Double to compact ratios

gwillis

I'm just in the process of building up a winter frame using a kinesis tk2 and had planned on using campag veloce, a friend has offered me a new shimano 105 group set for less than the veloce build the only issue being it's a double .

Is there any way I can get a similar gearing as my compact with 11-25 cassette using a double on the front?

I'm happy to use either group sets as the shifters both fit my hands etc but the deal seems pretty good

prawny

12-28 won't be a million miles away, and you get stick a 38T inner ring on. But then it starts getting a bit more expensive.

Edit - Actually 38/28 is lower than 34/25 albeit only a teeny tiny bit!

gwillis

Cheers was trying to work it out and was thinking 12-28 would be about right.

Will go for it if he still wants to do the deal if not then it's campag..

prawny

Only £28 now for a 10 speed Tiagra cassette, thank you shimano!
I'm might buy a 12-28 to go with my new compact so I can pussyfoot up the tiny hills round by me

gwillis

£28 seems a good price and i would have been more than happy with tiagra but 105 or veloce would be a bonus

prawny

Is there much difference with the cassettes other than weight? The shifting on my boardman is pretty faultless.

gwillis

With somebody of my fitness not a lot. I find tiagra good tbh. It's been faultless on my cx bike. My only real preference for campag is that if I want to use a better set of wheels I've for a few spares.

zippypablo

Wheel size in inches (use 27 for 700c wheels) x number of teeth on front chainring. Divide by number of teeth on rear cassette for gear size in inches.
This will allow you to compare gear ratios.

gwillis

cheers guys, the 105 deal fell through and my LBS offered me a similar deal on tiagra 10 speed. Given the bike is to be used for winter duties and light touring it seemed the more sensible / frugal option. Just got to build it up now

prawny

TBF apart from the looks now I really cant see the point of 105 now tiagra is 10 speed. Is there much weight difference? But if you're really concerned about weight you'll be looking higher up anyway.

Tiagra is good and reliable, and you gane stick a 30T cassette on the back, you can't (allegedly) do that with 105

graeme_s-2

I have two road bikes, one with a compact and one with a double. Due to the cassette's I'm using the double has a lower bottom gear and a higher top gear than the compact.

To find out for sure, use Sheldon Brown's gear calculator and compare the gears you'll get with both set ups.