Compact chainsets - are they universal?

[swee'pea99]

Looking to replace the 39/53 chainset on my new +1. It's Shimano BB. Will any compact chainset fit (so long as it's not Campagnolo, presumably). Thanks.

 

[Dusty Bin]

Any chainset will fit (compact or otherwise) providing it is compatible with a BSA standard 68mm threaded BB shell and its associated BB axle or BB cups.

 

[swee'pea99]

Thanks, but it's got one of those new-fangled BBs - I should've said. What are they called? External? I'm not sure. The best pic I have is

...don't know if that helps.

 

[Sterba]

Why not just change the rings, if you need different gears, then any Shimano rings will fit. It's an easier swop than changing the whole chainset

 

[swee'pea99]

I believe you can't go below a 39 on a 'standard' chainset - to go to 34, you have to get a compact.

 

[Sterba]

Sorry, my mistake, you are right

 

[Dusty Bin]

Thanks, but it's got one of those new-fangled BBs - I should've said. What are they called? External? I'm not sure.

The answer is still the same. Shimano external BBs still attach into a standard BB shell. Any HT2 Shimano compact chainset will fit straight in anyway, without changing the BB.

 

[swee'pea99]

Thanks Dusty - and to others who responded.

 

[Nigelnaturist]

I believe you can't go below a 39 on a 'standard' chainset - to go to 34, you have to get a compact.

Its 38th, the Bolt Centre Diameter is usually 130mm on a normal double/triple, 110mm on a compact doubles and triples, and usually 74mm on the inner ring (though this can vary, as can the outer)

 

[Mr Bunbury]

That type of BB is a Shimano design called "Hollowtech II". Any compact chainset that is designed for Hollowtech II will fit.

 

[jdtate101]

Yep, all Shimano cranks are 24mm axle so any other 24mm type crank will work just fine. As others have said, standard rings use 130BCD and compacts 110BCD, so you cannot swap rings between the two types. You're probably best off just buying another crankset and selling the 53/39 to offset the costs, or just get stronger and ride with the 53/39. FYI fitting a 28 on the back with a 53/39 gives you the same ratio at the bottom as a 50/34 with a 25 cassette.

 

[J1780]

Yep, all Shimano cranks are 24mm axle so any other 24mm type crank will work just fine. As others have said, standard rings use 130BCD and compacts 110BCD, so you cannot swap rings between the two types. You're probably best off just buying another crankset and selling the 53/39 to offset the costs, or just get stronger and ride with the 53/39. FYI fitting a 28 on the back with a 53/39 gives you the same ratio at the bottom as a 50/34 with a 25 cassette.

that's what I did a few years ago instead of buying a new chain set I fitted a cassette with 28 sprocket