MiloFrance

So bob and I are taking 3 bikes, one as a spare. I just finished cobbling it together, but the chain line is so bad in first gear, that the chain will not stay on the chainring. I've had the other way round but not this, and the BB is the correct length, so I can't really put a shorter one in to bring it in. Cassette spacers? something along those lines maybe?

Salamandrine 

Did you measure it? Can you provide more details as to what the bike and the components are?

Assuming it is a road double, it should be 43.5mm from between the chainrings to the center of the seat tube.

My gut reaction is that if the chainline is that far off, then you do not actually have the correct BB spindle length.

due ruote 

Agree with previous post. That doesn't sound like the right spindle.

If it's just a spare bike and you are rushed, maybe use a different freewheel with an unnecessarily low gear, and block out the large cog with the RD limit screw.

USAZorro

How's the spacing on the rear wheel? Can you re-arrange the nuts and spacers to bring it over a couple/few mm and then re-dish the wheel?

79pmooney

No measuring is required. Just stand behind the bike (on a stand makes it a lot easier) and sight down the groove between the chainrings (or along the middel chainring in the case of a triple and only chainring in the case of just one).

That gap or chainring should be exactly in line with the middle (or only) cog of an odd number or the gap at the middle of an even number of cogs.

If this is the case, the BB spindle is right for the FW, cog or cassettes and your issues are elsewhere. Worn chainring, too much space between the chain on the small ring and the inside of the front derailleur, poor derailleur height or angle or possibly a bent cage. Modern chainrings with their ramps and pins can cause the chain to fall off to the inside more easily than happen with the old ones, but even then it happened. The front derailleur settings for the common Sedis chains in 1977 would cause the Shimano Uniglide chain I used for races to fall off to the inside regularly. I remedied this by tightening up the stops until the chain rubbed in both the lowest and highest gears.

Edit: the bike cares little as to whether the chainline is any magic number from the bike centerline. It sometimes is an issue getting front derailleurs to reach far enough in or out but if it can do the job, it matters zero until you plan to buy new parts like BB spindles or cranks or rear hubs.

Ben

John E

Good advice all around. Start with the lateral alignment test/sighting and chain elongation wear test (should be less than 12-1/16" per 24 half-links of chain, i.e., <1/2 percent).

Michael Angelo 

Wrong spindle, bottom Bracket. The rear wheel has nothing to with it.

repechage

Campagnolo made a nice straightedge to hold against the inside of the front big ring to evaluate chain line.
Test, don't guess.
This includes the frame alignment.
On cheap bikes with steel chainrings a bent fine or teeth can mess things up effectively.

Steve Whitlatch 

If the chain ring is too close to the chainstay to put a smaller spindle in the BB, how can it be the wrong size spindle?

randyjawa 

For a chain line that off, I would start by checking if the stays are in line with the center line of the bicycle. This is easy to do if you take the time to String The Frame...



Are you sure the wheel is dished to meet the center line of the frame set. If the hub is too far to the non-drive side, then you will have chain line problem like the one pictured.

Is your small ring bent? That has nothing to do with the actual chain line but it could contribute to the chain running off of the ring.

It does look like the gap between the crank rings and drive stay is a bit big. Is it possible that you have an incorrect spindle? Might want to try switching it from end to end to see if that makes an acceptable difference.

Other than that, I dunno but I do wish you luck with finding the source of the problem.

Michael Angelo 

[QUOTE=MiloFrance;19077269]So bob and I are taking 3 bikes, one as a spare. I just finished cobbling it together, but the chain line is so bad in first gear, that the chain will not stay on the chainring. I've had the other way round but not this, and the BB is the correct length, so I can't really put a shorter one in to bring it in. Cassette spacers? something along those lines maybe?



It also looks like the hub can use a 6 or even a 7 speed freewheel. Doing that alone can bring to chainline center.

bulldog1935

you have really big clearance between the inner chainring and chainstay - that crank was made for 107mm spindle

I'm betting a Strada-clone crank (e.g. Sugino Mighty Comp) would give you the right chainline

MiloFrance

Thank you all for the replies. I thought about it falling asleep last night and now have a 110mm BB.Next is to swap the Sugino Mighty for the dura ace and see if it helps...

Slash5

What is the rear axle spacing? Looks like a 5 speed on a 126 mm rear hub.

MiloFrance

Apparently Faggin checked all the geometry when they renovated it and all is OK. So, with limited shops open I bought the 110 BB as mentiond. Sadly I'm a part time idiot, and got ISO. On a hand built Italian Frame? I don't think so.Poking through my parts box, I found a Campag Chorus that I was saving for the Titanio, 110mm Italian thread. That coupled with the Sugino mighty (thank you @bulldog1935 for that suggestion) has brought the inner ring to about 3mm of the chainstay. As they say in aviation, 6inches is a miss as long as it's under control. Looks like the Holdsworth will get the DuraAce cranks to go to Gaiole.
Again, thank you all for the suggestions. It looks pretty mean with the black chainrings, bottle cage and rings. I think I like it. First ride tomorrow...

FBinNY 

Check and confirm two facts.

1- is the freewheel outboard as far as possible?
With the chain on the outermost sprocket there should be 1-2mm space between the chain and frame. Less than 1mm is OK as long as it clears, but if there's 2mm or so you might want to space the freewheel out from the hub a bit more.

2- Is the crankset inboard as much as possible?
The minimum clearance between either ring and the chainstay is 1-2mm. If there's also room between the crank and BB cup, you might find a shorter spindle that works. Keep in mind that both chainstay and BB cup clearance conditions need to be met.

Assuming you've confirmed the freewheel is out, and the crank in, then there's nothing fundamentally wrong. It's possible the rear triangle is shifted to the left, confirm with string, but if not you need to think out of the box.

Options

1- if this is a 120mm frame, spreading it to 126mm will buy you another 3mm in chainline, and make room to go from 5 to 6, or 7, or 6-7.

2- You can also recontour (not a storyteller) the inner rings tooth profile to improve pickup of the chain coming from an inboard angle. This was a fairly common remedy back in the Bronze Age, when steel rings were crudely formed and chain drop a common issue. To do so, you'll want to bring the tooth points inboard. Use a half mill file placed at a shallow angle against the outer flank of the inner ring, and spin the crank to "turn" some material off the outer side of the tooth profile. The goal is to change the profile from /\ or something closer to l\, though not so extreme.

Which are your best options depends on the severity of the problem, and in some cases both working together may be the best option (plus you get another gear).

bulldog1935

glad it worked out - I think they're the prettiest cranks ever.
I ran one from 1978, and now it's on my daughter's Team Fuji