You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Hi. I have a Spesh Diverge with 10 speed GRX 400. Currently running 11-36 rear cassette.
I would like to swap this to a Deore 11-42.
Is this a simple swap over (Inc new chain) or does everything need re adjusting?
Thank you.
Depends if your rear mech will take a 42 cassette.
I’ve just gone up from a 42 to a 46 cassette with the same mech, but it’s SRAM.
As a matter of interest, see if there’s anything on the back of the mech that indicates how big a cassette it’ll take. Mine plainly has ‘46T’ on the back plate, which I assumes means 46 teeth max.
Ah, cheers. I'll have a look. Thanks
The mech is only officially rated for a 36t max
https://bike.shimano.com/en-EU/product/component/grx-10-speed/RD-RX400.html
I run a 40t cassette on 2x grx 10 spd, it’s fine with the standard mech.
Ok, so fitted the cassette but it catches on the top two cogs. I take it it's a no no or can it be adjusted?
You can try with the B tension adjustment, but you may end up with poor chain wrap.
This was the issue when I built up my cross bike in 2020. It's a bit confusing with the 400, 600 and 800 to what cassette sizes you could use.
People have ran all sorts but how well they perform I'm not too sure.
If you run out of B Screw length then you can buy longer ones.
Here's an article that may help.
https://road.cc/content/feature/how-get-ultra-low-gearing-gravel-bike-adventures-246424
Or add a mech extender.
https://www.sjscycles.co.uk/gear-spares/aluminum-rear-derailleur-hanger-extender/
That one is out of stock but there is other makes out there. It's just to give you an example.
You'll also find YouTube videos on how best to fit and adjust your gears to suit.
I’ve got grx 800 and run an 11-46. Works perfectly. Think the mech is only meant to do 42 max but shimano is always a bit conservative. Grx 400 I can’t help with, but there is some scope to put beyond the shimano ‘max’
My GRX 815 is supposed to be 36t max, but runs fine with an 11-40 cassette using just b-screw adjustment.
Of course another option might be to run a MTB double chainset. I have a 28/42 on my bike and with a 32 biggest tooth cassette it's ridiculously low. Too low for almost anything.
Of course another option might be to run a MTB double chainset. I have a 28/42 on my bike and with a 32 biggest tooth cassette it’s ridiculously low. Too low for almost anything.
I wonder how that compares to my mates 42/50 setup in leg spinnage?
It’s not just how big a cog you can get the rear mech to shift to, you also need to consider it’s max capacity to handle the chain. I’ve not tried it with GRX400, but I would anticipate you would end up with either slack in the small/small combo or too tight in large/large with a 42T cassette. Some may say that’s no problem, just avoid those combinations, but IMO that’s a bad idea as all it could take is one accidental when tired and you mangle your drivetrain. At the very least ensure the chain is long enough to handle the large/large combo without damage or jamming.
Cheers for the advice guys. I adjusted the B screw and it works except for largest gear front and biggest gear rear. All others work fine.
I was wondering if I went 1 x 10 up fron with a 40t would the set up work?
It's GRX 2 x 10 at the moment
Did you add a couple of links to the chain? Sounds like it may be a bit short if it works fine across the whole range with the small front ring...