External BB bearing solution?

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reohn2
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Joined: 26 Jun 2009, 8:21pm

External BB bearing solution?

Post by reohn2 »

I had an idol hour today so decided to look at the possibility of changing the Genesis Longitude from EBB to S/taper when the hopelessly inadequate Shimano BB bearings fail.
The problem is that it's 10sp and S/T isn't generally available in 10sp so I measure the thickness of the chainrings (2+mm)and found that 8/9sp chainrings are exactly the same thickness,and low and behold the pitch between chainrings is the same.
I have an Shimano 104 BCD chainset and plan,when the time comes, on fitting a 22t inner and either a 32 or 34t ring in the middle position making a 2x10 drivetrain,which TBH would give a plenty big enough top gear and the same low end as now.
Can anyone find a problem with this?
Last edited by reohn2 on 25 May 2015, 6:42pm, edited 2 times in total.
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531colin
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Re: Extrenal BB bearing solution?

Post by 531colin »

only that the BCD is likely to be 104mm...... :wink:
reohn2
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Re: Extrenal BB bearing solution?

Post by reohn2 »

531colin wrote:only that the BCD is likely to be 104mm...... :wink:


Fumble five finger now squared :)
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Brucey
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Re: External BB bearing solution?

Post by Brucey »

the only potential snagette that occurs to me is that the middle ring often has extra ramps on the left side these days. Without such ramps it is sometimes possible for a narrow chain just to sit on top of the small chainring teeth on a downshift, and upshifts may be less brisk too.

So if the ring you intend to use in the middle position is designed to be a middle ring, I think it'll work OK but if it is repurposed outer chainring there may be a few quirks...

BTW if you wreck your EBBs in short order, I think it is worth trying to extend their life using the methods I have previously suggested in other threads. If this works for you it could be a £10 fix.

cheers
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reohn2
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Joined: 26 Jun 2009, 8:21pm

Re: External BB bearing solution?

Post by reohn2 »

Brucey wrote:the only potential snagette that occurs to me is that the middle ring often has extra ramps on the left side these days. Without such ramps it is sometimes possible for a narrow chain just to sit on top of the small chainring teeth on a downshift, and upshifts may be less brisk too.

So if the ring you intend to use in the middle position is designed to be a middle ring, I think it'll work OK but if it is repurposed outer chainring there may be a few quirks...

I'd be using a 9sp middle ring in the middle ring position so it should shift OK I'm thinking.

BTW if you wreck your EBBs in short order, I think it is worth trying to extend their life using the methods I have previously suggested in other threads. If this works for you it could be a £10 fix.

cheers

It's a bit of forward thinking really,and an option instead of continual maintenance of short lived EBB's.It's either the ST option or an EBB that lasts,such as a Hope,but @ £67 a pop :shock: there's not much hope :? .
The total cost to go ST would be around £30 for a UN54+32t c/ring as I already have an inner ring which should IME last for 15 to 20K miles.
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Brucey
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Re: External BB bearing solution?

Post by Brucey »

well I think that a £10 shimano BB could be made to last, it is just that no-one (not shimano, not the people who use them) seem to want to give them half a chance.... :wink:

cheers
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reohn2
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Re: External BB bearing solution?

Post by reohn2 »

Brucey wrote:well I think that a £10 shimano BB could be made to last, it is just that no-one (not shimano, not the people who use them) seem to want to give them half a chance.... :wink:

cheers


It's the the constant tending that I'm trying to eliminate,the present one is OK for the moment but I could feel some slight roughness on the LH bearing after around 50 hours off road riding,even though I stripped it and packed it with grease from new,and have been careful set it up without preload according to recommended instructions,and squirted semi fluid grease between crank arms and bearing faces after mucky rides or after cleaning in an attempt to preserve them.
The bearings show no sign of water ingress.
It's a very bad design IMHO and will be ditched if possible,in favour of ST when the bearings fail.
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meic
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Re: External BB bearing solution?

Post by meic »

I have just taken apart my Tiagra bottom bracket shells after 4,000 miles of use because I was having a small clunk from that region.
The left shell had some emulsion around the outside of the seals. The thing which I noticed was that both of them had a lot of grit ingress, it had got past the top hat and had filled up behind it up to the seal lip on the seal "plate". I think that some must then get past that too. I do wonder if my spraying spray lube there had actually helped the grit to get in!

The design is quite different to the FSA which has the seal lip at the rim of the tophat and the bearing cartridge is a 2RS sealed on both sides. The Tiagra tophat comes on and off much more easily and less damaged.

They have been cleaned and filled with waterproof grease to see how they then feel.

I didnt knock the bearings out of the cups as you can only get a tool onto the inner race and I dont like knocking out bearings which I am going to use again in that way.

I did wonder why I was spending (wasting?) time washing and re-greasing bearings which only cost £7.61 a pair as complete cups. I guess just a pigheaded determination to give them a chance. :wink:
Or a refusal to let them beat me and to find a way to get this right.

I already bought a lifetimes supply of cartridges for my FSA a few years ago for just £20. 8)
Yma o Hyd
Brucey
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Re: External BB bearing solution?

Post by Brucey »

if you are worried about damaging the bearings when knocking them out,

a) use hot water on the cups beforehand, and

b) don't be; if the races are indented during removal, note that it is the other side of the races that is used in service, so a little marking won't really matter.

In use these bearings soon start to work like angular contact bearings, but the angle is high and the preload is low.

My scheme is to remove the bearings, remove the inner seals, refit the bearings, then fill the cavity between the axle and the BB sleeve with a semi-fluid grease. The grease will fill the airspace inside the unit; this space when filled with air instead, as per normal, tends to make the unit 'breathe' through the bearing seals, with temperature changes, and this drags water, dirt etc into the bearings; by contrast a slight weep of lube outwards will deter the ingress of most stuff into the bearings, as well as keep them well lubricated.

This should render the system maintenance free for a year or two at a time. When you do need to do anything with it, it will be a five minute job to top up the lube in the cavity. If needs be this could be done by using a drilling into the cavity and simply applying a grease gun. NB it is very important to use a semifluid grease; anything thinner will simply run out and anything thicker won't keep the seals wetted.

cheers
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Steveo2020
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Re: External BB bearing solution?

Post by Steveo2020 »

I have just tried Brucey's scheme on a new build. Only 400 odd miles so far so too early to judge. I may not have used a runny enough grease though - I in fact used the Mobilith 'forum grease'. It must be an improvement over the small amount of grease that it came with.

I have previously had reasonable longevity from shimano ebb units, but this is the first I have fitted to a commuting bike that lives outside.

If it works I shall get a disproportionate amount of satisfaction from spending a fair amount of time prolonging the life of a £7 part!

Cheers
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: External BB bearing solution?

Post by Brucey »

IIRC the Mobilith grease is a #2 consistency. This is too thick for this scheme really, ideally you need a #0 or #00 consistency grease for the scheme I propose.

But having said that almost anything you can do with Mobilith grease is a better arrangement than shimano's....

cheers
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meic
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Re: External BB bearing solution?

Post by meic »

meic wrote:I have just taken apart my Tiagra bottom bracket shells after 4,000 miles of use because I was having a small clunk from that region.
The left shell had some emulsion around the outside of the seals. The thing which I noticed was that both of them had a lot of grit ingress, it had got past the top hat and had filled up behind it up to the seal lip on the seal "plate". I think that some must then get past that too. I do wonder if my spraying spray lube there had actually helped the grit to get in!

The design is quite different to the FSA which has the seal lip at the rim of the tophat and the bearing cartridge is a 2RS sealed on both sides. The Tiagra tophat comes on and off much more easily and less damaged.

They have been cleaned and filled with waterproof grease to see how they then feel.

I didnt knock the bearings out of the cups as you can only get a tool onto the inner race and I dont like knocking out bearings which I am going to use again in that way.

I did wonder why I was spending (wasting?) time washing and re-greasing bearings which only cost £7.61 a pair as complete cups. I guess just a pigheaded determination to give them a chance. :wink:
Or a refusal to let them beat me and to find a way to get this right.

I already bought a lifetimes supply of cartridges for my FSA a few years ago for just £20. 8)


Three hundred miles later the Tiagra bottom bracket is still smooth and silent. So regreasing them is worthwhile, preferably before they corrode.
Yma o Hyd
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