If you think you need more than 24H rear, you might as well go all the way to 32. 28 is a weird no man's land which might have been a viable minimum in the 70s when rims were soft aluminium about 15mm deep, but now it offers practically no performance advantage over 32 and just cuts your hub options in half.
If you think you need more than 24H rear, you might as well go all the way to 32. 28 is a weird no man's land which might have been a viable minimum in the 70s when rims were soft aluminium about 15mm deep, but now it offers practically no performance advantage over 32 and just cuts your hub options in half.