So yesterday I broke my sunrace gear hanger extender on my drop bar gravel bike. The rear mech got dragged into the spokes by mud and twisted it, snapping the extender that I was using. I have a 11-40 cassette and was using a sunrace extender (like Woolf tooth) to get my tiagra mech to work with the 40 tooth sprocket.

Now I need to replace the tiagra mech and the extender but I am considering other options. I didn't expect the tiagra mech to last as long as it did and was expecting to replace it at some point with a clutched mech because I ride in pretty rough conditions. I would appreciate opinions on either..

- a Woolf tooth extender and a grx 400 rear mech
Or
- a Shimano slx rear mech with wolf tooth tanpan (to adjust pull ratios and allow it to work with my road shifters)


I have tiagra shifters and I am aware of the various compatibility issues and how to get around them. So I would really just like to get opinions of which of the options you would think we're better for fairly rough gravel riding... If there are other solutions like drop bar shifters that will work with MTB mechs I'd love to hear about them.. thanks all :)

I'm using an Ultegra rear mech with 11-40T cassette and 50/34T cranks. No extender. Way outside Shimanos published recommendation but works fine. Not sure if it'll play well with your Tiagra shifters but certainly an indication that you can stretch the specifications a bit.

Yes I've just been reading about poeple using the grx400 without and extender and getting it to work with 42t sprockets. Some people have said that could be done with the tiagra mech but I couldn't get it to work....I might try the grx without the extender before I shell out the £20 for the wolf tooth. How is your setup if you cross ring it does the chain go super slack?

It all works fine. I can cross-chain both big-big and small-small. I think the clutch mech helps on those occasions that my muddled brain forgets to shift correctly.

10 speed or 9? If you are on 9 then try and acquire a non shadow rear mech (as in the old style ones). The top jockey wheels are slightly offset which allows them to work fine with a 40. No clutch but no issue if you are using a thick/ thin chainring.

htrider wrote: ↑Sun Jan 10, 2021 4:39 pm 10 speed or 9? If you are on 9 then try and acquire a non shadow rear mech (as in the old style ones). The top jockey wheels are slightly offset which allows them to work fine with a 40. No clutch but no issue if you are using a thick/ thin chainring.

Sadly a 10 speed... And a 2x (46/30)....I think I'm going to try the grx400 and see if it can cope without the extender. If not then I'll add a wolf tooth to it, which worked ok with the tiagra mech..... In the future I may well go 1x using a grx 812. Although I've just seen a video of someone using the grx 810 with a 46/30 double!! Shimano spec is definitely conservative..

I've got the grx400 on a 40t cassette with no extender, and it works perfectly. It is on a 1x setup though...but should be fine on 2x as shimano are always conservative with range compatability and it's only a 4 tooth increase. Nice to have a clutch mech too.

faustus wrote: ↑Tue Jan 12, 2021 10:06 am I've got the grx400 on a 40t cassette with no extender, and it works perfectly. It is on a 1x setup though...but should be fine on 2x as shimano are always conservative with range compatability and it's only a 4 tooth increase. Nice to have a clutch mech too.

I can confirm the grx400 rear mech works absolutely fine (without an extended) with a 40 tooth cassette and a 30/46 double :) there is even room to spare on the b screw. Cross chaining is ugly but still shifts fine even in 46/40

Nice one.

Glad it worked

Also worth noting that if you go 11speed in the future the mech will still work as its the same cable pull, I use mine with 11 speed rs685 and works perfectly

faustus wrote: ↑Mon Jan 18, 2021 12:14 pm Glad it worked

Also worth noting that if you go 11speed in the future the mech will still work as its the same cable pull, I use mine with 11 speed rs685 and works perfectly

Thanks :) have to say for a £50 mech it shifts great. The clutch makes a lot of difference! I tend to use my drop bar as a MTB so it gets banged around a lot. I have very little noise from the chain now. It's really nice too have such a big sprocket in a 2x set up, its turned my gravel bike into an everything bike.

Yeah, I think it's a decent mech and a big saving over the grx812 mech, and as you say a blessed relief to have a quieter drivetrain like the mtbs