I've decided the 52-47-34 gearing on my Miyata 610 is just not working that great for me. Does anyone know of a decent source for old chainrings outside of eBay? I'd prefer to swap out the 47 with something in the 39-42 range, and if I am really lucky bring the 52 down to a 50, but I can't find much (or anything) in the size I need. According to Sheldon Brown's site, I am looking for a "Stronglight 80, 99, 100, some SR triples. (Obsolete)", with a 50.5 nearest/81.8 non-adjacent spacing. Makes sense, since it is an SR triple. I'm not reassured by that obsolete marking...

Or, am I better off to just go find a new square taper crank in a gearing I like? Are all square tapers the same size?

Also, the front derailleur is a Suntour BL, if I were to go to something like a new 48-38-28, which is close to what I am looking for and seemingly readily available, would it be able to handle the smaller little chainring?

A lot depends on the BCD measurements of your triple. If it takes 110/74 bcd rings, then you're in luck as rings are readily available, old or new. 110/74 BCD was pretty common back in the day esp. for Japanese touring bikes. Pics would help of the crank.

Measurements would be really helpful, Sheldon Brown's Bicycle Crank/Chainring Bolt Circle Diameter Crib Sheet

If they don't need to be old-stock SR brand, I learned in an old BF thread that Stronglight still makes 86 BCD rings for Spa Cycles. Availability depends on what they have in stock between runs, though: STRONGLIGHT :: Spa Cycles, Harrogate - The touring cyclists specialist.

What cassette/freewheel are you running? A cluster with a larger smallest cog (for example, going from 12 to 13) would have a similar effect to shrinking your big and middle rings.

Also, I use C&V "road" front derailleurs with 48T big rings all the time.

Mine has 118 bcd chain rings and I couldn't find much option to work with as far as replacement rings. In my case I just bought a Sakae 28-38-48 off eBay that uses common bcd rings.

Oops, had some of the measurements in the original post, didn't realize BCD was the key measurement! Looks like an 86.

Nah, don't need old stock. This bike is a workhorse, not a period correct representative! The rear is the stock gearing 14-17-20-24-28, if anything I'd want to tighten that up a bit for the mostly flat roads I'm on. That site looks like what I need, but for those prices I may just grab a whole new crank. The bike was well loved before I got it anyhow!

Yeah, a different crank makes way more sense here, and fortunately 48/38/28 cranks (or similar) are really easy to find.

The sugino XD 600 (or 500) are fine cranks and will look right on this bike.

In my book, chainrings are consumables, and I take this into account when choosing a replacement crankset for any bike that I intend to ride a lot. So unless you're trying to work with a certain obsolete standard such as 122 BCD or what not, your best bet is a 110/74 or 130/74 triple, if you're going to lay down some long green for the basic crankset. Chainrings for these can be had in a wide range of tooth counts, into the foreseeable future.
You don't need to get used/NOS chainrings from Ebay, either, xxcycle.com has a wide selection of new chainrings in all sizes for reasonable prices and shipping.

Yep, coming to that same conclusion after this thread, and that gearing is pretty close to what I want. I've got a vintage bike shop by me, I may swing by after work and see if they have anything that fits in the parts bin, otherwise it'll just get something new!

Doesn't your Pro Tour have a Sugino AT?

If I'm not mistaken, that crank shares rings with some versions of the SR Apex, as well as the Stronglight 99.





IMO- a 110/74 crank is SO much easier to find rings for.

I'm casually looking for some inexpensive drilled 86 BCD rings.

It's got a pretty uncommon crankset.





118 bcd SR. It pains me to change much on this bike because it's probably the nicest bike I've ever owned and I respect it as a class act, but I want to do some gearing swap to make it more enjoyable. The old parts will be carefully packed away in a storage crate though.

I'm replacing it with this 110/74 bcd. Before installing it I will strip, polish, and generally pour the heat to it until it looks like new.

I have always hated deviations from standard BCDs. Why did Campag. need 135mm instead of 130? Why did Nervar insist on 128 instead of 130, although in that case it's pretty easy to adapt a 130 ring to the 128 spider (been there ... done that with a Shimano 44T, worked like a champ).

John E may have a different opinion if He were the manufacturer, seeking, as is a common motive, to maximize profits,
by making yourself the sole source of replacement, consumable parts ..



Sekai, SR, is still making chainrings new to day, though some bolt patterns have passed into discontinuation,

130 & 110 & 74 are still going strong..





./.

Glad someone is stalking my old pics

Has nobody mentioned Hilary Stone ? Chainrings Intro as a source for chainrings. Best source I know, though he is in England.

I like the look of the Aerox. Did you drill it for the triple?

Pretty sure I've got a pair of 52/40 NOS 118 bcd rings in my stash. They're the Apex style but they'll fit. PM if you're interested.

That's a good source to have in my back pocket, too! Just as much/more than the new Spas, though.

I have the stock Suntour BL FD on my Gran Turismo but swapped the original crankset (identical to yours) to a 48-38-24 110/74 triple and the BL derailleur works great with it. No need to upgrade.

You're over 18; it's "research."

I think there are 118BCD SR chainrings listed on Ebay.

Well, I must have dug though a hundred vintagy cranks and chainrings today, no luck on anything that even matched the bolt pattern. Did find out about a vintage bike swap meet this weekend while there, though, so it was a beneficial trip!

If nothing turns up there, guess it'll get used another month and a half as is til the white stuff flies, and get a shiny new one for Christmas!