Chainline Predicament
 

I have an old Schwinn traveler frame, converted to a fixed gear. I
have Sugino Messenger 46T cranks, a 120mm Miche Primato rear hub, a
17T cog, and a KMC singlespeed chain. The problem is the chainline. I
put on the cranks on today and the chainline was quite bad. The chain
was making noise and the chainring was too far from the frame. I tried
to solve it by moving the chainring from outside the spider to inside,
which reversed the problem. Now the chainring is too close to the
frame. I would like to avoid dishing the wheel, but what can I do? (I
can't flip the cog around.) I was considering putting the chainring
back on the outside of the spider and putting a small washer over the
cog's threads between the cog and the flange to move the cog out a
bit. The lockring has plenty of room to move outwards and the cog's
threading is wide enough that it wouldn't suffer significantly.
I need your help!

Thanks.

One very important component: How about a shorter BB?

mmmhmmm

First of all, measure the chainline at both points to see how much mm difference there is between chainline in the front and in the back.

If you have the tools to replace bottom brackets, I would try to flip around the bottom bracket (left to right). If that doesn't help, get a new bottom bracket (should be around $20). Make sure to take some measurements in order to figure out what size BB you need.

^^^^ word up.

well if you have the original BB in there just remove it and switch it around so then youll lose a couple MM.

Even with the correct BB (sugino 103) these cranks still have bad chainline, 45mm. It sounds like you're using the existing BB in the bike, so try moving the chainring to the inner position, this will buy you 5mm (6mm on 1/8" chainrings). If it's still too far out, try flipping the spindle as others suggested. If you want to do a new BB, a 107mm works with the chainring in the inner position, possibly with a 1 or 2 mm spacer under it depending on your rear setup and whatnot. I basically don't recommend these cranks unless you're running the paul hub or something else with a nonstandard chainline in the back, the 45mm chainline is just dumb.

the sugino rd is weird. i had a 107 BB and the chainline was terrible, i figured i need the 103 mm BB to make it work, but my lbs guy tells me he can make it work with a 110 mm bb, which he does, with the chainring on the inside of the crank.

110 and 107 are the same on the drive side, you'd get the same chainline either way. This produces a 42mm chainline with 3/32" rings, which is good, though with 1/8" stuff or some of the slightly wider than normal cogs it's worth popping in a spacer.

I'm using a UN 54/107 with my shimano 105 cranks, the chainline is about 44mm can I flip the BB and lose a couple of mms? I'm running a 3/32 set up.

thanks!

The cup on the right side of the bb is fixed and won't be the correct threading for the opposite side.

Yup, flipping BB's only works for loose ball rigs and Italian thread setups.

haha, don't forget the french.

that is confusing. this leads to a couple questions, and i apologize in advance if these are stupid questions that could have very easily been answered with the search function.

1. the difference between a 3/32 and 1/8 chain is pretty small, should i be able to tell with a ruler which one i have, even if i am a clumsy oaf?

2. arent the two chain widths effectively interchangeable anyways? havent i read here about people who switch back and forth and it really doesnt matter too much?

4. the 110 and 107 mm bb are the same on the drive side? arent sugino rd cranks made for use with a 103 mm BB? how come my 107 mm bracket wouldnt work but 110 does?

I just put a small cassette spacer behind the cog and it's fine. A cartridge BB doesn't flip and I didn't want to buy a new one, so I went the cheap way.

1. At least one part of your setup (cog, chainring) is almost certainly marked. You can also measure, it's the distance between the inner plates.

2. 1/8" chain can be used on 3/32" cogs and/or chanrings, that's the only real interchangeability. 3/32" chain is made for geared bikes, so people say it can theoretically take a little more misalignment than track chain, though personally I think this is kind of bunk when you're talking about a few mm. Track chain has plenty of horizontal play for that.

3. What do you have against the number 3?

4. The 110 and the 107 are the same on the drive side, 107's are symmetrical and 110's are longer on the left when used in a 68mm road BB shell. Throw a 110 in a 73mm mountain bike shell and it's effectively symmetrical, though not many people here need to worry about that. Sugino RD cranks are currently made to give a 45mm chainline on a 103 BB. This is simply wrong, and the bike companies should have howled and screamed when they made the change, but some were lazy (Bianchi just went to a cheaper crank) and some were really lazy (see the earlier thread where the Surly guy came on and basically said they just put on road chain and called it good enough) and anyway there are no Sugino reps in the US for them to to complain to. Either a 107 or a 110 would give a 42mm chainline with the ring in the inner position assuming 3/32" chainrings. 1/8" chainrings are a little thicker and you therefore get a little more difference when you move it to the inside position, this is where I would put a 1mm spacer in and move the whole thing out a little.

As long as the lockring threads on three(3) full turns after you have the spacer behind the cog, you are fine. A shorter bb may also work if you have room between the frame and the crank which you should have with a traveler. Otherwise, respace the hub and redish the wheel. Putting the chainring on the inside of the crank looks..., ok, it may not look funky to you.

If you are using a 1/8" chain on a 3/32 cog, your chainline problem will be very pronounced. Less so if you use a 3/32" chain on 3/32 cog.