Cracked XT Hub - Pics

[splat]

It happened again!

 

Almost 2 years later, the replacement XT hub's bearing race cracked in the same way.

 

I had an interesting chat with the guys at the LBS about why Shimano hubs are crap.

I bought them because I thought they were good!

Anyway, it was about sealed bearings vs cup/cone/open bearings.

 

Luckily I have a set of Hope/ZTR wheels for Sani!

[The Drongo]

It happened again!

 

Almost 2 years later, the replacement XT hub's bearing race cracked in the same way.

 

I had an interesting chat with the guys at the LBS about why Shimano hubs are crap.

I bought them because I thought they were good!

Anyway, it was about sealed bearings vs cup/cone/open bearings.

 

Luckily I have a set of Hope/ZTR wheels for Sani!

 

Splat.

 

I am a Shimano fan, simply because they make components that are strong, reliable, and relatively inexpensive.

 

The kind of damage you show in the pics you have posted is usually a result of poor maintenance, lack of grease, and worn ball bearings. The cups become so worn that they can eventually crack through. But any rider worth his salt should have felt the rattling, binding and rear wheel play long before that takes place.

Cup and cone bearing hubs require regular maintenance, simple as that, and no way around it.

 

In your instance, you felt the wheel dragging, and you had only done about 300k as claimed. The hub was also XT! I say this because I have seen this happen twice, on a relatively new 756XT and a 970XTR rear hub.

 

My only conclusion in both instances being this:

 

The hubs are forged from a lighter grade alloy than the lower end models ??(TBC)

That when the hubs are assembled the lock nuts are not properly locked against the cones, allowing the cones to tighten as the wheel is ridden. >>>OR>>>

That when the hubs are assembled the cones are over tightened onto the bearings, once laced to the rim, and fitted to the bike this over tightness is not evident to most.

Insufficient grease is placed into the cup on assembly (usually the case with cup and cone AND sealed bearings)

 

The combination of these factors leads to early failure.

 

What you are seeing in the damaged hub is the result of aluminium being 'melted' off the inside of the cup as the poorly lubricated bearings revolve (under force), the 'melted' aluminium is redeposited on the inside of the cups and cools to form the ridges an 'cracks' that you see here. It does not adhere to the bearings or the cone as they are steel.

 

When I install new hubs on a wheel I disassemble, re-grease, and tighten up the hub on the wheel until I am satisfied with the spin.

The same applies to any component using sealed bearings. If you take a new sealed bearing off the shelf, remove the dust seal and look inside, I guarantee that all you will see by way of grease is a squirt of same in about 1/3 rd of the race. I always repack sealed bearings before installing.

 

In terms of maintenance, a sealed bearing hub is probably the way to go if you want to fit and forget. But again, not forever, and also dependent on terrain and weather .

 

If I may ask now for an honest answer to this question. Your XT hub that you ran for two years, how often was it serviced?

 

I would also be interested to hear a little bit more about what the LBS's had to say about Shimano being crap. Their being a sufficient number of them that are unable to correctly set cones, or lock the nuts down properly, themselves.

After all, it is always easy to blame product failure on the product, rather than human error.

[splat]

Splat.

 

I am a Shimano fan, simply because they make components that are strong, reliable, and relatively inexpensive.

 

The kind of damage you show in the pics you have posted is usually a result of poor maintenance, lack of grease, and worn ball bearings. The cups become so worn that they can eventually crack through. But any rider worth his salt should have felt the rattling, binding and rear wheel play long before that takes place.

Cup and cone bearing hubs require regular maintenance, simple as that, and no way around it.

 

In your instance, you felt the wheel dragging, and you had only done about 300k as claimed. The hub was also XT! I say this because I have seen this happen twice, on a relatively new 756XT and a 970XTR rear hub.

 

My only conclusion in both instances being this:

 

The hubs are forged from a lighter grade alloy than the lower end models ??(TBC)

That when the hubs are assembled the lock nuts are not properly locked against the cones, allowing the cones to tighten as the wheel is ridden. >>>OR>>>

That when the hubs are assembled the cones are over tightened onto the bearings, once laced to the rim, and fitted to the bike this over tightness is not evident to most.

Insufficient grease is placed into the cup on assembly (usually the case with cup and cone AND sealed bearings)

 

The combination of these factors leads to early failure.

 

What you are seeing in the damaged hub is the result of aluminium being 'melted' off the inside of the cup as the poorly lubricated bearings revolve (under force), the 'melted' aluminium is redeposited on the inside of the cups and cools to form the ridges an 'cracks' that you see here. It does not adhere to the bearings or the cone as they are steel.

 

When I install new hubs on a wheel I disassemble, re-grease, and tighten up the hub on the wheel until I am satisfied with the spin.

The same applies to any component using sealed bearings. If you take a new sealed bearing off the shelf, remove the dust seal and look inside, I guarantee that all you will see by way of grease is a squirt of same in about 1/3 rd of the race. I always repack sealed bearings before installing.

 

In terms of maintenance, a sealed bearing hub is probably the way to go if you want to fit and forget. But again, not forever, and also dependent on terrain and weather .

 

If I may ask now for an honest answer to this question. Your XT hub that you ran for two years, how often was it serviced?

 

I would also be interested to hear a little bit more about what the LBS's had to say about Shimano being crap. Their being a sufficient number of them that are unable to correctly set cones, or lock the nuts down properly, themselves.

After all, it is always easy to blame product failure on the product, rather than human error.

 

LBS reckons it must be a bad batch of hubs or something as this is the 3rd one with the same failure recently.

 

I haven't kept track of service record, but original clean grease is still in bearings. i.e. as good (bad) as it was when it came out the box. They are waiting for Shimano agent to swing past and get warranty replacement.

[TNT1]

I doubt that this kind of lightning would strike the same place twice. This is poor maintenance or abuse.

[The Drongo]

LBS reckons it must be a bad batch of hubs or something as this is the 3rd one with the same failure recently.

 

I haven't kept track of service record, but original clean grease is still in bearings. i.e. as good (bad) as it was when it came out the box. They are waiting for Shimano agent to swing past and get warranty replacement.

 

Hmmm..

 

I suspect my point about poorly tightened locknut on cone is to blame here. The drive side (freebody) cone and locknut assembly are fixed onto the axle when it is out of the hub (once pushed into the freebody the cone nut is not accessible with spanner).

The non drive side cone then has to be tensioned against the bearings, then locked with the locknut, then resistance checked, and adjusted again. If those two are not properly locked together the cone will tighten onto the bearings.

 

If you ride far, and often (not sure of your two year milage) then 2 years is a bit of a stretch between services.

 

Shimano are usually good with a valid complaint.

 

LBS should be a little less casual about slapping on an "out the box" item without checking it first.

[Cassie]

I doubt that this kind of lightning would strike the same place twice. This is poor maintenance or abuse.

 

I tend to agree wioth TNT here!

And Drongo is 100% spot on with his diagnosis...

 

I speak from self taught experience here: End of last year i decided to "service" my hub and i'm sure i did not tighten the locknut enough OR overtighten the entire bussiness, forgetting that the assembly onto the skewer also puts more pressure on the hub...

 

Anyway, result was a similar hub meltdown - mine more towards the freehub body...

expensive lesson learnt - check and double check next time!! An early warning on mine was the fact that when I stopped pedalling the freehub would not engage proerly and did a bit of chainsuck...I totally misdiagnosed that issue!!

 

AND there I thought the forged hub wasn't "bliksemed" enough... Almost like J Malema??

 

Good post!

[javadude]

Were you using a 12-36 cassette by any chance? I read something a while back about Shimano hubs not being able to handle the torque of a 36 tooth sprocket, which is why they designed a hub specifically to handle the extra torque.

[The Drongo]

Were you using a 12-36 cassette by any chance? I read something a while back about Shimano hubs not being able to handle the torque of a 36 tooth sprocket, which is why they designed a hub specifically to handle the extra torque.

 

That IS a good q? Velo.