bottom bracket ??

[stuee147]

i have a solid square end axle with bearings on either side, my question is could i change this for one of these new cassette type systems without having to cut or weld new parts on ?

and if it is possible how do i do it do i need new bolt bits as the ones one there are recessed for the bearings obviously so im guessing i would need to change them but do i get them with the bearing cassette or do i need to get them separately ?

i know this is probably a really silly question but iv only ever had the old style bearings and axle set up

stuee

 

[KneesUp]

Yes you can change them - you throw all the old one away and get a cassette-type, which come with all the bits.

You need to make sure you get the same width so the chain line is right, so keep the shaft out of the old one.

I couldn't get the last one I changed out, and it didn't seem worth buying the proper tools to use once, so I got the LBS to do it - it was £20 to remove the old one and put a new one in.

(And now I've another bike that needs doing, and I still don't have the tools!)

 

[Brommyboy]

It sounds as though you have a square taper BB, which can be replaced by a similar sealed one. There are two measurements to take into account: the length of the spindle, and the width of the BB cup. The latter is usually 68 mm or 72 mm. The spindle length determines the chain line and clearance of the chainset, so get the same size. A Shimano UN55 should be fine. When removing the old and fitting the new, remember that the RH cup has a reverse thread! You will also need the special tool for this. http://www.wiggle.co.uk/cyclus-bottom-bracket-tool-shimano/

 

[smokeysmoo]

^ this.

Once you know the size just get a Shimano UN55 BB, job done

If you don't have the tools then your LBS is your friend. If you do have the tools then YouTube is your friend, and lastly, if you've got the tools but can't get it undone, then a bench mounted vice is your best mate

 

[HovR]

Seems like the other posters have pretty much got your sorted! Just thought I'd chime in with a bit of terminology though.

When you refer to the new "cassette type systems", I assume you're talking about the type of BB that smokeysmoo has linked? If so they're called "sealed" bottom brackets. The old style bottom brackets with seperate bearings are often called "cup and cone" bottom brackets, or just "loose bearing" bottom brackets.

A cassette is generally the cogs/sprockets that the chain runs over on the back of your bike, as shown below.

Not trying to be too nitpicky, it's just that knowing the correct terminology can be really useful when trying to explain an issue.

 

[stuee147]

Seems like the other posters have pretty much got your sorted! Just thought I'd chime in with a bit of terminology though.

When you refer to the new "cassette type systems", I assume you're talking about the type of BB that smokeysmoo has linked? If so they're called "sealed" bottom brackets. The old style bottom brackets with seperate bearings are often called "cup and cone" bottom brackets, or just "loose bearing" bottom brackets.

A cassette is generally the cogs/sprockets that the chain runs over on the back of your bike, as shown below.

Not trying to be too nitpicky, it's just that knowing the correct terminology can be really useful when trying to explain an issue.

i was wondering what the proper terms were lol i had said cassette as iv just recently learnt about freewheels free hubs and cassettes now i know the different bottom brackets now i just need to learn all the other parts of modern bikes lol
and thanks to all for the advice i did have a feeling that i could interchange them i just wanted to make sure

 

[smokeysmoo]

I did have a feeling that i could interchange them i just wanted to make sure

FYI - you can even fit newer outboard BB cups to an old frame if you wanted to.

I'm not suggesting you do as there are other factors to consider, but I did a modern 10 speed conversion on an early 80's Peugeot a couple of years ago

Knowledge is power

 

[RecordAceFromNew]

Yes you can change them - you throw all the old one away and get a cassette-type, which come with all the bits.

You need to make sure you get the same width so the chain line is right, so keep the shaft out of the old one.

I couldn't get the last one I changed out, and it didn't seem worth buying the proper tools to use once, so I got the LBS to do it - it was £20 to remove the old one and put a new one in.

(And now I've another bike that needs doing, and I still don't have the tools!)

Unfortunately this is not true.

Traditional (i.e. cup and cone, non-cartridge) bb spindle actual lengths are usually one of those shown in Sheldon's bb database, with codes like 3H or 3NN etc. stamped on the axle. While Sheldon has also provided the equivalent symmetric spindle length, neither length is reliable for picking the best Shimano UNxx to achieve the same chainline - Shimano square taper cartridges don't follow the same system and don't use the same code - some Shimano spindles are longer on the drive side, some are symmetric, one is longer on the non-drive side (but it is not the one with the same characteristic in Sheldon's list).

You can either let me know what length you have (and let me know what clash clearance is there on both sides) so that I can try to work it out for you, or preferably take it to a good LBS, who usually just try with what they have got until one works. The latter is preferable because even a minor change in spindle taper manufacturing tolerance or wear of chainset taper will change the insertion depth and therefore chainline and clash clearance.

 

[Dogtrousers]

If you have a "traditional" cup-n-code BB with free bearings then yes, you can replace with a cartridge. Subject to getting the right size one (described above).

When you take the axle and bearings out you will be left with the fixed cup on the RH side (which will almost certainly have a reverse thread). This may be quite easy to get out, or it may be super difficult. Sheldon describes a home made fixed cup removal tool which should be right up your street. See here