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Swapping cranks from another bike
#1
Hello, Great website and tutorials!
I like to swap my chainrings which is a 42/34/24T to a 48/38/28T to help increase the cruising gearing. Coupla questions...
- is it worth swapping?
- if so, anything I need to watch out for?
- Since it is an increase of additional 6 teeth, I like to also swap the chains two.
- Any other tips would be appreciated!

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#2
BTW, the cranks of the two bikes are of the same brand. See here
From XCC-150
http://www.srsuntour-cycling.com/SID=si7aa62e0a741b47bceb194ae3ce9bd4/index.php?screen=sh.detail&tnid=207
to XCC-100
http://www.srsuntour-cycling.com/SID=si7aa62e0a741b47bceb194ae3ce9bd4/index.php?screen=sh.detail&tnid=208
Apart from the chainring sizes, they look the same. It will be a swap of the entire chainring set.

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#3
Two points:
- you might want to change the front derailleur too, the new ones (from the 90's on) are specified for a certain maximum chainring size and work best with that. Look up the specs on the manufacturer's page. You might be OK, though.
- some crank sets are for certain front derailleur types and bottom brackets... my coworker ran into that problem. They have different chainlines (see http://sheldonbrown.com/chainline.html) and he bought the wrong crank set / bottom bracket combination. I could not find any information on that on page you linked, so they should be the same.
Well, just give it a shot!
Oh, and btw. you should not fix the cranks to the bottom bracket axle dry. They will get stuck and be difficult to remove. Also grease the pedal axles before you screw them into the cranks!
Last remark: when you replace the chain, you should also replace the cassette (rear cogs).
I cannot comment on how much the 'hassle' might be worth, for me it would be about 30 minutes of work (maximum, well depends on how stuck your pedals / cranks are), so I would do it. Consider: do you ride the bike often? Do you want higher gears?

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#4
Looking at the spec' sheets there shouldn't be any problem and it should be a straight swap. The bottom bracket is the same.
You will have to lift the front derailleur a fraction and adjust the shift cable to suit.
Also possibly add a couple of links to the chain length.
If you change chains frequently then the rear cassette may or may-not need changing when fitting a new chain.
Make sure you get the same length crank arms unless you want to go different to your existing ones?

[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#5
Thanks for the replies! The crank arms measure 170mm each! what a surprise considering the other bike is a bit smaller in frame size than mine.
I plan to keep the current cassette. I don't see the need to swap the rear cogs as well. Why do I need to change the rear cassette when fitting in a new chain?
In terms of greasing the BB and pedal axles, can I use motor oil? I don't have anything else handy at the moment.

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#6
When the chain gets worn out, it "stretches" (though this is the wrong term, see links below why). The pins and the side plates form a joint, sort of like a hinge. During use, the pin and the side plates get worn and the chain gets longer. The distance from link to link increases and the links do not fit on the cogs. So the cogs get worn, too. When you put a new chain on an old cassette, it will wear out much faster, than if you had started with a new cassette, too.
See also :
http://bicycletutor.com/chain-wear/
and
http://sheldonbrown.com/chains.html
As for the grease: drop by at a (car) repair shop, I got a film can of grease from our mechanics workshop at the university. Motor oil is too thin, I fear.

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#7
Will this work as a grease for the bike?
http://www.canadiantire.ca/AST/browse/4/Auto/AutoTools/GreaseGunsOilPans/PRDOVR~0280853P/Marine%2B%2526%2BTrailer%2BGrease.jsp

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#8
Should be fine.

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