Ultegra 6703 triple derailleur with SPA touring Triple Chainset

[Phil W]

You may have read in other posts that my frame broke last weekend. I am hoping to hear the news shortly on a replacement frame under warranty. I have taken the opportunity to go for a frame with disc mounts, and rear dropouts spaced 132.5mm to take road or mountain bike hubs.

I would like to lower the gearing.   I have retained the front Ultegra 6703 triple derailleur which claims a capacity of 22 teeth. I presume this would work just fine with a 46 / 34 / 24 front chainset such as a SPA XD-2 touring option as it is the same capacity as a Shimano 52 / 39 / 20?  I will be using a Dura Ace 10 speed bar end friction shifter, so no issues on pull ratios. 

I notice the SPA XD-2 is square taper and it mentions a Q factor but there is no mention of the Q factor of the Shimano 105 / Ultegra triple chainsets.   Also the Shimano use the external bearing style bottom bracket (Hollowtech II) whilst the square taper does not look like an external bearing type.  What do I need to aware of / do if I opt for one of these touring cranksets with square taper?

I also have kept the Ultegra medium cage rear derailleur and will probably just get a disc hub and cassette option to match that as lowering the front chainring ratios should be sufficient.  The thought of a mtn bike rear hub and cassette laced to a road rim has crossed my mind though.  Dura Ace 9 speed bar end shifters can put the rear shifter in friction mode, which is a thought, if not more expense, together with a mtn bike rear derailleur.

I ought to add that I have a couple of spare Hollowtech BBs that I bought as a set of three when my BB last broke.  So if there is an equivalent touring triple crankset that is hollowtech compatible, then I am all ears.



 

[grams]

Road and MTB disc hubs are both 135 mm. You can also freely mix MTB and road cassettes and hubs (for Shimano at least).

(the only exception being 11-speed road cassettes, which are wider and thus need a wider freehub)

[Torslanda]

Our very own Blodwyn Pig is selling such a chainset in the classiieds.

if you look carefully both Deore and Deore LX can be found with intermediate triple rings 28/48 or similar. Both use HII bb but the MTB version.

[sojournermike]

You should be fine with the front mech, possibly subject to vagaries if the frame is a bit odd dimensioned.

Not sure whether you mean the longer cage Ultegra rear mech? If so you might struggle with a wide range cassette at the back, although 12-25 works well on this sort of set up. However if you need a wider range then you could fit a mountain bike rear mech - 9 speeds work well with 10 speed road, and will index with 10 speed road Stis.

[Phil W]

you could fit a mountain bike rear mech - 9 speeds work well with 10 speed road, and will index with 10 speed road Stis.

Does that mean a nine speed mtb derailleur would work the same as a road 10 speed derailleur as the amount the derailleur shifts is controlled by the shifter?

[sojournermike]

Exactly - they share the same pull ratio. I’ve got one set up with 10 speed stis and an 11-36 cassette with a double at the front, but the cage is long enough to handle a triple front with that cassette.

Be aware that the compatibiltybended with 10 speed mtb and 11 speed road - you need adaptors to play with all that and I’ve not tried it.

[Phil W]

Quite happy with 10 speed, and it means I can keep using my 10 speed bar end shufters. 

[Torslanda]

XT-M771 is the one to go for. Pricey in comparison to some but bulletproof & reliable.

[Brucey]

or RD-M772, which may (do check) have a theoretically larger capacity. BTW both RD-M771 and M772 do not have a barrel adjuster fitted, you will have to have one somewhere else in the cable run.

cheers

[Phil W]

or RD-M772, which may (do check) have a theoretically larger capacity. BTW both RD-M771 and M772 do not have a barrel adjuster fitted, you will have to have one somewhere else in the cable run.

cheers

Thanks, that is fine. The replacement frame will have barrel adjusters in the cable runs. Looked up 771 and 772 and they have some capacity and front mech requirements. The latter just appears to be the lower profile shadow version with a consequently higher price.

Thanks all, think that is my gearing options decided.

[Brucey]

RD-M772 operates in a quite different way to RD-M771; the latter has a sprung B pivot and the former does not.

 I think the RD-M772 may

- last longer before it wears at the upper knuckle and stops being accurate and
- may shift better over a wide-range cassette and
- more consistently regardless of chainring size; the guide pulley remains at an almost fixed distance from the sprockets whereas in RD-M771 it doesn't quite.

RD-M771 may shift a bit better if you intend to use a narrower range cassette from time to time, and (before the mech gets too worn) the shifts are sometimes palpably smoother because of the way the mech can articulate.

But despite sharing the same shift ratio, similar capacities and parts like pulleys,  they are very much 'not the same' in fact. There are also small differences in cable run and so forth, that may or may not be important in some cases.

cheers

[Phil W]

I have an XTR mech from 2003 still running perfectly well on mtn bike. So I think longevity between xt m771 and m772 is not going to be a major concern.