Finding a replacement crankset (and maybe a bb to go with)

Question

I am in need of replacing my crankset on my hybrid discovery 401 - although all that is left of the 401 now is the frame and the bb/crankset. it has a sealed bb 113/68 square taper. I am struggling to find a triple crankset on the web that would suit, as all of them seem to be hollowtech or some other bb type.

What I am unable to work out is if any of these whizzy new types are going to fit my frame.. or what I need to check to know. I have removed the existing bb hence knowing it's measurements. it is threaded only at one end, and all the pictures on the wiggle or wherever for different types of bb seem to have threads on both ends. I use the bike to cycle to work each day, about 20 miles round trip, it is a 24 speed bike currently, and i have some fairly nice shifters and thus need s 3 sprocket crankset. I also take one of the little ones in a hamax seat, or both of them in a trailer thingy.

Can anyone offer some assistance? An square taper bb seems to be about £10 so not a bank breaker, the newer hollowtech or whatever are a little more expensive and don't necessarily want to change it all up, but finding a crankset that is square taper, and for a hybrid rather than a mtb is a nightmare. along with not really being sure on what teething to go for..

any recommendations or links happily received

Thanks

Nat

Answer 1

This is one I prepared earlier, the question is slightly different than the original Can I replace chainrings without replacing the rest of the drive train? but the answer suits. You have the same considerations for a selecting a new chainset as this question.

Chain line

When selecting a new crank set you need to ensure it aligns with the current chainline of your bike. If you change the chain line you may not be able to use all of the gears on your rear cassette in all gears up front.

Bottom bracket

You need to ensure that a new crankset will be compatible with your current BB spindle length and interface. (square, octo, isis, hollowtech etc.) If your BB has a lot of wear once you have the cranks off its not a bad idea to change the BB at the same time as they're not that big a cost. Also it's sometimes if you get a good deal on a crankset to get a matching BB as they're the cheaper item.

Chain length

You may need to shorten the chain going to smaller rings if the derailleur doesn't provide enough tension.

Rear derailleur capacity

Not a problem when shifting to a smaller crankset but if going larger you would need to ensure that the rear derailleur would handle the additional cogs. There are tools online to help calculate this.

Wear

If the chain and rear cassette are showing signs of wear it's often wise to replace these at the same time as they will wear a new crankset faster.

Chain width

If you are buying a new crankset it has to be appropriate for the number of gears on your bike, this is because chains are different widths to accommodate more gears on the rear cassette. The rest of the drive train is sized to fit the chain width.

Answer 2

A square taper crank set with triple chain rings is a straight forward search item in google, or the local bike shop. If you are aiming for a pure drop in replacement, make sure you get the same tooth count on the chain rings, and the crank arms are the same length.

You mentioned the BB is only threaded on one end. I suspect this means you still have the 'fixed cup' in the frame, and probably have a cartridge BB. Its probably worth the extra money to replace that at the same time as the cranks since its a relatively small portion (guessing, 15-20%) of the overall cost.