Replacing Hollowtech II Bearings

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Brucey
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Re: Replacing Hollowtech II Bearings

Post by Brucey »

IIRC the first type of HTII bearing used about 12 or 15 3.5mm dia balls.

I have not looked inside the later type to see what is inside them.

cheers
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Cyckelgalen
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Re: Replacing Hollowtech II Bearings

Post by Cyckelgalen »

The older type HT II has 15 balls, and they may well be 3.5 mm, cannot measure accurately without getting them out
The new type should have a few more, if you reduce the size of the balls you simply need more balls to go around the same 25 mm inner race.

Still, while the load sharing will be improved, I'd rather have a better sealed bearing with bigger balls. The new bearing may be stronger because of the better load sharing but that would only be initially and under optimal conditions. Once any deterioration sets in, be it contamination or the slightest corrosion or wear, the smaller size of the balls will accelerate further deterioration and failure.
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SimonCelsa
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Re: Replacing Hollowtech II Bearings

Post by SimonCelsa »

Timely thread. I heard a barely perceptible ticking coming from the drive train today after a particularly onerous hill and thought it was time I had a look at the EBB bearings. These were given a good greasing around October last year in readiness for the winter.

On removing the non drive side cap and seal it was obvious from the rust staining that my maintenance regime was not sufficient, I should have given them another good seeing to probably late December. The drive side was clean and shiny. This is exactly what happened to the previously fitted one i.e NDS knackered, DS OK. Mileage on both around 5000 before failure.

Fortunately I had kept the previous good drive side bearing shell so I just knocked the bearing out with a screwdriver and replaced the knackered NDS bearing. This should give me a few more months prior to purchasing a new one.

HT EBB.jpg


Not the best of pictures but the balls are definitely not silver anymore and there is a gritty feeling during rotation even after flushing with aerosol spray and light oil.
Brucey
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Re: Replacing Hollowtech II Bearings

Post by Brucey »

Cyckelgalen wrote:The older type HT II has 15 balls, and they may well be 3.5 mm, cannot measure accurately without getting them out

I needed some 3.5mm balls in a rush and I think I got them out of such a bearing, which is why I remembered the size, if not the exact quantity. That the ball dimension is metric was a surprise to me; most cartridge bearings (even ones with metric external dimensions) seem still to be built round imperial-sized balls.

Still, while the load sharing will be improved, I'd rather have a better sealed bearing with bigger balls. The new bearing may be stronger because of the better load sharing but that would only be initially and under optimal conditions. Once any deterioration sets in, be it contamination or the slightest corrosion or wear, the smaller size of the balls will accelerate further deterioration and failure.


With almost any current cartridge bearing that is used on a bicycle, they will only work adequately if the balls are able to share the service loads. The slightest deterioration in the bearing usually means that the load hasn't been shared adequately and/or it soon won't be. With traditional bicycle bearings (that are slightly damaged but still well-lubricated) they can rumble on for years, but with cartridge bearings they are almost invariably on a very steep slippery slope once there is the slightest deterioration.

I was surprised to find that the Rohloff hub runs on two 'ring' bearings which are of small section (~7mm from memory), with small balls inside. These don't have any reputation for unreliability because

a) they are kept well lubricated
b) the weather is kept out of them (the seals carry on working for longer provided the seal lips are kept wetted with lubricant) and
c) the bearing installation has been designed/manufactured correctly so that there isn't too much preload on the bearings and
d) the housing, bearing and shaft have stiffnesses and are toleranced such that the service loads are controlled and the bearings are always able to share the load between multiple balls.

The Rohloff ring bearings in question are in fact a not uncommon bicycle part; however when used elsewhere, they are used as headset bearings!

When it comes to bearings on bicycles, things are not always as they appear to be.

cheers
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alexnharvey
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Re: Replacing Hollowtech II Bearings

Post by alexnharvey »

Could the inside/rear face of a hollowtech cup be drilled to make a sort of grease port through which fresh grease could be injected if the inside seal was left off? Or could a hole be drilled diagonally so that it could be greased without the cup being removed?

Brucey, maybe you are saying the plastic tube will retain enough grease to provide a reservoir if the inner seals are left off so we don't need to bother with drilling.
Brucey
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Re: Replacing Hollowtech II Bearings

Post by Brucey »

alexnharvey wrote:Could the inside/rear face of a hollowtech cup be drilled to make a sort of grease port through which fresh grease could be injected if the inside seal was left off? Or could a hole be drilled diagonally so that it could be greased without the cup being removed?


yes this sort of thing is possible. Unfortunately adding grease to the inside of a standard BB unit isn't going to be entirely effective; the seals on the bearings will not work in your favour and should be removed.

Brucey, maybe you are saying the plastic tube will retain enough grease to provide a reservoir if the inner seals are left off so we don't need to bother with drilling.


yep that is about it. Lots of things are likely to be an improvement over the standard arrangement.

cheers
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Cyckelgalen
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Re: Replacing Hollowtech II Bearings

Post by Cyckelgalen »

Drilling a grease port on a HT cup is not the best idea IMHO. The outer cap and seal are very easily removed and you have the bearing fully exposed for cleaning and lubing, just as SimonCelsa's photo shows. The outer seal, below the cap, is not an integral part of the bearing, it is only superposed on it and that allows easy extraction without damage.
gregoryoftours
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Re: Replacing Hollowtech II Bearings

Post by gregoryoftours »

The new htII BBS are a marked improvement on the older bulkier ones, having outlived them several times over on some of my bikes (which is really not saying much), but I haven't run any of the new ones long enough yet to see if they'll get anywhere near the lifespan of a decent Shimano square taper BB. Still, I don't think of them as crap anymore as I did until this generation.
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

SimonCelsa wrote: 5 Mar 2020, 8:19pm Timely thread. I heard a barely perceptible ticking coming from the drive train today after a particularly onerous hill and thought it was time I had a look at the EBB bearings. These were given a good greasing around October last year in readiness for the winter.

On removing the non drive side cap and seal it was obvious from the rust staining that my maintenance regime was not sufficient, I should have given them another good seeing to probably late December. The drive side was clean and shiny. This is exactly what happened to the previously fitted one i.e NDS knackered, DS OK. Mileage on both around 5000 before failure.

Fortunately I had kept the previous good drive side bearing shell so I just knocked the bearing out with a screwdriver and replaced the knackered NDS bearing. This should give me a few more months prior to purchasing a new one.

HT EBB.jpg

Not the best of pictures but the balls are definitely not silver anymore and there is a gritty feeling during rotation even after flushing with aerosol spray and light oil.
[I know I am resurrecting an old thread but I took the time to find it because a) I knew there would be one :-) and b) I thought it would be good to keep everything on the same thread]

Anyway, after years in square taper land, one of my bikes now has a HT2 BB, and I have of course worn it out. Like Simon C said above its the non-drive side that is knackered (horrible and graunchy) and the drive side is perfectly smooth.
Tiagra HT2 BB.JPG
This leads to my first question. Is there a reason that the NDS gets worn out first?

I have put a brand new BB on for now but then there is the question of how to maintain going forward - lots of good suggestions in the thread of course. I like Simons idea of humanely extracting the DS bearing and putting it in the NDS next time. Anyone else doing this ?

Now I have been considering the issue of just replacing the sealed bearings. Looking in the thread when all this first came up 25 x 37 x 6mm sealed bearings were unavailable - you could only get standard 25 x 37 x 7mm ones - these didnt fit (although Brucey did try and work out a way of getting them in). However the correct size 25 x 37 x 6mm bearings ARE now available - according to eBay - at about a fiver a pair.
ht2 bearings.JPG
I really baulk at throwing away the carefully crafted aluminium HT2 'cups' and spending £20 on a complete new BB if its possible to just swap the bearings over - less waste/recycling etc. So my final question is - has anyone tried these eBay replacements ?
tim-b
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Re: Replacing Hollowtech II Bearings

Post by tim-b »

This leads to my first question. Is there a reason that the NDS gets worn out first?
IMHO it's because the NDS isn't protected in the same same way as the DS. The DS has a lump of aluminium that stops water running down the crank from the pedals and rider and along the axle. The same lump effectively shields the bearing from external weather as well.
Anecdotally, a rubber o-ring on the NDS crank diverts water off the crank in the same way as a window sill drip groove works, I haven't tried one on the NDS axle
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boblo
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Re: Replacing Hollowtech II Bearings

Post by boblo »

IME it's the constant washing of my bikes over winter that causes most of the issues on the NDS bearing. I don't point any water directly at it but it still goes relatively rapidly. I've taken to protecting it with the long cuff off a rubber glove sleeved over the crank arm/BB and zip tied in place - just for cleaning. So far, so good.

You can now get 24x37x7 bearings that fit straight into the HT2 cups without using the silly plastic top hat. When HT2 first appeared, this size wasn't readily available (cheaply). If you must use the top hat, 25x37x7 is the correct size but I wouldn't bother.

As for longevity, give GXP a go and for extra silliness, 22mm on one side and 24mm on the other <sigh>
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

tim-b wrote: 28 Nov 2022, 6:32am
This leads to my first question. Is there a reason that the NDS gets worn out first?
IMHO it's because the NDS isn't protected in the same same way as the DS. The DS has a lump of aluminium that stops water running down the crank from the pedals and rider and along the axle. The same lump effectively shields the bearing from external weather as well.
Anecdotally, a rubber o-ring on the NDS crank diverts water off the crank in the same way as a window sill drip groove works, I haven't tried one on the NDS axle
Ah right..I'm glad it's not just me Tim. I was beginning to worry that the NDS threads were misaligned. Thanks for posting, I will have a look at the O ring idea - I do something similar with my pedals 😀
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

boblo wrote: 28 Nov 2022, 10:38am IME it's the constant washing of my bikes over winter that causes most of the issues on the NDS bearing. I don't point any water directly at it but it still goes relatively rapidly. I've taken to protecting it with the long cuff off a rubber glove sleeved over the crank arm/BB and zip tied in place - just for cleaning. So far, so good.

You can now get 24x37x7 bearings that fit straight into the HT2 cups without using the silly plastic top hat. When HT2 first appeared, this size wasn't readily available (cheaply). If you must use the top hat, 25x37x7 is the correct size but I wouldn't bother.

As for longevity, give GXP a go and for extra silliness, 22mm on one side and 24mm on the other <sigh>
I am a bit of a tinkerer so there are some good options for me to try there Boblo!! Thanks for responding 😀
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SimonCelsa
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Re: Replacing Hollowtech II Bearings

Post by SimonCelsa »

zenitb wrote: 28 Nov 2022, 12:24am

....... - you could only get standard 25 x 37 x 7mm ones - these didnt fit (although Brucey did try and work out a way of getting them in). However the correct size 25 x 37 x 6mm bearings ARE now available - according to eBay - at about a fiver a pair.

I see your image of the eBay fiver a pair bottom bracket bearings zenitb but I can't see anything cheaper than £7.50 on my eBay search. Could you elaborate a bit, maybe advise who is the seller so I can improve my search, everyone likes a bargain!
boblo wrote: 28 Nov 2022, 10:38am
You can now get 24x37x7 bearings that fit straight into the HT2 cups without using the silly plastic top hat. When HT2 first appeared, this size wasn't readily available (cheaply). If you must use the top hat, 25x37x7 is the correct size but I wouldn't bother.
Apologies for querying your post here boblo, but are you saying that the 25 x 37 x 7 mm is the correct bearing as opposed to the 25 x 37 x 6 mm item??

Cheers, Simon
boblo
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Re: Replacing Hollowtech II Bearings

Post by boblo »

Apologies for querying your post here boblo, but are you saying that the 25 x 37 x 7 mm is the correct bearing as opposed to the 25 x 37 x 6 mm item??
Either will do. If you're using the plastic top hat, the 6mm thick bearing will be just below the surface/rim of the HT2 cups and the plastic top hat will be almost flush with it. The 7mm thick bearing option would mean the plastic top hat will be a little proud of the HT2 cup but there's plenty of room for it between the cups and the crank arms so no issue either way.

I've never bought 6mm thick bearings, always 7mm and now I buy 24x37x7 to avoid using the fragile plastic top hats.
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