Gearing gurus , will this combo work?

Triathlon Forum
1

Hi all,

I currently run dura-ace 7800 with 53/39 and 12/27.
I am looking at changing to a 50/34 on the front and was wondering whether the new DA7900 11/25 cassette would work without changing derailleur cages etc?

I am considering riding the Marmotte in France in July and this set-up appears to give me a better range of gears with smaller increments. Have ridden the etape before and all these mountains in the 27, just feel this combo provides better options.

Thought I recalled a Slowman article where he said you couldn’t have a total difference of 30…e.g. 53-39 + 27-12 = 29 so is OK…whereas 50-34 + 25-11 = 30 :frowning:

any comments, suggestions appreciated

cheers
shep

2

IF you have chairings that fit your cranks, then you will have no problem. I didn’t know that regular cranks could hold a 50/34… My FSA compact ones do, and I have used a 52/34 combo with an 11/25 on the rear before, and it shifted fine with the stock shifters…

3

Fine line between “functional” and “optimal” - it will function, probably good enough for anyone on this site, wont be optimal, but will work.

4

Thanks Monty,

I should have been more specific; was considering swapping out entire front for compact set-up, chainrings and cranks…not just rings.

Main concern was DA7800 rear derailleur handling set up.

ta

5

Yes, you’ll be fine - With a 50/34, I’ve run 12-25 and 12-27 cassettes with a standard cage derailuer.

6

Thanks
.

7

I would run the 34 and the 27 for the Marmotte. Lots of steep stuff on the Croix de Fer/Glandon that you don’t want to burn up the legs early. Plus those last 9K of the Galibier at 9 percent. And then the Alpe awaits. Man, now I’m I’ve living in the past, remembering things I did 15 years ago. I am old.

Chad

8

Thanks Chad,

you are correct, Croix de Fer is not so bad…in isolation…however the cumulative effect of them is the worry. Haven’t ridden the Galibier from that side only from the Lautaret side and that is bad enough.
Have been doing heaps of research and reading articles/blogs from people who have done it and it is a daunting prospect. I knew that there was 5000m of climbing but on weekend I found a stat that said 82km of the 174km is uphill :frowning: OUCH !!!

9

Hi all,

I currently run dura-ace 7800 with 53/39 and 12/27.
I am looking at changing to a 50/34 on the front and was wondering whether the new DA7900 11/25 cassette would work without changing derailleur cages etc?

run a 12-25 or 12-27.

unless you’re racing, are you really worried about spinning out at 65km/h instead of 70km/h?

10

For me it is always the steep stuff that you have to grind in 38x24 (my gear when I did it) that wore me out. The Croix de Fer had two pretty steep sections that one at 13 percent for like a mile, that wear you down for later. The the Telegraph is a consistent, unrelenting 7 percent out of St Michel de Maurienne and that is right on the edge of 38x24 during a long day. The Galibier gives you about 8K that is not too hard and then finishes with the kicker at the end. I had to stop once when I did it because I couldn’t turn over the gear on the 9 percent slope.

Then you have the Alpe waiting with its first 2K at 10 percent …

Chad