Chain ring wear - a little help please!

[dayofsuffering]

Hi!

New guy, and I hope I don't mess up first thing I do (hope this is the right place for this question)...

I'm about to build an old bike (I'll make a proper post once I get going for real) this summer, and I've got most bits, but when I cleaned the crankset the other day I noticed how worn it was.

I'm uploading a couple of pictures here, to get some help deciding on whether it's too far gone, or if it might be possible to save it.

The middle, and smallest chain ring are quite worn, especially the middle one. Looks to have been some proper chain suck going on. Finding new 5 bolt chain rings with the correct BCD doesn't seem so easy.

Is it possible to make some sort of judgement from these pics?

Cheers

 

[FluffyChicken]

Re:

They look quite new and hardly used. Certainly not a lot of shifting has gone on.

I'd use them looking at that picture.

Crank arms look more worn.

 

[dyna-ti]

Looks fine to me too.

 

[konacarl]

Re:

Outer looks most worn to me.

 

[Thias]

I think you misunderstand how those chain rings wear. Those sides are "sharpened" an grooved intentionally to make shifting easier.
A worn chain ring looks like this middle ring:

You have to look for the shark fin shaped teeth.

 

[dyna-ti]

This is what worn rings look like. The middle was only just starting to slip though the outer was and is fine for use.
I used the cranks for something else but theres no point in throwing out perfectly good rings

 

[drystonepaul]

Re:

As others have pointed out. Those teeth are profiled to aid shifting and although there is a some visible wear to all three rings, nothing looks too serious.
If you do get chainsuck with a new chain in the middle ring then I'd look at filing off the burrs on some of the teeth which will act like hooks on the chain.
The inner ring would be the most likely candidate for chainsuck though. The teeth do look to be showing some wear at the chain contact points. The hooking effect this creates when combined with the chain wrap around you get on small rings, could present with issues.

Stronglight still do 5 arm rings with the 94 and 58 BCD you'd need for those cranks.
Available here: --> http://www.spacycles.co.uk/products.php?plid=m2b0s149p0

 

[xxnick1975]

some people would class those rings as NOS mate - keep riding!

 

[dayofsuffering]

Thanks everyone for the replies! I knew about the "ramps and pins" (if that's the proper terms), but thanks for clarifying with photos of the shark fin look! Good to know how I can hit it with a file if I have any problems.

It was a bit hard to capture what I meant with "wear" in the photos, as it's more visible when you hold the crankset in your hands. Mainly it's the fact that the chain seems to have been stuck between the middle and largest in a place where it has bent the middle chain ring somewhat. It has also made the teeth a bit "thinner" in that area, as the chain forced its way between the rings. Someone seems to have used quite a bit of force to get it out of there as well. I'll see if I can snap a photo of it...

 

[dayofsuffering]

Photographing this was harder than I thought... I don't know it it's any more clear now what I originally meant?

Anyway, thanks a lot for your comments. I will definitely be using it. I'll just try to flatten the bump in the middle chain ring, and possibly file the teeth if they give me any trouble.