So I’ve fitted a 27/39 double chainset to my bike.

I’ve adjusted the stops to minimise how far it can move the chain, and still using a 3 spd shifter, but using just two clicks it seems a bit easy to sling the chain right over and off the outer chainring.

Would a derailleur specifically for a double chainset prevent this? Would I also need a new shifter?

Also, do double front derailleurs sit closer to the chainring? The existing one sits a long way from the chainring, presumably because it would normally be used with a bigger outer ring. I can’t lower the existing derailleur because its a direct mount one.

Your ‘H’ screw is right in, I assume? If not, the obvious solution is screw it in more. I’ve not had a problem with the stops on Shimano mechs being insufficient for just two rings.

The ‘H’ screw is right in.

I might have pulled the cable too taught, so essentially from small ring to big ring, the whole shifting range is further outboard?

I just wondered if dedicated dual ring derailleurs are any easier to set up? And also if they run closer to the outer chainring i.e. like the usual ~2mm gap from a 44t outer ring but for a 39t. Currently the gap on a 39 is massive and I can’t get the mech any lower.

I’ll persist with the cable adjustment.

I have an SLX dual-ring front mech. It seems to have a tighter curve to follow the smaller ring.

Mine is standard not direct-mount, so getting it at the right height was just a case of setting it in the right position on the seat tube.

Does anyone know if one of these fit my Zesty, and also work with a 3 spd (X9) shifter?

I’m having problems with my existing mech firing the chain over the outer ring. Would a bash ring help prevent this and does anyone do a vaguely XC one for a 39T outer?

Problem is these stupid new standards such as direct mount mech’s and press fit bottom brackets, all roadie stuff that isn’t needed on a MTB and makes life harder. I’m doing a similar conversion, was told to leave the front mech high up as will aid shifting for some reason, also if the ‘H’ screw needs to be longer purchase a longer one from local hardware shop and fit, this will solve your problem and be cheap.

Yep…I have a max of about 5mm adjustment on the derailleur height cos thats how long the slots are in the mech.

I didn’t think running 27-39 would be too dissimilar from just ditching an outer ring and running a double and bash…???

I get the feeling that lowering the mech or using a double specific would decrease the likelihood of the chain dropping off on the inside when changing down? Which has also happened.

Good point on the adjustment screw, will source a longer one to start with!

Yes if the chain can still move over the outer ring your stop screw needs adjusting, so get a longer one. Try your LBS, they will probably have a pile of old mechs to raid. Then it should work perfectly with your existing mech.

Thanks guys, longer screw first stop!

And just to confuse matters further, i’m pretty sure Lapierre aren’t a direct mount(even though they mount directly), but an e-type with the BB mount removed.

Yes, I had a look at Shimano mech’s and it does seem the only ones you can get are E-type with the mount to be removed. So that’s different from proper ‘direct mount’ is it?

I have 27-40 and managed to lock down my XTR front mech enough to work fine.