Center chain ring damage

[IdahoBrett]

Thought I’d do a quick clean and lube on the M500 this morning. I set it in the stand and did a check on my recent FD adjustment. Hmmm something isn’t right. Chain is binding.

 

[IdahoBrett]

It’s supposed to look like this

 

[IdahoBrett]

Now I know why it was parked. Cool! More tools...and I get more use out of the expensive repair stand....

 

[black lightning 1987]

I've never seen a ring torn like that. It's a 42 isn't it? I have NOS Dura Ace 42 rings on hand but not black. They were meant for doubles but might work fine. Probably have some other 130 mm/42T used options.

 

[IdahoBrett]

I've never seen a ring torn like that. It's a 42 isn't it? I have NOS Dura Ace 42 rings on hand but not black. They were meant for doubles but might work fine. Probably have some other 130 mm/42T used options.

No it is 36T. This is the chain ring on my purple 1993 M500 (Altus A10 26/36/46) . I thought I'd work on it while I awaited the FD to show up for the R400.

 

[black lightning 1987]

110 bolt circle diameter then?

 

[IdahoBrett]

110 bolt circle diameter then?

I do not know. I’ll have to measure.

Brings up a thought I’ve had lately. I mentioned in another thread that I suffer from a self described condition I call PMD (precision measurement disorder). I’ve got a couple drawers and a cabinet full of calipers, micrometers, machinist rulers, etc. And none of them are metric! As I head down the path of bike tinkering I’m beginning to want for metric measuring devices….

 

[IdahoBrett]

Yes 110 mm bolt circle diameter.

I repressed my PMD and used two 5mm allen wrenches and measured across with dial calipers. Being that the bolts are not straight across from each other and crank arm is installed there was a fudge factor to come up with approximately 4.5” and subtract the allen wrench dimension, yielded me about 4.33”. Which when converted equals 110mm. Yes I do realize I cheated because I knew what the end dimension should be per your question. See, I told ya’ll I’ve got PMD!

 

[black lightning 1987]

I might have extra 34T rings, more common than 36T Have gobs of 46, 48, and 50T, some even Cannondale branded.

 

[IdahoBrett]

Other than it’s tooth count being 2 fewer, what in practical terms does that mean?

I’ve barely scratched the surface of tooth count/gear ratio specifications. I’m basically ignorant as far as bicycles. But willing to learn.

 

[black lightning 1987]

Early on, MTB rings tended to be in the 28/38/48 or 26/36/46 range with a 30 or 32 tooth large cog on the cassette/freewheel. After SunTour introduced their Microdrive range the whole industry moved to smaller chainrings and in general - smaller cassettes and freewheels at least for the small cog. There was never an 11 tooth cog in the freewheel days, the standard was in the 13-14T range. I've seen freewheels with a 16 tooth small cog.

What ring is optimal for you is up to you to sort out. The nice thing about that era of bike is that the mechanical bits were made to work with a wider range than some later developments, which we've already gone into.

 

[IdahoBrett]

I’m not that knowledgable enough or experienced enough rider to know the difference I would suspect.

Finding a replacement chainring no matter the tooth count is what matters most to me.

Interesting of note: the few vintage chainrings that I was able to find on epay I did find a set that had the identical “damage” on the center ring. Whatever those holes purpose was I don’t have clue. Initially I thought someone had stop drilled some cracks. Looking closer I determined that was a no.

 

[IdahoBrett]

I dunno. I fiddled with the FD and cable whilst watching a Park Tool video. All 3 gears are selectable. When riding around the block, selecting to go to the largest chain ring it seemed as though cable tension was not there. A second push on the gear selector yielded cable tension and a gear change. It only occasionally happened and seemed to get better the further I rode and more times that I selected the largest chain ring. Me thinks someone may have done a gratuitous cable lube in the past and inside the sheath may be gunky.

Damage? Maybe not. Let me try to explain; Center chain ring: There are 2 offset teeth towards the frame separated by 3 teeth. At the bottom of the offset teeth is a small hole with a section of the chain ring that looks cracked that meets with the hole. And exactly 180 degrees on the other side of the chain ring are identical pair of offset teeth.

I’d say it’s a feature not a flaw. Possibly chain transition or retention aid designed into the teeth. The condition of the bike and parts suggest to me it didn’t have a hard life.

 

[black lightning 1987]

Doubt a gunky cable would have much effect when shifting to a larger ring unless it's so gunky you can't move if fast enough. Cable friction usually results in problems going the other way, when the spring needs to move the cable.

I see what you mean about the ring. Guessing it's steel. Still don't remember seeing that hole and slot in a ring before.

Bike looks great. What's the engine?

 

[IdahoBrett]

Thanks. 351W for my wife’s 72 Mach 1. Yet another project….

 

[black lightning 1987]

Thanks. 351W for my wife’s 72 Mach 1. Yet another project….

Been so long since I worked on a Ford I've forgotten what they looked like.

 

[IdahoBrett]

Been so long since I worked on a Ford I've forgotten what they looked like.

I’m a Chevy guy, so they look weird with the dizzy up front.