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Hi guys I just bought my first gravel bike and I want to change the chainset from a 105 double to a sub compact one for easier lower gearing. Any advice on a sub £120 set that will fit my shimano bb or is it a case of new bb too? Thanks as this is all new to me.
There's not really much choice that I've seen despite sub-compact being heralded as a 'thing'. Praxis and FSA make them but both need a different bottom bracket. You can though get a triple chainset and run it as a double using the inner/middle rings only.
Thanks I hadn't thought of that option.
Could you fit a Shimano MTB double crankset like this 26/36 for £80? https://www.merlincycles.com/shimano-deore-xt-m8000-double-11-speed-mtb-chainset-85185.html
Or 28/38 https://www.chainreactioncycles.com/shimano-slx-m7000-double-11sp-chainset/rp-prod148291
Best Shimano price I can see in road cranksets is ~£150 with promo code for 36/46 https://www.probikekit.co.uk/bicycle-cranksets-and-chainrings/shimano-ultegra-fc-r8000-chainset/11465204.html
Would a cassette change give you low enough gearing? 11-34 for ~£35 https://www.merlincycles.com/shimano-105-cs-r7000-cassette-11-speed-117086.html (might need a GS rear mech too for ~£37 https://www.merlincycles.com/shimano-105-rd-r7000-rear-derailleur-11-speed-117065.html)
As an alternative, have you considered expanding the cassette instead? A thread on here linked to a successful attempt to get an XT cassette running with a 105 chainset/ mechs.
Slight thread hijack - my gravel bike has also got a compact double and I've been looking at going 1 x but see all sorts of conflicting info about what works with what. It's 10 speed, so I'd ideally stick with that but will consider 11 and a new shifter. Are MTB cassettes and road cassettes the same spacing? Do road shifters work with MTB casettes? I'm assuming my medium cage 105 mech will work with anything. I'd put a single ring on my existing 104 pcd spider, I guess.
@failedengineer 10spd Shimano road (apart from tiagra) works with 9spd Shimano MTB so you can mix the shifters and rear mechs. The cassette spacing is close enough on 10spd to work. I have 10spd 105 shifters with 9spd XT mech and a subrace 11-40 cassette - it all shifts perfectly.
What size is the current 105 one ?
I think it's 50/34. I've already got a new rd7000 gs mech and longer chain to up the rear to either 40 or 42 but I would like around a 30 front as I want the bike more for off road than road.
If your current chainset is 4 arm 105 you can replace the standard 34/50 with an Absolute Black 30/46 oval set. I did and they work well. Swap the cassette for an 11/40 and you can climb walls.
If you want a cheap option...
My cx50 chainset is for sale in the classifieds - 36/50 or 36/46
It would be a direct swap for your existing chainset
That chainset (with the 50 as it goes) was on my cx (for riding, not racing)and with an 11-32 cassette was as low as I found I needed
With the rd7000gs you could go 44/34 on the front and 11-40 on the rear. 34:40 is going to get you up most climbs that are rideable on a gravel bike I would imagine.
Have a look on spa cycles and see if they do smaller pairings of chainrings?
Thanks for all the advice guys. Looks like new smaller rings is the answer. 👍👍 Time to go shopping 😊
I put an ultegra r8000 50/34 on an old road bike which I also do some cyclocross racing on.
The 50T ring is better for on road stuff, just need to hop a bit higher over logs than if I had a smaller chainring. Furthermore, the set is lighter than the CX50 crank which has a solid scalloped, rather than hollow, crank arms.
I replaced a SRAM Rival 22 compact (34/50) chain set with a SRAM X9 mtb (22/38) chain set and all that was needed were two spacers on the bottom bracket and to shorten the chain. Worked superbly.
Try absolute black oval chain rings. You can fit 48/32 or 46/30 on a 110bcd Shimano crank