Bicycle Mechanics - Cartridge BB--torque it down, or snug it up??

I find conflicting advice on Cartridge Bottom Bracket installation, especially those with plastic adjustable rings. My experience with these is limited, so I've searched the forums and there have been numerous problems with the plastic rings cracking when torqued down to 360 in-lbs as recommended by the Parktool site, and also the Barnett's manual. One poster said that several bike shops he went to for a replacement ring said to always just snug up that adjustable ring against the body, don't torque it down, because it's not a press- or taper-fit.

My question is, if you have already just snugged the body into the shell, then if you just snug the adjustable ring against that, where's the torque?? Doesn't at least one of these parts need to be torqued down to prevent movement and creaking? I'm so confused. Would you tighten the body to a torque spec, and *then* just snug up the adjustable ring?

My experience with cartridge BB's has mainly been with steel or aluminum stabilizing cups on the non-drive-side, although I've built one bike (http://www.unc.edu/~cupery/pics/bikes/Ari_Schwinn) for a friend with a Shimano BB with plastic stabilizing cup, and also a plastic cup on the bottom bracket on my Centurion (http://www.unc.edu/~cupery/pics/bikes/Centurion_Comp_TA_repainted/).

The non-drive-side cup is there mainly to keep the non-drive-side of the cartridge unit from moving around inside the BB shell (which would stress the shell, and the BB body). It also functions a bit to increase preload on the drive-side threads.

But if you tighten the non-drive-side cup too tight, the bearings get compressed and don't turn as freely. You can easily try this by tightening the non-drive-side cup (if you've got a metal one) and seeing how the spindle becomes more difficult to turn between thumb and forefinger.

So what I've done is tighten the drive-side, which is always steel or aluminum threads, quite tight (I don't have a torque wrench, but it's probably near spec). I'll snug up the non-drive-side a bit, but keep testing the spindle between thumb and forefinger to see if I've increased bearing resistance. If I have, then I'll back off on the non-drive-side cup.
With the plastic cup, I just go by feel and don't tighten it to where I'd worry that it would crack or threads would strip.

Tim, that sounds like great advice. In the research I've done, there are very few mentions of testing the turning resistance of the spindle.

Here is a synopsis of the methodologies I have found:

Parktool site: Snug the drive (body) side of the cartridge into the shell, then tighten the non-drive (adjustable ring) side to manufacturer's spec (around 360 in-lbs usually). Done. They specify there is no need to torque the drive (body) side since the flange is against the shell and stops it when tight.

Barnett's manual: Snug the drive (body) side into the shell, then torque the non-drive (adjustable) ring to spec, then torque the drive side to spec. Done.

UBI instruction: TORQUE the drive (body) side to spec after installing into the shell, then TORQUE the non-drive (adjustable) ring to spec. Done.

See why I'm confused? :(

Your method is different than any of these, but it makes sense to me to get that drive side in there good and tight, and then only tighten the non-drive adapter side as much as necessary, thereby not risking breakage of a plastic ring, and also not adding too much preload.

lawkd, Thanks for asking this question, and saving me from asking the same question:o next week when I make the same change.
EDIT: Tim, thanks for the response.

I torque the drive side to spec. I just snug up that non-drive plastic piece. As near as I can tell, it's only a spacer to keep the left side of the cartridge from slipping.

It does look like it's more or less just a spacer, but I'm interested in exactly why and how it can affect the freedom of movement of the bearings, like Tim said. In my research, I only found mention of this as an issue when the cup or cartridge wasn't threaded in straight. If the torque on the adjustable cup can affect spindle rotation, it must be applying significant pressure to the cartridge body somewhere. I'm just curious about that.

I'm one of the posters you researched. When I asked these LBS mechanics why they only snug them down, most responded that in their experience, that's all it needs. A few also suggested to only snug the driveside as well in order to ease removal. None were able to give me any theory on the matter when I probed, but I decided to give some credence to their advice, assuming they have all likely done hundreds of these in their careers.

One thought I have is that because the spindle and cups are one piece, and the the bearings only apply pressure to the inside of the cartridge body, there is less of a need to secure the cups. On an adjustable cup bearing assembly, the bearing balls are constantly working on the cups independent of the spindle. There's no body to hold it together.

But if you tighten the non-drive-side cup too tight, the bearings get compressed and don't turn as freely. You can easily try this by tightening the non-drive-side cup (if you've got a metal one) and seeing how the spindle becomes more difficult to turn between thumb and forefinger.

This shouldn't happen. The non-drive side cup is there only to support the cartridge against the frame. If the bearings get compressed something is wrong.

One thought I have is that because the spindle and cups are one piece, and the the bearings only apply pressure to the inside of the cartridge body, there is less of a need to secure the cups. On an adjustable cup bearing assembly, the bearing balls are constantly working on the cups independent of the spindle. There's no body to hold it together.

I think that's exactly right, in fact Sheldon Brown has mentioned that before on these forums. That's why cartridge BB's put less stress on the threads of the shell, and are therefore often a good solution for shells that have had their threads compromised in some way, previously.

I have definitely experienced bearing tightness when I've tightened the NDS cup too much. Depending on the profile of the cup, I think it can squeeze the cartridge and restrict the bearings. But as I type this, it sounds really stupid.

Your method is different than any of these, but it makes sense to me to get that drive side in there good and tight, and then only tighten the non-drive adapter side as much as necessary, thereby not risking breakage of a plastic ring, and also not adding too much preload

I cannot find the original post, but some guy on the forums does it this way:

Snug driveside, then backoff half turn.
Snug non-driveside.
Torque driveside to spec.