Understanding Bottom Brackets & Shells

[MacB]

I got an Alfine crankset this morning and it's the two piece with external bearing bottom bracket rather than the one for a cartridge BB I intended...my own fault. But this has got me looking at stuff and thinking, could people help verify, or correct, my understanding of some things...warning this will be lengthy:-

Cartridge BB's - inboard bearings and you select to match cranks and BB shell, assuming no chainstay interference, can you select any axle length to get a preferred chainline?

Outboard Bearing BB's - like the one I have in error, again I get that you match BB to cranks but how can you mess about with chainlines? Can you use spacers or are you limited by the axle length supplied? I'm thinking for single chainring use here. What's the longevity of these sorts of BB's like compared to cartridge ones and are the bearings more vulnerable to leakage/ingress being on the outside?

BB30, BB91 etc - these are outward bearing ones again but need special BB shells?

Eccentric BB's for EBB shells - I understand that these require a special oversized BB shell and that the EBB is an insert to this that allows a normal cartridge, or OBB, bottom bracket to be inserted off centre. The EBB can then be rotated within the shell to alter the length of the chainstay and tension the chain, the alterations vary from 1/4" to 1/2"? The different options are:-

Split Shell EBB - this is where the shell has a lengthways split which can be tightened by two bolts thus holding an EBB insert in place? not sure of any examples of EBB inserts for this use but assume you can use any ones that would normally work via set screw? - critics claim the split allows for too much water/muck ingress and it is prone to creaking and slippage?

Set Screw EBB - shell is complete but has two holes underneath for set screws to be inserted. The EBB insert is fitted to shell and then the set screws are used to stop rotation, this is how the Phil Wood ones work? - again tales of creaking, slippage and the set screws creating indentations that limit the positions you can use?

Expanding Wedge EBB - again shell complete but a bolt is tighted from side of EBB insert to expand the insert and hold it in place? - gets worst write ups for creaking and slippage but easiest to maintain? Bushnell is well thought of and there's a Carver model that claims to have sorted the slippage/creaking issue by having a nylon sleeve that provides better surface to surface grip.

Outboard gripping - Niner have a new insert that bolts through to the other side and the cups grip round the outside ends of the BB shell. Claims to solve creaking and slippage problems but I've read some horror story reviews that indicate poor performance unless everything is absolutely perfect.

Eccentric BB's for normal shells - these only work with 2 piece cranks with 24mm axles and the EBB itself contains the bearings and replaces the OBB? These give a 1/4" of throw and adjustment is to each side of the BB and so misalignment is possible thus overstressing bearings? I'm aware of 3 models:-
Excentriker from Trickstuff - setup is fiddly but ongoing adjustments are the easiest, one set screw each side, needs special tool for installation which you buy on top of the £150 EBB.
Forward Components - similar setup to the Excentriker but adjustments are via 12 set screws, 6 on each side, special tool again but at least they throw it in with the EBB, about £120
Philcentric from Phil Wood - they have the 1/4" EBB insert for EBB shells introduced to minimise changes to ride position via EBB and this is their take on the EBB for normal shells. Workings are similar but the initial setup requires special tools and they are only supplied to bike shops at present. The maintenance adjustments are by the user after that but do require removal of the crankset to achieve. Unlike the other two this isn't infinitely adjustable there are set points at 15 degree intervals, About £150 again.

I have seen claims around slippage, but not creaking, for all 3 of these but generally associated with heavy duty SS use. I was wondering if these would be an ideal solution for hub gears in a normal vertical dropout frame? One of the criticisms of them is that they don't provide enough throw to be able to change gears around for SS or fixed riding. but if you're only wanting one to take up slack due to chain wear, and won't be brutalising it via SS/fixed use, then wouldn't it be more than enough? Obviously you'd want to start with as close to a magic gear combo as possible but a total of about 7mm horizontal should be enough shouldn't it? I've seen writeups about SS/fixed conversion where they've almost got a magic gear and have just taken a file to the vertical dropouts to give them the required 1-2mm to make it work. This would be a positive luxury of ajustment in comparison to that, I'd also be employing a halflink if need be. So, work out chainring/cog combo, install with EBB and just tighten as chain wears. When you run out of adjustment, and the chain is too slack, then time for new chain. As for the BB itself, I understand the cups last for ever(or at least a darn long time) and you just keep replacing the cartridge bearings as they wear out?

Would be interested in sanity check info re the above and any real world experience of the Excentriker, FC EBB or Philcentric...as I've got the 2 piece cranks the £150 outlay is looking a bit less painful.

Merry Xmas

 

[Zoiders]

I wouldn't piss about with an EBB I would go for a frame with sliding vertical drop-outs instead.

The EBB is a design cul-de-sac.

 

[accountantpete]

I did read in some forum that you can pinch a few mm with spacers for alignment - but being a Campag man I have no direct experience.

If you are fitting the Alfine then the first thing to do is get the faces of the BB shell on the frame faced off square. This ensures a snug fit for the BB shells and stops them unscrewing - although I just scraped off the paint and stuck some pdf tape on the thread which sort of does the same job (ie they work loose after a couple of months and need re-tightening).

Re the EBB - there is quite a considerable load going through the BB and anything that complicates matters to my mind throws up more problems than answers - I might be wrong MacB but I'd keep things simple as Zoiders says.

 

[e-rider]

er

 

[Ticktockmy]

I just fitted a Truvativ Noir Carbon Chainset, which has external BB bearings, and have had no problems fitting them in place of my old internal BB, as on the drive side the external bearing tucks inside of the Chainrings, and on the nondrive side the crank design, counters the extra external width, also the spacers provided allow adjustments to be made..Hope that helps in some way.

 

[MacB]

Hmmm, as usual I think my ability to convey clearly in type is letting me down:-

Zoiders - I get the idea of sliders and they are an option on a custom frame but they do bring in rack/mudguard/disc fitting concerns. They also place ultimate frame alignment in the hands of the user, which creates its own potential problems. But I would be interested to hear why the EBB design is a cul-de-sac? It's all about altering the effective length of the chainstay to create the correct chain tension. It can be done by dropout movement, BB movement or via chain tensioner. Personally I can see the simplicity, or lack of pissing about, in keeping the dropouts and BB as fixed points and using a tensioner. To be fair no-one ever looks at a derailler bike and says that's a shoot way of achieving chain tension.

AccountantPete - I'm not planning on fitting these at all, the write up on the Alfine 2 piece indicates a chainline of 42.7mm and the I-9 has a 49mm chainline. If I'd received the Alfine 3 piece cranks, as expected, then I'd have been matching them to a cartridge BB that gave me a better chainline. It was more that I'd previously dismissed the standard BB fitting EBBs as it meant new OBB cranks etc. Whereas I now have some outboard bearing cranks and it just got me thinking, honestly, I've not even disturbed the packaging in case they need to go back. There was also the fact that I kept seeing things like, forget EBBs unless it's from Phil Woods and don't bother with the gimmicky Exzentricker or Forward Motion offerings. Then I look at the Phil Wood website and, lo and behold, they've brought out their own mini version, called the Philcentric, and are prepared to put the Phil Wood reputation behind it. Also when I'm reading in detail about the Exzentricker/FC ones I'm finding a lot of negatives from people that have never used them. Actual user feedback seems generally good and some of the bad can be put down to user error. The Exzentricker does receive a bit of a kicking from Sam at Singular Cycles but pinch of salt there. He has a business to run and that's heavily focused on SS offroad, far from the sort of riding an onroad, commuting, hubgear bike is going to receive, and he's committed now to oversize BB shells and Woods EBB inserts.
I do get what you say on the load bearing but the concerns around EBBs seem to be about their ability to stay in position rather than general load bearing capacity. To that end the standard shell EBBs seem to have less in the way of complaints, can't find much about slippage regarding them at all. It all seems to be about setup and ease of adjustment, with concerns on the seperate alignment of the two sides. Whereas slippage is a constant complaint for normal EBBs yet many still recomend them as the best way for chain tension.

Tundragumski - cheers mate that helped.....but it's Xmas so I'll only think you're a twat instead of twatting you so hard you become one

Ticktock - thanks, I think I need to read more before I really get it, at the monet I'm thinking 2 piece crank = fixed axle length so fixed chainline whereas 3 piece crank = cartridge BB so take your pick of axles and chainlines. I know this is a simplification but I do need to move beyond that level of understanding.

 

[P.H]

Split Shell EBB - this is where the shell has a lengthways split which can be tightened by two bolts thus holding an EBB insert in place? not sure of any examples of EBB inserts for this use but assume you can use any ones that would normally work via set screw? - critics claim the split allows for too much water/muck ingress and it is prone to creaking and slippage?

Least likely to creak or slip, pqack it out with plenty of grease and unlikely to get any water ingress, it isn't going to go far if it does and so what if it's a ti frame. Advantage is one insert is going to last the lifetime of the frame. SJS have them in stock as will most Tandem builders, or you could as suggested use one designed for set screws.

Set Screw EBB - shell is complete but has two holes underneath for set screws to be inserted. The EBB insert is fitted to shell and then the set screws are used to stop rotation, this is how the Phil Wood ones work? - again tales of creaking, slippage and the set screws creating indentations that limit the positions you can use?

Not a good option on a ti frame, you can deform the shell too easily. Plus the insert is sacrificial, not a problem as they're cheap enough, but what if you have a unique size and sometime in the future it's no longer available.

Expanding Wedge EBB - again shell complete but a bolt is tighted from side of EBB insert to expand the insert and hold it in place? - gets worst write ups for creaking and slippage but easiest to maintain? Bushnell is well thought of and there's a Carver model that claims to have sorted the slippage/creaking issue by having a nylon sleeve that provides better surface to surface grip.

Far more complicated that it needs to be, the latest Bushnell on the Van Nick Rohloff creaks and creaks, hearing on put me off for life. They also have a reputation of siezing up if not properly maintained.


For me the split shell is working faultlessly. As did the set screw type on a steel Thorn. Zoiders cul de sac is populated by just about every manufacturer who produces any volume of hub gear specific frames, there's good reason for that. You could read what Peter White says about EBBs, when detailing the split shell type as used by Tout Terrain "Why all frame builders don't do it this way is a mystery."

http://www.peterwhit...out-terrain.asp


Singular Cycles use the set screw type on their steel frames, but the clamp type on the Ti ones;


http://www.flickr.co...in/photostream/

One of the criticisms of them is that they don't provide enough throw to be able to change gears around for SS or fixed riding.

??? half an inch of movement will take up the entire difference between links, with this amount of adjustment it isn't possible not to be able to get a tight chain if that's what's required.

 

[MacB]

Thanks PH, I reckon split shell seems to get the best of the reviews and you go along with that. The Tout Terrain is one impressive beast but far more bike than I need.

 

[Zoiders]

There seems to be a bit of mis-understanding about sliding drop-outs.

They are a commonly used device by several manufacturers now and they are not just a "custom" feature, IIRC Giant have gone with this system on their alfine equiped bikes, Voo-doo use it on all there MTB's and On-One have been offering it as well as an option, sliders are the future IMHO. They in fact over come the problems involved with discs and S/S setups, racks or guards, the disc is in a fixed position in relation to the hub as the drop out and disc mount is part of the same modular unit along with the gear hanger. If one moves so does the other, it's not like running a track end with disc tabs at all. Guards will mount easily enough if you pick a manufacturer that includes the eyes on the frame seperate from the drop outs - like Giant do, or go for P clips.

Adjustment wise for a S/S or hub gear they are very very easy to set up and get wheel alignment correct, hub gears and S/S run with no where near as much tension as a fixed so getting correct wheel alignment is very very easy, there a very few moving parts to the system and the stresses involved are very low.

I don't like EBB's as they are far too reliant on large amount's of torque to hold the BB in the correct place while at the same time being intolerant of infrequent maintanance and "just so" settings of torque.

Frame builder mysticism is what leads to to design dead ends, like the EBB. They just don't like sliders because they didn't think of it first and they see a simple yet effective mass produced design feature eating into their complex and rather expensive/steep "custom" profit margin.

MacB's comment on derailuers gears - people never saying that they are shoot way of maintaining tension - a hell of a lot of people have most certainly said they are a shoot way of doing it - hence the interest in hub gears at the moment, or fixed, or S/S. I mountain bike with derailuer gears and I would happily ditch them for a decent hub gear set up - with sliders.

 

[MacB]

well I'm giving the mini EBB, the Forward Components version a go, ordered one today, it still won't work with the alfine chainset, wrong chainline, but I think I've picked up a cheapie set of cranks to test it with. They aren't without their negatives but seem to lack the slippage/creaking complaints that full EBBs rack up. The main criticism is that they only have about 7mm of throw and so limit the options for gears. As I'm using a hub gear this bit isn't really relevant, I wouldn't expect to be swapping out ring/cog to change ratios as with SS/fixed. I expect to work out a ring/cog combo that gets me as near the start of the 7mm throw as possible. Then it should be changing chain time before I run out of adjustment. From what I've read one of the big limitations on mini EBB takeup has been the compulsory OBB crankset. A lot more people would give it a go if it didn't mean changing as many bits as it does. I've seen quite a few posts saying £150 compared to £50 for a good chain tensioner, that seems ok, but then factor in another £80+ for a new crankset, maybe some new rings/cogs as well and suddenly it's far less appealing.

Sliders have plenty of fans and one way around it is to have the rack/guard mounts higher up the seatstay, the Singular Peregrine does this. Having them on the dropouts, along with the caliper mount, means that when you move the dropouts you need to sort the upper rack/guard mounts at the same time. PH made the point that he feels frame builders are going with sliders as an easier, rather than superior, option, depending on intended useage. I accept that I have no personal experience of sliders and nor of EBBs. I'm going with what I've read and my gut feel, but I don't think I misunderstand sliders. There are complaints of slippage and having to source better bolts and creaking. There're also negatives around the stock frame ones compared to versions like Paragon.

Hey, I'm not ruling out anything for the custom build just yet, this is all going to be trialled on the Salsa Vaya frameset, if I don't like the EBB then it'll be a chain tensioner. At that point I'll consider my options for the Ti custom frame. Rest assured I'll give an honest report back on how the EBB works etc.

 

[P.H]

I don't like EBB's as they are far too reliant on large amount's of torque to hold the BB in the correct place while at the same time being intolerant of infrequent maintanance and "just so" settings of torque.

What is this dislike based on? I can't imagine it being experience, I don't recognise any of it. Infrequent maintenance? I stick a bit of grease on when I tension the chain every few thousand miles. Just so torque? I wouldn't know what that was. Large amount of torque? We're talking about a bicycle here! In engineering terms the torque is tiny and I doubt the BB stresses are any greater than those at the rear dropouts where sliding fitting are held in sheer, not what screws are designed for. I have no dislike of sliding dropouts, I just think EBBs are simpler and neater. Moving the rear wheel dose affect other components, even if the brakes move with it, brake cables, gear cables, mudguard clearance...

IIRC Giant have gone with this system on their alfine equiped bikes

I've yet to see a manufacturer change from EBBs to sliding dropouts, though I know of a couple who've gone the other way. The couple of Gaint bikes I've seen, City Speed and another? Seek?, use EBBs;

http://www.wheelies.co.uk/p39399/Giant-City-Speed-CS-2011.aspx

 

[Zoiders]

What is this dislike based on? I can't imagine it being experience, I don't recognise any of it. Infrequent maintenance? I stick a bit of grease on when I tension the chain every few thousand miles. Just so torque? I wouldn't know what that was. Large amount of torque? We're talking about a bicycle here! In engineering terms the torque is tiny and I doubt the BB stresses are any greater than those at the rear dropouts where sliding fitting are held in sheer, not what screws are designed for. I have no dislike of sliding dropouts, I just think EBBs are simpler and neater. Moving the rear wheel dose affect other components, even if the brakes move with it, brake cables, gear cables, mudguard clearance...




I've yet to see a manufacturer change from EBBs to sliding dropouts, though I know of a couple who've gone the other way. The couple of Gaint bikes I've seen, City Speed and another? Seek?, use EBBs;

http://www.wheelies....ed-CS-2011.aspx

I think you are trying to convince yourself that the most expensive and elaborate system is the superior one.

The whole thread is an enablement for someone looking to spend a big wedge of cash - that still doesnt mean it was money well spent.

 

[MacB]

I think you are trying to convince yourself that the most expensive and elaborate system is the superior one.

The whole thread is an enablement for someone looking to spend a big wedge of cash - that still doesnt mean it was money well spent.

Sorry Zoiders, I'm not getting you, you've said up thread that you'd happily ditch deraillers etc for a MTB with hub gears and sliding dropouts, I'm assuming you'd have disc brakes as well. So the only thing we're differing on is how to provide chain tension. You favour moving the rear axle and I'm currently favouring moving the front axle, in a two axle system. You've clearly stated that you don't like EBBs and given a couple of reasons, but PH just asked if they were based on experience?

Not sure where you get the expensive and elaborate bit from, I've already said my baseline was standard drops, standard BB and a chain tensioner, the cheapest and simplest of all the methods. I just got the wrong cranks by mistake and it got me thinking and I wanted to try and crystalise my understanding of bottom brackets. Maybe you don't like threads like these but I post them because I've found similar threads, from other people, a great help when I've been experimenting. Cost wise the FC EBB was £120, the Paragon sliding dropouts range from about £100 to £200. I've also picked up a cheap set of OBB cranks on YACF for £18 to experiment with. The Vaya frameset I was getting anyway and this is all working towards finalising my build options on a custom Ti frame. Maybe I like to think aloud via the keyboard, and maybe I like to over analyse stuff, but that's me and I'm not committing to a custom frame without being sure of what I want. Maybe an oversized EBB is dead end technology but the standard shell ones must be doing something right, otherwise you wouldn't be seeing a company like Phil Wood developing one to bring to market.

I appreciate we all have a view on things, and if yours is that I started the thread to enable some sort of mental/wallet style masturbation, then fine. But if you have got anything concrete to add that would be great as well.

 

[MartinC]

Without intruding on the esoteric discussion going on here I think a fair summary is:

EBB's are an elegant but complicated and expensive solution to adjusting chain tension on a hub geared bike. There are other equally effective solutions that are a lot simpler because you're only trying to adjust the bracket spindle to hub axle distance by less than 1/2".

EBB's will be around for a long time because they're the only satisfactory solution for tandems.

 

[P.H]

EBB's are an elegant but complicated and expensive solution to adjusting chain tension on a hub geared bike. There are other equally effective solutions that are a lot simpler because you're only trying to adjust the bracket spindle to hub axle distance by less than 1/2".

If by simpler solutions you mean chain tensioner or horizontal dropouts, then yes, except they each bring other disadvantages. If you mean that sliding dropouts are cheaper, only if we're talking about a limited production, where it's easier for the builder to buy off the peg. When it comes to volume production, I doubt there's anything in it cost wise. The two types of EBB I've used have two set screws and one moving part, half that of sliding dropouts, neither are complicated.


There's a new thread over on the CTC forum that lists the 2011 bikes available with the Alfine 11 hub. Different manufacturers have chosen different options, across the price range, there's a few sliders and plenty of EBBs, just as I'd expect. The only rational choice is whether you prefer to move the front or rear point, talk of dead ends and people trying to convince themselves of something is plain nonsense, even by internet standards it's a poor argument.