BB sizing help
- Thread starter jim55
- Start date
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RecordAceFromNew
Swinging Member
- Location
- West London
You can ask him.
FWIW I suspect* the chainset is a knock-off of a Sugino Messenger. If so 103mm JIS would likely deliver a 45mm chainline. What you might want to know though is that typical fixie/ss chainline is usually 42mm if the dropout distance is 120mm, but you will find it hard/impossible to get a JIS bb shorter than 103mm. In fact Shimano don't make any shorter than 107mm.
* why possibly a knock-off you might ask? I think so because I saw new ones being sold just over a year ago, and they also look just like these, and I have never seen real Sugino with that emblem or being sold so cheap (around £20 brand new iirc). Also the seller didn't have a clue what bb the chainset needs when I asked, and has since "left" ebay...
FWIW I suspect* the chainset is a knock-off of a Sugino Messenger. If so 103mm JIS would likely deliver a 45mm chainline. What you might want to know though is that typical fixie/ss chainline is usually 42mm if the dropout distance is 120mm, but you will find it hard/impossible to get a JIS bb shorter than 103mm. In fact Shimano don't make any shorter than 107mm.
* why possibly a knock-off you might ask? I think so because I saw new ones being sold just over a year ago, and they also look just like these, and I have never seen real Sugino with that emblem or being sold so cheap (around £20 brand new iirc). Also the seller didn't have a clue what bb the chainset needs when I asked, and has since "left" ebay...
Citius
Guest
I think you could be on to something there. Sugino stuff is rarely that cheap, even used.
Surely chain line is the distance from the centre of the hub to the centre of the sprocket. I can't see how dropout width can affect this.
Citius
Guest
Chainline is the line the chain takes from front to rear sprockets. Drop out width will be a factor, because it will affect hub choice, which will affect chain line.
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I was thinking from the point of view of having the same wheel. For example,a wheel that is 120mm OLN has a sprocket screwed on giving a chainline of 42mm. ie the distance from the centre of the hub to the centre of the sprocket is 42mm. But I want to use it on a bike with 130mm OLN. So I add a 5mm spacer to each side, bringing the OLN up to 130mm. The distance from the centre of the hub to the centre line of the sprocket is still 42mm.
RecordAceFromNew
Swinging Member
- Location
- West London
I don't believe you found me saying that the dropout width of a hub affects the rear chainline. I think you read something I did not write.
What I suggested was that if a single ring chainset requires a 103mm JIS bb to deliver a 45mm front chainline (which some of these Sugino's do), then one needs to do something about the "typical" rear chainline of c42mm of fixie/ss with 120mm dropout, for the simple reason that you won't find a JIS bb shorter than 103mm to shorten the front chainline by 3mm.
Thinking about it, if one must a 102mm ISO from Campag might* do it, given a JIS chainset should go inboard another 2.2mm on an ISO taper.
* assuming various symmetry / asymmetry / tolerance / clash chances all turn out favourable...
Iv found an old bb from a bike I stripped ages ago ( I cant even remember which bike, ).it's an old type but the bearings are caged , its 107 mm so I'm gona try it and see if it lines up , if not at least it gives me a starting point.
Can u use Vaseline in place of grease? Iv no grease but Iv got a jar of Vaseline in the bathroom
Can u use Vaseline in place of grease? Iv no grease but Iv got a jar of Vaseline in the bathroom
Citius
Guest
Is your BB JIS or ISO taper? If the taper is ISO, then not only is it 4mm wider than it (possibly) should be to start with - but the difference in taper will probably add another 4mm on top of that. So your chainline could potentially be up to 8mm wider than it should be - which would give you alignment problems with the rear.
Citius
Guest
Unfortunately not so simple - things rarely are.. There are two square taper standards - JIS and ISO. Both are interchangeable in the sense that JIS chainsets will fit on ISO BBs and vice-versa, but the taper angle is different, meaning that (for instance) a JIS chainset will sit on an ISO BB about 4mm further out than it should do, than if it was a ISO chainset - if you see what I mean...
Not always an issue - but for a single speed chainline, it might be.
Citius
Guest
It will fit either way, but yes, the chainset might be sitting slightly further out - or it might be fine!
Citius
Guest
It will be better than nothing - fine as a barrier on the BB threads. Not really a long term solution for bearings though.
