Hollowtech Bottom Bracket

[Roy]

Went out for a ride this afternoon which was brought to an abrupt halt when the hollowtech bottom bracket axle failed at the face of the RH crank. Now, is this a common occurrence, should I fit another one or should I put my old square taper one back on. What is the advantage of hollowtech anyway? I only bought it because it looked nice!

[BobScarle]

Hollowtech are supposed to be lighter and stiffer. I have had a crank fail on the left side (Non drive) but not the right.

[Brucey]

Hollowtech I (both cranks are meant to come off the BB spindle) or
 Hollowtech II (only the left crank is meant to come off the BB spindle)?

In theory HT is stiffer and lighter than ST cranks. In practice it might be one of those things that wasn't broken but they fixed it anyway.

cheers

[Feanor]

the hollowtech bottom bracket axle failed at the face of the RH crank. Now, is this a common occurrence?

No, it's not.

Can you tell us the model of chainset that failed?
And perhaps give us some pics?

[Roy]

The chainset is a five arm hollowtech II Ultegra FC6600. It looks as though there has been a small crack in the axle for some time.

[Torslanda]

Interesting to find out if the axle failed under load or if a RH bearing seizure damaged the axle - which is pretty thin by itself.

Most of the failures I've seen have come about through poor maintenance.

[Brucey]

is the spindle steel or aluminium in this model of crankset?

Any pics of the fracture?

cheers

[Torslanda]

From memory, steel and very thin walled. Never seen a failure in an alloy axle.

BTW just as alloy frames aren't forever, I suspect that HII is the same. 6600 has got to be around a decade old.

[zigzag]

6600 has a thick alloy axle which doesn't look it could break easily, unless there is some manufacturing defect

[ElyDave]

From memory, steel and very thin walled. Never seen a failure in an alloy axle.

BTW just as alloy frames aren't forever, I suspect that HII is the same. 6600 has got to be around a decade old.

When you say alloy frames aren't forever, how long is that particular piece of string?  I have a 12yo Al alloy framed, carbon forked Giant, with no obvious issues.  This is my winter bike as well.

[Roy]

I dismantled the B.B. yesterday. The axle was alloy and had ''crystalised'' at the brake. I think that I can rule out poor maintenence as it was checked over anf re-fitted by my LBS in April.

[Brucey]

I dismantled the B.B. yesterday. The axle was alloy and had ''crystalised'' at the brake. I think that I can rule out poor maintenence as it was checked over anf re-fitted by my LBS in April.

If I had a quid for every time I heard that.....

Probably the part suffered a fatigue failure.  If there is a much darker part to the fracture face, that is probably the oldest part of the fracture, containing the initiation point. 

If you can manage a photograph of the fracture it might be of interest to others.

cheers

[Morat]

From memory, steel and very thin walled. Never seen a failure in an alloy axle.

BTW just as alloy frames aren't forever, I suspect that HII is the same. 6600 has got to be around a decade old.

When you say alloy frames aren't forever, how long is that particular piece of string?  I have a 12yo Al alloy framed, carbon forked Giant, with no obvious issues.  This is my winter bike as well.

Having had an alloy stem fail within a year (ouch) and an alloy MTB last about 15 years so far I'd say it's down to careful and regular inspection. Small cracks, especially at joints/welds, are what you're looking for. I'm sure the more experienced on here have their own views but that's where I start.

[Roy]

Brucey is correct, there is a darker part to the fracture. Both bearings however are nice and smooth, so definately nothing has seized. I wil try to post a photo when my son shows me how to do it!
Thank you all for the replies.

[ElyDave]

From memory, steel and very thin walled. Never seen a failure in an alloy axle.

BTW just as alloy frames aren't forever, I suspect that HII is the same. 6600 has got to be around a decade old.

When you say alloy frames aren't forever, how long is that particular piece of string?  I have a 12yo Al alloy framed, carbon forked Giant, with no obvious issues.  This is my winter bike as well.

Having had an alloy stem fail within a year (ouch) and an alloy MTB last about 15 years so far I'd say it's down to careful and regular inspection. Small cracks, especially at joints/welds, are what you're looking for. I'm sure the more experienced on here have their own views but that's where I start.

can't say I inspect ultra closely, but on normal cleaning I haven't seen anything adverse