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GRX gearing

Hi all.
I currently run a GRX 800 set up.
42T up front with an 11-42 at the back.
Shimano GRX di2 817 rear mech.
I’m hoping to change the front to a 44T but will have to go to another brand as Shimano don’t manufacture one.
Anyone have any knowledge if this gearing is possible with the 817 rear mech and any advice on a decent chain ring brand Wolf Tooth etc?


  • Mad_MalxMad_Malx Posts: 4,776
    Can't see any reason that changing the front ring would affect the rear mech here, you may need an extra chain link.
  • t_willot_willo Posts: 16
    I’m a bit censored when it comes to the tech stuff. Something about drive train capacity came up on another forum. Any knowledge?
  • Mad_MalxMad_Malx Posts: 4,776
    If you had a 2x on the front then the front difference has to be taken into account , but I'm assuming your 44T front will be a single.

    The rear derailleur takes up the loose chain as you move through the rear cassette.
    Rear derailleurs have limits on how much slack chain they can take up as you move up through the gears to the small cog, mostly determined by the length of the rear deraiilleur cage (the long arms that separate the two jockey wheels). If you are running a single at the front you need a capacity of 42-11= 31 (biggest to smallest cog tooth difference). The GRX RD can easily cope with this and you aren't changing it. RD are limited by the maximum cog size at the back too, but again you aren't changing this.
  • Mad_MalxMad_Malx Posts: 4,776
    ...But I'm not sure you will notice much difference going from a 42 to 44 (less than 5%), so unless your 42 needs replacing I wouldn't bother.
    A more expensive alternative is to get a rear wheel with an XD hub, and fit a cassette that has a 10T. This will get you a 10% harder gear.
  • t_willot_willo Posts: 16
    Ok mate. Thanks for taking the time to reply and your advice
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