Budget square taper BB

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SimonCelsa
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Joined: 6 Apr 2011, 10:19pm

Budget square taper BB

Post by SimonCelsa »

Has anyone any experience of these cheap offerings from SJS; https://www.sjscycles.co.uk/bottom-brac ... sh-thread/

I fully understand you normally get what you pay for but sometimes you find a hidden gem! I only ask as I'm experimenting with chainlines and have found that sometimes spindle lengths are not quite symmetrical. This can get quite expensive if experimenting with the more established brands.
Mud-Plugger
Posts: 24
Joined: 18 Jul 2018, 9:03am

Re: Budget square taper BB

Post by Mud-Plugger »

There's a lot of 'generic' bottom brackets around. Presumably for £7 you could just use it to check your spindle lengths. The Shimano ones are £15 or so.

The easy way to check spindle lengths is just to order a couple of sizes, and return the ones that are 'wrong.' :-)

I have a Decathlon bike with an anonymous sealed bottom bracket. It rides fine.
Last edited by Mud-Plugger on 20 Jul 2018, 10:04am, edited 1 time in total.
random37
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Joined: 19 Sep 2008, 4:41pm

Re: Budget square taper BB

Post by random37 »

There's nothing wrong with the old fashioned pre-cartridge ones, and you can change spindles. Best way to experiment, IMO.
Nigel
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Joined: 25 Feb 2007, 6:29pm

Re: Budget square taper BB

Post by Nigel »

SimonCelsa wrote:Has anyone any experience of these cheap offerings from SJS; https://www.sjscycles.co.uk/bottom-brac ... sh-thread/

I fully understand you normally get what you pay for but sometimes you find a hidden gem! I only ask as I'm experimenting with chainlines and have found that sometimes spindle lengths are not quite symmetrical. This can get quite expensive if experimenting with the more established brands.


If its anything like the "thread in frame broken, this will fit instead" replacement, then my experience is 2 years before its a corroded grinding mess in need of replacement. The "two year" version is fitted to a bike which is well cared for, and whilst it is my wet weather bike, it doesn't go out that much in extreme conditions.

I'm trying a more expensive version, and if that has a short life, I've a decision: bottom bracket as annual service item, or frame rebuild to fix the threads, or new frame/bike.
NetworkMan
Posts: 727
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Budget square taper BB

Post by NetworkMan »

318 grams for 110 mm is towards the top end of the ones I've seen but in any event the lighter ones are still around 250 grams and that's not an issue for you in this case. Bike-discount.de have a selection of Shimano and Suntour for £7.33 if you want a make you've heard of:-
https://www.bike-discount.de/en/shop/bottom-brackets-8611/brand-shimano.suntour/o-preis
Postage is £5.95 though
fastpedaller
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Location: Norfolk

Re: Budget square taper BB

Post by fastpedaller »

I've had FSA ones at a fairly cheap price and been impressed. I suspect what you have there is pretty much a "generic" bottom bracket and the performance will be good like I've found. Maybe the bearings in all these come from the same place? I had a Shimano one that only lasted about 2k miles before clicking, and the exact same item as a replacement that went on for about 50k miles when I gave the bike away it was still good - It can be the luck of the draw. The only thing I would say is that if you find one spaced as you want it, there is no guarantee that one (of the same length) from a different manufacturer will be spaced the same.
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531colin
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Location: North Yorkshire

Re: Budget square taper BB

Post by 531colin »

fastpedaller wrote:...........The only thing I would say is that if you find one spaced as you want it, there is no guarantee that one (of the same length) from a different manufacturer will be spaced the same.


^^^^^THIS!
I think there is sufficient difference between manufacturers in things like the shape of the taper (both axles and cranks) and the distribution of axle length (length added to the left or right or both sides) to make it impossible to use one make of anything to predict how another make will line up.
Added to that, I'm sure we have been round this loop before, I'm sure I remember reading (from Brucey?) about how the left and right axle length changed (with "overall length) in Shimano UNxx BB units. Google should find it, I have more luck with Google than the Forum's own search. Failing that, just wait for "Gaz.".....he finds stuff I can't....and can we have it in Too good to lose?

I would fit a UNxx unit, see what difference I wanted, and go to a bricks and mortar bike shop to offer up the axle to other UNxx units
slowster
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Re: Budget square taper BB

Post by slowster »

Poster nsew helpfully tabulated the different measurements for Shimano square taper bottom brackets here viewtopic.php?f=5&t=119052&start=15#p1190698
Brucey
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Re: Budget square taper BB

Post by Brucey »

there are presently loads of cheap ST BB s that are made the same way; beneath the cups there are two cartridge bearings, located on axle shoulders, and there is a tube spacer that separates the bearing outers and is intended to withstand the installation loads.

Brands include sunrace, neco, chin huar, TH, RPM, and posher versions using the same size bearings include token and tifosi. They all suffer the same problems which are that

1) the bearings don't have much grease in them
2) the seals are not that good
3) the bearings see some weird loads if the BB threads are not machined true to one another
4) the service loads on the bearings are quite high because they are not very far apart
5) the centre sleeve is usually not strong enough to withstand the installation loads

The last of these is a serious issue; if you tighten a BB fully (so that it won't loosen) then the centre sleeve is slightly crushed and the preload on the bearings quickly becomes excessive. On the plus side a worn BB can often be made play-free again by (over-) tightening the LH cup. But it is probably best to install these BBs with threadlock on both cups and to go easy on the torque in the LH cup.


Longevity-wise, these BBs can fail within a year if subjected to average installation and all-weather use. I have prolonged the life of one considerably (from new) by stripping it, removing the inner seals, adding better seals/shields to the outside, and packing the whole space inside with decent grease, but it is a lot of work for relatively little gain (unless perhaps you are using a Token/tifosi unit on a campag chainset; this is one of the few alternatives that is vaguely workable). After about two years use (about 5000 miles on that bike) some free play developed in my 'upgraded' unit, and it has been slowly getting worse since then (another two years or so). I keep meaning to give the LH cup a fraction of a turn more, and to turn the cranks 90 degrees on the BB spindle; this may even out the wear and give the thing a slightly longer life.

The usual failure mode is that water enters the bearings, some free play develops (or the bearings start to bind), and then the clip that holds the balls apart breaks up and pretty soon it is 'game over'. Because there is nominally zero clearance in the bearings to start with, running over clip fragments causes some very high loads and the bearing outers quite often shatter.

One of the things I have noted is that the bearings themselves usually accept 3/16" balls; with a little cunning grinding etc it may be possible to convert the bearings to an angular contact, full complement version, that ought to be a good deal stronger. By shortening the centre sleeve, and installing a spacer between the LH bearing and the cup, it may be possible to make the LH cup protrude slightly, and thus convert the BB so that the LH cup is an adjusting cup, to be locked with a lockring. Not quite a traditional three-piece BB, but perhaps an acceptable alternative...

If you are intending to use such a BB in a 'mock up' (to determine the correct BB length for a build) then note that spindles vary very slightly in taper dimensions from one manufacturer to another; not all 'JIS' models are really the same as one another. Also not all BB spindles are similarly symmetric. This being the case, you may as well use a scrap unit (LBS may have one) of the type you intend to use finally, to mock up. Also note that In most cases you can use a spacer (between the RH cup and the frame) to push the chainset rightwards if you need a touch more clearance, so a spindle that is shorter than ideal isn't always the end of the world.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Brucey
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Re: Budget square taper BB

Post by Brucey »

slowster wrote:Poster nsew helpfully tabulated the different measurements for Shimano square taper bottom brackets here viewtopic.php?f=5&t=119052&start=15#p1190698


Actually he reproduced a table that I'd prepared in this thread,
https://forum.cyclinguk.org/viewtopic.php?f=5&t=105385

with one added set of measurement,
nsew wrote:113................114..0..............23.5.............22.5..............115.0. (UN54)


but less the footnotes without which it may not make good sense. Note that the 113mm BB gives almost the same chainline as a 115mm unit.

This is my original post;
Brucey wrote:the actual axle lengths and symmetry of UN55 BB units has been discussed quite a lot recently but without the benefit of any accurate measurements. I just spent a while in front of a pile of BB units with a set of verniers in my hand and I have the following information (all measurements in mm);

Nominal size---actual length------RH stickout-----LH stickout----Equivalent (symmetric) length

107---------------108.0---------------21.0-------------19.0--------------110.0

110---------------111.5---------------21.0-------------22.5--------------110.0

115---------------115.6---------------24.0-------------23.6--------------116.0

118---------------118.5--------------25.6--------------24.9--------------119.2

122---------------123.2--------------28.6--------------26.6--------------125.2

Note that

- the stickout measurements are w.r.t. the BB shell.
- if you need to know the measurement vs the RH end of the BB cartridge, subtract 3.6mm (the thickness of the flange on the RH cup) from the stickout value.
- the LH stickout value is calculated assuming a 68.0mm BB shell; real BB shells vary somewhat.
- all measurements are likely accurate to about 0.2mm, but the LH stickout measurement will vary by more than this because of cumulative measurement errors, plus any variations in the BB shell width.

- the equivalent (symmetric) length can be used to compare between other BB units (with a similar taper, and symmetrically constructed) on a 68mm shell, for chainline purposes. Variations in equivalent length produce variations in chainline of about half the equivalent length variation. Thus running through these BB units, the chainline varies by 0.0mm, 3.0mm, 1.6mm, 3.0mm respectively. Finer increments than this are possible if spacers are used between the RH cup and the BB shell. The scope for using such spacers is limited however, because the present design of LH cup also has a flange on it.

NB; as mentioned by others in previous discussions, the aluminium LH cup in several of the units I looked at was a very loose fit, so loose that the BB unit is almost certain to work loose in service (and probably wreck the frame).

What are shimano thinking of...???? :shock: :shock: :shock:

If you must use such a BB with a loose LH cup, I'd advise only to fit it with Loctite and/or shims between the LH cup and the cartridge unit.

cheers
edit for typo


cheers
Last edited by Brucey on 24 Aug 2018, 6:32pm, edited 1 time in total.
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SimonCelsa
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Re: Budget square taper BB

Post by SimonCelsa »

Some good food for thought. It's not all to do with the chainline, I also need a bigger gap between crank and BB shell in order to (possibly) fit a pedelec sensor on the tandem. I will get a couple of the longer, cheaper ones and try and pack them full of grease prior to fitting. Should last a couple of years as the tandem seldom exceeds 1000 miles a year.
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Gattonero
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Re: Budget square taper BB

Post by Gattonero »

Am I the only one that doesn't go mad with BB measurements?
I just went to the LBS and offered to clear some of their metal scrap by taking several old BB's. When I need a particular size, I would quickly install those BB's which are surely unusable (and quickly wiped off from rust/grease) but definitely a great help to see how they will behave with a given chainset, in terms of length and taper engagement. They all have a known length of axle, and their offset is measured only when needs to.
I've saved countless friends with this method, always finding a substitute and often saving a considerable amount of money, when a "bespoke" £140 BB seemed the only solution :wink:
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...
Brucey
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Re: Budget square taper BB

Post by Brucey »

Gattonero wrote:Am I the only one that doesn't go mad with BB measurements?...


it is a bit of a minefield. If you buy a new crankset with a new BB that is a match it can seem deceptively simple but beyond that it can all go horribly wrong. Things that trip folk up include

- that the crank manufacturer has used more than one taper type and your old cranks are (unexpectedly) the 'wrong' sort
- that your old cranks are slightly worn and the correct BB isn't correct any more
- that you are trying to use chainring sizes that the frame designer never expected, and they clash with the chainstays
- that you are trying to use a 'road' chainline on a frame that isn't meant for that
- that the RH crank is OK but the BB spindle is so asymmetric that the LH crank is in danger of hitting the chainstay
- that the RH crank has a protuberant centre boss and it not only needs a certain spindle length but also needs a particular construction of BB if there is not to be a clash between the boss and the RH cup.

and so forth. There are a load more things to worry about if it is a three-piece BB. If you confine yourself to fitting new MTB type chainsets to every frame that comes your way then life can be deceptively simple. Stray beyond that though, and it can be a recipe for all kinds of excitement.

cheers
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Gattonero
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Re: Budget square taper BB

Post by Gattonero »

Brucey wrote:
Gattonero wrote:Am I the only one that doesn't go mad with BB measurements?...


it is a bit of a minefield. If you buy a new crankset with a new BB that is a match it can seem deceptively simple but beyond that it can all go horribly wrong. Things that trip folk up include

- that the crank manufacturer has used more than one taper type and your old cranks are (unexpectedly) the 'wrong' sort
- that your old cranks are slightly worn and the correct BB isn't correct any more
- that you are trying to use chainring sizes that the frame designer never expected, and they clash with the chainstays
- that you are trying to use a 'road' chainline on a frame that isn't meant for that
- that the RH crank is OK but the BB spindle is so asymmetric that the LH crank is in danger of hitting the chainstay
- that the RH crank has a protuberant centre boss and it not only needs a certain spindle length but also needs a particular construction of BB if there is not to be a clash between the boss and the RH cup.

and so forth. There are a load more things to worry about if it is a three-piece BB. If you confine yourself to fitting new MTB type chainsets to every frame that comes your way then life can be deceptively simple. Stray beyond that though, and it can be a recipe for all kinds of excitement.

cheers


I'm having a look at my bikes and I don't see any "new mtb type chainset" :mrgreen: indeed I have pretty much everything from ISO to JIS to ISIS and the new Campag (which I successfully adapted to single-ring).
The use of given measurements is good to know where to start, but this does not always give a satisfactory result in practice, i.e.

...
- that your old cranks are slightly worn and the correct BB isn't correct any more
(that's where using different BB's gives a better idea of the state of the crank taper, since a BB axle is unlikely to have a lot of wear)
- that you are trying to use chainring sizes that the frame designer never expected, and they clash with the chainstays
(this is a very odd situation that is most likely to result with a wrong chainline to begin with)
- that you are trying to use a 'road' chainline on a frame that isn't meant for that
(a track frame with a double chainset? wrong chainline for no purpose. An Mtb frame with road cranks? Can't see the reason for that and won't accept large chainrings to boot)
- that the RH crank is OK but the BB spindle is so asymmetric that the LH crank is in danger of hitting the chainstay
(pretty much all the times I've seen this it happens the other way round: the Lh crank is actually too far, exception are those narrow Q-factor track cranks)
- that the RH crank has a protuberant centre boss and it not only needs a certain spindle length but also needs a particular construction of BB if there is not to be a clash between the boss and the RH cup.
(those are almost always very narrow Q-factor track or road cranks, where the BB cups had to be wide enough to accept the inner side of the cranks, a typical example is the Sugino cranks that are machine from the factory to reuse their "road" cranks with a narrow spindle)


I'm not sure the jungle of square taper BB's is actually an "excitement", often an hassle that disrupts a design that is actually simple it the way it works. One can't really blame the "one way" of most cranks with integrated axle, there's very little that can go wrong in terms of compatiblity, right because of the very little exceptions to be made off the standard for their fitment. My usual thing is to make single-rings crank to work in different situations on road or CX frames, best results are almost always made by using good components to begin with.
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...
Brucey
Posts: 44519
Joined: 4 Jan 2012, 6:25pm

Re: Budget square taper BB

Post by Brucey »

perhaps you have not encountered some of the situations I describe. There are plenty of instances where they may apply; I don't think I should need to give examples for you?

cheers
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