Is this very difficult? Does it involve packing bearings? How do determine what size crank will fit your bike?
Installing a new crankset onto an existing bottom bracket is simple. You don't have to open up the bearings. You do need a crank puller to remove the old cranks if they are still on there.
Unless you're doing something weird like putting a mtn crank on a road bike, etc. pretty much any crank will fit on any bike. The tougher question is will it fit on the bottom bracket you have. Is the BB square taper, octalink, etc.? Also, the length of the spindle (axle) of the BB is usually determined by the crank. So you're new crank may need a different length than your old one.
I'd say either post more specifics about what you have and what you want to switch to. Or visit a bike shop for advice.
Dave said: "pretty much any crank will fit on any bike."
regret to say this is not so, unless you are replacing the same make and model with ditto, because of differences in design between makers, you can find that the chain line can be completely different and may even take it beyond the range of adjustment of the front changer.
This applies particularly at the bottom end of the market.
Advise you consult your LBS and buy from them, not on-line.
Quote:This applies particularly at the bottom end of the market.
It happens in the mid and high end markets as well. I recently replaced an FSA Omega triple crankset with a Shimano Tiagra triple and had to change the BB because the BB cups on the FSA were shorter in height than the Shimano causing the crank spindle to become too long. I ended up having to replace the BB as well.
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