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Have looked at all kinds of guides for sub 155 mm cranks and can’t find anything that’s both better and fits boost.
Vpace look good but only come in boost 155 and over. With a Raceface n/w on these cranks weight penalty is about 70 grams compared to the Vpace 155 mm.
Although - would these fit the current BB: https://www.vpace.de/en/vpace-children-s-crankset-incl.-chainring
We could probably live w/ 3 mm to avoid changing bottom brackets :)Also had my eye on Kids who race (or something website) but I think Brexit has made those a little uncertain when it comes to budget.
Larmen-
Didn't realise you needed short ones, hope make 155 now if you want some bling. Otherwise, ignore the shell width apart from buying the correct one it doesn't affect anything else, you essentially want to move the chainline out to meet the now further out middle of the cassette if that's what you deem the most important match up, so 3mm outwards so your 110 would be 116 as it's 3mm each side. I'd be tempted to consider whether you want to go outwards unless needed though, if it's a kids bike you probably want to keep the Qfactor down as well as the crank length and they're likely not going to be smashing it around in the highest gears so an inboard chainline shouldn't lead to excess wear. I'd fit the drive side current BB and crank and check clearance with the chainstay and assuming the frame is symmetrical and if you've got 2.5mm for the shell difference (it would affect this as it's in the wrong shell) plus some room, go with the same length BB.
snottyotter
Just buy better cranks innit.