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Old 10-22-07, 06:49 PM   #1
JBMCsr1
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Converting 27 inch wheels to 700c

I have a mid 80's Schwinn Passage touring bike with 27 inch wheels. Everything is mostly stock. I'm thinking about updating the wheels to 700c and a rear cassette to have stronger wheels for loaded touring. I took the bike by my LBS and was told that I would need new brakes that adjust up and down and that I need a new shifters and a rear derailleur because they thought my friction Suntour bar-cons and stock Sach-Huret derailleur would only handle up to 7 speeds. Is that all correct? I could see the need for the brakes but how about the shifters and rear derailleur?

Do you have any other advice for me?

Thanks, Jason
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Old 10-22-07, 07:00 PM   #2
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If you want stronger wheels for touring, convert to 26". Of course, you would need to reposition your canti posts to do that...
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Old 10-22-07, 08:13 PM   #3
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The brakes are a toss up. It is possible that they would adjust down to 700's. I got a Shogun touring bike earlier this year, and it had a 27" on the front, and a 700 in back. The brakes were adjusted properly and had no problem working well with either wheel. Most cantilever brakes had quite a bit of adjustment. Of course the only way to know is to try it, unless someone here has already done it? Offhand I would say it would work.

The only bike I have with barcons is a Voyageur with a 6 speed uniglide. To make the levers a little more accessible I loosened the cable and pulled the lever up some. That way they start off closer in line with the bars, instead of a right angle. I have no doubt they could handle at least 7 if not more? Friction derailleurs can handle a pretty wide range also, and the gears are closer together to begin with on higher speed bikes. I put 8 speed Cannondale 700's on the aforementioned Shogun, without even cold setting the frame. I ony changed the derailleur because I thought it wouldn't work. On the big gear the upper jockey wheel was riding on the gear, making a nasty vibration. It may have worked if I had only shortened the chain two more links.

I recently built up a 7 speed Schwinn tempo with a triple front, and ran into the same problem. Shortening the chain solved it, and it can still cross chain to big/big if I ever wanted to do it, lol. It's running a like vintage Deore long cage RD, and shifts like a dream. If you're still in doubt about the Sachs
I can understand it. I have never tried upping the gears on one of those.

How many speeds were you contemplating?



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Old 10-22-07, 09:02 PM   #4
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Making a little assumption here...

Which 700c wheel were you going to use and expect to be stronger than the 40 spoke 27 inch wheel you have on there now?

Admittedly going from a freewheel to a freehub will give you a stronger hub, but you can have a 27" wheel built with an updated hub.
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Old 10-22-07, 09:31 PM   #5
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Thanks for the replies so far. I'm looking at a set of wheels with Shimano XT hubs and Mavic A719 rims in a 40 rear, 36 front. As far as speeds are concerned, I haven't given that much thought. Everything on ebay seems to be 9 speed cassettes. I want a 34 or 32 tooth large sprocket for my granny gear up front.

I think going to 26" wheel would lower the bottom bracket too much and force me to move the canti-posts and then repaint the frame.

I guess I was hoping for a fairly easy swap--that hope may be fading.
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Old 10-22-07, 10:07 PM   #6
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Thanks for the replies so far. I'm looking at a set of wheels with Shimano XT hubs and Mavic A719 rims in a 40 rear, 36 front. As far as speeds are concerned, I haven't given that much thought. Everything on ebay seems to be 9 speed cassettes. I want a 34 or 32 tooth large sprocket for my granny gear up front.

I think going to 26" wheel would lower the bottom bracket too much and force me to move the canti-posts and then repaint the frame.

I guess I was hoping for a fairly easy swap--that hope may be fading.
I've got a wheelset with XT hubs and A719 rims, it's indeed a very nice, bombproof touring wheelset. Your current rear dropout spacing is very likely 126mm, the modern XT hubs have an OLD of 135mm, so you'll need to cold set the frame to use them. I did exactly that on the bike I use that wheelset on (cold set from 126 to 135), just follow the instructions for cold setting on Sheldon's site. If you do this, I'd also have the dropouts re-aligned. But as for the canti's, I think that bike probably has crummy Dia Compe canti's, I'm not sure you can adjust them to work with the 700c rims (I've got some, and I couldn't). And unfortunately, the brake bosses aren't spaced for canti's that are more adjustable, at least if they are I don't which brakes they would be. One option is to ditch the canti's altogether and mount nutted centerpull brakes in the fender holes of the seatstay bridge and fork crown, you can usually find centerpulls with enough adjustment range to do it. It just depends on what you're willing to do-

Last edited by well biked; 10-22-07 at 10:17 PM.
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Old 10-22-07, 11:56 PM   #7
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To go from 27" to 700c you'll need to be able to move your brake pads down 4mm. By down, I mean towards the hub.
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Old 10-23-07, 08:51 AM   #8
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I run Sun Tour friction barcons with a 9 speed casette & haven't had any problems. Best way to find out what your derailleur can handle is to try it, you may be surprised. Everyone told me my setup wouldn't work but it is a smooth shifting delight. Here are some pics of the bike.
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Old 10-23-07, 09:41 AM   #9
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The one question I would have would be the brakes... Does your passage have cantilever? If so, what brakes will you be using to give you the adjustability?

If you move to caliper brakes, that may help, but I don't know.

On my Voyageur, I am not setting up for loaded touring, but for fun rides, and I am building a 36 spoke rear wheel on a modern hub (for better axle support) on a 27" rim. I don't know if anyone is making 40 hole 27" rims still, but if you can find a 40 hole rim and hub, you can get the added strength of a freehub and retain the 40 spoke without the need to change brakes...

I agree that a new rear derailleur may not be necessary, it would be something you could experiment with by putting any existing 8 or 9 speed wheel on the bike and playing with the limit screws...

EDIT: By the way, to put a 7 speed cassette on a 10 speed freehub requires the use of a 4.5 mm spacer... So the only difference between 7 speed and 10 speed seems to be 4.5 mm... The spacing between cogs gets narrower. Also, 9 and 10 speed systems specify a narrower chain, but I have heard these narrower chains work ok with older RDs.
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Old 10-23-07, 09:48 AM   #10
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Originally Posted by JBMCsr1 View Post
I have a mid 80's Schwinn Passage touring bike with 27 inch wheels. Everything is mostly stock. I'm thinking about updating the wheels to 700c and a rear cassette to have stronger wheels for loaded touring. I took the bike by my LBS and was told that I would need new brakes that adjust up and down and that I need a new shifters and a rear derailleur because they thought my friction Suntour bar-cons and stock Sach-Huret derailleur would only handle up to 7 speeds. Is that all correct? I could see the need for the brakes but how about the shifters and rear derailleur?

Do you have any other advice for me?

Thanks, Jason
I put 700c wheels on my 83 trek 600 w/o any problems
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Old 10-23-07, 09:56 AM   #11
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A couple of quick thoughts.

(1) As already mentioned, 700c is only 8mm smaller on the diameter; which corresponds to 4mm smaller on the radius, which is the amount by which the brake pads must be moved closer to the hub center.

(2) The quality of the build is far more important than the minor difference in diameter. A 36 or 40 hole hub, quality butted spokes, properly tensioned and tension balanced, and a decent rim are going to make for a long lived touring wheel. Noodle around over on Peter Whites site for some more ideas from someone with experience in this matter.

(3) Modern 7speed freewheels are perfectly acceptable, and a good way to freshen up an older wheelset, if you don't have to have 8, 9, or 10 gears out back. For my commuter bike, I put a IRD 13-28, 7 speed freewheel on an older, but primo Campy hub, and it is smooooooth, like butta. I'm running in friction mode, with some modern Shimano bar cons, and don't feel I'm missing much over indexed, which I have on some of my other rigs.

(4) I wouldn't be surprised if the Suntour bar-cons worked just fine with a modern 9 speed rear end, if you don't mind friction. For touring, it really shouldn't matter much. In fact, it is one less thin to worry about and adjust, and you can always get a silent driveline with a little trimming. Don't know about the derailleur, but it wouldn't be a big deal to try it.

(5) Find a bud with a modern wheel to stuff in there and try. Maybe, if you caught your LBS when they weren't too busy, they could be persuaded to do this for you. Perhaps try a friendlier shop?

(6) Don't know about the XT hub in particullar, but is there a chance it could be respaced to 130mm? Sometimes it is just a matter of taking a spacer out, or swapping for a smaller spacer. You must do this symmetrically, and you would need to shave the axle length by 5mm. Sounds better than trying to cold set your frame to 135mm. A 130mm hub will pop right in a 126mm rear end with only a moderate amount of persuasion.
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Old 10-23-07, 07:07 PM   #12
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Unless you are really determined to spend at least a few hundred bucks for a totally new wheelset, and cassette, and spacing the rear end, and a new 9 speed derailleur, and 9-speed chain, and new shifters, I would simply stay with the wheels you have. You can always buy a smooth operating newer Deore or XT rear derailleur for very little.

You can easily find a 7 speed Shimano "mega-Range" freewheel with a 34t large cog at you local bike shop for around $30. These have modern cog profiling just like new cassettes so shifting through the cogs is a breeze even in friction mode. You will simply not have a couple additional gears which a 9-speed would offer - these would be basically ultra-high gears from an 11 and/or 12 tooth cog usually included on a modern wide range MTB cassette and perhaps an additional middle gear or two.

Get some new heavy duty good quality tires from Continental or Specialized (still available in 27") and you should have no worries about even crossing the country on your bike. If I recall correctly, your bike already has a 40 spoke rear wheel. Building up a wheel for a wider cassette would require greater wheel dish for the spokes and this is inherently a weaker wheel construction.

Personally, I'd keep the old wheelset and spend more money on other components which may actually make a significant difference: New GOOD tires, new rear derailleur to easily handle even a huge gear range, new good quality chain, and a new freewheel, and of course new pads for the cantilever brakes.

Since you have plenty of time, keep an eye open for off-season sales. Just this week, with a 10% off coupon from Nashbar, I bought a long cage Deore rear derailleur for $14.39 and 7-speed indexed or friction Shimano shifters including new cables for $7.19. The shifters are for down tube braze-ons, but I'll mount them on Barcon "Pods".

But... your call!
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Old 10-23-07, 08:11 PM   #13
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Thanks for all the replies to my question! I will probably keep weighting my options all winter long and trying this and trying that. And just like and use what I have too.

Stronglight, you have some beautiful bikes!
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Old 10-24-07, 08:43 AM   #14
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I'm with Stronglight on this one. New tires, brakepads and possibly a mega range freewheel with derailleur will give you a lot of bang for the buck and leave you with strong wheels. For loaded touring you may need even lower gears which means a triple chainwheel. You may be able to keep the same front derailleur for that.
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Old 10-24-07, 10:14 AM   #15
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One reason I'm contemplating going to 700c on the last of our 27" bikes is tire selection.

There seems to be less and less available for 27".
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Old 10-24-07, 01:43 PM   #16
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(4) I wouldn't be surprised if the Suntour bar-cons worked just fine with a modern 9 speed rear end, if you don't mind friction. For touring, it really shouldn't matter much. In fact, it is one less thin to worry about and adjust, and you can always get a silent driveline with a little trimming. Don't know about the derailleur, but it wouldn't be a big deal to try it.

I use Suntour barcons with a 9-speed rear (135mm XT no less) and everything works ok. It doesn't have quite the travel to shift smartly onto the biggest cog. It will shift correctly seven times out of ten but occasionally I'll have to stop, get off the bike and manually give it that extra nudge to get it onto the big cog. Luckily I rarely need that low a gear.
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