I am building a vintage Reynolds 531, Harry Havnoonian, frame from the late seventies. I am installing a shimano 105 1050 groupset. I have installed the bottom bracket but when I tried to install the crank arms I notice the chainring is wobbling when it spins. I removed the crank arms and the chainring appears perfectly straight. The bottom bracket also appears to be spinning perfect. Any ideas why the chrainring is crooked?

I believe you have a Shimano 105 biopace crankset. Theyre more ovalized than circular

If it's a used crankset it's possible that the square tapered holes in the crank arm are uneven. Check those holes and the BB ends for any burrs or debris. As a last resort, try installing the arm with a different "clocking" with respect to the bottom bracket spindle.

Here's a 1050 with Biopace rings and good tapers for reference. Happened to have this one out today.

Wobbling?
If what you are describing is the biopacity of the chainrings I'm giggling a little.

Could be a language barrier here, but when I hear of wobbling, I think of side-to-side movement. Which would indicate a bent spindle or damaged flats on the crank.

I would describe the elliptical variance in Bio Pace rigs to be a 'bounce' rather than a wobble.

By definition, it is indeed a variance of side to side movement.

So I used a torch wrench that went up to 250 pounds per inch. According to shimano I should go to 300-400. My LBS said if I tighten the crank it on it will straighten out. What do you think? The wobble is side-to-side

Wobble side to side tends to be worn out tapers on the crank arms themselves. At that point, they are trash. Chain rings and chain ring bolts should be saved.


But in person inspection by a knowledgeable person beats guessing on the internet.


Realize bottom bracket spindle is steel, crank arms are aluminum. When they do battle, steel wins! (aluminum wears out). All it takes is for someone to install the crank but not tight enough, and the arm starts to wobble and wear. Then they retighten it further, for a repeat wobble and wear. Its fairly common failure and would inflict only one arm at a time. If both sides wobble, I'd remove them both. Then see if the bottom bracket has play in it (up and down motion). Doubtful but possible. When I find crank arm taper problems, its typically just one arm. Replaced one recently, it was a 105 crank too.


OK, I am re-reading your description again. Sounds like a bent chainring.

You might want to remove the crank arm and inspect the tapers. Check the bottom bracket axle tapers as well. If there is a lot of corrosion or dirt you might use a fine brass brush and some wd40 to clean things up a bit. Then wipe with clean paper towels. You could rotate the crank on the tapers just to try a slightly different position. Then reinstall. Reserve your torque wrench for final tightening. I would recommend a longer ratchet, a "T" wrench or a medium breaker bar. Something that will give you tactile feedback that the crank arm is tightening onto the tapers of the bottom bracket axle correctly. The "T" wrench is ideal for this since you can apply more balanced force to overcome any resistance. Just don't go crazy. Don't grease the tapers of the bottom bracket axle but you can apply a little bit of grease to the bolt threads, the washer and the socket inside the crank arm where the washer rests. This will keep that part of the system well lubed and easy to disassemble later. It will also permit more seamless tightening of your crank arm as you approach the torque figure you provided. Not sure what type of torque wrench you are using but 250 inch pounds is at the top limit of a 1/4" torque wrench. You might do better do use a conversion into foot pounds and use a longer 1/2 drive torque wrench.