chagzuki

I have an Axix light ti bottom bracket that I've been thinking of installing. Before I do so I thought I'd better get some advice on the subject since a proportion of users seem to report problems, largely creaking.

AFAIK I'm supposed to use anti-seize on the tapers and threads. I've not heard of the internal threads stripping out with excessive crank bolt tightening but I wonder if it's possible or whether less torque is advised than with steel BB axles? Having said that a loose crank arm might be more likely to damage the tapers.

Is there anything else I should look out for?

FBinNY 

Mount the cranks as you normally use. If you use anti-seize, be careful not to over-torque the spindle bolts, not because of fear of stripping, but because you can easily force a crank arm on too far and damage the arm.

Also note that Ti spindles aren't recommended for heavy mashers, since they are only 70% as strong as their CrMo counterparts, so flexing and breakage are more likely. (their history is such that they've proven adequate for most people, so don't read more into this than intended, it's only for heavy riders, or high torque pedal mashers (you know who you are)).

Mark Kelly 

Don't know where you got that figure but I don't think it's right. From the figures I can find, 6Al4V Ti (as used by Stronglight) is actually stronger than 4130 CrMo. For Ti: 6Al4V Yield strength 880 MPa, shear strength 550 MPa in annealed condition. For CrMo: 4130 Yield strength 500 - 700 MPa, shear strength 300 - 400 MPa, values dependent on heat treatment. The poor reputation of Ti BB spindles comes form the early Campy examples which were made (badly) from the wrong alloy. IIRC they were CP and the machining left a stress riser right in the weakest spot.

Where Ti falls down is that it is much more flexible, having roughly half the modulus.

chagzuki

Hmm, sounds like I shouldn't worry about over-torquing then.

Thanks for your help.

Kimmo 

I bought a bike ten years ago that had a Syncros Ti BB. Turned out the BB threads were trashed because the previous owner hadn't noticed the NDS ally lockring had cracked, and had kept riding it...

So yeah, if it has the ally lockrings, keep an eye on it.

DannoXYZ 

I've had an ActionTec Ti BB on my race bike for 20-years. Replaced the cartridge bearings after 5-years with higher-quality SKF ones and haven't had to service it since. If the Axix BB uses aluminium cups, be very careful when installing. Be sure to clean out the BB-shell threads of old grease and grit. Wrap 2-4 layers of plumbing teflon tape around the cups before installing. This will help prevent galling, corrosion and creaks.

Also lube the crankarm-bolts before installing them. I've had good luck with replacing the flat washer with a star lockwasher. This will keep the bolt from backing out in the event there's insufficient torque. Just in case...

Oh yeah, use a torque-wrench to install that bolt. The recommend range is 25-33 lb*ft and I'd aim for right about 30.

Drakonchik

You are not factoring in that you must compare parts (ti vs cro-mo) that displace the exactly the same dimensions, volume and thickness etc. Then plug in your analysis and ti will fall down in the shear strength dept vs high-end cromo.

Kimmo 

The Syncros one I had wasn't any beefier than a typical steel BB: https://i1202.photobucket.com/albums/...i/IMG_1517.jpg

Those shoulders taper back down to roughly the diameter inside the bearings, IIRC.

HillRider

Mark Kelly's strength numbers are per square inch or per square mm so, if 6/4 Ti is stronger than the commonly used Cr-Mo alloy per square inch and the square inches (spindle cross sections) are the same, the Ti spindle is indeed stronger.

That said, many load bearing Ti components have a recommended maximum rider weight. Speedplay says the Ti axle versions of their pedals should be limited to riders under 185 pounds.

ivan_yulaev

In my case I've been installing Al BBs into a Ti frame but this is 100%. Tried greasing the threads first - creak creak creak. Replaced grease with teflon tape - silent. I also recommend teflon tape around pedal threads but it's not strictly necessary here.

Greasing or oiling the crankarm bolts helps get an even tension to torque relationship.

HillRider

My experience exactly.

Booger1

Ti likes to gall,use anti-sieze.

HillRider

If you assemble the cups without the teflon tape, then yes, anti-sieze is recommended. With the tape, none is needed.