I have two concerns with that shim.

First, because the material is unsupported, you do risk the material extruding under pressure. Regardless of the fact that the aluminum is as hard as the crank, your shim material is not connected to the material of the crank. You've effectly created an unbonded laminate which will never be as strong as solid material. Aluminum is a relatively soft material which makes this condition worse.

Second, I believe that the corners of a square taper spindle do interact with the crank arms and your shim design will prevent that interaction.

Between those two issues, I think you run a pretty good risk of damaging your crankset. I'd be wary of using a stainless steel shim because of the interference fit design of the crank. Stainless steel and aluminum are not friendly materials to one another.

If I were to shim a crank, I would put the shims between the spider and the chainring. I see no reason for you to do the taper shim, when you have fixed the problem at the bb. I agree with joejack951 on all of his points.

Personally, I am most worried about the shim extruding out the back of the crank (towards the BB).

I am going to try it for a short while, maybe just one ride. Then, I will disassemble it and inspect the parts and the shim. Let's call it an experiment.

Maybe I should just call Phil Wood and get a custom spindle machined for a new BB cartridge. I could do it in titanium this time.

I think you misunderstood me. I want to move the inner chainring outboard. Shimming between the spider and the chainring does not achieve that.

I also don't think you could move the outer chainring as much as 0.1" to 0.2" with that method. I am not talking about shimming it out a few thousandths here. Where would you get the extra long chainring bolts? What would support the inner diameter of the chainring?

Well, after several months of riding with the shimmed crank, I've given up on it. Here's my problem with it. The shim did not move uniformly during crank bolt tightening. The legs of the shim were unevenly placed inside the taper.

This means the crank was tilted relative to the axis of the bottom bracket spindle. Because of this, it behaved as if it was bent. I measured the deflection at the tip of the 49T chainring. It was 0.09" (almost 1/8"). That's a lot - too much.

The chain would rub on the front derailleur cage unless the cage was perfectly aligned. This means I was constantly fiddling with the lever to adjust the cage. What a pain! Who needs it, not me.

I am going to direct-mount the crank and go back to the 42T inner chainring so nothing rubs. I will figure out what I need and buy appropriate parts.

It is a bit of a puzzle, though. If I just move the crank outboard (reposition BB cartridge in BB shell or buy a BB with a longer spindle), it will adversely affect chainline. Perhaps I need to move both the BB spindle and the freewheel outboard. The freewheel can be moved with a spacer. The BB cartridge can be moved by moving the lock rings.

Yes, you've found the problem with shimming the square-taper. Part of the problem is that you reduce the length of the contact area between the crank and spindle. This allows for more squirming and mis-alignment as you've found.

You can only move the freewheel outboard until it rubs the chain on the inner dropout face in top gear. This requires about 4mm of clearance between the top cog and the dropout. If you've got 9mm there now, you can reduce this to 4mm to match the 5mm outboard movement of the bottom bracket.

However, if you're moving entire BB to the right by 5mm, it also moves the left side inwards by that same amount and may introduce knee problems. Best solution in this case is to get a 10mm longer BB-spindle.

I made some additional measurements last night, too. I found the BB spindle is only 113 mm long, not the 120 mm I was expecting. The BB shell is 67 mm, not the 68 mm I expected.

If I go with a wider spindle it will certainly affect chainline. Which I will have to deal with.

I think what I'll do today is just put everything back to original equipment - 42/52 chainrings and 5 speed freewheel. I'll be sure to get the freewheel aligned with the chainrings. Once, that's done I can rethink this whole situation.

The geometry of this frame is so tight, you are limited on which chainrings you can use! I may be limited to using a 5 speed freewheel, too. Who'da thunk it?

Sounds like you wanted the 47 tooth inner chainring in order to run a classic half step gearing system. I would suggest going ahead and installing the longer spindle to at least see how things work with the resulting chainline. After all current 3/32" derailleur chains are more flexible than chains made when the bike was built.

BTW Lickbike has excellent prices on Phil Wood spindles. A lot less in steel than the $200 you mentioned for one.

Lickbike does not show it as something they carry. I guess the spindle I need is somewhat special due to the age of the bike and components (from 1975, Campagnolo Record crank set).

I'm actually a little "confused" by this whole thing. I rode this bike for years (decades, really almost two generations) with everything misaligned.

Never measure anything unless you WANT to know!

Never ask a question whose answer you don't want to know.

Measure the OD of the spindle. It goes through standard cartridge-bearings so the OD is something standard. You may be able to source a spindle from numerous other vendors that make cartridge-bearing BBs. ActionTec some to mind.

Okay, so everything is back to original equipment now. I took it for a short little spin. It rides more solidly now. The chain doesn't rub the front derailleir cage. It shifts better, is less sensitive and shifts more easily between gears on a five speed freewheel, as opposed to a six. This is how it was made to work.

I have 42/52T chainrings and a Suntour Pro Compe freewheel back on it (14, 17, 19, 21, 24T). The gear ratios cover a wider range. The shift pattern between successive gears is decent but not great. I've put a brand new, drilled Regina Oro chain on it.

I'll keep working on it but this time, I'm going to do it right.

I say upgrade it to 13-24t 10-spd with a 38/50t chainrings. You'll end up with the same gearing range with much closer spread between the gears; and no need for double-shifts.