Replace Rudge Chainring?
 

I inherited a late 60's Rudge that had been converted into a single speed with 27" rims and racing tires. I've replaced the single speed with an 8 speed internal S/A hub and it works fine. The problem is the chain ring (original Rudge hand) is too large a diameter. As a result the 1st gear ratios are too high.

I'd like to replace the Rudge 7 1/2" ring with a smaller one. But isn't the chain ring welded to the crankset? If so, do I need to replace the complete lower unit? Any suggestions?

Why not a bigger rear sprocket? That chainring is cool BTW.

I took a stronglight competition from an old Raleigh GP, removed the big ring and ended up with this

http://farm3.staticflickr.com/2759/5...607a0bf1c6.jpg
27 107 by barnstormerbikes, on Flickr

+1

Get a 22T sprocket and pull stumps.

Indeed. I'd keep the "Red Hand of Ulster" and replace the rear cog instead.

I'm afraid that the 8 speed SA hub was a poor choice for a bike with 27" wheels. The hub was designed for 20" wheel bikes and first gear is 1:1. Usable gearing requires the use of a chain ring that is ridiculously small. I think that SA makes a crank that will work, but be prepared for people to point and laugh. I'd rebuild the wheel with a SA 5 speed if it was mine.

The hub typically comes with a 25T.

Grand Bois' suggestion is probably the most workable.

Changing the crank is possible, but can be quite a headache. The Raleigh BB is wider than usual, so common cotterless spindles don't work. You might be able to find a cottered crank with a 50.4 or 2" bcd but even so, finding a single chain ring small enough would be difficult.

I had the same problem with a Nexus 4 IGH. The original 21T was meant for a 20" wheel. Replaced it with a 24T, works OK with a 26" wheel.

You still could try a 27 or 28.

The gearing will still be way too tall with a 28t cog. Do the math or use Sheldon's calculator. The OP should have done that before buying the hub. It's a shame because it's a great looking hub at a great price, but it's made for Dahons and the like.

For those that aren't familiar with this hub, you need a rather small chainring to accommodate this hub because of the 1:1 first gear. If you want to keep the original character of the bike, dump the SA 8-speed hub and get a 5-speed instead. As much as I like this hub, I don't like the fact that I need to use a small front chainring. I wish SA would re-engineer this so that the hub has underdrive and overdrive.

Also, IIRC, the largest cog available for this hub is a 25t, so going to anything larger on the rear is not going to be possible.

Also, IIRC, the largest cog available for this hub is a 25t, so going to anything larger on the rear is not going to be possible.

You're right, just checked it out at Sheldon Brown's. This hub uses a different cog than other Sturmey Archers.

Well, while this is a work in progress, it is a limited budget work in progress. As to pointing and laughing...we're talking about an overweight (not tooo overweight) 67 year old riding around on a vintage (looking) bike wearing his kid's skate board helmet, so pointing and laughing is a given...

So...a newbie stupid question...I've never pulled the chain ring off a (cottered) Rudge. Is the chain ring attached to the right crank on these bikes, or does it just slip off the crank shaft once the cotter is removed? Now...(assuming I get it off)...I assume the diameter of the ring and not the number of teeth determines the leverage, right? Assuming that's correct, why can't I pull a cottered crankset off an older road bike, pull the smallest ring off it and use it? Aside from losing that great Rudge "hand" ring, what's the downside? I'm not looking to race this bike, just get easier hill climbing on my thrice or so weekly jaunts around the village...

I already said that.

The chain ring is swaged to the crank arm. The two will come off as one piece and the only way to separate them would be to cut the ring off, after which you would have no way to reattach it, or another one. I suppose it might be possible to have a machine shop cut the Rudge ring down and bolt a smaller ring to it, but frankly this is crazy talk.

You should be able to get a Continental European (as opposed to English) cottered crank, such as this one:
http://www.ebay.com/itm/Vintage-Soli...item2a2a3b29de
and use the only smaller ring. But if I recall correctly, these cranks have a 116 mm bolt circle, so the 36T ring on this one is probably the smallest available. I'm not aware of any other cottered cranks that will allow a smaller chain ring than that. Cottered cranks with a 50.4 mm or 2" bolt circle do exist, but they have not been made in 50 years and when they turn up on ebay (rarely) they don't go cheap; and anyway, chain rings to fit them are/were made only in larger sizes. It would be possible to get one of those cranks, fit a relatively large outer chain ring to the crank arm, and a smaller chain ring to the large chain ring; but this is throwing good money after bad.

My best advice, echoing what has been said many times in this thread, is to cut your losses. Return or sell the Sturmey Archer 8 speed hub and get a different hub. Almost every other internally geared hub on the market is suitably geared for your original chain ring (the two exceptions being the Shimano Nexus 4 speed hub, and the Sturmey Archer 8 speed hub).