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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 08-01-08, 07:43 AM   #1
The_Mickstar
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Need new crankset for older road bike, but don't know (specifically) what I need...

I have an early-90s Raleigh Technium Olympian road bike. It is currently outfitted as follows:

Shimano Exage 400EX (Narrow) front derailleur
Shimano Exage 300EX rear derailleur
Shimano Exage 300EX crankset with Biopace 52/40 (for Narrow Chain Only) chainrings
downtube shifters
SRAM PC-58 chain
Shimano Hyperglide "E" 12/28 7-speed cassette
Shimano Ultegra 8/9/10-speed freehub wheel with 4.5mm spacer (to accomodate 7-speed cassette) (frame has 130mm rear spacing)

The only non-stock pieces are the chain and the wheels. It functions just fine, with one exception...

The non-drive side crankarm continually comes loose. It's to the point now that even cranked down fully, the arm still has a little play. As you may have guessed, I think the actual problem is that the taper in the aluminum crankarm is "wallowed out" from riding with it loose. So, long story short, I want to get a new crankset to solve not only this issue but a couple of other things I'm not thrilled with on the bike.

What I would like is 180mm crank arms (I'm 6'2, have long legs and prefer longer crank arms) and standard, round rings.

And, while I'm at it, it probably wouldn't be a bad idea to install a new bottom bracket, since the current one has ~5000 miles on it, and is the stock piece. This may also make things easier, if I could go with something more modern on the cranks by switching the bottom bracket at the same time. (???)

Can you tell me, specifically, what I'd need to pull this off? Can I use a modern 9/10-speed crankset, or is the chainring spacing/width different? What about the bottom bracket? Can I use a modern external bearing design? (Anyone know what bottom bracket this frame takes? English? 68mm?)

Finally, I'm thinking of switching to either 8-speed (new cassette) or 9-speed (new cassette & chain. Would that change the answers to the above?

Thanks.

Steve
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Old 08-01-08, 11:29 AM   #2
Creakyknees
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Just get anything that's English thread, internal (not the new "outboard bearings" bottom bracket). Shimano 105 is a good example.

Your bigger challenge will be to find the 180 cranks.

If you get modern stuff, they'll be compatible with 8/9/10.
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Old 08-02-08, 07:46 AM   #3
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I want to say 68/109 English Thread. Whatever crank you go with...make sure you buy a compatible bb.
ISIS bb with ISIS crank
square tapered with square tapered

To remove, you are going to need a crank puller tool, a pin spanner, and a lockring tool.
To install a newer crank/bb, you will need probably another compatible bb tool to accommodate these newer versions.
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Old 08-02-08, 09:12 AM   #4
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Eaby... shimano 105 squared tapper (180 mms? super hard to find, go with 175 that are easier to find, hope your knees do not complain) Axle? a shimano UN 109 will fit fine.

Good luck
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Old 08-02-08, 12:01 PM   #5
The_Mickstar
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Thanks, guys.

Two final questions...

1. Are any of the systems (square-taper, ISIS, Octalink...) considered "better" or more reliable than the others? (Square-taper obviously isn't idiot proof!)

2. Do you agree with my completely uneducated diagnosis - that the aluminum crank arm is the damaged part [vs the steel (???) BB axle]? The reason I ask is because, to be perfectly honest, the current BB functions just fine (no grinding, etc - even with ~5000 miles on it). I could probably just keep it, if I decide to stick with square-taper.

Steve

Last edited by The_Mickstar; 08-02-08 at 12:04 PM.
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Old 08-02-08, 12:13 PM   #6
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For the crank, since you are using an 8 speed chain, I would stay away from any crank intended for 9/10 speed applications. You may have issues with the chain being too wide (I did trying to use an 8 speed chain with 9 speed Shimano chainrings) unless you change your chain too.

Cranksets differ as to where they bottom out on the bottom bracket so you will want to make sure whichever crankset you buy will either fit your current BB or that you buy a compatible one with it. Usually, when you buy a new crankset, the manufacturer tells you what bottom bracket length is needed.
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