If I was running the GSM on a 26" bike I think I would have 46-32 on the front and an 8 speed 11-34 on the back. Looking to the future of the 28" I would just change the cassette for the same 8 speed and keep the front as it is or maybe go for just a narrow/wide 42.
Having the spider opens up all the options.
As the industry is already at 11 speed they are not making the higher quality cassettes for the 8 speed any more so there is less choice both quality wise and ratio wise year after year on the 8 speed. Also think about in the future if you go to a cassette body if it all aluminium engagement. Will the TQ of the electric motor dig the cassette into the alu hub body never to be removed!!
I have american classic wheel which have a steel insert in the hub body to stop the cassette digging in. 9/10 speed
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