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Cool. Well, I now have 3 sets of cranks for the Surly and a couple of BB and chainring options. :)
It says it wants BB-MT801 but is the 501 the same thing just cheaper or do I need a different BB too.
EDIT: Just looked and I did buy a 73mm MTB BB for the GRX cranks. Maybe I bought them at different times and just wasn't thinking straight at the crank purchase time.
I presume there's a way I can work out what my chainring size limit will be? ie. approx how wide will the chainring sit + diameter of 38T ring or whatever?
hippy-
Both 801 and 501 will fit, 801 will need the plastic TL FC25 tool which will fit any regular HTII BB tool, basically a step down washer.
Surly says Chainring Clearance 24/36/48t so you should be able to clear quite a bit more than 36T.
Nothing beats actually trying one on though.
What's currently on there?
Photo of full biek?
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I presume there's a way I can work out
Yes, it's called maths. The pitch circle radius of a roller chain sprocket is very close to Pitch×Z/2π, then add 4mm to get the top of the teeth
(12.7×38/2π) +4=80.8mm, so your stays need to be 2×(chainline-4mm*) apart at a point 81mm from the BB centre*half the ring thickness + clearance for flex
coventry_eagle
gbj_tester
Yup, yes they would.
There are other funny variations of it, do not go for anything XX20 which is the ones for 148 rear.