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Old 06-17-14, 07:48 AM   #1
MikeD1
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Convert 6spd shimano 600 to 7 spd?

My bike is a 1986 Centurion Dave Scott Ironman with 600ex 6spd 13-21 cluster. My 60 yr old legs cannot get up some of the climbs anymore with nothing lower than 42/21. I have read in a couple places including Sheldon Brown that I should be able to switch to a 7 speed freewheel (thinking 14-28), new chain and index shifting will still work? Just making sure before I order parts. Any and all ideas are appreciated!
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Old 06-17-14, 08:35 AM   #2
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A 28T cog is too much for most short cage derailleurs, which is why I use a hard-to-find 26T low on most of my road bikes. Coupled with a 42T inner chainring, this is much better than fighting a 42/21, or even a 42/23, up a steep hill. Although the Bianchi came with 52-42/13-15-17-19-21-23, I changed it to 50-42/14-16-18-20-23-26, which is still a 12-speed configuration. I have also used a 13-15-17-19-21-23-26 7-speed freewheel on a different rear hub.

See other recent threads regarding the relative OLD requirements of 6-speed and 7-speed freewheels. Usually, a 1 or 2mm spacer on the right side is all that's needed to make the smallest cog usable.
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Old 06-17-14, 03:51 PM   #3
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Thanks John. I thought that might be the case. I will keep looking for a freewheel with a 25 or 26T low. I mention the 25T because I did see one on ebay. I'll also check w/ one of my LBS who I know happens to have quite a bit of "stuff" in the back. Maybe I'll get lucky and he'll have some cogs he can just replace on my current freewheel. If anyone knows of any 7 spd freewheels out there with a 25 or 26 low, I'd love to hear it!
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Old 06-17-14, 04:07 PM   #4
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Originally Posted by MikeD1 View Post
If anyone knows of any 7 spd freewheels out there with a 25 or 26 low, I'd love to hear it!
Sunrace makes a 13-25 7speed that you can pick up cheap (I've got their 13-28 7 speed on a bike)

To be honest, I think you'd need to go lower (bigger) than 25t to make a big change (52.5" to 44" development on lowest gear). If you can swap in a 39t small chainring at the same time, that should be a help (52.5" to 41" development).

Last edited by CO_Hoya; 06-17-14 at 04:15 PM. Reason: Math is hard
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Old 06-17-14, 04:11 PM   #5
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There are some pretty reasonable climbs in Wisconsin and your knees aren't getting any younger. I'd get your idea of a 14-28 freewheel is a good one. I'd get a modern shimano rear derailleur as well; it will handle the freewheel and index. You can pick up a shimano 105 RD for aroound $50; you can pick up a Tiagra if you prefer for less.
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Old 06-17-14, 06:08 PM   #6
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600EX RD will work with a 28t low cog. Therefore, installing an alpine 14-28t 7 speed freewheel will be the quickest and cheapest route. I recommend a new chain like a KMC X.8.

If more clearance is required on the drive side, adding a 1mm washer under the locknut usually is all it takes.

But if you want indexing:
You'll need additional hardware.
1. a Shimano SIS spec rear derailleur.
2. 7-speed DT indexed shifters, or 7-speed brifters.

For a better low range, I also recommend replacing the 42t inner ring with a 39t ring. The crank should be 130mm BCD. Try a local bike co-op for parts. I find chainrings for $5 each. Look for indexing derailleurs and shifters while there.
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Old 06-17-14, 06:25 PM   #7
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I thought the Ironman had a cassette (that era would be an uniglide version, totally obsolete).

So it starts with verifying whether you currently have a cassette or a freewheel, and if a cassette, whether it is hyperglide or uniglide.


http://sheldonbrown.com/k7.html#hyperdrivec

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Old 06-17-14, 07:48 PM   #8
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I have that same RD with a 28 tooth 7 speed freewheel on my 1988 Centurion. The placement forward and back of the rear wheel is critical.
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Old 06-17-14, 08:57 PM   #9
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I thought the Ironman had a cassette (that era would be an uniglide version, totally obsolete).

So it starts with verifying whether you currently have a cassette or a freewheel, and if a cassette, whether it is hyperglide or uniglide.


Shimano Cassettes & Freehubs
2nding this, I could easily be wrong but I would assume Uniglide cassette rather than a freewheel on a higher-level mid 80s Shimano setup.
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Old 06-17-14, 09:24 PM   #10
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Nobody answered the question about indexing yet, so I'll take it. Six speed shifters won't index seven speed gear clusters. If you have a freewheel on there, you can easily replace it with a new 6 speed freewheel with a lower gear (28T). If the bike has a rd-1050 rear derailleur, it'll handle it.

What is the reasoning behind wanting to go to 7 speed? Changing to 7 speeds will get you 1 extra middle gear from a 6 speed cluster that has the same range. A 14-28T freewheel whether it's 6 or 7 speeds will give you the same high and low gears. I can see if you find the difference too great between gears on a 6 speed, or you cannot find the exact tooth counts you want in 6 speed. If those aren't concerns, stick with 6 speed. If you have a UG cassette, all hope is not lost, but you've got to be creative to find reasonable cost replacements.

I think a 39T small chainring in conjunction with the new cluster would make those hills more manageable.
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Old 06-17-14, 10:44 PM   #11
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Nobody answered the question about indexing yet, so I'll take it. Six speed shifters won't index seven speed gear clusters. If you have a freewheel on there, you can easily replace it with a new 6 speed freewheel with a lower gear (28T). If the bike has a rd-1050 rear derailleur, it'll handle it.

What is the reasoning behind wanting to go to 7 speed? Changing to 7 speeds will get you 1 extra middle gear from a 6 speed cluster that has the same range. A 14-28T freewheel whether it's 6 or 7 speeds will give you the same high and low gears. I can see if you find the difference too great between gears on a 6 speed, or you cannot find the exact tooth counts you want in 6 speed. If those aren't concerns, stick with 6 speed. If you have a UG cassette, all hope is not lost, but you've got to be creative to find reasonable cost replacements.

I think a 39T small chainring in conjunction with the new cluster would make those hills more manageable.
+1 to all of this. A 39T small chainring will help (a little) on the low end, and 6-speed 14-28 freewheels are cheap and would work with your existing shifters. (The 20-22-24 toward the bottom of current 7-speed Shimano freewheels is really dumb, IMO -- the top end is where tighter-spaced gears should be.)
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Old 06-18-14, 05:04 AM   #12
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Originally Posted by MikeD1 View Post
My bike is a 1986 Centurion Dave Scott Ironman with 600ex 6spd 13-21 cluster. My 60 yr old legs cannot get up some of the climbs anymore with nothing lower than 42/21. I have read in a couple places including Sheldon Brown that I should be able to switch to a 7 speed freewheel (thinking 14-28), new chain and index shifting will still work? Just making sure before I order parts. Any and all ideas are appreciated!
Mike As mentioned above I have a Centurion also with the same 600 set up as yours. Your setup will work with its 6 speed indexed setup if you change to a 28 tooth 6 speed freewheel. Why go to a 7 speed. I used a 7 speed as I had the 7 speed freewheel and 7 speed down tube shifters to match. What helps all the above is using 39 tooth small gear on the chainring. I am 74 and my knees gave out long ago. The 39 tooth in the front and 28 in the back make most climbs doable. I am using a 30 tooth on another bike with a short cage 600 tricolor RD. Here is shows it will work VeloBase.com - Component: Shimano RD-6207, 600EX
Here it shows the sis version and it says 26 tooth but they will do 28 easily VeloBase.com - Component: Shimano RD-6208, 600EX (SIS)
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Old 06-18-14, 05:26 AM   #13
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You could convert your bike to a modern gearing system with a new 130 mm rear wheel, a 10 speed cassette, 10 speed downtube shifters or brifters, a new rear derailleur, and a compact crank.

This won't be cheap but you will end up with a lot of really usable gears that will get you up all sorts of hills and mountains too for that matter.

I like my old bikes but that's what I would do for a bike that I rode on a regular basis. You'll get more usable gear ratios this way while significantly improving your climbing gears.
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Old 06-18-14, 05:49 AM   #14
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You could convert your bike to a modern gearing system with a new 130 mm rear wheel, a 10 speed cassette, 10 speed downtube shifters or brifters, a new rear derailleur, and a compact crank.

This won't be cheap but you will end up with a lot of really usable gears that will get you up all sorts of hills and mountains too for that matter.

I like my old bikes but that's what I would do for a bike that I rode on a regular basis. You'll get more usable gear ratios this way while significantly improving your climbing gears.
This would be a viable option if you have a UG cassette and don't want the hassle of hunting down cassettes.
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Old 06-18-14, 06:28 AM   #15
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If you're only looking to get a lower gear- why not replace the freewheel/cassette for a 14-28 and stay 6 speed. The indexing stays the same- the RD may work.

I really only care about the range- having the steps between makes a difference when racing and to some extent, comfort. I've found I'm perfectly comfortable with a 6 speed- and actually just started using 3x5 bikes- I don't notice a whole lot of difference.
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Old 06-18-14, 06:42 AM   #16
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If that is a 1050 RD it will work with a 28T cog and a triple. You just have to experiment with chain length to make sure the RD pulley is not riding the biggest cog. I have this setup on an 87 Ironman. 52/42/30 FC-1057 and 12-28 7speed in back on hard climbing days. Normal is a 13-23 in back. Shimano L-600 barcons handle the shifting since I like friction. About as good as it gets for a friction setup.

The triple in front is the best option in my opinion. You can change out the cassette if you desire, but a new spindle and crankset will get you 6 more gears and a lower end. You can find both on the cheap. Some of the others members can recommend a good crank to put on. I've bought 2 FC-1057. One was NIB and the other slightly used. I spent less that $100 for both and the 2 spindles. Triple FDs are cheap. So are used long cage RDs. Why more people don't go this route baffles me.

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Old 06-18-14, 07:23 AM   #17
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You are all awesome! This is my RD: 6208, 600EX (SIS). Since there are tons of 6spd 14-28 freewheels for not much money, that and a new chain are a great start for me. My low gear will be 39.7 instead of 52.9. I'll keep an eye out for a 39 chainring as well. This goes with my idea of keeping the investment real low. Part of me wants to buy a new bike in the next year or so. Main use is training and competing in Triathlons. So I might want a dedicated aero bike. Or I might want a newer, smoother riding road bike I can also use for Tris.




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Old 06-18-14, 07:40 AM   #18
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When I posted, I got the impression you had friction 600EX, if that is not the case and you have 6 speed indexing DT shifters, it's best to get a 6 speed freewheel.
If you actually have a Uniglide freehub system, that becomes more complicated since these cassettes are obsolete. But a little grinding or filing of a HG cog will allow it to fit.

Then you can install your 28t low cog.
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