tony_merlino

I'm still looking at doing something to lower the gear ratio on my early-70s Raleigh Record. It occurred to me that, if a small chainring were available, I could keep the existing BB, crank, and FD, and just make my current inner ring the new outer ring, and this hypothetical small replacement ring the new inner ring. The current FD is bolted on, so I think I could keep it and just move it closer to the BB to get it to work with this scheme.

Is there such a thing as a small chainring that would fit this crank available? I noticed online that some new chainrings that were 3 bolt, but have no idea what the bolt spacing is. Also - it appears they're meant to be used with a 10-speed cassette in the back, so they're probably meant for a thinner chain.

Is what I want to do possible at a reasonable price? Possible at all? How hard is it to make a chainring?

Bianchigirll 

It is possible if you can figure out you BCD to find a ring somewhere to fit it, but it will likely take alot of hunting to find one. Do you know the brand of your crankset?

It will undoubtedly be quicker to just replace the crank and BB with something more inline with your needs.

Perhaps these guys could make you a ring to suit... https://cycleunderground.com.au/chainringdesigns.htm

echo

I have late 60's/early 70's record that sports the "thimble" fork. My inner chainring is a 40 tooth/3 bolt pattern and a spacing of approx 100mm from center hole to center hole, not sure if one multiplies that for a BCD as with a more modern crank or not. What's your current tooth count?

Airburst

From their website "Because our chainrings are not designed for front gear changes....."

It'll shift like a track ring.... That said, how well does the standard front ring on a Raleigh Record shift?

tony_merlino

The spider is the old 3-bolt style, with 100mm between centers on the bolts. If my trigonometry still serves me, that would give a BCD of 115.47mm. (That would be 2 x 50/sin(60) ). The inner ring is 40 teeth, IIRC. My largest cog on the freewheel is 28, I think. I would love to be able to put a 28-tooth chainring on as the inner ring. Again, if my HS math still serves me, that would have an outer diameter of 75.0555 mm, which is smaller than the BCD supported by the spider.

I did check into BB replacement, etc, and it's really expensive, not even considering having to buy the rest of the stuff to support it. The front ring currently shifts nicely, and I'd like the final solution to shift nicely, and reuse the current stem shifter and FD.

I had a really wacky idea I'd like to run by folks here: Since, to get a significantly smaller ring on here, I couldn't use the existing bolts/holes on the spider anyway, I'm thinking about creating a "dummy" ring, the same thickness as the current inner chainring, drilling it and the spider so that it could be mounted concentrically with the chainring (I hope this is clear). That new, dummy ring, could be drilled for a standard 5-hole chainring, like from a MTB.

Has anyone heard of anything like this ever being done? I know it will add a small amount of weight, but that should be fairly trivial. What would be involved would be cutting (or getting cut) a 1/8" thick circle of steel, and drilling a total of 8 holes in it. It seems like it should be simple, but what do I know?

Airburst

I think Sheldon Brown did something like that, not sure though.

You might be able to get those guys at cycleunderground to make the adaptor for you... They use aluminium, so it'll be lighter than your steel one, plus they can be sure to drill everything exactly centred.

dedhed

Something like this?

https://www.bikeforums.net/showthread...dapter-spiders

tony_merlino

Yep, that's exactly what I had in mind. Thanks!