12/25 v 12/28

BeepBeep67

Thinking of replacing my 12/25 with a 12/28 rear cassette to make the hills a bit flatter while I work on my climbing fitness.
Any disadvantages when you're going through gears with a 12/28?

Lumen

Bigger gaps

ashleey

Wider spacing so harder sometimes to maintain a constant cadence. In practice it's unlikely to cause a problem unless you are becoming more pro. Check that your rear dérailleur is specced for 28 teeth. I use a 50/34 compact and an 11/28 rear SRAM and its great for me

Daithi BC

I have an 11 speed campagnolo 11-27 on the back (and a compact on the front), and I find it great to be able to drop to the 27. It means I can get up hills with much less effort and be fresher for the rest of the ride.

The disadvantage is that you get a bigger gap between the bigger sprockets, so you may find on some hills that you have a gear that's too easy and a gear that's too hard, but nothing in between. Having said that, I wouldn't go back to a 25 as my bottom gear.

smacl

13/28 back, 53/42/30 front, pure lazy b'srtrd set-up and I love it, though wouldn't mind an 11 or 12 as smallest sprocket.

BeepBeep67

From what I can find the different set ups seem to be as per below:

12/23 = 12-13-14-15-16-17-18-19-21-23
12/25 = 12-13-14-15-16-17-19-21-23-25
12/27 = 12-13-14-15-16-17-19-21-24-27
12/28 = 12-13-14-15-17-19-21-23-25-28
11/28 = 11-12-13-14-15-17-19-21-24-28

Maybe the 12/27 is a better option it's only the last 2 cogs that are different, so I'm loosing the 23 and 25, but have a 24 and the added benefit of the 27.

smacl

BeepBeep67 wrote: »

From what I can find the different set ups seem to be as per below:

12/23 = 12-13-14-15-16-17-18-19-21-23
12/25 = 12-13-14-15-16-17-19-21-23-25
12/27 = 12-13-14-15-16-17-19-21-24-27
12/28 = 12-13-14-15-17-19-21-23-25-28
11/28 = 11-12-13-14-15-17-19-21-24-28

Maybe the 12/27 is a better option it's only the last 2 cogs that are different, so I'm loosing the 23 and 25, but have a 24 and the added benefit of the 27.

Worth remembering that the gappiness between sprockets is based on the change the percentage of number of teeth or circumference, not the difference in number of teeth. For example, the difference in moving for 11t to 12t is 9.1%, whereas moving from 27t to 28t is only 3.7%.

Check out Sheldon for more details; http://sheldonbrown.com/gears/

Lumen

BeepBeep67 wrote: »

Maybe the 12/27 is a better option it's only the last 2 cogs that are different, so I'm loosing the 23 and 25, but have a 24 and the added benefit of the 27.

The biggest (24-27) jump on a 12-27 is 12.5%.
The biggest (15-17) jump on a 12-28 is 13.3%.
The biggest (24-28) jump on a 11-28 is 16.7%.

For me that rules out 11-28 because an 11 cog is unnecessary except maybe for mass start races or flat windy time trials, and you wouldn't use a 28 sprocket for that sort of racing anyway.

Between 12-27 and 12-28, it's really a choice between having narrow gaps mid-cassette with a gappy bailout gear (12-27) or a biggish gap mid-cassette with closely spaced bailout gears (12-28).

I personally prefer the 12-28 as I'm not very cadence sensitive in mid-cassette and the extra tooth helps a bit on the steep stuff.

I got my 12-28 from IRD as (AFAIK) they are not available from Shimano or SRAM (happy to be corrected on that). It was expensive and doesn't shift as well as Shimano, but I like it nonetheless.

smacl

Lumen wrote: »

I got my 12-28 from IRD as (AFAIK) they are not available from Shimano or SRAM (happy to be corrected on that). It was expensive and doesn't shift as well as Shimano, but I like it nonetheless.

SRAM PG-1070 and 1050, and Tiagra CS-4600 appear to be available in 12-28. Don't see a 12-28 in Campag which is a pity, though the 13/28 is generally good enough.

Lumen

smacl wrote: »

SRAM PG-1070 and 1050, and Tiagra CS-4600 appear to be available in 12-28. Don't see a 12-28 in Campag which is a pity, though the 13/28 is generally good enough.

Interesting. The Tiagra one isn't that much heavier (at well under 340g) than the IRD (291g) but is much, much cheaper.

Must be new with the 10sp Tiagra.

BeepBeep67

Ordered the 12-27 PG1070 from bike.de and accidently ordered the Fulcrum Racing 5 wheelset also :rolleyes:, will keep the rear 7 with the 12-25 for the turbo.

Daithi BC

BeepBeep67 wrote: »

accidently ordered the Fulcrum Racing 5 wheelset also :rolleyes:,

That can happen!