Can I increase the size of chain ring on my 2021 Whyte V3 Portobello ?

LateJunction

Currently my V3 Portobello bike is fitted with an 11-42T cassette and an un-identified factory spec 1x 42T, 4-bolt 110 BCD chain ring. I would like to increase this to 44T. Shimano info for the derailleur (RD-M4120-SGS) suggests a maximum capacity of 41T with a maximum front difference of 10T. Since this is a 1x drive train the front difference is always 0T so it shouldn’t matter what size front chain ring I am running (aside from implications of chain length) – should it ?

whyamihere

Correct, you can run whatever size chainring you want.

LateJunction

After a lot of discussion with Whyte rider support team, it seems that I cannot run ANY other (larger) chain ring than my current 42T one. Reason given is potential fowling on drive side chain stay. I 'borrowed' a used/worn 44T ring from my local bike shop, who is also a Whyte dealer (and advised it wouldn't work, reliably) and, yep, Whyte are correct: the clearance with this used ring on my newish chain was paper thin; there would be interference with a new ring when applying high torque on hill climbing.

The only solution to get more gear inches on this model is to convert to 12 speed cassette with 10T smallest cog. This requires replacement of the derailleur, chain and shifter at the same time. Total cost about £220, which adds no value to a £250 bike, so idea is abandoned

Wheelspinner

See other thread here about chainring offset. You might find some options like the Garbaruk ones mentioned in that thread which have some negative offset in bigger ring sizes to specifically adapt for the clearance issue.

Also, depending on type of BB, can you shift a spacer from non-drive side over to the drive side to effectively move the crank arm a bit further out from the frame?

iIt would make the non-DS move in closer, so check that clears ok still. Also means the cranks are not quite symmetrical about the frame centre line, but if it’s with flat pedals you won’t notice. If you use cleat shoes, just adjust the cleat lateral position on your shoes to accommodate the difference.