Chainline Question

cheers for the advice olly! still considering phil if i'm totally honest.

Aye, no worries, each to their own like :)

I could be talking total rubbish, but I have recently been reading about all things chainline. It may not help but...

You could either mount chainring on inside of crank spider, ugly yes but easy to do. Also probably more like -4mm
Or possibly a spacer between the hub wall and cog, only OK if theres enough thread for the lockring.

Or theres always chainring stack bolt spacer thingys.

I'm not sure if any of this is frowned upon or even allows for just minute adjustments but thats my two pence.

Yeah, i've noted the spider and other spacers, however not heard of stacking chainring bolts. I would def. be curious as to it's sketchy or stable nature however....

Did the person you bought the frame from have it built up- and if so what setup did they run to get it to work?

it's from phil (aka pajamas) - he had a bb in it and never built it all the way, just had him put a 700/650 combo so it'd fit, he's the one who reckons 109-111.

he also had a cassette trispok' (tm) specialized on the rear, no chain, 170mm cranks just to show where all the clearances and such were.

I had a fixed rear wheel on a previous frame. I purchased a new frame and wanted to use the same set of wheels (+cog) from the old frame. In order to ensure that there'd be no issues with chain alignment, I checked the width of the BB on the old frame and purchased a new one with the same width...the old BB measured 68-127mm.

Now, having put together all the parts on to the new bike, the chainline is well out:
I'm a bit confused as to why this is. I think maybe it has something to do with the tapering on the BB perhaps...meaning the chainring won't go closer to the frame???

I'm also concerned about whether it will at all be possible to get chain alignment with this frame. The chainring on there at the moment is a 48T. If anyone can suggest anything that'd be appreciated.

are you using the same crankset?

Yes, same crankset.

b/b looks too long

most singlespeed/track b/b's are 107/111mm not 127mm

ISO vs JIS taper problem? What brand is the new BB?

mount the chainring on the inside

the rear hub should have a 42mm chainline, that b/b gives a 63.5.

b/b looks too long

most singlespeed/track b/b's are 107/111mm not 127mm

Listen to this man.

Um.. yes, BB spindle look too long on both sides.

Also.. did you check the width of the rear triangle on both frames? Maybe just the way the pics have been take but the gap between the rear cog and the derailleur drop out seems rather wide to me.

The older frame may have been narrower across the dropouts.

The new frame - did you discuss with the vendor you'd be running it as a fixed?

ISO vs JIS taper problem?

This plus BB spindle too long

the rear hub will have a 52mm chainline, the b/b gives a 63.5.

If that's true, the problem is easily fixed by flipping the ring to the inside position on the cranks. Still won't be spot on, but it will be 7-8mm closer. I doubt that either of your numbers is correct (42 & 53 would be more likely), unless you have a very different idea of what constitutes chain line than normal people do, but looking at the pix it seems that this simple adjustment will get things near enough to be ridable.

you are correct, got me measurements confuddled.
42mm is the general one. goldtec and aerospoke hit 45mm

BTW - thanks for the awesome photos. These will be useful for future reference.

The BB is a Shimano Bottom Bracket Square Taper UN54 (J.I.S. spindle?)

Yes, according to Sheldon Brown, "ISO crank on a J.I.S. spindle, it will sit about 4.5 mm farther out than it would on an ISO spindle of the same length"

So, after all that, if I just buy a 107mm BB, that'll solve my problem right?

What cranks are they?

This is a rare instance of Sheldon Brown not necessarily being the way, the truth and the life. In theory he's probably right, but people who have measured the stuff which actually comes out of factories are much less convinced that one can be so precise about the matter.

The main issue is that 127mm is a huge BB length whether it's JIS or ISO, even most road triples use no more than 118mm, and your problem is compounded by the fact that your particular cranks are sitting a long way out on your particular BB spindle.

The cranks look like Campag; if they are, then try a 110mm or 111mm ISO BB like a Campag Veloce assuming you're on a budget. If they are a Japanese clone marked JIS on the back, try a 107mm JIS BB, e.g. another UN54

The cranks are old Raleigh ones and so according to S.B. they are ISO.