Changing double to triple - BB choice/Crankset choice?

[MikeF]

Seems like 86 BCD needs to make a comeback especially now that 11spd cassettes with large sprockets are available?

[the snail]

Pretty sure the 105 5703 crankset has 74mm BCD and will take small granny rings like the ones from Spa. I'd be interested if anyone can confirm, as I'm thinking of trying it on my 5703. Rosebikes have the 5703 crankset at a good price at the moment. It could be that 30T granny ring with 34T sprocket would be low enough for the OP, it gives a pretty low ratio.

[Stevek76]

The cx front mech is designed for doubles not triples though.

Regarding the overall capacity issue how about a mtb rear mech? As long as you stick to '9sp' or lower the ratio is the same as the road so will work ok with the 10sp shifter. Eg an alivio rd-m4000 is stated for 34-11 (or 36-12) and has a total capacity of 45t which would let you use a 28t, probably could get away with a 26t.

[poppet]

And just so I've explored all possible options, has anyone used these Jtek Shiftmates? Then a wide range cassette /small granny ring with a mtb RD to take up the slack chain...

http://www.sjscycles.co.uk/jtek-shiftma ... prod19046/

[freeflow]

Well my m770 chainset is coupled to a sram 11-36 cassette and an XT 9 speed shadow rear mech. That's with Ultegra 6603 sti. I'm shortly to cross grade to 105 5703 sti for the greater cable pull on the brakes.

[Brucey]

Pretty sure the 105 5703 crankset has 74mm BCD and will take small granny rings like the ones from Spa. I'd be interested if anyone can confirm, as I'm thinking of trying it on my 5703. Rosebikes have the 5703 crankset at a good price at the moment. It could be that 30T granny ring with 34T sprocket would be low enough for the OP, it gives a pretty low ratio.

I also think it does;

http://web.archive.org/web/20150629132031/http://www.paul-lange.de/support/shimano/explosionszeichnungen_archiv/FC//FC-5703-3004.PDF

(I will amend my earlier post accordingly)

BTW a snag with this approach is that if you retain a large outer chainring when using a very small inner ring, you may run out of capacity in the front mech .

cheers

[GRAVELBIKE]

What about the SRAM 42/28 x 11-36 combo that Salsa specs on the X9 Fargos?

http://salsacycles.com/bikes/fargo/2016_fargo_x9

The SRAM 10s road and mtb bits are compatible, and the clutch-style rear mech all but eliminates chainslap.

[Stevek76]

And just so I've explored all possible options, has anyone used these Jtek Shiftmates? Then a wide range cassette /small granny ring with a mtb RD to take up the slack chain...

http://www.sjscycles.co.uk/jtek-shiftma ... prod19046/

Why the need for the shiftmate? The sprocket pitch on shimanos 10spd MTB and road is essentially the same. A 10spd road shifter, 10spd MTB cassette and a 9spd MTB mech should work fine, I'm sure I've read others here have this working. Just don't use a shimano 10spd mtb mech, the pull ratio is completely different.

[poppet]

Any 9 speed Shimano MTB derailleur?

[Brucey]

Any 9 speed Shimano MTB derailleur?

pretty much, yes; just make sure that it has the correct capacity for the sprockets you intend to run.

cheers

[531colin]

Pretty sure the 105 5703 crankset has 74mm BCD and will take small granny rings like the ones from Spa. I'd be interested if anyone can confirm, as I'm thinking of trying it on my 5703. Rosebikes have the 5703 crankset at a good price at the moment. It could be that 30T granny ring with 34T sprocket would be low enough for the OP, it gives a pretty low ratio.

I also think it does;

http://web.archive.org/web/20150629132031/http://www.paul-lange.de/support/shimano/explosionszeichnungen_archiv/FC//FC-5703-3004.PDF

(I will amend my earlier post accordingly)

BTW a snag with this approach is that if you retain a large outer chainring when using a very small inner ring, you may run out of capacity in the front mech .

cheers

Or you could just use a touring chainset, http://www.spacycles.co.uk/products.php?plid=m2b0s109p3
24/34/46 works for me, but you can have what you want

[poppet]

What front derailleur do you use with it Colin? Are you using D/T shifters with it?

[531colin]

Because I can I mount my downtube or bar end levers next to the brake hoods...http://forum.ctc.org.uk/viewtopic.php?f=5&t=57027&hilit=skinflints&start=120
I have 3 bikes with relatively modern MTB 8 or 9 speed front mechs. with a deep backplate, like "Freeflow's" mech on the previous page. Because I am using them at or near their "design" range of chainrings I can set them up like you are supposed to with the deep inner backplate just above the middle ring, and the outer plate just above the big ring.
I have 2 bikes with old Sachs or SunTour front mechs. which pre-date the deep backplate business, and they seem to work just as well.
However, road STI units won't play nice with MTB front mechs, so you have to make some decisions. I decided I wasn't going to let some brake levers dictate what gears and brakes I could have.
If you are fixed on road STIs, I'm not the best person to advise, because I don't use them, but there are no end of threads exploring just how far you can push the design spec. of road front mechs.
If for example a road front mech. is designed to work with a 30, 39, 50 road triple, its probably best to stick to 11 teeth difference between middle and big ring, and there is a formula which tells you how far you have to drop the front mech. for a given decrease in number of chainring teeth, so it doesn't foul the chainstay (like "Freeflow's"), and there are threads where people say how small a chianring works for them with a road front mech.