SRAM Rival 1 rear derailer replacement: NX?
 

As a follow on to my post about a replacement hanger, I need a new rear derailer as well.
The stock derailer on my 2017 Kona Rove ST is the Rival 1.
When I wrecked it in a stack a couple of years ago, I replaced it with the Rival 1 3.0.
However, as they're quite expensive, I'm wondering whether there would be any issue replacing it this time with an NX?

Different pull ratio. NX is an mtb group using X Actuation, Rival is road and uses Exact Actuation (SRAM's original 1:1). The step down from Rival is Apex, it'll work fine if you can find one with the same length cage. I don't know what cages that series offers.

As mentioned, you can use a MTB RD if it's Exact Actuation. I use older X9 and GX but make sure it's the Exact Actuation version. You just need to match the cage length/capacity.

Thanks Joe and tFunk. I'll have to look into X and Exact Actuation as I know nothing about them and their differences. Until now, I thought Rival 1 was a mountain bike- or at least a gravel bike group. I can't imagine it being much use for roadies as it spins out too quickly in top, say at ~30kmh. Unless it's meant for 2-11 rather than the 1x11 set up on my Kona. I switched to Apex shifter when I swapped my drops for flats a while back. I'll check out the Apex cages. I guess it would need to be a long to cope with my 10-42 (mountain bike?) cassette.

Ps, tFUnk, I can't find any exact NX RDs, all the one's I found for sale are X-Horison. eg Velogear , Amazon, Bikebug, etc Even the Apex is X- actuation so I guess I'll just suck up the extra cost and buy the Rival 1 3.0, which works really nicely. Appreciate the help.

I think the X-Horizon refers to something else; Exact Actuation and X-Actuation refer to the pull ratios. The Apex RD will work (expand the specifications tab and you'll see the pull ratio is Exact Actuation).

Thanks tFUnK, I bought the Rival 1 RD this time but will try the Apex next time, which I hope won't be for some time. I'm sure it will pair nicely with my apex shifter.

One more question about drivetrain, Even in lowest gear, I struggle with a couple of hills on my regual ride with stock set up, ie 40t chainring and 11-42 cassette. Would there be any issues going down to this 38t x-sync? Is two teeth enough to make a difference? TIA

Shouldn't be an issue going from 40t to 38t up front. You may not even need to shorten the existing chain.

You may not gain much for the climbs, though; I ride 2x with a 34/40 climbing gear on my gravel bike. That gets me up most of the steeper stuff. Over the years I've gone from a 28t, 32t, and 36t large cog in the back, to the 40t I have now. I can probably get away with just having a 34/36 climbing gear but the 34/40 removes all (most) doubt.