An alternative to using a compact crank

KL.

I have not done this yet, but I plan too, I just need a little help with sourcing the right components. So ...

I currently have a DA 7800 53/39 groupset on my road bike and was considering changing the crankset to a 7950 or 6750 crankset. It would appear that the new compact crank can be installed, the FD adjusted down to suit, and it will work (almost plug and play).


But after discussions with another rider the following idea arose:

That is to use one of the new MTB XT Dyna Sys 10 spd 11-34 cassette with an MTB 9 spd XT(M772) or XTR(M972) SGS RD (long cage). I am not sure if the new MTB 10 spd RD's are compatible with the DA 7800 STI lever).

We think that the 9 spd derailleur will become a 10 spd derailleur when used with the DA 7800 STI, because it has the required pull ratio that will work with the DA 7800 STI lever. Any ideas regarding this would be very welcome. Without trying it, this is the uncertain part

This option would give more range than using a 7950 compact crankset and if I really needed to I could then later go to a compact crank. Nearly as much range as one of the internal geared hubs?

What do you think of this idea for lots of touring and lots of hill climbing?

The local Shimano fellow does not think that it will work, but per chance, has anybody already done this

ex-pat scot

You might get it to work (sorry I have absolutely no idea whether it will or not) but I have to ask "why?"!

KL.

I like to ride with a higher cadence (90 to 110), up hills 85+. When I am touring for pleasure I really prefer to stay on the saddle, even up hills.

Even with 39 chain ring and 27 sprocket, to maintain a cadence of 85+ you have to ride at about 16kph(10mph). Up a 6% gradient hill with this gearing and a packed backpack, I need to get out of the saddle. With this gearing, for steeper hills, its impossible for me to achieve a cadence of 85+, so it's just a grind and not enjoyable.

I am getting older and I like my touring to be pleasurable not a grind

But the above is nearly as good as an internal geared hub (12-38 ), but much lighter

antfly

Rear derailleurs will work with 9 speed or 10 speed. You would only need a medium cage mech on a double although 34T might be stretching it a bit. I have done similar with a 32T cassette.

KL.

antfly wrote:

Rear derailleurs will work with 9 speed or 10 speed. You would only need a medium cage mech on a double although 34T might be stretching a bit. I have done similar with a 32T cassette.

Hi antfly, was that a 10spd 32T cassette.

If you don't mind me asking, what model RD did you use?

antfly

No it was 9 speed, I have just switched to 10 speed and am now using a 28t cassette but i'm pretty sure a 32 would be no problem. The mech is a 9 speed Shimano xt M770 medium cage. I am using a compact crank as well.

KL.

Hi Antfly, what model STI lever are you using with the XT M770 RD

antfly

It's an ultegra 6600 10 speed.

KL.

Thanks Antfly, that's sensational

Do you think the XT M770 RD shifts as smooth as an ultegra 6600 RD

Is the compact crank the reason you changed from the 11-32T to the 11-28T? ... or was it another reason?

antfly

I always had the compact it's just that I got fitter and better at climbing hills so didn't need the 32 as much.
The XT shifts just fine but I think you could use an ultegra GS, mine's a GS so they should work pretty much the same. The GS is meant for a triple really but apparently you can use them on a double if you want a bigger cassette. I only know all this because a very good LBS set it up for me, originally.

KL.

Thanks antfly, for the good information, appreciated

The Rookie

My Commuter (Carrera Gryphon hybrid road frame) runs an 11-32 cassette with an LX Short cage rear mech (single front wheel), I did a check last night and I can wind the cage off the largest wheel far enough to accomodate a 34T no problem. Like you I sit and spin on hills (with circa 4Kg in the panniers, standing up is a little unwieldy!)

Simon

KL.

Thanks Beginner, is this the one you have ... Shimano LX RD Rapid Rise M580 SS.

This one definitely works ... Shimano XT RD Rapid Rise M770 GS/SGS.

Looking at this one ... Shimano Saint RD M810 GS/SGS ... and this one ... Shimano XTR RD Rapid Rise M970 GS/SGS.