Is it possible to reduce chain ring size (50/34) on Utlegra 6700?

[DanAyo]

I'm wondering if I can reduce the smallest chain ring from 34 to say 28 or 30? I'm runnng an Ultegra 6700 groupset (double chain rings). I'd like to get down to possible a 28 or 30. If need be I could go down to a 48 or 50 on the large ring. How many teeth difference can the FD handle?

Or would it be a better option to get a higher cassette? I run an 11-28 cassette. I think Sheldon Brown shows a 34 or 36 cassette. If I went this way I think I'd need a mountain bike derailler.


I'm 58 and typically ride flat land. The climbing could present a problem for my knees.

Thanks in Advance for help any with this.
Dan Ayo

 

[oldbobcat]

No, 34 is as small as they go on compact road. If you need smaller, consider a road triple or a MTB triple. But remember that your Ultegra derailleur might not work with a MTB crank. And remember that if you convert to triple, you'll need a triple-capable front STI lever.

 

[swampy1970]

34 is the smallest that Shimano sell but TA do a 33.

It's impossible to go lower than 33 as the chainring bolts would interfere with chain/chainring operation.

Running a MTB rear mech and a wide spaced cassette would work well for you. I used a 2006 XTR rear mech with Dura Ace STI shifters and an IRD 10 speed 11-32 cassette from time to time and it works very well, so well infact that although I may change the cassette for something a little more 'normal' when I'm not doing very long rides in the big hills, I often leave the XTR mech on because it shifts as well as the Dura Ace 7900... If there is a difference then I can't tell. Click, shift...

The SRAM XX cassettes are lighter than the IRD and are probably quieter too as the IRD are steel sprockets.

Also note that the max rear sprocket size for the Shimano MTB rear mechs is 34.

 

[alfeng]

I'm wondering if I can reduce the smallest chain ring from 34 to say 28 or 30? I'm runnng an Ultegra 6700 groupset (double chain rings). I'd like to get down to possible a 28 or 30. If need be I could go down to a 48 or 50 on the large ring. How many teeth difference can the FD handle?

FWIW. IMO, to achieve what you want, you should investigate buying a Hollowtech II MTB crankset -- Deore, LX, SLX, XT, or XTR ([COLOR= #808080]i.e., whatever suits your budget & aesthetic sensibilities[/COLOR]).

Shimano makes a 48t 104BCD chainring in both steel & alloy which will fit on most MTB cranks which use 4-arm 104BCD chainrings ... but, a 46t-or-44t-or-even-42t outer chainring may be adequate if your cassette's smallest cog is an 11t.

A 950-vintage bottom pull, top swing XTR rear derailleur would probably be the best option BUT you should be able to use the existing front derailleur which is currently on your bike AFTER you lower it ...

The inner plate on a ROAD Triple front derailleur may interfere with lowering the front derailleur if you are using a 42t chainring ... and so, there is no reason to buy a Road Triple Front derailleur, IMO, unless you opt for a Road Triple OR (if you are like me) you simply prefer installing the component with the greatest latitude when spec'ing the build -- that is, the Triple front derailleur with a MTB crank may not be a wise use of your funds & should only be chosen IF-and/or-AFTER you determine the Double Front derailleur isn't shifting adequately..

The matter of whether your Front shifter is Triple-capable or is only capable of shifting on a Double crankset is another matter ...

• ONE thing which you can do is to adjust the derailleur stops AND cable on an ad hoc basis (i.e., as needed for a given ride) ...

• OR, you could turn the MTB crank into a Double with whatever "large" ring you wanted to use mounted on the inner shoulder of the crank + a suitable Granny -- a 44t & a 28t should be well within the capability of almost any front derailleur BUT I would think that you could use a smaller Granny if you wanted.

BTW. The so-called Q-factor on a typical MTB crank is about 170mm (vs. 145mm-to-150mm for a Road Double ... about 160mm for a Road Triple) ... so, you'll want to lower your saddle by a few millimeters ...

I personally don't think that 10mm on each side is that big a deal, but it may be a concern for some riders.

BTW2. Of course, you don't have to be married to the Hollowtech II BBs & cranks ... but, continuity is a good thing.