Chainwheel sorting, Where to start?

[Andy in Germany]

I'm trying to organise the chainwheels which are infesting our storeroom and I think it would help to classify them.

Our biggest compatibility issues are the size of the wheel and the distance between the edge of the square hole and the back of the smallest gear.

The chainwheel size is obvious and easily determined. I haven't been able to find if there's any kind of standard for the other measurement, mainly because I don't know what that would be called. Does it have a name and any standard? If not how can we check which part is compatible with which BB Axles, and how exact does this need to be?

 

[Ian H]

Are you talking about chainrings on their own or cranksets complete?

 

[Andy in Germany]

Are you talking about chainrings on their own or cranksets complete?

Oh dear, too long overseas*, I meant crank sets.

*That's my excuse anyway.

 

[Ian H]

I imagine they are mostly square taper, but firstly file by bottom-bracket type. Then crank length; then number of teeth on chainring(s).

 

[richardfm]

distance between the edge of the square hole and the back of the smallest gear.

I wouldn't worry too much about that. You will get variations in bottom bracket axle length and frame geometry. Get all three right and almost anything will work (possible exaggeration)

Have a look at https://sheldonbrown.com/chainline.html

 

[Ajax Bay]

As Ian says.
Chainset taxonomy: I love it!
You ask about standards and leaving BB types aside, dealing with chainsets:
Crank length (centre to centre in mm, but very often marked on inside of crank)
Teeth number combo / number of chainrings
and for those with chainring bolts, BCD (a sophistication too far, given likely storeroom population which I expect will mostly be riveted triples).
You allude to the (ST) length of spindle each chainset might require. This is effectively impossible to determine even with searching each model of chainset individually (if identification possible) and hoping reliable data are available.

 

[presta]

Our biggest compatibility issues are the size of the wheel and the distance between the edge of the square hole and the back of the smallest gear.

The dimension of interest is the chainline, which is the lateral distance from the centre of the frame to the centre of the chainset (defined as halfway between the large and small rings, which is not necessarily the centre of the middle ring). This determines which derailleurs it will work with so that you don't run out of adjustment range.

The chainline is adjusted by picking the correct BB length, but the problem is that it's not standardised, so that two different chainsets may produce different chainlines even if mounted on the same BB. If you can't look up the chainset manufacturer's specification, you can only measure it by putting it on a BB and torquing it down.

 

[Cycleops]

You might sort them firstly by:

Road cranksets
Mountain cranksets
Cottered

Marking each by crank length.

Then by chainring type:

Single
Double
Triple

Maybe you could a smaller category for 'oddballs', such as pressfit Hollowtech and Octalink.

 

[C R]

Maybe you could a smaller category for 'oddballs', such as pressfit Hollowtech and Octalink.

That would be bottom bracket for Hollowtech, the chainset is the same regardless of how the BB attaches to the frame.

 

[DaveReading]

The dimension of interest is the chainline, which is the lateral distance from the centre of the frame to the centre of the chainset (defined as halfway between the large and small rings, which is not necessarily the centre of the middle ring).

If it isn't, does it cause shifting issues ?

 

[presta]

If it isn't, does it cause shifting issues ?

If it's a long way off it will exaggerate any rough running when it's increasing chain misalignment in a gear where the chain's already a long way out of line. Other than that, the front mech may run out of adjustment range if the chainline is too far from what it was designed for.

 

[Ajax Bay]

No it does not. @presta is dealing in less than a mm possible differentials here. If the three rings of a triple are equally spaced then clearly the middle ring is is the 'centre' from which to measure.

If Andy's (OP) primary consideration is that, then sort all these (ST) chainsets by that dimension, by "measur[ing] it by putting it on a BB and torquing it [up]" one at a time, and then by the other categorisations.

 

[richardfm]

That would be bottom bracket for Hollowtech, the chainset is the same regardless of how the BB attaches to the frame.

Pretty sure the chain set from my bike with a square taper BB wouldn't swap with the one on my bike with a Hollowtech BB

 

[C R]

Pretty sure the chain set from my bike with a square taper BB wouldn't swap with the one on my bike with a Hollowtech BB

I meant that hollowtech chainset works the same whether the hollowtech bb is push fit or threaded.

 

[Ming the Merciless]

If it isn't, does it cause shifting issues ?

Only if any of the chain rings sit outside the range of your front derailleur. For instance on a triple you may not be able to shift to big ring, if chain line is too far out than recommended. If the chain line is too far in, compared to recommended, then you may not be able to shift to the granny ring. Front derailleurs generally say what chain line they are designed for , in their instructions, but a few mm either way is usually fine provided inner ring is not too close to chain stays.