How to replace a Sora front triple with an MTB crankset

Hi all,

I have a touring bike on which the gearing is way too big for comfortable hill climbing. Haven’t used the big ring once in about 1,500 miles, but been out of the saddle on steep climbs far too many times.

It has a 9sp XT rear cassette/mech but a Sora road triple up front (2012). I’d like to swap the crankset for something more appropriate – e.g. Deore, Alivio – but I’m not sure what bits are compatible with what. How can I keep this simple? Are there any MTB lines which have Sora-compatible BBs, mechs, shifters, or am I going to have to change out the whole lot?

TIA!

Could you not just replace the granny with a 22t ring?

Get the LX crankset on offer at JEJames for £65.
http://www.jejamescycles.co.uk/shimano-fc-t661-lx-triple-chainset-44-32-22t-170mm-id49056.html
This has a BB suitable for a 68 or 73mm shell, and an e-type mech.
You may also need an MTB front mech…WoollyHatShop had E-type LX on offer at £10 recently.
http://www.woollyhatshop.com/Front-Derailleurs/Front-Mountain-Bike-Derailleurs/Shimano-Deore-LX-E-Fit-Bottom-Bracket-Mount-Front-Mech-Derailleur/prod_3593.html
Chain should need a haircut for a 44T large ring.
Job done.

PaulD

My workmate did it the other way round (road replaced MTB) with no difficulties or indeed faff. Didn’t have to change mech, just a longer chain.

iirc all road bikes are 68mm, mtb can be 73 or 68 adjustable with an extra spacer, so the chainline will change slightly, will probably make no difference in practice.

Because of the smaller inner chainring, it could cause the chain to catch on the frame.

Is the front mech on a clamp or brazon?

I would beg borrow or steal some bits to make sure it works before buying.

Road chainsets have a different chainline to MTB’s & so you may also have to change the front mech & then you will find that road shifters don’t work with MTB front mechs as they have a different pull ratio (even though rear mechs & shifters are fully compatible).

You may find it cheaper & easier just to change the chainrings in the long run

Thanks all, I’ll look at just replacing the granny ring. If not, it’s a clamp-on front mech so should be able to move it without issues. Cheers for the LX crankset link, that’s a pretty good deal!

smaller granny ring..

sora triple has a BCD for middle and outer rings of 130mm and 74mm inner..

so you could go 48-38-26 or 48-38-24 (24 is the smallest with 74mm bcd)

this would be a big change from the std Sora of 50-39-30

also what size is your XT cassette?

what shifters you running?

I’m running bar-end shifters. Front is friction, rear is 9sp indexed. I’m hoping the front shifter will remain compatible with whatever front mech I end up using. I have a spare XT front mech if the Sora one doesn’t work.

I’d love to swap out the 30t granny ring for a 24t one. No idea where to find such a thing, unfortunately – any ideas? I hope it’s just a case of pulling the cranks, unbolting the old chainring and sticking the new one on?

Sorry, rather new to road bike components!

Chainrings here[/url]