Are these cranks normal?
 

Hey, (my newbness will be showing)

Picked up a set of 600 cranks and had some questions.

It's like the holes in the spider weren't 100% centered and the rings are off to the side a bit on a couple arms. It's definitely in the spider as I took the rings off and checked. It doesn't bother me, I'm just wondering if there's any problem running a crank like this or if it's fairly common?

Also the teeth on these look funny to me. They don't appear to shark finned or overly worn, but the metal has worn enough around most of the teeth to leave a sort of 'burr' on the chain side of the tooth.

Do they still look like they have some life in them or would you replace them? FWIW, I'm assuming they are fine but want to double check.

Lastly, how impact resistant are these big aluminum rings? I run steel rings on my MTB but these are huge and aluminum. I only ask cause I just dropped the crank on my tile floor taking pictures.

Thanks.

Things were less refined back then and what you have has some miles. We're pretty spoiled these days. Nice find though. Does is have the bio chainring that's oval?

Nah. Biospace is not my thing. The cranks themselves are in beautiful shape which is why I picked them up. Would you change out rings or keep them? I haven't run them with a chain yet to really see how bad they are... Maybe try that first?

The teeth have many more miles in them. Don't sweat the slight off register between the bolt holes and the cut away edges. Andy.

[QUOTE=Shinkers;18678107 I haven't run them with a chain yet to really see how bad they are... Maybe try that first?[/QUOTE]

That would be my approach. No point to toss them if there may be useful life in them. I'd probably knock the burrs off with a deburring tool or fine round file, though.

I had considered using a rat tail to clean the burrs off but don't want to do more harm than good either.

I don't ever remember Shimano having a sloppy fit with anything. It appears that the chainring has shifted the same on all arms. Possibly it has the wrong chainring bolts or someone enlarged the holes at some point or ??? Notice how both the rings have shifted rearward. It may still be OK this way but check it out and check the bolts for tightness every so often. I've seen burrs on chainrings like that before from running the cranks with the bolts a little loose for long periods of time which may also explain both your conditions.

This was my thought when I looked at the pics too. I would at least remove the chainring bolts to see if the holes are wallowed out or if they were machined offset as a defect in manufacturing. I have never seen even a low end Shimano product with this type of defect. Their quality control was always pretty good.

I would stay away from using a file on the chainrings. If there is a clearance problem the steel chain will work it out with the alloy chainring pretty quickly. I think a file would potentially do more harm than good.

Having taken a second look at the photos here's my conjecture. The rings and their bolt holes are properly done, as are the bolts the right ones. But the bolt holes in the spider are what's off by a degree or three rotationally. My point from before still stands. Try riding the set up and be happy. Andy.

The bolt holes in the spider are rotated a bit with respect to the proper target in each of the spider arms. This is a simple manufacturing error that occurred because the arm was not fixtured properly when the 5 were drilled. However it's a cosmetic issue only and has zero effect on function. All the bolts are on the correct circle and the same distance apart, they're just off a degree or so.

Contrary to what someone posted above, there's no possibility that they somehow were distorted or moved after drilling.

However, there is some wear or the teeth. It's not severe, and was most likely the result of hard service with a worn chain. There's no fix, and the best thing for you to do is ride the bike and let the chain wear the rolled burrs off.

I did pull the rings because at first I thought the bolts were just loose and the fit was sloppy. It is indeed the drilling in the spider that's off.

Cosmetically I could care less. So I'll take your advice and happily ride them into the sunset.

Thanks guys.