Need vintage Shimano gearing advice

[warren128]

This is for my 80s, vintage Nishiki Tri-A. Of my current fleet, this bike has been with me the longest, but it is not in my regular rotation because of the gearing on it.

It has Shimano 600EX, indexed DT shifters, Biopace crankset (52/42), and 6 speed freewheel (13-24). It's my last and only current bike with DT shifters, and I enjoy the feeling of simplicity and directness when riding this bike.

I was wondering if you can suggest some simple equipment changes that will retain the feeling and vintage nature of the bike without having to do too much to it. I'm not familiar with old Shimano compatibility issues.

I have a couple of bikes that use 53/39 13-29, and 53/39 12-27, and hopefully I can get my Nishiki close to those ranges.

I've been on the fence about whether I should finally let this one go, or not. If I can do a few things so I can add it to my regular ride rotation, then maybe I'll keep it for a while longer Or alternatively, I'll just leave it as-is, all original, and keep it around for nostalgia.

TIA.

[Ralph]

14-28 6 speed Shimano freewheels are usually on E bay cheap.

[warren128]

Originally Posted by Ralph

14-28 6 speed Shimano freewheels are usually on E bay cheap.

Thanks, is there a particular type, I should be looking for? (Uniglide?)

Also, which round rings can I use to replace the Biopace 52/42? I believe they are 130bcd? Will any 130bcd rings work? Do they need to be 6 speed compatible?

[warren128]

Will my current derailleur shift up to 28 teeth?

What about if I go to a 39 inner w/ 28 largest, will the rear DR work with this combo?

[Ralph]

If you are experienced at setting up a rear derailleur with correct chain length, B adjustment, etc.....pretty sure the stock RD will shift to a 28. If you put a 39 in front.....that increased the wrap the RD has to do. 42-52= 10 and 14-28 is 14 more for a total of 24. Switch out to a 39-52 with 14-28 and you are trying to wrap up 27. That era RD might do that...if not you can run small to small kinda slack chain length wise. 39-50 would work better (less wrap) especially if you found a 13-28 600EX. I think any of those cheap FW will work fine. They come on Walmart bikes and seem to last a long time. Believe they use the same removal tool as your current FW. Good thing about staying with a 52 ring is you probably won't have to damage the seat tube paint by moving FD. Beautiful bike BTW. Don't sell it.

[gdw]

Someone will correct me if I'm wrong but I believe that rear derailleur's stated chain wrap capacity was 27 but it will work with 28 so it should be able to handle a 52/39 or 52/38 paired with a 14-28 freewheel. If anyone has a copy of Frank Berto's Complete Guide to Upgrading Your Bike handy they can confirm those numbers. Ebay used to be a great source for freewheels and old Shimano and Sugino 130mm chainrings. Good luck.

[Peter P.]

Maximum CHAINRING difference the RD-6208 derailleur can handle is 13T.

The TOTAL Capacity (freewheel difference + chainring difference) is 28T.

Maximum FREEWHEEL cog size is 28T.

So I think a 53/39 is out of the question.

You can use a Shimano narrow (Hyperglide 7 or 8 speed) chain with the existing system.

All the above is from the Sutherland's Manual.

Your problem is, due to the age of the components, should you try to replace just one item, you'll likely experience skipping due to a worn component trying to mesh with a new component. You either experiment one component at a time to see if you can get away with it or replace everything.

Chainring spacing is a uniform 4.5mm, but chainring thickness at the tooth contact point has reduced to accommodate narrower chains. So new chainrings should work on your older crank. 130mm bolt circle is correct.

I'm not sure whether your hub uses a cassette or freewheel. That will determine the availability of a replacement. I'd guess eBay or any vintage forum site would be the places to look.

[ColonelJLloyd]

Originally Posted by Peter P.

I'm not sure whether your hub uses a cassette or freewheel. That will determine the availability of a replacement. I'd guess eBay or any vintage forum site would be the places to look.

He said 6s and it's original 600EX so he has a FW hub.

OP should be able to use a 7s FW if he wants to get 7s DT shifters or put his current shifters in friction mode. And long cage (GS) RD from 6-10s era (excluding Tiagra 10s and Dura Ace 7/8s era) will index perfectly with Shimano 7s indexing shifters.

New Hyperglide 7s freewheels are available in 12-28 and 12-32 at pretty low cost from Shimano and Sunrace. IRD may make a 12-30, but higher cost.

[zennmotion]

Warren, dude PM me. I have a box of 130bcd rings, I'm sure I have some 42t, probably 38t, 52t, 53t, maybe some others. Let me know what you're looking for and I'll put them in the mail. Pay me later with a post-Covid beer or something.

[zennmotion]

Originally Posted by gdw

Someone will correct me if I'm wrong but I believe that rear derailleur's stated chain wrap capacity was 27 but it will work with 28 so it should be able to handle a 52/39 or 52/38 paired with a 14-28 freewheel. If anyone has a copy of Frank Berto's Complete Guide to Upgrading Your Bike handy they can confirm those numbers. Ebay used to be a great source for freewheels and old Shimano and Sugino 130mm chainrings. Good luck.

It depends on the frame, but I'm using a 14-28 six speed freewheel with a compact 34-50 crankset on my 80s Marinoni with Dura Ace 7200 short cage derailleurs with the b-screw nearly all the way out. It's a stretch but it works if you don't completely cross-chain.

[Ken Robb]

Sheldon Brown's posts via Harris Cyclery may have some info to help you.

[choke]

Originally Posted by Peter P.

Maximum CHAINRING difference the RD-6208 derailleur can handle is 13T.

So I think a 53/39 is out of the question.

The specs may say that but in my experience you almost always can go with more than what the specs say is the max. I would be amazed if a 53/39 wouldn't work.

[warren128]

Happy 4th of July!

Thanks for all the great info, everyone! I'll have to check some things out and come up with a plan.

Zenn, you're too kind, I'll PM you in a bit.

I love Paceline.

[Tandem Rider]

I have some 6spd stuff I'll never ever use. I can help you out, especially if you aren't in a big hurry, I plan to be in SF later this year and can bring along what I have that you need. I'll have to let you know what I have in the bins after I look.

[oliver1850]

I would suggest changing the rings to 38-39/50 with a 13/14-28 freewheel. I have a box full of new 6 speed freewheels with 28T large cogs, but am not sure how many teeth on the small cog. Cheap though, around $15 shipped.