BB - External cups to square taper

[reohn2]

.....I tend to seek perfection......

Don't bother,it doesn't exist as the mind is subject to change.
The best you can hope for is the best compromise

I suppose that’s why I prefer square-taper bottom brackets to external ones. They’re both disposable, but the former is slightly less disposable. Never mind the exact costs; I prefer knowing that my bicycle is built of bits that last.

Ah,the goal of longevity,then the mind tires of the sameness of longevity and seeks newness....

[robc02]

While I agree, in general, with the sentiments about square taper BBs, I would also point out that they are not all equally durable. I have had a succession of Campag Chorus ones wear out after just one or two winters, even when they have been filled with a mixture of grease and oil in an effort to keep the seals wet. I've heard similar complaints about some Stronglight units.
I am currently using a Token equivalent, that I filled with semi-fluid grease after first removing the inner bearing seals. It's now on its second winter and is showing no signs of wear, so hopefully this will be more successful.
The Shimano UN series do seem to be remarkably durable and economical. A good buy if they fit your chainset.

A small redeeming feature of external BBs that hasn't been mentioned is the predictability of chainline. - It's always the same (though not adjustable). I've had a number of square taper chainsets where the chainline varies significantly between different samples of the same manufacturer/model, making bottom bracket length selection a bit of a lottery.

[Brucey]

While I agree, in general, with the sentiments about square taper BBs, I would also point out that they are not all equally durable. I have had a succession of Campag Chorus ones wear out after just one or two winters, even when they have been filled with a mixture of grease and oil in an effort to keep the seals wet. I've heard similar complaints about some Stronglight units.

interesting.... did you similarly remove the inner seals? Were there signs of water ingress? Was that the kind of chorus with the double bearing in the RHS? If so what did you do with the seals on that one...?

I am currently using a Token equivalent, that I filled with semi-fluid grease after first removing the inner bearing seals. It's now on its second winter and is showing no signs of wear, so hopefully this will be more successful.

one of the few that you can get in the right length; I am doing likewise for campag of that vintage but for me this kit sees neither miles nor weather so it doesn't tell me that much if it carries on working....

I have a feeling that for BBs with some riders you might well need the EP additives and solid lubricants etc found in some greases, and without them you might well still get wear. The reason I think this is that the BB bearings are the slowest moving and see the highest loads. What kind of SF grease did you use?

The Shimano UN series do seem to be remarkably durable and economical. A good buy if they fit your chainset.

yup, my only quibbles (in which they are not alone BTW) is that the bearing preload is not entirely independent of the installation torque; if you (say) reinstall one that is slightly worn, often the play in the bearing mysteriously disappears as you torque the cups up. The other quibble is that they are somewhat uh, 'economical' with the grease fill. You can normally add about four times as much grease to these units if you pop the seals out.

A small redeeming feature of external BBs that hasn't been mentioned is the predictability of chainline. - It's always the same (though not adjustable). I've had a number of square taper chainsets where the chainline varies significantly between different samples of the same manufacturer/model, making bottom bracket length selection a bit of a lottery.

EBB chainline is adjustable with shimano systems if you are canny; Mountain cranksets and BBs use BB spacers anyway (on a 68mm shell) but if you have a 'road' chainset and you need to move the chainline, the trick is to use a 'Mountain' BB set in which the cups are 1mm narrower each side than a 'Road' set. You can immediately shuffle the chainline +/- 1mm this way on a 68mm BB shell, more than this is the shell is slightly narrower. If you use a (supplied) 2mm spacer then the chainline adjustment is 'permanent' (or at least requires the BB cups to come out if you change it).

If you instead screw the 'Mountain' cups into the frame without spacers, you can add (different) spacers on the spindle (i.e. between the cups and the cranks) to a total thickness of ~3mm or so (the extra 1mm comes from the tolerance of the LH crank to being 1mm further out if necessary). This gives ~+/- 1.5mm chainline adjustment.

cheers

[reohn2]

Shimano Unquestionably Nice



For over 55's only

[531colin]

.......
FYI I have a few of my bikes running with sq. taper and feel ok..............

I have at least 3 Mtb's running ISIS bb...........

And presumably at least one or two more bikes running external BB bearings?

I only have 3 bikes in anything like regular use, but it means that each bike only gets relatively light use. Apart from at least one chain and set of brake pads each year or so, and occasionally tyres, hardly anything wears out or fails. (ceramic rims on 2 bikes used in mucky conditions have made regular rim replacement a thing of the past)
The recent failures (that i remember!) have been;-
Sticky freewheel pawls in a Sachs Neos hub this winter, cured by introducing some light oil.
In a previous year, the matching front hub developed play, the axle was a slack fit in one of the cartridge bearings, cured with a drop of Locktite thread and bearing fix. (I won't be re-rimming those hubs)
A couple of years back, bent a F. mech. in a "chain suck incident".
So far, I have never worn out a square taper BB unit, and I have an ISIS one still going, although its one with nominally "replaceable" bearings and I have picked out the (inner) seal and re-greased.
The old loose ball BB sets with the adjustable left cup I wore out regularly, although I never had a Campag. one. I was stronger then, and did more miles, running fewer bikes.....

[fastpedaller]

However I have used a similar approach on inexpensive ST BB units that employ 'sealed' cartridge bearings.
I have taken such BB units and fitted external shields to supplement the extant seals (which by themselves are not fully effective and I would say render the sealing comparable to a typical shimano EBB), removed the inner seals from the bearings and flooded the centre cavity with suitable lube.

Sorry if I'm being dense, but how is it possible to get to the inner seals?

[jk49]

Brucey, you've explained how to inject grease past the external seal on un55 style bbs. Does this work better than the punching a hole in the middle of the body after applying a bit of angle grinder method,then forcing grease into the bearings from the inside>outside.

[hondated]

Having had external BB on my own bikes and serviced many others, I would disagree that changing to square taper is downgrading in any way.
Even with the BB shell faced and the pre-load correct there remains the problem of water ingress with this system which places the BB in the most vulnerable position for this to happen. To swap back to square taper is the first job I do with a new bike as I know from experience that this will save me the trouble of having to replace the external BB sometimes in as short a time as a year.

Oh dear and theres me thinking an expert like Roberts who built my bike with outside BB would know that !

[hondated]

I think Gattonero has a fair point. I would choose ST for most applications but if the OP already has an external BB chainset then the simplest and cheapest solution to try is a better quality external BB. The External v. ST debate is a bit of a red herring.

I don't believe the EBBvS/T is a red herring at all.
The EBB has been proven a to be bad technology unless you pay serious money(upward of £40)for BB bearings to last if anyone so much as sneezes on them.

There has been talk on here about EBB's being stiffer,I've used both and can't detect any difference,perhaps heavier/stronger riders would,I don't know I can only speak from experience.
There's a weight 'penalty' for S/T,I'm sure an EBB system is lighter but by how much I don't know,but it would need to be 500g> to be significant enough to outweigh the benefits of S/T IMHO,and even then it'd be debatable if it were any benefit.

Changing over to S/T will cost £35+post(£5?) for a Spa c/set and £14.50 for a UN55 from CRC,to reap something back from his EBB chainset he could sell it on Ebay,possibly for £20 net(?)=total outlay £34.50.
Replacing the existing EBB with something that will last(possibly)would cost upward of £25.

On the plus side with an S/T system he gets out of constant mollycoddling the EBB bearings by having to regrease them regularly,or renew them in under 10K miles and possibly under 5K,by having a 15k+ mile trouble free run.

The only people making sense out of EBB's IMHO are the manufacturers,everyone else other than weight weenies,is on a loser.
My 2d's worth,YVMV

I do wish your post had been copied to paul hewitt before i bought my tourer. Nice man, good service, nice bike, but i do feel i should have been talked through the BB options, especially as i said i was looking for something tough and simple. I can see myself having to swap the chainset and BB out pretty soon. For something basic and cheap and reliable which i can forget. So i do rather feel that i paid a premium for nowt. My old ridgeback will celebrate its 20th birthday very soon and only fairly recently went onto its second BB.

God knows how anyone ever thought that worrying about bearing tension and regreasing was an advance. I am almost unconscious of my ST even having bearings.

If its any small comfort Roberts built mine with them as well.

[hondated]

However I have used a similar approach on inexpensive ST BB units that employ 'sealed' cartridge bearings.
I have taken such BB units and fitted external shields to supplement the extant seals (which by themselves are not fully effective and I would say render the sealing comparable to a typical shimano EBB), removed the inner seals from the bearings and flooded the centre cavity with suitable lube.

Sorry if I'm being dense, but how is it possible to get to the inner seals?

Great question and something I was also thinking about.

[Brucey]

in most such BB units, the cartridge bearings are a snug sliding/very light interference fit onto the spindle, and the cups are a similar fit over the bearings. Once both cups are off the bearings (tip; mount the RH cup in a BB shell, and then you can give it a knock with a soft hammer).... the centre sleeve can then be knocked sideways. Once you have done this you can rest the bearing inner edge onto the jaws of a bench vice. A few taps with the soft hammer and the bearing is off the axle and you can remove both inner seals, add lube etc

cheers

[Brucey]

Brucey, you've explained how to inject grease past the external seal on un55 style bbs. Does this work better than the punching a hole in the middle of the body after applying a bit of angle grinder method,then forcing grease into the bearings from the inside>outside.

I've used both approaches at various times. I think it is more difficult to entirely fill/purge the BB with grease if you remove one seal; the seal itself (which you can't easily replace with another, they seem to be a special part) can be damaged, and because the BB unit doesn't necessarily have to come out of the frame, it might be more likely to get stuck in there.

The grind-until-thin-then-make-a-hole method is better in some respects but if you break through early or push debris into the BB it is a PITA to sort out. In some cases you can 'burp' the seals out of the unit by using a burst of compressed air, and this makes cleaning the unit a fair bit easier, should this prove necessary.

cheers

[robc02]

interesting.... did you similarly remove the inner seals? Were there signs of water ingress? Was that the kind of chorus with the double bearing in the RHS? If so what did you do with the seals on that one...?

There have been a number of iterations of this experiment, but in the most recent version I did remove the inner seal of the larger bearing. - This is the one that was suffering most wear. There were no obvious signs of water ingress but I presume there must have been some, because the same BBs are fine when used in summer. I always put oil/grease in the small void between the bearing outer seal and the cup seal, as I suspect it is the cup seal that is the source of the problem. I contemplated removing the bearing outer seal so that lubricant could get right through the bearing and onto the cup seal. I didn't do this, hoping that the lubricant I applied, possibly topped up by oil seepage through the bearing seal (doubtful but I was progressing using the "one step at a time" principle) would do the trick. Had I continued the experiment, I would have remove the seal as described, and drilled a lubricating point through the top of the casing via the BB shell. I foresaw that realigning the holes after disassembly might be a bit awkward, but the results might be worth it. In the end I turned my attention to the Token units.
All of the BBs I used had the double RHS bearing. I didn't touch these until I had to, as they are held in place by a pressed on ring. I thought removing it might be destructive (I was later proved right!). These bearings held up much better than the larger single one on the other side.

I have a feeling that for BBs with some riders you might well need the EP additives and solid lubricants etc found in some greases, and without them you might well still get wear. The reason I think this is that the BB bearings are the slowest moving and see the highest loads. What kind of SF grease did you use?

In the Token BB I am using Penrite Semi Fluid Grease. It's recommended for slow speed applications and has corrosion inhibitors so I thought it was probably a good choice.

EBB chainline is adjustable with shimano systems if you are canny; Mountain cranksets and BBs use BB spacers anyway (on a 68mm shell) but if you have a 'road' chainset and you need to move the chainline, the trick is to use a 'Mountain' BB set in which the cups are 1mm narrower each side than a 'Road' set. You can immediately shuffle the chainline +/- 1mm this way on a 68mm BB shell, more than this is the shell is slightly narrower. If you use a (supplied) 2mm spacer then the chainline adjustment is 'permanent' (or at least requires the BB cups to come out if you change it).

If you instead screw the 'Mountain' cups into the frame without spacers, you can add (different) spacers on the spindle (i.e. between the cups and the cranks) to a total thickness of ~3mm or so (the extra 1mm comes from the tolerance of the LH crank to being 1mm further out if necessary). This gives ~+/- 1.5mm chainline adjustment.

cheers

Good point. I was thinking of the standard expedient of swapping axle lengths - not possible with EBBs.

In principle, putting the bearings as far outboard as possible is sensible, and it should be possible to design and manufacture such a system that works well. However, in most cases the implementation seems to be lacking.

[robc02]

There has been talk on here about EBB's being stiffer,I've used both and can't detect any difference,perhaps heavier/stronger riders would,I don't know I can only speak from experience.

The only manifestation of the extra stiffness that I could notice was slightly less tendency to get chainrub against the front derailleur cage. However square taper and EBB cranksets are normally differently designed (mine were) so it is difficult to be sure which feature is having the most effect*. I can well imagine someone not noticing the difference in practice.

*Some older chainsets were quite flexible and, coupled with the narrow derailleur cages of the day and the small gap between chainring and crank, it could be nigh-on impossible to completely eliminate chainrub in top gear.

[fastpedaller]

In principle, putting the bearings as far outboard as possible is sensible, and it should be possible to design and manufacture such a system that works well. However, in most cases the implementation seems to be lacking.

I don't understand why that would make any difference (unless there is play in the bearings). The stiffness pertains to the frame....... Taken to an illogical conclusion, if you put the bearings 30cm out on either side (very high Q ) all it would do is bend the frame more as you pedalled! ISTR when Grahaem Obree broke the hour record he had a very slim BB, with (reported at the time in a way to grab peoples attention) washing machine bearings. Of course washing machine bearings are the same as other stock bearings (water seals may be better though )