Hollowtech bearings

[I like Skol]

I'm not sure that Hollowtech hasn't got a bad name for the wrong reasons. My hybrid came with the Shimano Deore Hollowtech set-up and I was unimpressed when the bearing got rough at only around 1,800 miles of commuting. I replaced these like for like as they were cheap and I refitted them exactly as the originals were fitted at the factory with the same size spacers (why wouldn't I?). These didn't last any longer and began to fail before the bike had covered 4,000 miles. I was now extremely disappointed and considered ripping out the hollow tech junk and going back to a chainset that would use a good old square taper UN55 BB that just lasts for almost ever. I decided to give it one more go and ordered the higher spec SLX/XT bearing cups. I suspect these are the same bearings and seals just fitted into a lighter housing but thought it might be worth trying to see if they would last any longer.
While fitting these new bearings I paid much more attention to the fitting process rather than just relying on the factory set-up. It was at this point that I noticed the flaw in the set-up. There was insufficient shims fitted either side of the bearings so that the removable L/H crank was bottoming out on the splines just before butting up to the bearings. This must have been allowing the bearings to run out of true as now I have slipped in an additional thin shim on the left side (I didn't want to move the chainrings away from the frame) the bearings have so far lasted around 8,000 miles.

Of course, none of this helps you Crackle, if you insist on soaking your bike in corrosive salty sea water then you only have yourself to blame!

 

[djb1971]

You'd be amazed how little or how useless the grease is in some of the bb's. I always strip them down and fill with Mobil xhp222 grease, just pop the seals, fill, refit seal. This pushes grease through the rear seal. Do this a couple of times and the bearing will be done. They last me a long time.

 

[Crackle]

Of course, none of this helps you Crackle, if you insist on soaking your bike in corrosive salty sea water then you only have yourself to blame!

Can I borrow your GT next time?

You'd be amazed how little or how useless the grease is in some of the bb's. I always strip them down and fill with Mobil xhp222 grease, just pop the seals, fill, refit seal. This pushes grease through the rear seal. Do this a couple of times and the bearing will be done. They last me a long time.

I was thinking that there couldn't have been much grease in there to start.

Anyway my spanner has arrived, so I might remove the cups and see if I can pop the seals and have a look

 

[djb1971]

Take your time popping the top hats out. I use a Stanley blade to lift the front up and slide the blade under as much as possible. Then use a finger nail to lift the inside of the lip and lift out with the blade. Do them when warm, the plastic is brittle when cold. Save any spare top hats from dead bb's as spares if you're heavy handed. Lift the seal of the front of the bearing with the sharp knife blade layer with grease pop seal back on, pop off and repeat. This pushes grease through the bearing. Then carefully pop the top hat back in

 

[Yellow Saddle]

I'm not sure that Hollowtech hasn't got a bad name for the wrong reasons. My hybrid came with the Shimano Deore Hollowtech set-up and I was unimpressed when the bearing got rough at only around 1,800 miles of commuting. I replaced these like for like as they were cheap and I refitted them exactly as the originals were fitted at the factory with the same size spacers (why wouldn't I?). These didn't last any longer and began to fail before the bike had covered 4,000 miles. I was now extremely disappointed and considered ripping out the hollow tech junk and going back to a chainset that would use a good old square taper UN55 BB that just lasts for almost ever. I decided to give it one more go and ordered the higher spec SLX/XT bearing cups. I suspect these are the same bearings and seals just fitted into a lighter housing but thought it might be worth trying to see if they would last any longer.
While fitting these new bearings I paid much more attention to the fitting process rather than just relying on the factory set-up. It was at this point that I noticed the flaw in the set-up. There was insufficient shims fitted either side of the bearings so that the removable L/H crank was bottoming out on the splines just before butting up to the bearings. This must have been allowing the bearings to run out of true as now I have slipped in an additional thin shim on the left side (I didn't want to move the chainrings away from the frame) the bearings have so far lasted around 8,000 miles.

Of course, none of this helps you Crackle, if you insist on soaking your bike in corrosive salty sea water then you only have yourself to blame!

If there were insufficient shims fitted either side, then you would have had some end float (which can be taken up by the funny-shaped plastic gadget that screws into the axle). However, end- float does not damage the bearings. It just causes the odd clunk from time to time.

It isn't as easy as just fitting shims both sides. There is a formula according to which these are fitted.

On English thread (BSA) threaded bicycles, the BB shell comes in two widths - 68mm and 73mm. The difference is 5mm. New BBs are supplied with three 2.5mm shims to make up the difference. If you have an e-type FD on your bike, it already acts as one 2.5mm shim and should that then be fitted onto a 68mm BB shell, you only need to fit one more 2.5mm spacer on the left to make up the missing 5mm. If you don't have an e-type FD, you then add the shim on the right and one on the left, giving you 5mm in total. If you have a 73mm BB on your bike and an e-type FD, you add nothing. If you have a standard FD, you add one shim.

The idea is that the crank spindle is 2.5mm too long for the widest style BB and you have to shim up the BB adapters to make up the missing space based on the shell width and the type of FD o the bike. Even then, BB shell widths are not precise, so the preload adjuster cap is used to snug the cranks up to the bearings.

SRAM uses a wavy spring washer to make up for the differences.

With too many shims in there you end up with not enough grip between the crank and the spindle and the crank comes off.

 

[Yellow Saddle]

Take your time popping the top hats out. I use a Stanley blade to lift the front up and slide the blade under as much as possible. Then use a finger nail to lift the inside of the lip and lift out with the blade. Do them when warm, the plastic is brittle when cold. Save any spare top hats from dead bb's as spares if you're heavy handed. Lift the seal of the front of the bearing with the sharp knife blade layer with grease pop seal back on, pop off and repeat. This pushes grease through the bearing. Then carefully pop the top hat back in

You are pretty dexterous. It is one precarious procedure that. Shimano did it's utmost to make it impossible.

 

[I like Skol]

Can I borrow your GT next time?

You wouldn't be able to handle a real bike

Anyway my spanner has arrived, so I might remove the cups and see if I can pop the seals and have a look

From what I can remember (and it was 8,000 miles ago) there is nothing to see when you remove the cups. Curiosity has got the better of me so of I trot to route in the parts bin....

Now don't ask me why I have 2 x knackered hollowtech BB's in my spares cache?

As can be seen, nowhere to insert grease and the top hat doesn't appear to want to come out without force which I suspect may render it unserviceable!

 

[Crackle]

Take your time popping the top hats out. I use a Stanley blade to lift the front up and slide the blade under as much as possible. Then use a finger nail to lift the inside of the lip and lift out with the blade. Do them when warm, the plastic is brittle when cold. Save any spare top hats from dead bb's as spares if you're heavy handed. Lift the seal of the front of the bearing with the sharp knife blade layer with grease pop seal back on, pop off and repeat. This pushes grease through the bearing. Then carefully pop the top hat back in

I found one youtube vid which showed me the basics but not the finesse.

I shall carefully prise at things but back off if I lack the skill until I have a spare standing by.

 

[I like Skol]

If there were insufficient shims fitted either side, then you would have had some end float (which can be taken up by the funny-shaped plastic gadget that screws into the axle).

You didn't read what I said or think about what your reply says, did you?

 

[djb1971]

Once you lift from under the front, the top hat does come out reasonably easily.

Practice on the knackered ones

 

[Yellow Saddle]

You didn't read what I said or think about what your reply says, did you?

I am not sure which part is so offensive? I disagreed that you can make the bearings run out of true by removing/not having enough shims and then I explained how the number of shims are calculated. Where did I go wrong?

 

[I like Skol]

There was insufficient shims fitted either side of the bearings so that the removable L/H crank was bottoming out on the splines just before butting up to the bearings.

If there were insufficient shims fitted either side, then you would have had some end float (which can be taken up by the funny-shaped plastic gadget that screws into the axle).

I am not sure which part is so offensive? I disagreed that you can make the bearings run out of true by removing/not having enough shims and then I explained how the number of shims are calculated. Where did I go wrong?

Offensive? I'm just amused that you are suggesting I could pull the L/H removable crank onto the un-splined section of the axle/spindle with the plastic preload screw to make up for the lack of sufficient spacers. The arm had bottomed on the splines and no amount of torque on the preload adjuster was going to remove the endfloat!

 

[Yellow Saddle]

Offensive? I'm just amused that you are suggesting I could pull the L/H removable crank onto the un-splined section of the axle/spindle with the plastic preload screw to make up for the lack of sufficient spacers. The arm had bottomed on the splines and no amount of torque on the preload adjuster was going to remove the endfloat!

But I didn't suggest that. I only said that the preload screw makes up for inaccuracies in BB shell width. Nevermind...

 

[I like Skol]

If there were insufficient shims fitted either side, then you would have had some end float (which can be taken up by the funny-shaped plastic gadget that screws into the axle).

But I didn't suggest that. I only said that the preload screw makes up for inaccuracies in BB shell width. Nevermind...

I'm sure I have not misinterpreted what your post stated. Whether that is what you meant to say is another matter.

 

[potsy]

I've had a couple of these type of bearings go over the last few years, never thought to try and service them just bought replacements.
If I have an old one I will have a practice at removing the seal.