Upgrade to double, advice?

N_laplaca said:

Hi, I bought my bike a year ago with a triple.(52,42,30) It was recommended to me to get the triple for climbing steep hills. It was a good idea at the time since I had not been on a bike in quite a while and never really rode that much anyway.

Well I am pretty much addicted now and ride all the time. I rarely ever use my little ring anymore. This weekend I did my first century. Halfway through was the toughest climb on the ride. A (average)9% grade that rose to 2500 feet over 4.5 miles with the last 1/8 of a mile or so at 15%. Not once did I ever consider getting out of my 42. So I am planning on moving to a double.It just seems to make more sense to me.

My question is what I should shoot for in the rear. Right now I have a 12-25. Someone recommended getting a 12-27 for the really steep climbs. I don't race yet but my fitness is at the point now that I am really thinking about it. Not this year but next when I have more group riding experience and better paceline skills. So should I go for the 12-25 or the 12-27. Oh and am I going to need anything else? Everything on the bike is Ultegra. Can the shifters be set for double or am I going to need them also?

Nick

What you get for the rear depends on what you got now. Your middle ring is a 42 and with a double it will be a 39, so if you have a 25 the 39 will give you lower gearing without going to a 27. Who knows about the shifters?You haven't said what you've got.But, almost any shifter for a triple will also shift a double.

boudreaux said:

What you get for the rear depends on what you got now. Your middle ring is a 42 and with a double it will be a 39, so if you have a 25 the 39 will give you lower gearing without going to a 27. Who knows about the shifters?You haven't said what you've got.But, almost any shifter for a triple will also shift a double.

My shifters are Ultegra Sti. I was thinking that if I did get a 12-27 as suggested it would be better if I did encounter some really steep long climbs. Another question, how much different is a 39 from a 42? Doesn't seem like 3 teeth would be much different but I have never ridden one so I don't really knoa.

N_laplaca said:

My shifters are Ultegra Sti. I was thinking that if I did get a 12-27 as suggested it would be better if I did encounter some really steep long climbs. Another question, how much different is a 39 from a 42? Doesn't seem like 3 teeth would be much different but I have never ridden one so I don't really knoa.

Take a gander at:
sheldonbrown.comgearsOpen ↗

As you can see from the following a 39/42 swap makes in the neighborhood of a rear cog shift difference on a 9-speed cassette.

App. small chainring Gain Ratios for 700c:
39T chainring with typical 12-25 cassette:
6.4, 5.9, 5.5, 5.1, 4.5, 4.0, 3.6, 3.3, 3.1

42T chainring with typical 12-25 cassette:
6.9, 6.3, 5.9, 5.5, 4.9, 4.3, 3.9, 3.6, 3.3

As Boudreaux inferred, a 25x39 is going to feel like a 27x42.

Advice is tough for someone else. You are talking about a 24 vs 23 for your second lowest gear, which you ought to think about which is of more value to you, as well. I was going to outfit my newest ride with a 12-27 for extra range, but ended up with a 12-25 because my LBS was having difficulty getting it and I was impatient. Now less than two months later I am probably going to switch it out for a 12-23 for most rides, because I find myself wanting the 16T cog which the 12-25 and 12-27 lack. (53x16T on flats with moderately strong headwind suits me much better than flopping back and forth between the 15 and 17 and cursing!!)

The good thing is, it's only $35-40 at a lot of e-tailers for an Ultegra cassette; and a couple of minutes to swap out.

serenaslu said:

Take a gander at:
sheldonbrown.comgearsOpen ↗

As you can see from the following a 39/42 swap makes in the neighborhood of a rear cog shift difference on a 9-speed cassette.

App. small chainring Gain Ratios for 700c:
39T chainring with typical 12-25 cassette:
6.4, 5.9, 5.5, 5.1, 4.5, 4.0, 3.6, 3.3, 3.1

42T chainring with typical 12-25 cassette:
6.9, 6.3, 5.9, 5.5, 4.9, 4.3, 3.9, 3.6, 3.3

As Boudreaux inferred, a 25x39 is going to feel like a 27x42.

Advice is tough for someone else. You are talking about a 24 vs 23 for your second lowest gear, which you ought to think about which is of more value to you, as well. I was going to outfit my newest ride with a 12-27 for extra range, but ended up with a 12-25 because my LBS was having difficulty getting it and I was impatient. Now less than two months later I am probably going to switch it out for a 12-23 for most rides, because I find myself wanting the 16T cog which the 12-25 and 12-27 lack. (53x16T on flats with moderately strong headwind suits me much better than flopping back and forth between the 15 and 17 and cursing!!)

The good thing is, it's only $35-40 at a lot of e-tailers for an Ultegra cassette; and a couple of minutes to swap out.

Thanks for that link. That's pretty useful. I think what I may do is get a couple of cassettes for different rides, if swapping them out isn't too big a deal anyway.

Nick