Dylansbob 

Saw this on a local ad for a 531 Romic. I'm guessing this was originally NR triple with a more useful 74mm bcd pattern added.

unterhausen

That's interesting, I wonder what chainring that is

SwimmerMike 

I’m thinking both sets of holes are aftermarket. The outer holes on the OEM triples don’t touch the slots (the slots are shorter).

interesting that they did two sets.

3alarmer 

.
...the old Avocet cranks (most of which broke at the drilled holes after a while) were double drilled like that.

merziac

Not a factory triple but I like the smaller set, hmmm.....

John E

Looks like 30T to me.

SwimmerMike 

I agree. The smallest custom chainring I've seen on the standard NR triple drilling is a 31, and this one looks like it might be a tad smaller.

bulgie 

I and others have made plenty of them at 30t, not too difficult if you start with an existing 74 mm BCD ring and just make 5 new holes at 100 mm BCD, the cut the old holes off. I also made one at 29t, a bit harder. Just finding a 29t ring to modify is pretty hard.



29 tooth. I didn't counterbore the holes, because there's so little extra "meat" around the holes, I didn't want to remove any more. So the bolt heads do protrude, requiring a tad more chainstay clearance.

Those are titanium bolts! I hadn't made the custom Al alloy spacers yet when I took the pic, so those are generic spacers from an industrial supply, not quite right.

Making rings from scratch — actually cuttung all the teeth from aluminum stock — has also been done. Like Jim Merz did in the '70s, except he stopped at 31t minimum. Bob Freeman had a small run of 30t rings made, with his brand name "Crampandgoslo" CNC-milled into them. Probably sold out now. Highpath in England made a business of it for some number of years, though I think they're out of that biz now. I have heard of folks in Australia and Japan also, sorry no details.

BTW if you want to be excruciatingly correct, there never was a "NR triple". The triple only came in Record, not Nuovo. It's totally cool to call it NR though, because people know what you mean. "Record triple", though correct, is ambiguous — they recycled the Record name for a later crankset. NR actually describes it without that ambiguity.

Mark B

SwimmerMike 

@bulgie thanks for the additional information. I hadn't seen any 30's before. I have a 31 that Bob Freeman, when he saw it on my bike, told me that he's pretty sure it one of his based upon the way it is laid out. This one is probably one of his earliest ones. On a different bike I have a 32 that I bought from Cupertino Bike Shop. When I talked to Greg Davis about it a few weeks ago, I mentioned the Bob Freeman 31 and he told me he got the 32 from Bob also (Now that Cupertino is shut down Greg is more open with sources). This one was a recent modification (2 years ago) of a TA I believe.

Completely agree the term "Record" is the most accurate, but is also potentially confusing to anyone that has moved on from the 70's era Campy products.

bulgie 

If I remember correctly, Jim Merz stopped at 31 because he thought with a 30t, there wouldn't be enough metal around the chainring bolt hole for safety or lengevity. I hope I'm not putting words he never said in his mouth! Bob F, who made his in this millennium, also had his doubts about the strength of a 30t on this BCD, but came to trust them after enough people had put enough miles on them.

A couple things I do to conserve a little more strength around the bolt hole:
(1) 30 is divisible by 5, so it is possible to have each hole adjacent to a tooth, rather than the "valley" between two teeth. How much this matters, I dunno, but it's got to help.
(2) I drill the ring at 8 mm instead of 10 mm. Campy granny rings have 10 mm holes, so their stand-off spacer/bolts (part #818) have a raised lip that goes into the 10 mm hole. So if you want to use #818 bolts with rings drilled 8 mm, you need to remove that lip from the bolt. Like so:

Original with lip on the left; after lipectomy on the right. Best to remove the lip on a lathe, but I have done it by spinning the #818 in a hand drill while holding it up to a belt-sander or bench grinder. Poor-man's lathe. Super precision is not required, just try to make them all the same. Note, after you remove the lip, the bolts will still work if you go back to a ring with 10 mm holes — those lips aren't necessary, in fact I'd say they don't do anything. Good riddance, and free weight savings!! Save a milligram or two here and there, pretty soon you've saved a whole tenth of a gram!

There are lots of other choices for the bolts though, like Ofmega/Avocet, Stronglight Mygal, and standard industrial shoulder bolts like you can get from McMaster-Carr. The shoulder bolts need a little touching up on the lathe to give best clearance with the chainstay; their heads are a bit "tall" as delivered. Though there are also thin-head shoulder bolts. If you can find them in the right length and diameter, they might bolt right on to a Campy triple with no mods needed. Bob Freeman knows which bolts to order. I haven't done that research because I still have plenty of real Campy #818 bolts.
I even have one set Jim Merz made out of titanium. He made them for me sans lip, at my request.

On my 29t ring, I conserved a tad more metal around the hole by drilling them to 6 mm, and not counterboring. I predict it will be perfectly fine strength-wise, but it has zero miles so far, has not been put on a bike yet. Since 29 doesn't divide by 5, the holes coincide with a tooth here, a valley there. The chain actually touches a couple of the bolt heads as the crank goes around, but only barely, no extra noise, no chain skipping or chain-suck — I think! Ask me again after I've ridden it.. I think it does prove 29t is the definite, really-for-sure minimum ring size for 100 mm BCD. At 28t, the chain rollers wouldn't be able to nestle into the valleys between the teeth, and it'll likely cause skipping and/or chain-suck, if indeed it's even rideble at all..

mpetry912 

I think you are right @bulgie about sufficient support for the chaiinring bolts

the Nuovo 41T ring was like that too. I had a couple. the chain links would scar up the ends of the spider arms.

they were sold for tandem synchronizing rings

That looks like a very nice crankset there ! I think that picture validates that the OP's crank is a backfit, that is, was drilled after market for triple setup.

the milling on yours is different

/markp

repechage

Bike Shops as marketers, the shorthand to describe “full Campagnolo”. All most likely as the rear mech had a model name.
this was before the gran sport level stuff was a full ensemble.

JohnDThompson 

Even more excruciatingly correct, "Nuovo Record" is the context of cranksets only refers to the bottom bracket, the arms were always "Record."

JohnDThompson 

Avocet/Ofmega also offered a 41T, 144mm BCD ring, but they machined the ends of the spider arms to create a little more chain clearance for the 41T ring. I see this also on the Ofmega "Mistral" crank spiders.

79pmooney

Guess I got a good pair. The inner ring holes stood up. But the pins broke, sending me to a minor spill. Later it broke at the pedal threads.

79pmooney

This is getting oh, so close! I've never actually seen a 41t Campy ring. Known they've existed and people who had them for 46 years. But for me, they've been un-ubtainium.

bulgie 

A few other companies made them besides Campy, TA for example.
Campy only made them in the old-record (NR) style, with the extra inner reinforcing ring, unlike Super Record, that removed that ring. The TA 41t is shaped like SR, not NR, just a little swoopier and a few milligrams lighter.

Old style chain had taller side plates, and they impinge on the Campy spider arms, but it works fine anyway. Newer chains (Sedisport and most everything after) miss the spide arms completely.

Mark B

JohnDThompson 

I have a NOS Campagnolo 41T ring, and a TA 41T, 144mm BCD ring.

79pmooney

Thank you John! (Now if I could only not just see but get to own and ride a road width set of full fenders in yellow.but I might have to live another lifetime or two for that one,)

52telecaster

I just bought the t.a. version for my son. Why that is needed instead of a 42 I have no idea. It's cool but so little difference.

mpetry912 

here's the reason. In another thread I posted a pic of a "Narrow Wide" chainring on an ebike, where the tooth profiles alternate and each chain link (between wide link plates) fits onto the wide teeth, and each narrow link goes on the narrow teeth. This was a new one on me.

So years ago, what I heard was that the 44t chainrings used on track tandems developed an odd wear pattern where "every other" chainring tooth would wear because the same links fell on the same chainring teeth. So Campagnolo made a 41t chainring (note that 41 is a prime number) for use on the synchronizing rings and the chain "walks around" on the ring teeth, evening out the wear.

This story came to me from someone who really did know ! And I believe it.

as I think about it the "narrow wide" rings will only work on even numbers of teeth, a 47 (for example) would not behave the same way.

anyway

/markp

52telecaster

Excellent! As a math student I appreciate the prime aspect.

bulgie 

Sheldon Brown insisted that you should only use even numbered timing rings, for maximum lifespan. You even need to make a note, when removing the chain (like for cleaning), of which teeth have "innie" links and which have "outies", and keep it that way when you put the chain back on.

I believe Sheldon way more than I believe Campagnolo. I know that might sound counterintuitive, but Campy has done more nonsensical and wrong things than St. Sheldon ever did.

Odd-numbered narrow/wide rings could be made, but it would be expensive. Each tooth would have to have moving segments to allow it to be either narrow or wide, and there'd have to be a mechanism that flips the tooth from one to the other while it's in the rearward part of the ring with no chain on it. Methinks the technical hurdles are just too much and/or the number of people with deep enough pockets to afford it would be too small.

Ooh that sounds like a "Carapace Completed Umber" ShelBroCo product from April 1st.