 Race Face taperlock BB's are still doing just fine and the red anodized finish on the cups is pretty cool. However, one of the front ones began clicking and popping after two seasons and after diagnoised as terminal failure it was replaced by a UN72. So, 3 out of 4 Race Face square taperlocks have held up as well as the UN72s which is a good thing. However, they are pricey but, on the plus side, they do have that bling-thing going for them.

Oooh. that reminds me. I've got a 3rd Generation Bushnell eccentric sitting here that I need to install. The red RaceFace taperlock should look really nice nestled in this black-beauty!

[zonatandem]

Have used Phils on several tandems for lotsa miles.
Matter of fact, had a Phil BB that developed a minor problem after 30,000+ miles. Sent BB back to Phil; Mr. Phil Wood sent a nice note plus a a new BB at no charge.
Nice!