Which rear derailleur?

markos1963

Probably been asked a million times but which one do I need? Looking to fit a 12-30T 10spd Shimano cassette to my bike which is fitted with a 50/34 compact. Looking at 6700 Ultegra and the Wiggle site says both SS and GS cages take 30T max. Which will be best/work? Ta

mr_evil

The important spec here is "total capacity", which is the difference in teeth between the chainrings, plus the difference between the largest and smallest sprockets. For your gears that is (50-34)+(30-12)=34. This is one tooth over the maximum for the SS cage, so you should get the GS.

Elfed

I'm running a 12-30 Ultegra 6700 cassette on a 105 5700 short cage rear derailleur, works fine.

dj58

The Shimano RD-6700-A SS is designed to work with a maximum low sprocket of 30T and is for use with a double/compact crankset. The RD-6700-A-GS also has a max low sprocket spec. of 30T, though is designed to be used with a triple crankset.

fatdaz

Based on forum replies it seems lots of folks have got a 50/34 chainset and 30T rear cassette combination to work with 6700 SS RD just by adjusting the B screw. Personally I couldn't get it working and had to buy a GS RD. I'm not sure whether the type of 6700 SS RD matters - I have a feeling there may have been 2 different models depending when it was manufactured.

dj58

Correct, the earlier iteration RD-6700 SS was designed for a maximum low sprocket of 28T, the later RD-6700-A SS and GS are designed to work with a maximum low sprocket of 30T, hence the CS-6700 12-30T 10 speed cassette.
The upper pulley cage is stamped 30T on the RD-6700-A SS, that is how you can distinguish it from the earlier model.

svetty

The Tiagra 4700 GS rear mech takes up to a 34 sprocket - worth considering if you want a low gear.

markos1963

DJ58 wrote:

Correct, the earlier iteration RD-6700 SS was designed for a maximum low sprocket of 28T, the later RD-6700-A SS and GS are designed to work with a maximum low sprocket of 30T, hence the CS-6700 12-30T 10 speed cassette.
The upper pulley cage is stamped 30T on the RD-6700-A SS, that is how you can distinguish it from the earlier model.

So would this one be the correct one then as it's advertised with a 30t max?
http://www.wiggle.co.uk/shimano-rd-6700 ... erailleur/

dj58

markos1963 wrote:

DJ58 wrote:

Correct, the earlier iteration RD-6700 SS was designed for a maximum low sprocket of 28T, the later RD-6700-A SS and GS are designed to work with a maximum low sprocket of 30T, hence the CS-6700 12-30T 10 speed cassette.
The upper pulley cage is stamped 30T on the RD-6700-A SS, that is how you can distinguish it from the earlier model.

So would this one be the correct one then as it's advertised with a 30t max?
http://www.wiggle.co.uk/shimano-rd-6700 ... erailleur/

Yes, although the description on the Wiggle website is incorrect, I have asked them to amend it, though it seems to have fallen on deaf ears. I queried this with them last year when I was looking to purchase one, they assured me that the model I would receive would be the RD 6700-A SS which it was.

dj58

Svetty wrote:

The Tiagra 4700 GS rear mech takes up to a 34 sprocket - worth considering if you want a low gear.

It does, however Shimano have change the pull ratio of the 4700 components so would not work with the OP's existing 10sp STI's.

markos1963

DJ58 wrote:

Svetty wrote:

The Tiagra 4700 GS rear mech takes up to a 34 sprocket - worth considering if you want a low gear.

It does, however Shimano have change the pull ratio of the 4700 components so would not work with the OP's existing 10sp STI's.

Thats a point! I'm using 5600 shifters, does that make any difference?

keef66

markos1963 wrote:

DJ58 wrote:

Svetty wrote:

The Tiagra 4700 GS rear mech takes up to a 34 sprocket - worth considering if you want a low gear.

It does, however Shimano have change the pull ratio of the 4700 components so would not work with the OP's existing 10sp STI's.

Thats a point! I'm using 5600 shifters, does that make any difference?

The earlier 10 speed stuff won't work well with a 4700 rear mech. I too have 5600 kit and was disappointed to hear this. The bike was new in 2007; apart from consumables like chains, cassettes and cables, I've had to replace the LH STI lever (Ebay used but pristine 5703 for £25!) and the rear mech (5700 which does work). But I'm not sure for how much longer the older 10 speed stuff will continue to be available.

I'm not going 11 speed because I run a triple chainset. I suppose I should be grateful they've continued with the triple with the new Tiagra 4700

markhewitt1978

I've used a 12-30 cassette with both 5700 and 6700 deraileurs.

markos1963

So. Can I run 6700 rear mech with my 5600 shifters or do I need to change these as well? Don't fancy Tiagra 4700 as I have these on my tourer and they aren't my favourite. Would probably use 6700 but only if I HAD to( I did have plans to upgrade the bike to 7800 Dura Ace)

keef66

Can I run 6700 rear mech with my 5600 shifters?

Yes

Tiagra 4700 is the first 10 speed group using the revised cable pull

markhewitt1978

keef66 wrote:

Can I run 6700 rear mech with my 5600 shifters?

Yes

Tiagra 4700 is the first 10 speed group using the revised cable pull

Notably the revised pull is the same as the 11 speed pull. So while you can't use 4700 front/rear mechs with shifters from other 10 speed groups, you can use them with 11 speed shifters - if I'm assuming correctly.

markos1963

Thanks for all the help. I'll be getting a 6700 SS rear mech then as I can cope with the tight capacity, just have to avoid big/big, small/small combinations of gears.

dj58

markos1963 wrote:

Thanks for all the help. I'll be getting a 6700-A SS rear mech then as I can cope with the tight capacity, just have to avoid big/big, small/small combinations of gears.

FTFY