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25 vs 27 tooth cog... feel the difference?(20 posts)

25 vs 27 tooth cog... feel the difference?gnailuh
Nov 13, 2002 11:27 AM
looks like to much trouble and $$$ to convert my double record to triple... but do you think a 27 tooth cog will be noticable? if i go from 12-25 to 12-27? and do i need a new chain for the 2 extra teeth?
like they say, it depends...madstork
Nov 13, 2002 12:41 PM
It depends on how steep the climb(s) will be, what your fitness is, do you climb like an eagle or an elephant, and many other variables. But if you're thinking about the 27, you must think that it will help you. So I say go for it and find out. If you don't need it, sell it to someone who does.

I ride around all year on a 13-26 cassette. I do about 6 rides where I need the 26 - when I hit the mountains. And I mean I need it - I spend a lot of time in 39x26. For my hometown rides, a 23 gets me over the steepest hill. So for a few rides that I do, a 26 would be noticeable, compared to a 23.

Chain length? I will guess that you would not need to lengthen the chain, but you (or your mechanic) should verify this with a 27 mounted up. What about the derailleur?

p.s. If you have record double, be sure your rear derailleur can handle cogs larger than 26.
re: 25 vs 27 tooth cog... feel the difference?pmf1
Nov 13, 2002 12:55 PM
Yeah, its another 2 teeth. You'll feel it going up a steep hill. You probably do not need a new chain unless yours is pretty short.

For ride the rockies a few years ago, I used a 38 tooth chain ring as well -- $17 Sugino from Excel. Figured every little bit helps.

This is Shimano though. Doesn't Campy have a 13-29 cassette?
re: 25 vs 27 tooth cog... feel the difference?gnailuh
Nov 13, 2002 1:40 PM
well, if i got with a 29 then i'll probably need a new chain for sure... and there's the rear der cage problem... so i figure i can get away with 27 without changing anything else...

the hills in sf/bay area are pretty mean.
re: 25 vs 27 tooth cog... feel the difference?pmf1
Nov 13, 2002 1:46 PM
All I see in my Colorado Cyclist is a 13-26 and then some chain/cassette combo (13-29) for $170. I have no idea if you then have to throw in a new long RD for $190. Damn, that Campy stuff is expensive. I guess you need a long RD for the triple set up anyway.

If I lived in the SF Bay area, I'd probably have bought a triple to begin with.
SF Bay Hills - get the 27laffeaux
Nov 15, 2002 11:21 AM
I live in the bay area too, and I say get the 27 if you think you'll need it. The hills around here are steeper than what most people climb, so ignore the "you don't need a triple" or "no one needs a 27" advice. A couple of trips up and over the Santa Cruz mountains are enough to justify the lower gearing, and if you head to teh Sierra's, you'll really appreciate the lower gears. Unless you ride a whole lot, a double is not the best idea for our local rides.
not an option...C-40
Nov 13, 2002 2:20 PM
Campy doesn't make a 12-27 cassette, only a 13-26 or a 13-29.

The maximum cog size for a short cage campy derailleur is 26T, but some folks have managed to use a 13-29.

A 13-26 cassette will not require any increase to the chain length. A 13-29 will. If you try to exceed the derailleur's capacity by using a 13-29, the chain should be set to avoid over-extending the rear derailleur in the big chainring/big cog combo. This may leave the chain hanging loose in the little chainring and 13 or 14 tooth cogs. There's no way around this unless you want to set the chain an inch shorter and NEVER shift into the big/big combo.

Normally chain length is set to the maximum length that tensions the derailleur in the little/little combo. This insure that the chain will have it's full capacity without overextending or hanging loose.

The minimum increment to lengthen or shorten a chain is one inch. Each additional tooth uses 1/4 inch of chain.
You'll notice it, fershureAllez Rouge
Nov 13, 2002 2:23 PM
And I would recommend trying to maintain that two-tooth change on the lower end. I have a 13-26 (8 speed) with the next-to-lowest cog being a 23. Very often that three-tooth difference is a little too much ... I can't quite pull the hill at a decent cadence using the 23, but if I shift to the 26 granny I almost feel like I'm spinning out. If you can, I'd try to retain your current 25 and add the 27.

Brandford Bike's web site has some good info on the capacity of various model rear ders.
Lose the 12Kerry
Nov 13, 2002 5:03 PM
As a general rule, if you need the 26, you don't need the 12. Learn to spin and go with the 13-26. 53/12 is nearly 38 mph at 110 rpm. At that speed, aero drag is such that you'll go faster in a tight tuck than you will upright and pedaling.
Ditto Kerry - 13-26 - nmMcAndrus
Nov 14, 2002 5:56 AM
Lose the 12GMS
Nov 14, 2002 6:26 AM
This argument has never really made sense to me. The steeper the hills you have the climb, the steeper the hills you have to descend. Therefore, the lower the gear you need, the higher the gear you need.

I suppose if you need a 27 for a reason other than the terrain (fitness), then this argument might make sense, but not as a "general rule."
Here's the logicKerry
Nov 14, 2002 4:29 PM
Once you get over 30 mph (110 rpm in a 53/13 = 35 mph), the aero drag is huge. If you get into a good tuck once you spin up to 30+ mph, you will go pretty darn fast without pedaling. You can coast along side those who are pedaling (and often go faster) because they are catching so much more wind. I do this all the time in the hills - people say that it's my way of telling the lead rider to go faster. If they really pound the pedals, they can get away from you, but then you're resting and they're getting very tired. So, I get an extra cog where I need it, and those with 12s (or worse, 11s) lose gears. My 13-23 is a 13-19 straight block, and I put a lot of miles on that 18 (53/18 = 20.5 mph at 90 rpm) Top racers may need the 12 to win at the finish line. The other 99.9% of performance riders don't and are better off getting back the 16 or the 18 or getting a bigger cog on the top end of the cassette.
Well said, and..Chen2
Nov 15, 2002 11:04 AM
with closer ratios in the speeds you ride it's easier to find the "right" gear, the one that lets you stay in the "sweet" cadence range, while trying to maintain a certain speed.
Agreed, don't need 12 with 53.Chen2
Nov 14, 2002 6:40 AM
It's more important to have closer ratios in the speeds we ride. This keeps us turning a more efficient cadence.
Lose the 12willin
Nov 26, 2002 8:44 AM
This logic makes sense goin downhill. What would you advise for someone racing on the flats looking to go around at 38mph and sprint to 40? 53/13 or 53/12

re: 25 vs 27 tooth cog... feel the difference?tarwheel
Nov 14, 2002 6:59 AM
As others mentioned, Campy doesn't make a 12-27 cassette. If you need the extra climbing gears, I would opt for the 13-29. I've tried both the 13-26 and 13-29 and prefer the 29. If you need a really good climbing grear, the 39-29 combo is almost as good as having a triple. The 26 is fine for everyday climbs, but if you hit a really steep or prolonged climb, the 29 is best. After using the 13-29 cassette for a year, I tried out the 13-26 for a few months this summer. The 13-26 gives you one more gear in the middle (18 I think), which I hardly noticed, but I missed having the 29. I'm back to using the 13-29 with no regrets. It's too bad Campy doesn't make a 12-27 cassette because the 12 gear is nice to have on long and/or steep downhills.
27 is a granny gear..DINOSAUR
Nov 14, 2002 10:19 AM
I don't have a triple but I have a 12-25 (Campy) on one bike and a 12-27 (Shimano) on another. I only need the 27 gear if I am tired and climbing a really steep grade. I can handle anything with the 25 gear. Also you will be faster pushing yourself up the hill with a 25 if you keep the same candence. The last 3 gears will be bigger jumps in the 27, but as already mentioned Campy doesn't make a 27. You should do fine with a 25, especially with a triple.
Nov 15, 2002 11:24 AM
It all depends upon where you live, what kind of riding you do, and your fitness level. I can pretty much assure you that you'd be one unhappy camper if you spent any time with us in the SF Bay Area and the Sierras with just a 25 unless you're a Cat 1/2 racer.
Nov 15, 2002 5:45 PM
I live in the Sierra Nevada foothills. Just about all the roadies up here use a 12-25 double. The 25 gear saves the knees (especially for old guys like me).....
Nov 26, 2002 12:00 PM
So what do you consider your steep grades? In the SF Bay Area and Santa Cruz Mtns. it's really easy to be dealing with stuff in 12 to 15% range and some of it is sustained for several thousand feet. My limited experience on the SN foothills is that they're not that steep on the western side. Eastern side of the Sierra is a whole different story as well as some of the passes around Lake Tahoe. I've got good knees, I'm pretty light and considered a decent climber, but a 25 won't allow me to go all day in this kind of terrain. One or two hills maybe, but after that it can be trouble.