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I'm looking to expand the range of gears on my 1985 Centurion Ironman, Right now, it's running a correct RD6207 short cage derailleur, but I just picked up a long cage RD-6207. Is there any reason I can't swap out the 6-speed freewheel for a 7 speed one, essentially just adding another, large cog? It's friction shifting, so cog spacing isn't an issue. I just want to make sure it all fits in 126mm.

Thanks! BTW, are Sunrace freewheels any good?

No reason that won’t work out of the box, assuming new freewheel width can be accommodated. Otherwise re-arrange the axle spacers and re-dish the wheel.

The '85 catalog lists the hubs as also being 600EX, so I would doubt you'll have a spacing issue with those.

Just in case you are still on the original chain - real 6 speed chains don't work on 7 speed. Too wide.


I also like the Sunrace freewheels. Great shifting.

IME, it depends on both the hub and the freewheel. All you can do is try. I have done the re-space and re-dish route, but sometimes that is not feasible. I have left my '80s vintage Specialized wheels at 6-speed, not wanting to mess with the sealed bearings. And my French-threaded Zeus wheels are limited to 6-speed, simply because I can't find any 7-speed French-threaded freewheels!

The real trick is to make your wheels interchangeable, especially without derailleur fiddling. I would claim to have done it, but the next change might prove me wrong. ;-)

What is the range of your current cassette and the cassette you want to use?
The short cage RD may work fine.

7sp instead of 6sp really isn't a significant issue.

Lots of 13-28t Sunrace on EBay.
You probably want to avoid 14-28 because the small cog could touch the chain stay. Room is very tight with 7s freewheels

I've got a Sunrace 13-15-17-19-21-24-28 on my Holdsworth Avanti - 126mm.
Works fine.

Fairly sure it's a MFM30 7CS - it's chrome coloured anyway.
They're on Ebay UK for £21

All chrome 13-28: https://www.ebay.co.uk/itm/115406613617
Sunrace site has several pics which show a 34 megadrive cog - so the wrong pic.
https://sunrace.com/product/mfm30-7cs/
Text says "chome" for colour.

FWIW: Shimano indicates that the total capacity and max cog size of the RD-6207 (short cage) is 28 for each case, and that the total capacity and max cog size of the RD-6207-GS is 34.

https://si.shimano.com/en/pdfs/si/N2...000-00-ENG.pdf

I also used to have a beautiful 85 Ironman. I sold it as it was a bit too racy for me. I ran the Sunrace 13-28 seven speed on it along with a 39 tooth small sprocket in front. I think I perhaps had to rearrange some spacing on the rear, and I also seem to remember that the 14-28 wouldn’t work as the chain would hit the seatstay on shifting. The stock derailleurs worked fine and I did put a new Shimano chain on it. I did run the 13-25 for awhile before wanting some easier gearing. The 39 small front ring and 28 in back was very useful. Pics needed of yours of course.

https://cimg5.ibsrv.net/gimg/bikefor...0d968309d.jpeg
https://cimg6.ibsrv.net/gimg/bikefor...2dbd9b81d.jpeg

Yep, most of their images show the same 34 megadrive.
But the text does say 13-28

Right now, it's running a 13-26 MF-6208 6 speed freewheel. I'd like to basically keep all those gears and add a 30 or 32. 28 doesn't really do that much for me. As currently configured, I can do any of my usual rides but there are two 1/2 mile 6% climbs on any ride I do from home where 42x30 or 32 would be a real boon. And having that extra, lower gear might let me to a bit more climbing with it.

The bike is pretty much original. An early owner had swapped the 6207 RD and shifters for 6208, with SIS, but as often happens with 6208 shifters, all the tangs were broken off. So I found the authentic bits on Ebay and swapped them. I also replaced the later Dia Compe brake levers with some 6209 aero levers, which aren't correct but are close and not only work well but are more comfy.

https://cimg1.ibsrv.net/gimg/bikefor...f2e7079616.jpg

EDIT: I also got replaced the "Bernard Hinault" model Turbo saddle. I tried it, but it's too flat for me. And now it's also running gumwall tires for a more "classic" look.

Just going to mention SunTour New Winner freewheels (1980s).
If you buy enough old cogs you can knit your own ratios within limits.
I like them a lot, but only a good idea if you like mechanicing.

They include
..
I'm currently running
..

https://cimg1.ibsrv.net/gimg/bikefor...0fee8d5569.jpg

Okay, now I think I've got it. Get the freewheel, put it on. If it's too close to the chainstay, break out the cone wrenches and see if there's a thin spacer on NDS to move to DS, then re-dish the wheel back to center. I can't remember whether I repacked these hubs or the seller told me he'd done it, but it's no biggie. I've got the cone wrenches, I've got the wheel truing stand, I've got the dishing tool and I've got a spoke wrench.

I ran a 7 speed on my 86 and had no clearance issues. I also put on SLR brake levers and 6500 dual pivots. The bike was so nice with Dura Ace/GL330 tubulars that my Richard Sachs got jealous and kicked it out of the herd. I now have an 85 like yours and I’m tempted to go index, 7 speed, SLR, dual Pivots, and tubulars but — the RS. 😁

Me too. :thumb:

https://cimg0.ibsrv.net/gimg/bikefor...f4beb4dde9.jpg

As form follows function, your example of the Ironman looks awesome.

Mine probably cost less than yours, but unlike yours is definitely a Unitasker. ;)

When I bought mine, the seller had replaced the single pivot brakes with 7403 dual pivots, but he kept the 6207 single pivots and they came with it, so I decided to go back to them. They're not bad brakes for most riding. I'd prefer the dual pivots for long descents with lots of braking, but I have other bikes for those.

An option would be to get pastorbobnlnh at the freewheel spa to built you one. I had him clean and lube a 600 freewheel (my fave) and the made the low 30 teeth

I also have a new IRD 12/32 6 speed in my stash....we could work some thing out on

This has been an interesting thread. I do not give a second thought to interchanging 6 and 7 speed freewheels on a 126 OLD hub and rear spacing. I’ve been lucky to have not encountered any clearance issues up to this point. I did recently find that a Suntour V rear derailleur won’t come close to working with a 28 tooth cog. I’ve had many derailleurs with a stated max of 26t handle 28 just fine. Not the Suntour V, that’s for sure.

I've also never encountered a problem. I had an old Miche hub that seemed like it was too tight, but it actually was fine.

I swapped the 14-24 on my IM for the 14-34 megarange. The 6 original speeds were still available, but I had the bailout!

I had both frame-chain clearance issues (added a ~1mm washer from the HW store), and RDr clearance+capacity issues, 8-spd Shimano long cage + Wolf tooth.

Maybe I'll try to put it together again for the May BayArea ride...I was moving the wheels to a different project and thinking of a compact double on the IM,.but that other project stalled.

Really good collection of albums there. I got rid of all of my CDs last year and regret it already.

Yeah, I boxed up most of mine. Just keeping them in case I ever lose the mp3 copies. My dishing tool there is purely random choices.

I keep hearing cd's are coming back. If that's true, then surely vintage bikes can do the same. :lol:

I still have all of mine. In fact I still have all my LPs. But my CD player has finally decided it doesn't want to open at all, so I have to decide - do I get a new player?

Nah, that's silly. Of course I'm going to get a new player. I just have to find the right one.