10sp rear, 2 at front, but which size?

[Gingerbread Man]

I recently built a new bike. The biggest cog at the front being a 42t, and it's matched to a (10sp) 11t at the rear. I find that on open stuff, or short bits of road, my legs are spinning like mad due to the small front cog (?). Thinking of going to 44t at the front and wondered what you guys were running, or if it would make much difference.

The bike is lighter than my previous models, maybe I'm flying along at warp speed and just don't know it.

Edit: It seems that a front derailleur will only jump a chain up a certain difference in teeth. From reading online I have gathered that this is 14t difference (true?), which makes total sense. So I won't be over this threshold with a 44t. I've currently got 10 different in tooth at the mo. 42 to 32t. So enlarging to 44 will make it 12 different and it'll all still work I think.

Would it be best with a slightly larger smaller cog to allow for a better change of does anyone run this setup and have no complaints?

Edited by Gingerbread Man on Wednesday 25th September 11:22

[itsnotarace]

http://www.bikecalc.com/speed_at_cadence

How fast are we talking about here? And what size wheels and tyres

120 rpm in 42x11 is 36 mph with 26" wheels and 39mph with 29er

[Gingerbread Man]

26" wheels, Schwalbe Racing Ralph 26 x 2.1 tyres.

Unfortunately due to lack of use, my speedo has stopped working. Probably a dead battery.

My previous bike (26" wheels also) with 9 at the rear and 3 at the front, not sure on the cog sizes, but would have been around 42/44 at the front, so as guessing, not that helpful. But it was heavier, felt like I was really turning those wheels when in top all round and churning along. this one just seems too easy.

I'll look at the link when back home. Thanks for that.

[Bobley]

My 2010 bike has 3 x 9 and a 44 tooth chainring (XT 770). The change to 10 speed has brought about smaller chainrings but no change in smallest rear sprocket? My 2012 bike had 3x10 with 42 tooth chainring (SLX M660-10) I've sold it now.

Front chainring capacity is also limited by rear deraileaur capacity. You can find all the instructions on the Shimano tech docs website so check any potential purchases prior to pressing the order button...

I'm having the same grief with my road bike. I find a 50-34 annoying and would be much happier with a 30-39-52 triple but I need to change both mechs and find a triple Tiagra left shifter which looks like it'll cost more than a pair of 105 shifters?

[itsnotarace]

With those wheel and tyre sizes, going to a 44x11 will give you 37.42mph at 120rpm so an increase of a whole 1.5mph. Not worth it. Pedal faster

[TwistingMyMelon]

I feel your pain OP, I had a 42/11 as my top gear on my MTB commuter and found myself in that gear 90% of the time bar a 10% climb out my village

It was fine for comuteing, but would have liked something bigger, on even slight down hills I pedalled out of it (or at least felt like it)

On the downhill back home I easily hit 35mph so pedalled out of it, plus the geo and setup of the bike didn't facilitate high cadence as well as a roadie does, I also like grinding out a big gear, rather than spinning a smaller one.