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Old 05-04-10, 06:05 PM   #1
Saposcat
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Crankset upgrade

Hello,

I have a 1991 Cannondale road bike with a 53/42 Biopace crankset and 6 speeds on the rear wheel. The crank arms are 170mm. I would like to change the crankset to either a 53/39 or a triple with 172.5mm crank arms. I am not sure what kind of crankset would be compatible. I would appreciate any advice.
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Old 05-04-10, 06:36 PM   #2
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Should be able to put pretty much anything on there as long as you change out the BB to one compatible with the new crankset.
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Old 05-05-10, 04:04 AM   #3
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Thank you.
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Old 05-05-10, 05:09 AM   #4
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To go from 53/42 to 53/39 you shouldn't have to change the crankset -- just the smaller chainring.

If you want a wider range of gears but still like a double, you might try a compact crankset -- they *may require a different front derailleur for you though, because the difference in teeth on the two chainrings is larger on a compact.

You can basically do whatever you want, you'll just need to match the bb spindle length like CAcycling said above.
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Old 05-05-10, 09:29 AM   #5
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Thank you. Someone at a bike shop had told me I couldn't just change the lower chain ring because of it being biopace, but it seems like that would be easier to do. I also wanted the longer cranks.

Is this a relatively easy change that I could do myself? I have very little experience working on bikes, but would like to keep the price down as much as possible. Or is this something I'm likely to make an attempt and end up needing to take it to a mechanic anyway?

Thanks again. I appreciate the input.
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Old 05-05-10, 09:35 AM   #6
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Easy to do if you have the right tools. Different BB require different tools, as do the cranks.
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Old 05-05-10, 11:38 AM   #7
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Chainring replacement can be done with a 5mm allen wrench and a chainring bolt spanner. A pedal wrench to remove the pedal will make the job a little easier.

You should be able to remove both rings without needing to take the crank off the bike. Taking the crank off the bike (with the necessary tools) makes it a little easier, and you can clean and inspect it at the same time. but it's not necessary. If its a Shimano road double with biopace rings the bolt pattern is 5 arm 130. Alloy round rings are cheap-ish and abundant.

Most road front derailleurs should be able to deal with a 53/39 instead of a 52/42 configuration. Biopace vs round rings should not have a huge affect on shifting either.

Going from a 42 to a 39 may not give you the super low gearing you ideally want. A triple or compact double crank will give you much lower gear ranges. A compact double (110 bolt pattern and usually a 48t big, 34t inner ring) may allow you to use the same BB (depending on which brand/model/year crank you use), front derailleur and rear derailleur. A triple would require you to change out both derailleurs, BB, chain, and possibly left side shifter.
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Old 05-05-10, 04:41 PM   #8
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Thanks-that's food for thought.
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Old 05-05-10, 05:25 PM   #9
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Replacing the chainrings, however, will not get you the longer crank arms you included on your original question.
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Old 05-05-10, 06:28 PM   #10
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There's a very nice Sugino, the XD 500, triple that may well fit your bottom bracket. (it requires 110 or 107 mm spindle legnth, depending on the frame.) It's about 120 bucks.
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Old 05-05-10, 07:32 PM   #11
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Re- crankarm length. Well, that's that little detail...

If you are going triple, you will fit 175 crank arms much more available. Compact double has a decent enough range of options to choose either 172.5 or 175mm.

And we haven;t even mentioned the modern 2pc cranks with integrated external bottom brackets!
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Old 05-06-10, 07:28 AM   #12
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So if I wanted to keep the cost around $100 or less, what would give me the most bang for the buck in terms of making climbing a little easier? Would the 39 tooth lower chainring make a notable difference? From what I've read so far, the compact double sounds like it might be the best bet-it seems like theoretically I could make that switch without a lot of other modifications and get a more noticeable effect on climbing than just switching to the 39t lower chainring, although just switching the ring and the cranks seems like the easiest and cheapest option. Any opinions on that?
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Old 05-06-10, 07:59 AM   #13
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a 130 bolt pattern crank does not allow a ring any smaller than a 39t. If oyu want lower, then a switch to a compact double is necessary.

A notable difference is going to be up to you. Swapping out the chainring is pretty easy and cheap.You may be lucky and find a really cheap inner chainnring at the LBS or a swap meet. If it's still not low enough, 110 compact double cranks can be had for ~$100 in varuouys condition at the LBS, online, CL and eBay. Remember though, replacing the crank is going to need some specific tools if you do it yourself, and that's going to be $20-25 for a decent crankarm remover. I would not recommend trying to smack it off with a hammer and screwdriver. .....
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Old 05-06-10, 08:13 AM   #14
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Cheapest would be a compact double, and a new free wheel with a lower (higher tooth count) high gear. And a new chain.
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Old 05-06-10, 09:22 AM   #15
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Would the 39 tooth lower chainring make a notable difference?
About 7 or 8%, not even as much as a single shift of your RD. Going to a compact with a 34T will be closer to a 25% change.
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Old 05-06-10, 10:40 AM   #16
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Thanks-that's very helpful. I'm going to start doing some pricing. I appreciate all the input.
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Old 05-07-10, 10:36 AM   #17
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So if I wanted to keep the cost around $100 or less, what would give me the most bang for the buck in terms of making climbing a little easier? Would the 39 tooth lower chainring make a notable difference?
What's on the back? Replacing the cassette may be the best solution.

Replacing the small chainring is also an option. There is a regular market in Biopace 'rings. Check eBay. But as mentioned above, that may not give you what you need. (If you take the crank off, be sure to sell it rather than ditch it; there are people out there that want it.)
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Old 05-07-10, 01:00 PM   #18
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It has a 6 speed rear cassette. I was under the impression that the bike wouldn't accomodate a larger rear cassette, but I may have misunderstood what he was telling me.
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Old 05-07-10, 01:31 PM   #19
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As I read up on it a bit, I think he may have been talking about the indexing not being compatible with more than 6 speeds, so I guess I would have to change that out if I want to change the # of gears in the back.
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Old 05-07-10, 01:45 PM   #20
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As I read up on it a bit, I think he may have been talking about the indexing not being compatible with more than 6 speeds, so I guess I would have to change that out if I want to change the # of gears in the back.
With six speeds, you're likely to have a freewheel, not a cassette. You can easily put a seven speed on the wheel. What kind shifters do you have? If you have something that does friction, you can just flip them into friction, and shift anything. (there's nothing wrong with friction shifting, for seven speeds. You can get used to it in half an hour.)
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Old 05-07-10, 02:29 PM   #21
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It has Shimano index shifters on the diagonal bar.
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Old 05-08-10, 06:58 AM   #22
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Cheapest would be a compact double.
Years ago I converted my Klein road bike to a compact double. It gave me a couple of easier hill climb gears that I needed and gave up maybe 1 high gear that I never used.

I bought a crankset that matched my existing bottom bracket, retained my existing cassette, and the existing front derailleur worked just fine so the only thing that I had to buy was the crankset. The conversion process took me roughly an hour which included resizing the chain and reprogramming the Flight Deck computer. All-in-all it was one of the most satisfying equipment changes that I've ever made on a bicycle.
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Old 05-09-10, 12:16 PM   #23
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I definitely like the idea of replacing the freewheel-what tools do I need to change that?
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Old 05-09-10, 12:28 PM   #24
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Also, doing a search I see that they have 6 speed freewheels that go up to 28 teeth-I just counted and my current one goes up to 24t-would it make sense just keep it 6 speed but go up to the 28t?
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Old 05-10-10, 05:51 PM   #25
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Yes. The 4 tooth difference would make the big gear 4/24 or 17% easier to pedal. That may be enough. Remember, you're also getting stronger as you ride.
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