crank size
Mad Roadie
Posts: 710
help please on two new groupset issues:
crank sizing - when i look to order a new pair the size options are 170, 172.5 and 175 - I was told to look at my current cranks which are marked - indeed they are, but 142.5 - so what is this, a measurement to a different point, and what to order new?
and front mech - two size choices 32mm and 35mm - whats the difference, and what should I order with a compact groupset?
BTW: its all Super record
crank sizing - when i look to order a new pair the size options are 170, 172.5 and 175 - I was told to look at my current cranks which are marked - indeed they are, but 142.5 - so what is this, a measurement to a different point, and what to order new?
and front mech - two size choices 32mm and 35mm - whats the difference, and what should I order with a compact groupset?
BTW: its all Super record
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Comments
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You can get cranks of length 142.5mm, they are XX-small and almost impossible to find new. Specilities TA make them down to 155mm.
142.5mm could also be the "Q factor" ie the horizontal spacing between the pedal threads.
Get a ruler and measure your crank length (centre-to-centre)
If you are buying a new groupset, then the Q factor is set by the manufacturer. Some brands are known to be narrower than others. Narrow Q factor is good for aerodynamics.
Front mechs usually clamp onto the seat tube (unless you have a special bolt-on bracket stuck/welded to the tube).
The standard tube diameters are 31.9mm and 34.9mm. You may need to cut out a cardboard measuring jig to determine which you have.0 -
you have super record and you think your cranks are 142mm long... :roll:Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer0
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thanks - measured the cracks, and seen the imprint 172.5mm - 142.5mm is the Q factor. but its a braze-on for sure0
