cassette choice

Any advice on this gratefully received...have just bought a double chainset but it's not a compact (had a compact til now). I am fine on the hills generally but just wondering if I will notice the difference much and if so whether I should opt for a different cassette from the usual 12-25 - say 12-27/28?? Chain reaction have a selection (link attached) and I am being offered one on this forum. The kit on the bike is pretty much 105 throughout.

Thanks alot

http://www.chainreactioncycles.com/Models.aspx?ModelID=50454

Assuming your old compact was 35t small ring, with 25t on the back, would be approx 38gi. Therefore you'll need something like 42/30 on a non-compact chainset.

In case you dont know:
27(nominal wheel size) x 42 / 30 = 38

Ok Thks but confused now!!!

You'll probably be fine on the 12-25 until you hit something really big, then you'll briefly wish you had more gears. I did a rainy 1km stretch of 10-15% in the Brecons using 39/25 and I wished I'd had lower gears. But then I never any problems before or after this HTFU moment. For fitness comparisons sake, I was cycling probably 120-160 miles per week and usually did my 10 mile commute in around 30 minutes.

If you ever carry more than 8kg in a backpack or panniers then definitely opt for the 12-27, otherwise just think about what gear you usually use in serious hills and search for it on an online gear chart, then buy the cassette that allows you to reach that in your new 39 ring.

thanks for that. That is an eye opener. I do my 7.3 mile commute in just over 30 mins!! But can average 16.5 mph on the weekend jaunt away from old smokey. That'll be the 12-27 then...also - I am hoping to do ventoux soon....

thks

Ventoux? I'd love to do Ventoux... I suggest you search around forums for Ventoux gearing advice.

Averaging 16.5mph is very good if done solo. In a tight group of six we once rode a 17.5mph average, and I remember we were all chuffed with our pace.

My zippy commute had the advantage of being in the Warwickshire countryside with very few traffic lights or junctions. Or cars for that matter! Now I'm cycling in Nairobi, the name of the game is less about average speeds and more about staying on the bike, twisting through traffic and avoiding "pot holes" - some so big that you could happily curl up in them and let the traffic zoom overhead. I wish I had a GoPro so I could show people!