Bottom Bracket Size

Hi,
not all that clued up about bikes so was hoping for a bit of help.

Recently got an old Sun frame and have been slowly converting it over to being single speed. As it's an old frame when i was doing stuff to it i was finding that bits were not the same size as modern parts (unsurprisingly) and as i was going along had to make adjustments to accommodate stuff such as filing out dropouts on front forks to accommodate shimano hub.

Am looking to replace the bottom bracket and cotter pinned cranks at some point but was told the BB was a strange size ie doesn't tally up to a modern BB. There's no marking on the underside so how would i find out it's size in order to look at BB that would fit - is there a certain way of measuring it - would i have to remove it to do so?

Not looking to put loads of new bits on an old frame as i think i'd prefer to get nice vintage bits over a period of time as i can afford it, however i don't know where to start when it comes to the BB.

Thanks for any help.

Alex

Maybe with a photograph and some accurate measurements someone could help but your best bet is to whip it down to you LBS and see what they can do.

Saying that my Holdsworth came with a tired old BB made for cotter pinned cranks, took it out and put an English thread Shimano 107mm which gives it a pretty damn straight line.

wouldn't even know what measurements to take of it??!

the length of the axle through the cranks is 128mm would i need to measure the diameter as well?

some pics here

That looks as though it will take an English thread BB (same as mine) as for the length there are a few things to take in to consideration hub width, where the chainring/crankarm sits on the taper.

TBH if you live in South run it down to Brixton Cycles and I'm sure they could assess the situation and supply you with the necessary components and the knowledge. Cavendish are equally helpful when it comes to sharing a bit of knowledge.

That looks as though it will take an English thread BB (same as mine) as for the length there are a few things to take in to consideration hub width, where the chainring/crankarm sits on the taper.

TBH if you live in South run it down to Brixton Cycles and I'm sure they could assess the situation and supply you with the necessary components and the knowledge. Cavendish are equally helpful when it comes to sharing a bit of knowledge.

Manchester based so that's gonna be a bit of a mooch, will take it into GBH tho as the guys in there are really helpful. Thanks a lot for your help, kinda given me a better understanding of it at least. Cheers

Use the search utility on the forum. Search for "threadless BB", YST, "Raleigh BB" for info on non english/ISO threaded BB options.

BB width will depend on the cranks you are going to use. Most folks here use square taper. Also search for "transmission database" for some typical crank/BB/hub options.

Use the search utility on the forum. Search for "threadless BB", YST, "Raleigh BB" for info on non english/ISO threaded BB options.

BB width will depend on the cranks you are going to use. Most folks here use square taper. Also search for "transmission database" for some typical crank/BB/hub options.

great that's spot on, did do a search but not for those kind of terms, that'll help alot. cheers

a s
how did you go ? I am doing up an old sun as welll and looking for a decent BB ?

interestingly Cavendish Bikes told me that my Sun had a italian thread bottom bracket! Or perhaps its not a Sun after all.

Hello,

My bottom bracket does so much noise that you've probably heard it wherever your were these last days.
It's time to do something but I don't know much about the bottom bracket my cranks and bike need.

My bike is a Felt TK2. On the manufacturer's website is mentioned that the bottom bracket that comes with the bike is a SRAM GXP Team External 68mm.
Also, I use a recent Campag Record crank set so I guess there is a specific tapering, right?

Knowing the crank set and bike model, how can I know which bottom brackets I can or can not choose?

If you've got a Campag crank, use a Campag BB. That's the extent of my knowledge.

I am thinking of getting some new cranks to replace the crappy otp ones on my crappy SE draft.
How can I be sure to maintain the chainline?

From what I have read it's easiest to replace the BB and chainset to aim for 42mm. am I right?

If so how can I find out the BB size? the specs say only euro cartridge BB which doesn't give me too much info!

I don't want to take off the cranks yet as I don't have a torque wrench to replace them and I hear it is a necessary tool.

Just spent an hour measuring stuff on the bike and it is looking like it might be more complicated than I thought.
Not sure how I didn't notice it before but my chainline is already off plenty. The sprocket is 38mm off centre and the chainring about 51mm.
Is that normal? 51?

When I look at it, it isn't perfect but I read that there should only be a few mm difference.
I'm also fairly sure that if I found a chainring that matched the rear dimensions that it would foul the chainstays which leads me to think that the frame was built as a single speed MTB as sheldon suggestshttp://www.sheldonbrown.com/chainline.html
The space between the dropouts, however is 120mm, which I think is standard for fixed gears?

The bb shell on the frame is 68mm - does that mean it is an english thread? I managed to measure the spindle and it is about 122mm long.

So where should I go from here. do I have enough information to do anything? Should I scrap the bb, cranks and rear hub in an attempt to line up the chain or is there an easier solution?

The moral of the story is - DON'T BUY PIECE OF SHIT BIKES
Really I can't believe the trouble this bike has given me from the very beginning.

51mm chainring line vs a 38mm cog chainline.
I would change your 122mm bb spindle. that is way too long for a 120 OLD frame.
try a shorter spindle, maybe a 102, 107 or 109mm.

also make sure you measured everything correctly. pics and/or part lists might help here.

Pretty sure I measured everything properly. I just checked again - there is only about 13mm of clearance between the teeth of the current chainring and the chainstays. If I reduced to a 102mm spindle that would leave me with 3mm of clearance - is that enough?
Unfortunately I don't have a parts list as the parts are all no brand rubbish that it came with.

I've been picking up loads from Sheldon Brown.. HERE after years of lazy bones taking things for repair, I'm back to basics.. I just found out my 1" fork euro racer (1990 Columbus Aelle) has a standard BB, so there's room to be optimistic. ;)

Just noticed Nicky did that linky already...

as far as i can see you got a standard rear flip flop hub which should cooperate well with any cranks/bb combination that gives 42mm chainline. i think whichever combination you pick up from the transmission database list here on the forum will do.

i am gonna give you a suggestion for a good value for money option that will work fine:

http://www.chainreactioncycles.com/Models.aspx?ModelID=21848

plus the bb:

http://www.chainreactioncycles.com/Models.aspx?ModelID=22376

size 110 mm worrks with fsa chainset

if you can strech for a couple of quid more then instead of fsa bb buy a shimy un54 in 107mm size (put chainring in outer position) or 110mm size (chainring in inner position)

hope it helps

Pretty sure I measured everything properly. I just checked again - there is only about 13mm of clearance between the teeth of the current chainring and the chainstays. If I reduced to a 102mm spindle that would leave me with 3mm of clearance - is that enough?
Unfortunately I don't have a parts list as the parts are all no brand rubbish that it came with.

Genius - thanks, that looks ideal - How did I miss the trasmission database? Duh!
Much appreciated.

you're most welcome mate:-)
i am sure you will recognise a much better bike after you do that operation.