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There's a few reasons to upgrade your cranks: You have a crappy bottom bracket bearing set that needs to be replaced/upgraded; you want higher gearing; you want to upgrade crappy cheapo cranks to something better; your square taper cranks keep coming loose: etc.
If you find that your hub-motored bike can go faster than you can pedal, you need a bigger chainwheel, so, if you have to do that, you can upgrade your BB at the same time. This Shimano Hollowtech M590 crank-set includes the BB for £66, so is really good value for money. This one has 48 teeth and is a little more expensive than the others The cheapest is about £50.
Shimano Deore M590 2 piece design chainset, 9-speed 48 / 36 / 26T silver 175 mm | eBay
Fitting takes less than half an hour, but you need a crank extractor and BB tool to get your old ones off. Assembling the new one is very easy. You don't need any special tools if you have a tight enough grip to screw in the bearings, otherwise a simple strap wrench will do it, or you can use the special Shimano tool.
In the photo below, you'll see that I used one spacer behind the bearing holder on the crank side. This is an Oxydrive pedal sensor, but the standard Chinese ones are the same. You have to remove the sensor from its bracket and reassemble it on the other side so that the bracket reaches forward instead of back to clear the bearing holder. The Oxydrive one is sort of back to front compared with the normal ones. The actual sensor pokes through the bracket, and the main body is on the other side. I also ground off the inner flanges from the magnet disc to thin it down a bit and left a slight inner chamfer so that it didn't clamp against the lip of the seal. The magnet disk has to be flipped over so that it goes in the reverse direction when fitting to the left side. I left out the inner spacing tube because the bearing holders are now effectively closer together because the magnet disc takes up space outside the bearings. If all this sounds complicated, look at the photo. It's very straight-forward.
That's it. Now nice smooth relaxed pedalling, no more cranks coming loose, BB bearings falling out, or magnet disk coming loose. Plus, they look a lot nicer, are lighter and stronger than the other types.
If you find that your hub-motored bike can go faster than you can pedal, you need a bigger chainwheel, so, if you have to do that, you can upgrade your BB at the same time. This Shimano Hollowtech M590 crank-set includes the BB for £66, so is really good value for money. This one has 48 teeth and is a little more expensive than the others The cheapest is about £50.
Shimano Deore M590 2 piece design chainset, 9-speed 48 / 36 / 26T silver 175 mm | eBay
Fitting takes less than half an hour, but you need a crank extractor and BB tool to get your old ones off. Assembling the new one is very easy. You don't need any special tools if you have a tight enough grip to screw in the bearings, otherwise a simple strap wrench will do it, or you can use the special Shimano tool.
In the photo below, you'll see that I used one spacer behind the bearing holder on the crank side. This is an Oxydrive pedal sensor, but the standard Chinese ones are the same. You have to remove the sensor from its bracket and reassemble it on the other side so that the bracket reaches forward instead of back to clear the bearing holder. The Oxydrive one is sort of back to front compared with the normal ones. The actual sensor pokes through the bracket, and the main body is on the other side. I also ground off the inner flanges from the magnet disc to thin it down a bit and left a slight inner chamfer so that it didn't clamp against the lip of the seal. The magnet disk has to be flipped over so that it goes in the reverse direction when fitting to the left side. I left out the inner spacing tube because the bearing holders are now effectively closer together because the magnet disc takes up space outside the bearings. If all this sounds complicated, look at the photo. It's very straight-forward.
That's it. Now nice smooth relaxed pedalling, no more cranks coming loose, BB bearings falling out, or magnet disk coming loose. Plus, they look a lot nicer, are lighter and stronger than the other types.
