Noob question.

omri

I know it's noobish. I checked sheldon brown's web for it. But I'm still not sure about what I need to know.

So I need a bottom bracket. Now it's Italian frame. The width of this tube where BB is mounted is 70mm and diameter (outer edges) is bit less than 40mm. Did some more mesuring and I'm pretty sure it's 36mm. That gives me Italian bb 36 mm X 24 tpi with 70mm shell according to sheldon's. Both cups are right threaded. (I'm not exactly sure bout that 24tpi I don't know how to check it tbh)

It's my first fixie project and I'm bit confused. Will BB i.e. shimano 105 fit there ? Or do I need to get some special, old type BB ? Or BB for fixed geared bikes ?

blorg

Both cups right threaded sounds like an Italian BB all right, in the British standard the thread is reversed on one side. Most bottom brackets will be available in both British and Italian standard, you can certainly get an Italian threaded Shimano 105 BB. British is more popular but Italian is readily available.

You need to make sure to get a BB to match whatever cranks you are putting on - I am guessing square taper?

Note I have never actually installed a BB so someone with more knowledge than me will no doubt be able to fill you in better!

Morgan

You'll need a 70mm Italian threaded BB.

The specific model (and axle length) will depend on the cranks you'll be using.

omri

So I should get cranks first and probably rear wheel as well, and than pick the BB.

omri

I'm thinking of getting Sugino Messenger Cranks. In some nice color, maybe matching my eyes

thesunwashot

omri wrote: »

So I need a bottom bracket. Now it's Italian frame. The width of this tube where BB is mounted is 70mm and diameter (outer edges) is bit less than 40mm. Did some more mesuring and I'm pretty sure it's 36mm. That gives me Italian bb 36 mm X 24 tpi with 70mm shell according to sheldon's. Both cups are right threaded. (I'm not exactly sure bout that 24tpi I don't know how to check it tbh)

It's my first fixie project and I'm bit confused. Will BB i.e. shimano 105 fit there ? Or do I need to get some special, old type BB ? Or BB for fixed geared bikes ?

This area is the most confusing by far... Hope this helps a little.

There are various italian spec BBs at chain reaction. e.g.:
http://www.chainreactioncycles.com/Models.aspx?ModelID=906

tpi is threads per inch and it is the same for Italian as for ISO. You don't really need to worry about this too much.

You do need to worry about whether it is defo italian. You say both cups are right threaded and the measurements point to your conclusion so that is good.

Assuming it is italian, the cartridge will fit the shell. Italian is a standard so you can buy any italian BB cartridge.

Now you need to think about what cranks you want to fit to it. Do you have cranks already? If not, there are various interface types:

http://en.wikipedia.org/wiki/Bottom_bracket#Interface_types

Pick one and get a matching set of BB and cranks. Keep in mind that you are better off with track cranks if you are building a fixie but a repurposed double would do if you are doing this on a budget and have one lying around.

Finally, for a fixie you are going to want to dial in the chainline as close to perfect as you can so you need to know the width of axle you require (i.e. the 109mm or 118mm in the chain reaction link above) based on the rear hub you have.

You can work it out from reading this page:

http://www.sheldonbrown.com/chainline.html

Sorry if that is too much info. You have to know a lot of bits of information in order to get it right unfortunately.

stuf

omri wrote: »

I'm thinking of getting Sugino Messenger Cranks. In some nice color, maybe matching my eyes

can I borrow your wallet for my fixie supplies?

I got these cranks - arrived this morning and are gorgeous and I'm just trying to get me noggin around the bb length and chainline. I've decided to wait until my wheels are built until I worry about the bb. Got flip-flop hubs on the way so chainline is easily measured with no complications.

only problem with the crank is that I can't swap out the chainring and will have to change cogs instead

omri

So best option is to get rear wheel first. Like this one. Rear hub is 120mm and can be spaced up to 130mm and then I need to get BB with spindle length that will fit rear hub ? (109.5 &118.5mm thats the length of shimano's spindle) Or maybe I'm wrong ?

stuf

omri wrote: »

So best option is to get rear wheel first. Like this one. Rear hub is 120mm and can be spaced up to 130mm and then I need to get BB with spindle length that will fit rear hub ? (109.5 &118.5mm thats the length of shimano's spindle) Or maybe I'm wrong ?

I'm just going by the stuff from Sheldon Brown. Remember that even if you're spacing out the hub nuts to 130mm the cog is still going to be in the same place with respect to centre of the hub and that's the crucial chainline measurement.

thesunwashot

stuf wrote: »

I'm just going by the stuff from Sheldon Brown. Remember that even if you're spacing out the hub nuts to 130mm the cog is still going to be in the same place with respect to centre of the hub and that's the crucial chainline measurement.

Yeah 120mm or 130mm is the inside distance between the dropouts. Chainline as said above is measured from the middle of the bike.

If you are going with Sugino messenger cranks remember they are square taper (at least I haven't seen any other types). I'm not sure that Shimano do Square taper (they do mostly Octalink) but plenty of other companies do.

OP, you appear to have a good bit of cash to spend. Check out www.hubjub.co.uk for some seriously nice components. You could grab yourself a sweet Sugino 75. I've been eyeing up this Phil Wood wheelbuild for a while: http://hubjub.co.uk/philwood/wheelshf.htm

blorg

Shimano certainly used to do square taper, not sure if it is still readily available any more. Octalink has itself been superseded by the integrated cranksets.

But I am pretty sure you would be best off just buying the cranks and BB together from someone with an assurance that they are compatible.

http://www.sheldonbrown.com/bbtaper.html

stuf

square taper bbs are freely available on wiggle, CRC and ebay

Shimano UN54 seems to be the standard at the moment

There's all sorts of mad crap about symmetric, asymmetric and BB Mount - I thought I understood and now I'm just plain confused especially as I have no background on my crank and my preliminary calcualations are telling me I need a massive spindly so I'm not getting it right - trip to a good lbs in order

stuf

Managed to find out the recommended spindle length for my crank and have ordered the matching bb.

The ebay seller angpatten357 who supplied the crank and bb has been brilliant and he has given me incredibly good combined shipping deals. He's got loads of nice retro and cheap bits for the fixie.