How much wiggle room in chainline / BB spindle length?

[Neil]

It's always the same, you're putting a bike together, and think you have plenty of parts to cover it all, then realise that you don't have exactly what you thought you had.

So... Sheldon says 110-113mm for the correct chainline for the chainset I'm using (well would cover me for both choices I have). Thing is, I've got a new UN51 in 68 x 120 (I think - it's either 118 or 120, probably 120), or a new LP20 (ugh) in the right length, but they seem to go in the opposite way around (looking at the threads) and for some reason I'm missing the cup thingmy from what would normally be the non-drive side, but in this instance, the drive side.

All the rest of my UN54 / UN55s are 73 shell width ('cos I've got 3 bikes with 73mm shells).

So how bad would it be to try and use the 118 / 120 (think it's a 120, have to squint when I'm putting it next to a tape measure, and I've no idea where the original packaging went)? Would it:-

a) not really work at all
b) just about work but be horrible
c) with a bit of finagling could be acceptable for a couple of days until I can get a BB with the correct length spindle

 

[Gruff]

Re:

I reckon it would be pretty horrible.
I have just changed from a 113mm to a 110 because of poor shifting due to chainline.
The chainset in question is an M739 and i've used it on 3 different frames and each time i used a UN54 68 x 113.
When i tried it on my Orange C16-R it was awful. Tried a 110mm and its ok?

 

[FluffyChicken]

Re:

Grab a 2.5mm spacer if you have one and use a 73shell one.

Given a un55 isn't a lot if money is it with it?

Anyway, it'll fit on, it may well shift OK if you get the outer ring.
But it'll be a wider stance.

Find the code on the axle of the one you don't know the length. It'll be 118 or 122 if around 120.

That is assume you're running triple

 

[Neil]

Re: Re:

Grab a 2.5mm spacer if you have one and use a 73shell one.

Haven't got a spacer, and the 73mm are all longer, for DX era chainsets.

Given a un55 isn't a lot if money is it with it?

It's not the money, it's the time to get one, I was just being impatient because I wanted to ride it this weekend.

Anyway, it'll fit on, it may well shift OK if you get the outer ring.
But it'll be a wider stance.

Find the code on the axle of the one you don't know the length. It'll be 118 or 122 if around 120.

That is assume you're running triple

It didn't look horribly wide when I had it in and the chainset and cranks on, but when I nipped up in the loft to look at the other same bike, I could see the stock bottom bracket axle wasn't as wide as the one I'd put on this bike.

I'll look for a code on the axle, but next to a tape measure, it looked marginally longer than what I was expecting (11 but not as long as 122.

I've pretty much resigned myself to waiting for a new UN55 in the correct length, unless I can pick up one locally, over the weekend (unlikely, one way or another).

In the short term, I've considered taking the BB out of the first bike until I can get another UN55, but it didn't seem to want to easily budge, although is very smooth and in good condition, it's just been in there a long time. If I can get to a bench vice, I might be able to get it out easily.

 

[Neil]

Decided to remove the BB from my original 95 DB Apex to go in my hack 95 DB Apex.

Took a bit of effort to get it out, but now that I've got it out, I can see the markings on the spindle more easliy. It's the stock BB (a UN51, owned the bike from new, never replaced the BB, and it's as smooth as, and BB shell is nice and clean and rust free inside) and the bike came with a Sugino Impel 500 chainset. It's length, as stamped on, is 107mm.

The bike it's going in is another 95 DB Apex that's getting all the kit I care least about. So the orignal / donor Apex will get the new UN55 when I order it, and it comes - that'll probably get some new bits on, including a M570 chainset, which Sheldon says should be 110-113mm BB axle length. That said, he also says Sugino Impels should be 110-113.

If it had had the chainset from the rest of the groupset it used (M563 chainset) as opposed to the Sugino one, Sheldon lists that as 107-113mm.

The longer UN51 I've got (that was the motivation for starting the thread, given it appears to be too long), just has "D-NI" (not sure whether the last character is an uppercase i or a 1) stamped on it, where the shorter UN51 has 107mm stamped on)?

As he currently has the Sugino and STX chainsets (and M570 LX ones, too) as all taking a common size BB axle length, I'm going to try using this 107mm one - after all, I wouldn't have thought twice about putting an M570 chainset on - I was going to any time, anyways.

 

[andyz]

Re:

I'd say check the chainline whatever BB/crankset combo you use.

I fitted a 107mm BB with a Sugino impel 2 days ago, which resulted in a 47.5mm chainline (i.e. perfect). A lot of people just fit stuff according to accepted data and it isn't always correct.

I also found that using a 113mm BB, the same crankset gave touble running on the middle ring when the largest sprocket on the cassette was engaged - the chain kept slipping down to the granny ring.
It was all down to chainline.

Just my findings......

 

[Neil]

Re: Re:

I'd say check the chainline whatever BB/crankset combo you use.

I fitted a 107mm BB with a Sugino impel 2 days ago, which resulted in a 47.5mm chainline (i.e. perfect). A lot of people just fit stuff according to accepted data and it isn't always correct.

I also found that using a 113mm BB, the same crankset gave touble running on the middle ring when the largest sprocket on the cassette was engaged - the chain kept slipping down to the granny ring.
It was all down to chainline.

Just my findings......

I'd agree with that - with you there.

Either DB spec'd a 107 as a M563 would be the normal chainset if following the groupset, and just winged it using a Sugino - or trusting Sheldon's data isn't always the right answer - because he says it should take longer BB axle.

Given what you've said, and what was fitted to my bike stock / from new, I'd be inclined to think the data is wrong about Impel chainsets, and they look to want the same length BB axle as M563 LX chainsets.

 

[Neil]

Re: Re:

I'd say check the chainline whatever BB/crankset combo you use.

I fitted a 107mm BB with a Sugino impel 2 days ago, which resulted in a 47.5mm chainline (i.e. perfect). A lot of people just fit stuff according to accepted data and it isn't always correct.

Just further feedback, just put the 107mm BB in the target bike, and put on the chainset and crank (STX MC40), and so far, looking at the position of the rings in relation to the front mech, and the clearance to the chainstays for both the rings and cranks, it appear to be perfect.

When I've fitted them properly, I'll measure the chainline, but at least by eyeball, it looks in the right ballpark.

Now Sheldon's data says STX chainsets and M570 chainsets use the same BB axle lengths, so if that's trustable, then maybe I shouldn't be getting a 110, but 107 for the bike it came off (which would be the same length as removed from it). Which would suggest that 107 is correct for that frame with several chainsets from that era.

 

[FluffyChicken]

107 is shorter on the none-drive side than the 110. (it should say MM107, MM110 DN-L
drive side, should be pretty much the same if not the same. (give or take tolerances of fit. technically i think it's 0.5mm as the flength is really 110.5 at least that what this data says)

MC40 and all of that spider design 750/739 / 570/569 take, as specified by Shimano MM110 for 47.5 and LL113 for 50mm chainline.


D-NL is 122.5, it actually a proper bottom bracket 'code' and means somethin more than you get from the new 107/110/113 stlye code.

A little bit about it here viewtopic.php?t=198090 grab the book if you want to know more (a lot of Sheldon and bikepro uses data from the mentioned book)

 

[Neil]

107 is shorter on the none-drive side than the 110. (it should say MM107

The stock / original one I've moved from the original to my second, says MM107.

The other UN51, though does just say "D-NI" - no numbers, so it's either an upper case 'i' or lowercase 'l'?

drive side, should be pretty much the same if not the same. (give or take tolerances of fit. technically i think it's 0.5mm as the flength is really 110.5 at least that what this data says)

So 107 / 110 only differ in length on the non-drive side?

In which case I'll assume I'm golden with an MC40, over a Sugino Impel 500, as I've fitted and tightened the chainset and crank arm, now, and both look to be placed pretty good - haven't actually measured with ruler / tape measure, yet, though.

MC40 and all of that spider design 750/739 / 570/569 take, as specified by Shimano MM110 for 47.5 and LL113 for 50mm chainline.


D-NL is 122.5, it actually a proper bottom bracket 'code' and means somethin more than you get from the new 107/110/113 stlye code.

A little bit about it here viewtopic.php?t=198090 grab the book if you want to know more (a lot of Sheldon and bikepro uses data from the mentioned book)

The longer UN51 I've got, the last character definitely looks like either an uppercase 'i' or lowecase 'l' though - it's definitely not an uppercase L - was / is there a code "D-NI" and if so, what does the last character mean if not an 'l' but an 'i'?

Or is it an 'l' but just lowercase?