Help Me Figure Out What Gear Ratio I need

Secteur

I currently have a triple (50x39x30) x (12-27). 172.5mm cranks.

It's hilly where I ride. I am fairly fit but still plenty of room for improvement. I literally never, ever use the 30t chainring, so even on the steepest hills, the easiest gear I use is (39) x (27).

However, it's nice to know the 30t chainring is there should I ever need it.

My next groupset will be a double, but I am not sure if I need a compact.

Please could someone advise me what an equivalent double/compact would be, and is there a set up that would give me an extra couple of easy gears over and above the (39) x (27) equivalent, whilst still maintaining my hardest gear (50) x (12).

Does converting to a double/compact mean I will lose the ability to have those very easiest gears?

Thanks.

Wirral_paul

50/34 with a 12-25 cassette - should give you a lightly lower "bail out" gear than the 39x27 but a nice spread of gears where you need them most.

Current 39x27 = 37.9" on a 23mm tyre. 50x12 = 109.7"

A 34x25 (and also a 30x22) = 35.8" (34x23=38.9")

rothers_bikeo

My vote goes for a 50/34 11-28

oldwelshman

If you say you dont use small ring and just use 39 x 27 then just go for a standard 39/53 and same casette.
Personally I would go for a compact with a 12 25 on the back.

sfichele

My vote goes for a 50/34 11-28

+1

Note 50/11 is a higher gear than 53/12 so the compact will give you a pretty good range with a 28 on the back

springtide9

My vote goes for a 50/34 12-26 or 11-23

To get to the above, I went through...

50/34 11-23
50/34 11-26
50/34 12-26

The 34/23 was a struggle on some really steep hills or when needing to limp home.. so switched to the 11-26.
On both the 34 and 50 front, you spent a lot of time in those mid ratios... and having the 11 means you have a 'two cog jump' smack bang in the middle of the ratios.
So I bought 12-26 and have given that a try. It's much better.. you will spin out 50/12 on some downhill sections, but as long as you have decent cadence, I found it a better compromise than the 11-26 (120rpm with 50/12 is ~39mph)
With the closer ratios, I found I 'm much more comfortable sitting on the big ring 80% of the time rather than switching to the smaller ring to avoid the mid ratio jump - making it easier build up your speed.

I have also kept the 11-23, as I'm sure at some point I'll be strong/fit enough to switch.

briantrumpet

springtide9 wrote:

My vote goes for a 50/34 12-26 or 11-23 [...] I have also kept the 11-23, as I'm sure at some point I'll be strong/fit enough to switch.

With 50-34 on the front I've just gone from 12-25 to 11-25, and much prefer it: I don't miss the 16 ring at all (the ratios on the 11-25 are 11-12-13-14-15-17-19-21-23-25), and means both that I'm not spinning out as soon, and that I effectively have a wider range of useful gears on the 34 ring.

Round Devon or other hilly places I wouldn't ever want to be without the 25, as I know I'd end up grinding too often (and I say that as a pretty passable climber). I don't want to end up like Bradley Wiggins going up El Angliru.

Secteur

Someone recently mentioned "capacity" (not sure if that's the right word) - would a 28 sprocket be ok with a standard length derailleur?

morrisje

yes a 28 sprocket will work with a short length derailleur. I have one on my Cannondale with Dura-ace. No problems at all. It means I rarely move off the 53 chainring on the front.

Bobbinogs

Secteur wrote:

Someone recently mentioned "capacity" (not sure if that's the right word) - would a 28 sprocket be ok with a standard length derailleur?

It should work ok but you will probably need to adjust the b-stop (I had to go right to the max, or min, setting).

malcolmfrost

I'm running a 34/30 with a short cage (Ultegra) and the B screw set to max. All shifts well.
Shimano are conservative with their capacity.

Secteur

Brilliant - thanks everyone!