TricycleTom

Alas, my little fitness rides have worn my chain and freewheel beyond limits, and both need replacing. However, I don't see any 5-speed blocks at my LBS (on line) and wonder if my frame and wheel will even fit the new stuff. The new ratios offered don't even work evenly with my half-step plus granny front end. This could cascade into a whole new bike if I don't find some better compromises. Any advice on sources?

noobinsf 

What kind of freewheel? If you're a paying member (doesn't cost much), you could post a want-to-buy (WTB) ad in the classic/vintage sales section. Someone's bound to have something you could use. Also, KMC chains for 5/6/7/8 speeds will work for not much money, readily available.

non-fixie 

When I search for "5 speed freewheel" I get a lot of hits, ranging from 13-17 T corncobs to 14-34 T tree climbers. What are you looking for? Modern 8-speed chains will work fine.

brianinc-ville

IRD 5-speed freewheels are available in four configurations, from 13-26 to 13-32. One of them ought to work for you.

Alternately, you might get a refurbished freewheel from pastorbobnlnh : https://www.freewheelspa.com/ . It looks like he's taking a break through the end of June.

70sSanO

You need to search ebay. That is really the source for older parts. It can be hot or miss and the price really is driven by demand, or at least a perceived demand on rarity.

John

Salamandrine 

No, newer 6/7+ speed stuff won't work with your bike, to answer your first question. 5 speed used 120mm rear triangle spacing. It was superseded by 126mm spacing, used for 6 and later 7 speeds. Finally, it was bumped up again to 130mm in the 90s, the modern road spacing, which works with 8 to 11+ speed stuff. The frame could be respaced and realigned to modern 130 spacing, but this can add up to a fair amount of money, since besides a realignment, you'd probably be replacing the entire drivetrain, and at least one wheel.

I'd recommend you simply by a new freewheel and chain. Much simpler and infinitely cheaper. Besides IRD, Sunrace 5 speed freewheels are available. They're probably OK if you don't get a lemon. I've had good luck with the 7 speed ones. Ebay does have lots of stuff. Vintage Suntour or something is an option if you can find one without many miles on it. They do wear out.

Since you have half step, you'll need to work out your gear ratios in advance. A freewheel with even tooth spacing is needed for half step to work. FWIW a Sunrace 5sp 14-28 gives pretty even gear spacing with 30/49/52 chainrings. Ask again if you need help with that. Here is one online calculator, IMO the best one: Bicycle Gear Calculator

TricycleTom

Thanks for the tips. For the record, the original gearing was worked out with a calculator in '77. It was 13-16-19-23-28, with a 47-52 up front. The half-steps are extremely evenly spaced with those numbers.
I could stretch the frame and re-build the wheel, but the bike has other problems, so I'd rather put work into building something better. I'm not a purist, but there is some sentimental attachment to my old friend.

Chubby715

I agree with the previous poster who suggests checking Ebay. I have a 120mm rear dropout and bought Suntour NOS 5 speed freewheels from this seller: https://www.ebay.com/usr/bicyclists_retreat

TricycleTom

I just bought a new Shimano 14-28 on eBay for $20 USD, with slow shipping. Wish me luck.

noobinsf 

Great -- if you can live with the 14-tooth small cog, it's a much easier range to find.

TricycleTom

Yeah, I had to go 14-28 long ago. The 13 was for cruising down mountains. Now, I don't have those, and I seldom even use the 14 with a tailwind. <sigh> These old legs still have the revs, but not the torque.