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Replace 6 speed free-wheel with 7 speed. What issues will I encounter?

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Replace 6 speed free-wheel with 7 speed. What issues will I encounter?

Old 02-03-16, 04:33 PM
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Originally Posted by vintagerando
Its not the extra gear I really want. The freewheel that's on now is a Sunrace B0525, the largest cog is 24 or 25.....I have a very nice Sach with a 28t largest. I wanted to get that 28t to help with hills
Do you have a freewheel tool? (one for each type of freewheel you have).

It should only take a few seconds to pop one freewheel off and screw the other one and see how it fits.

There was a massive 5s or 6s freewheel at our local co-op. I don't know if it is still there. But, there are options.

However, if you already have the parts, just try them out and see if it works.
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Old 02-03-16, 07:27 PM
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Just do it!

Without having your bike to look at I can only guess what other changes will need to be done. A bicycle is a simple machine, however, so provided you have average or better mechanical ability, you can do this.

If it was my bike the first thing that I would do would be to spin on the new freewheel and test fit it on the bike. If you're lucky you'll find you have enough clearance between the smallest cog and the chain stay for your derailleur to shift into that gear. If that's the case, you can adjust the derailleur (if necessary), adjust the chain length (if necessary) and go for a ride.

If you find that you have cog to chainstay interference, the easiest thing to do is to find a spacer that's the right thickness on the left side of your axle and move it over to the right side. If you do that, the right thing to do is to loosen each left side spoke 1/4 turn and tighten every right side spoke by the same amount. If your wheel was straight before and you were careful, it'll still be true when you're finished. To be honest, however, you've probably ridden a bike that had worse rear wheel dish than that and didn't even realize it.

There's lots of 7-speed freewheel bikes out there. Lots and lots. Bent and broken axles do happen but not all that often. Even if it does, overhauling a rear hub will probably fall within your skill level too.
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Old 02-03-16, 07:33 PM
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Originally Posted by CliffordK
There was a massive 5s or 6s freewheel at our local co-op. I don't know if it is still there. But, there are options.
Suntour AG Tech. 14-17-21-28-38. I put one of those on my Schwinn Twinn tandem. It needed a specific rear derailleur to handle the 38 tooth big cog.
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Old 02-03-16, 09:19 PM
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Originally Posted by Retro Grouch
Just do it!

Without having your bike to look at I can only guess what other changes will need to be done. A bicycle is a simple machine, however, so provided you have average or better mechanical ability, you can do this.

If it was my bike the first thing that I would do would be to spin on the new freewheel and test fit it on the bike. If you're lucky you'll find you have enough clearance between the smallest cog and the chain stay for your derailleur to shift into that gear. If that's the case, you can adjust the derailleur (if necessary), adjust the chain length (if necessary) and go for a ride.

If you find that you have cog to chainstay interference, the easiest thing to do is to find a spacer that's the right thickness on the left side of your axle and move it over to the right side. If you do that, the right thing to do is to loosen each left side spoke 1/4 turn and tighten every right side spoke by the same amount. If your wheel was straight before and you were careful, it'll still be true when you're finished. To be honest, however, you've probably ridden a bike that had worse rear wheel dish than that and didn't even realize it.

There's lots of 7-speed freewheel bikes out there. Lots and lots. Bent and broken axles do happen but not all that often. Even if it does, overhauling a rear hub will probably fall within your skill level too.
RetroGrouch....your post identified what I was not understanding...specifically, "enough clearance between the smallest cog and the chain stay for your derailleur to shift into that gear.". Now I see. I was caught up with understanding solutions without grasping the potential problem. Off to the garage!
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Old 02-04-16, 11:03 PM
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So, the 7 speed is not going to happen on this bike, at least not the 7 speed Sachs I have. The stack is too high. The smallest cog hits the chainstay. The spacing is weird on this 80s Peter Mooney. It measures 123.5 or 123. It does not seem standard. Its not 120 nor 125. So, I will have to stick with the 6 speed or maybe buy one of those IRD Classica 13-28. What I am trying to do is keep the Campagnolo SR RD and get still have some gears for hills.
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Old 02-05-16, 02:56 AM
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Originally Posted by vintagerando
So, the 7 speed is not going to happen on this bike.....The smallest cog hits the chainstay.
Well, you were warned.
So add more washers or a bigger spacer.
Going to 125 is unlikely to upset the frame.
Being steel, it could be spread and realigned as well, if you want it.

Originally Posted by vintagerando
What I am trying to do is keep the Campagnolo SR RD and get still have some gears for hills.
Just mind your chain wrap capacity. It's annoying having to remember double shifts to avoid the derailer folding over....
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Old 02-05-16, 04:18 AM
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It looks like Shimano also has the megarange in a 6 speed, and they're dirt cheap.

Shimano MF-TZ20 6-Speed Freewheel

They come in a 14-28 & a 14-34, with I believe a big jump for the 14-34.

However, your Campagnolo RD may complain about the 34T jump.
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Old 02-05-16, 11:10 AM
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Originally Posted by CliffordK
It looks like Shimano also has the megarange in a 6 speed, and they're dirt cheap.

Shimano MF-TZ20 6-Speed Freewheel

They come in a 14-28 & a 14-34, with I believe a big jump for the 14-34.

However, your Campagnolo RD may complain about the 34T jump.
That's what I'd probably do, even if it means using a different rear derailleur. You get 5 relatively closely spaced gears to use for 90% of your riding and a bail out gear for grinding up steep hills.
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Old 02-05-16, 11:19 AM
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Originally Posted by dabac
Since 7-speed freewheels are notorious for axles bending/breaking, I wouldn't be too keen on that change.
Better either be a lighter-than-average rider or only stay on nice roads.
Yikes!

I went from a 6 speed freewheel to 7 speed in 1988. I wish someone had told me before I rode all those thousands of miles. Then I swapped out the original one for my current Sachs 7 speed freewheel.

It all depends of the rear spacing. A lot of 6 speed bilkes had 126mm spacing and a 7 speed freewheel just screws right on, provided you have the right threading. Derailleurs are not issue as I kept using my RD-7400 6 speed derailleur (26t max) with my 7 speed freewheel with a 28t. Derailleur hanger does impact max cog.

John
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Old 02-05-16, 01:47 PM
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No one else seems to be suggesting it so - Have you considered replacing your chainrings with a smaller set. I just built up a Nishiki International with a 6 speed shimano hyperglide 14-28 freewheel and a triple chainring with 48, 36, and 24 teeth.

The bike will go faster than I want to with the 14/ 48 gears and will climb a wall with the 28/24 setup. I am even thinking of swapping the freewheel with something even more close ratio. Other than the chainrings / cranks which I bought from the Bike exchange for about $20 and a new chain, the only thing I needed was a mountain style triple front derailleur. Everything is friction using shimano thumbies on 2" riser bars and mtb brake levers. Makes for a very nice ride.
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Old 02-05-16, 09:41 PM
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Another option the OP has is to widen the frame and then using whatever he wants, including cassettes. Peter Mooney frames seem to be (quite proudly) all steel so he could use a threaded rod/bolts/washers and spread to 126 or 130 easily.
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Old 02-06-16, 12:34 AM
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I went from six to seven and added indexed shifting. Had to add the 1mm spacer to stop chain rub, but the whole thing works flawlessly. The bike is a 1985 Gazelle with Shimano 600ex derailleurs and 126mm spacing.
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