I failed to make it very far on iab's classic ride yesterday:

I took a look this morning. I don't know what went wrong. When I installed the crank I tightened both sides up at the same time, so I am pretty sure I used the same amount of force on both sides (I use a 15mm thin wall socket and a ratchet, not a peanut butter wrench or a torque wrench). Thinking perhaps the tapers on the left arm were shot, I reinstalled it this morning. When slipped on (no bolt), the gap at the end of the spindle was 2-3mm. Plenty of room to tighten things up without the crank bottoming out. I tightened it back up. Once tight, there was still a bit of the spindle taper showing inboard of the crank.

We'll see if it holds. If not, I guess I'll be in the market for a new left arm. Is this assumption correct, or am I still missing something?

After removing and reinstalling crank arms, I am sometimes amazed at how loose the bolts are after one ride. I always check after the first ride and torque down the bolts again. Definitely check if crank arms are being instslled on a new BB spindle. The crank needs to "conform" to the spindle.

Crank arm is shot. You are going to need a new one.

I thought something similar was happening on my Raleigh (campy cranks). Bolts kept loosening up repeatedly. I replaced the bolts, end of problem.

Thanks for the replies. I'll give the current snugging up one chance, only ride near the house, and if it loosens again, I'll look for a replacement.

This won't work. It will only loosen up when you're very far from home and don't have any tools to fix it.

What kind of crank is it? If it's an expensive, vintage one, I'd give it one more shot. I might not work, but who can tell from here?

Loctite is your friend.

Which reminds me. Going down to check my cranks bolts right now.

I agree.

Is this thread supposed to be linked to a previous one?

Is there a photo of the crankarm anywhere here?

How can anyone judge the condition of this crankarm? I can hardly even follow this discussion!

In all probability, the crank arm is toast;
Just read the first couple paragraphs here:

Installing Cranks by Jobst Brandt

It's a 70s Campy Record Strada. Not exotic, but not a throwaway, either. Campy bolts and washers in good condition as well. If the bolts might really be the problem, I have a bunch of new Sugino 15mm bolts, those lovely chrome ones.

Snugged everything up and went for a short ride (~4 miles) this evening. So far, so good. If it looks like the weather will hold tomorrow, I'll ride it to work with a wrench tucked into my backpack.

No previous thread, really. I apologize for the rather disjointed thread. I'm trying to piece things together as I go along.

I was quoting a comment I added to iab's Chicago vintage ride thread. A discussion of the crank arm problem didn't seem appropriate there, so I started a new thread. I've taken no pictures of the crank or spindle. The bottom bracket is a Phil Wood. The spindle seems visually to be in fine shape. I got the bottom bracket from a bike I bought for its parts. It was connected to a Campy crank, so I assumed (perhaps incorrectly?) that it has ISO tapers. In my experience, you can't judge the condition of the tapers on a crank from a picture.

I was really just asking what my possible problems are. I'm using vintage parts which I hadn't previously used myself. I haven't experienced this problem before, and I've put together a number of bikes using used Campy cranks and bottom brackets. The new bit here for me is the Phil bottom bracket.

I'm on board.

Last (CX) season, at one of our early practice sessions, I had my left TopLine crankarm loosen after many, many years of needing no attention.

I feather-pedaled the bike home, removed the bolt and put Loctite on the threads. Previously I had relied on metal Sugino dust caps torqued against a plastic shim between bolt head and dust cap, and as I said, this endured many years of racing with no attention given.

Fast-forward to the second race of the season at Clarksburg, and I felt my crankarm start clicking at the start of the last lap. I was running 6th or so and sprinting the front straight to grab a higher spot, so decided to power out the last lap with the bolt holding things together.
Turns out the Loctite product I used was very old and no good at all. I lost my left crankarm/pedal halfway through the last lap. I one-legged it to 16th position, then retrieved my lost arm.

The square bore was chewed at the big end, but most of each flat's mating surface seemed still to be intact. "Hard metal" I thought.
I went home and this time used fresh blue Loctite on the bolt's threads, after re-testing (failed) the old stuff at an accelerated-cure temperature in my laboratory setting (using cig lighter).
I had no more crank trouble at all in the 11 or so races since then, including several extra hours of intense interval training using the big ring up a very steep local hill.

That said, I weigh only 150 or so and use the standard-model 110mm TopLine crankarms, not the SuperLights. I bought these in a well-used condition in 1996 or so, and have done over 100 races on them, including several hours-long MTB races, plus thousands of training miles. The bottom bracket is a "Real" 113mm cartridge unit from the same era.

I am considering a more-modern crankset with shorter crankarms, for easier sprinting atop my bike's "hammock" saddle.

If these TopLine cranks could talk... ...every race I ever did on the Pedersen.

Well if it is toast, it is toast, so you really have nothing to lose. On mine, the crankset/BB/bolts were all 1973. When it loosened a couple of times, I did ride lightly on it 1-2 miles, each time. After subsequent problems, I used a new set of bolts from an NOS Campy crankset I had. No more problems since (and it was the bike/crankset I rode on yesterday on iab's ride). And I have torn the bike down for a total rebuild winter 2013, reassembled with no further problems whatsoever.

If it were me, I would tighten the crankset quite tight (by 3/8" ratchet perspective), take it out for a short shakedown, re-check, take it for another short shakedown, and then evaluate. If the bolts feel like they are easy to remove, then remove them and torque them with blue loctite. I don't recall ever seeing torque specs for old Campy Record (NR/SR) cranksets, but I seem to recall someone saying around 20-22lb/ft, which if you compare to the old "standard" of tight with 3/8 ratchet, is quite a bit more force.

And I'm sorry you didn't get to complete the ride yesterday! Though you would have just been 1 more person in front of me

I was always told to re-torque (i.e. re-tighten) after the first 30 miles. Or was it 30 minutes, I forget. So I just re-torque them after the first ride.

The trouble with Loctite is that you can't re-torque it.

+1 plus you can righten blue mild loctite several times before it loses it's effect .

Skip, have you considered using a torque wrench to tighten those bolts?

+1 Yes on replacement cranks even nice ones I typical replace the bolts and torg them down as tight as possible with a basic socket then some. So I figure about 100 torge to set a a proper fit and 120+
for a slight mismatch.