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Old 08-19-06, 11:37 AM   #1
rp macpherson
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Crankset questions

I bought a 1983 Roberts touring bike that I am still in the process of upgrading for my first loaded tour this fall. I posted about it once before but I cant find the old thread. The bike is a little quirky and my approach to it has been a constant struggle between maintaining the original character of the bike and making it a practical machine. Since the rear dropout spacing is unconventional (126 mm i believe) i was initally torn between cold-setting the frame to accomodate a new wheelset or having the wheels rebuilt, replacing the tubular Mavic GP4 rims with clinchers, and maintaining the 6-speed freewheel. After much debate, I decided that the 32-13 freewheel was wide enough and I had the original wheels rebuilt with Mavic a719s.

So now, having decided to keep the freewheel, my focus is shifting to the original crankset. It is a double-chainring half-step (40-36) Sugino that leaves me in the dust when I ride with my roadie friends and I imagine would slaughter my legs on steep climbs when loaded. I eventually want to replace the crankset with a touring triple but I am wondering about compatibility. If I get a triple, will I have to get a new front derailer as well? What about the rear derailer? I'm trying to get this done as cheaply and efficiently as possible, but this project has proven to be a lot more work and money than I'd anticipated. Will replacing the crankset be another expensive upgrade? Any answers and advice would be much appreciated.
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Old 08-20-06, 03:49 PM   #2
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Quote:
Originally Posted by rp macpherson
I bought a 1983 Roberts touring bike that I am still in the process of upgrading for my first loaded tour this fall. I posted about it once before but I cant find the old thread. The bike is a little quirky and my approach to it has been a constant struggle between maintaining the original character of the bike and making it a practical machine. Since the rear dropout spacing is unconventional (126 mm i believe) i was initally torn between cold-setting the frame to accomodate a new wheelset or having the wheels rebuilt, replacing the tubular Mavic GP4 rims with clinchers, and maintaining the 6-speed freewheel. After much debate, I decided that the 32-13 freewheel was wide enough and I had the original wheels rebuilt with Mavic a719s.

So now, having decided to keep the freewheel, my focus is shifting to the original crankset. It is a double-chainring half-step (40-36) Sugino that leaves me in the dust when I ride with my roadie friends and I imagine would slaughter my legs on steep climbs when loaded. I eventually want to replace the crankset with a touring triple but I am wondering about compatibility. If I get a triple, will I have to get a new front derailer as well? What about the rear derailer? I'm trying to get this done as cheaply and efficiently as possible, but this project has proven to be a lot more work and money than I'd anticipated. Will replacing the crankset be another expensive upgrade? Any answers and advice would be much appreciated.
You can find inexpensive cranks all over the place. Bikeman has an Impel for $25 but it will probably have steel rings that would be difficult to find. Nashbar sells some for cheap and you can always go with a Shimano Tiagra or 105 which will probably be a 52/40/30. The 30 tooth cog can be replaced with something lower if you need it like a 28 or even a 24. Since you probably have an old bottom bracket you may need to replace it. I'd say, depending on the quality and whether or not you can find a deal, you are looking at $80 to $120 if you stay cheap. If you want better stuff...well the sky's the limit
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Old 08-21-06, 10:32 AM   #3
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Thanks for the tips. As for the bottom bracket, it is a Phil Wood that, according to my LBS mechanic, is still in great shape so I don't think it will need to be replaced. If i do get a new triple crankset, though, will my old front derailleur need to be replaced or can it perhaps be adjusted to shift through three sprockets instead of the two i currently have? Thanks.
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Old 08-21-06, 11:20 AM   #4
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the sugino xd 500 is currently the best cheap touring crank out there, and it comes stock 46 36 26. i would make it 48 36 26... its about 100 bucks. the impel i think is four bolt, so crappy ring options.
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Old 08-21-06, 12:07 PM   #5
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I believe that you need a new front derailer. But front derailers are not expensive.
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Old 08-21-06, 01:04 PM   #6
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Okay... one last question for you all. A lot of the cranksets I've come across, especially on eBay, specify that they are for 8,9, or 10 speeds. Since I have a 6 spd freewheel with room for no more than maybe one more sprocket, will there be compatibility issues if I buy a new crankset? Should I look for a vintage one made for a 6 or 7 speed freewheel?
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Old 08-21-06, 01:34 PM   #7
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no, get a sugino, it will work perfectly. 10 speed cranks cranks are a bit flimsy in the tooth wear dept but sugino cranks are made for 6,7 or 8 speeds...
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Old 08-21-06, 01:41 PM   #8
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You'll need a new front derailleur, which has the capacuity to shift across all three rings. And, regardless of its condition, you'll need a new bottom bracket that has a longer spindle, so that your cranks are in line with the cogs, and to keep your feet and knees in the right place. I ride a Sugino XD600 crank with 26-36-48 cranks and an XTR rear cassette that's 12-34. It's a great setup.
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Old 08-21-06, 05:14 PM   #9
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Before buying a new bottom bracket, try your new crankset with the one you have first.

Also if you want to try your current BB, be careful that when you buy a new crankset, you get one that fits square taper bottom brackets and not the newer splined BBs. If you get the Suginos everyone is recommending, then you'll be fine.
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Old 08-21-06, 05:27 PM   #10
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Quote:
Originally Posted by halfspeed
Before buying a new bottom bracket, try your new crankset with the one you have first.

Also if you want to try your current BB, be careful that when you buy a new crankset, you get one that fits square taper bottom brackets and not the newer splined BBs. If you get the Suginos everyone is recommending, then you'll be fine.
The reason I was suggesting that he might need a new bottom bracket is because of length. He might be able to get away with the old bracket (Do as halfspeed says and try it first) but my first guess is that it's going to be too long for the new narrower cranksets.

As for the front derailer, unless you are going with a indexed system, RP, you should be okay. You'll have to adjust the limiting screws but old derailers had excess travel in most cases. If you do have to replace it, they are cheap.
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Old 08-21-06, 06:12 PM   #11
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If I recall correctly, you are in DC. The guys at the Bicycle Pro Shop on M Street are considered some of the best mechanics in the area. All of them are "old-timers" that can help you out with this great bike.
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Old 08-21-06, 07:06 PM   #12
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Originally Posted by cyccommute
The reason I was suggesting that he might need a new bottom bracket is because of length. He might be able to get away with the old bracket (Do as halfspeed says and try it first) but my first guess is that it's going to be too long for the new narrower cranksets.
Oh, I agree that it might not work, but there's no sense tossing a Phil Wood BB until you're =sure=.
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Old 08-22-06, 05:23 PM   #13
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Originally Posted by halfspeed
Oh, I agree that it might not work, but there's no sense tossing a Phil Wood BB until you're =sure=.
I agree completely. I'm always in favor of trying to make do with what you have before you go looking for new stuff. If the current crank requires a new bottom bracket it might be worth the effort to see if you can get a new axle for the Phil that's the right length.
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New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
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Twisting Down the Alley. Misadventures in tornado alley.
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