Bicycle Mechanics - Up the Hill gear

Hi All,
I have a bike with a double 53/39 on the front and a 8 speed 25/12 cassette. I am 50 years old and ride about 100 - 120 miles a week. I am pretty happy with the gear selections except when I hit a real steep hill... I can ride up of them but I can not keep up any cadence and even have to resort to standing sometimes.
I am looking for opinions on if changing the cassette to a 27/13 or a 28/13 will it make much difference and can I do this without replaceing the derailer? It seems to me to be the most inexpensive modification to get a lower ratio.

a 39/25 combo results in a 1.56
a 39/27 combo results in a 1.44

is that the correct way to express the ratios?

your idea will work for you. what you might want to do is a triple up front. a "granny" gear would help you out. of course this would mean a new front dérailleur ,shifter,BB to make room for the gear.

That 25 low cog is pretty small for an old guy (hehe-I'm 62) who's likely not in the 130 pound range anymore...
You could likely go up to even a 32, but you might need a longer-cage rear DR.

You'll need to go with whatever you can find in 8-speed unless you replace the shifters and chain also.

Are you unhappy about standing? You don't have to be unhappy about it. I do not feel that you have to maintain a constant cadence when climbing, especially when the hill is steep or long. The fact that you can climb out of the saddle means you are strong. Change your gears if you want to, but you may not have to. The fact that you can make it up your hills indicates this is probably something you want to do, not something you need to do.

I also have a 53/39 paired with a 12-25 8 spd. Basically left over from when I was a decade younger (44 now) and rode much more. (It was a 12-21 when I was racing all the time, but I eventually gave in and went with the 25.)

Because of some back issues in the intervening years, and because I'm generally just a weaker rider, I've been looking at making some gearing changes kinda like you seem to be. I also wanted to update the bike from down tube shifters and such, so I'm making a pretty big change to an all-new 10 spd drivetrain with brifters, including a compact crank (50/34), which will give me lower gearing. All the new parts are in a box in my car right this moment, as is the bike, and it's going in to my local shop today to get everything swapped over. I live in a pretty hilly area, and am starting to ride a fair amount again, so it will be nice to have gearing that won't stress my lower back quite so much.

Thank you all for the replies.
Yes I can get up the hills the way it is but it starts to become work and not fun. I did consider going to a triple up front but that will be very costly (new BB, crank, derailer, shifter).
I can pick up an eight speed cassette on the cheap and as long as i don't exceed the capacity of the derailer, I should be ok....right? I am thinking that going from a 25 to a 27 or 28 should not be so drastic as to require a longer derailer or chain.

I am thinking that going from a 25 to a 27 or 28 should not be so drastic as to require a longer derailer or chain.

Is it a Shimano rear derailer? I think all Shimano road rear derailers are spec'd for a max cog of 27. But a 28 will work on virtually all bikes and a 30 will likely work for you, too. I have run an 11-30 8-speed cassette with my Shimano Ultegra rear derailer. Technically, a 53x39 paired with an 11-30 exceeds the wrap capacity for a short cage - spec is usually 29, requirement is 53-39+30-11 = 33, but if you are very careful about setting the chain length exactly right (not too short, not too long), that spec can also be exceeded by a few teeth. You could also swap in the 12,13 from your 12-25 and make a 12-30 instead.

Will a 27 or 28 be enough of a gear change? I dunno. Measure your cadence with the 12-25 during one of your steep climbs (c). Determine the cadence you would like to have (s). Your required cog is 25*s/c. For example: if your cadence is 50 rpm but you want it to be 60 rpm, you would need a 25*60/50 = 30 cog.

Besides the larger cogs, if the crank is 130mm BCD (i.e. not Campy) you can fit a 38t ring in place of the 39t. That will lower the gearing another ~ 2.5%.

Besides the larger cogs, if the crank is 130mm BCD (i.e. not Campy) you can fit a 38t ring in place of the 39t. That will lower the gearing another ~ 2.5%.

This is a really good idea. Simple swap, mechanically, and it will give you more/easier climb options on your small chainring, and you keep your 53 for the top-end.

You could, of course, swap to an eliptical chainring but I'm sure you have already considered this and discounted it already :lol:

http://www.sheldonbrown.com/gears/

Use the link to fiddle with various combinations before you buy anything. Try to find a combination that gives you the high and low you want, without too many duplicate gears. Also take note of what gear(s) you ride in most often with your current setup, and make sure those are covered. For instance, I seem to ride in a 42 x 16 a lot, and find it sort of irritating when I'm on a bike that doesn't offer that combination.

Are you unhappy about standing? You don't have to be unhappy about it. I do not feel that you have to maintain a constant cadence when climbing, especially when the hill is steep or long. The fact that you can climb out of the saddle means you are strong. Change your gears if you want to, but you may not have to. The fact that you can make it up your hills indicates this is probably something you want to do, not something you need to do.

+1

I'd think about getting a smaller chainring. Cheapest option.

Again, thanks to all who replied.
Hey I like the front ring idea...I got to keep an eye out for one, that is a really simple mod.
I will fool with The Sheldon Brown Gear primer... see what might work and keep an eye out for a chain ring or a cassette (whatever I can lay my hands on)...the other cheapest option is for me to just shut up and crank what I have:) (I have a kid in college.) I am not letting this "tall" gear thing become a problem
Funny that blue demon mentions the elliptical rings...I do have an 89 GT Passage with that shimanio drive set up, ok, kind of strange if you have never ridden one.