It was on an audax about eight weeks ago going up a 10% hill, that I experienced what it means to have a poor choice of gearing on your bike. I was running a 52/36*11/28. I had a pair of power tap pedals fitted and reviewing my data just now I was doing an average of 293w and an average cadence of 68. The power I'm okay with, just within threshold, but the cadence I found a grind and because I was grinding at the pedals the front wheel was starting to slip. In the end I had to get off and walk.
With this in mind and with some rather hilly rando's coming up, I've reviewed my choice of gearing and here he is:
Changes that I've made are:-
Installed a 104/64 BCD XT chainset with 40/25 Q rings.
Installed a triple front mech and shifter.
Installed a 11/32 cassette.
Problems I had and solutions:-
As you can see form the pic the front mech arm allows a front mech to go down only so far. This made shifting with a double shifter a bit of a mare. You can probably buy or get a shim from somewhere which allows the front mech to be placed nearer to the chainset. As it is, I went with a triple to solve this problem and it shifts just fine. Needless to say you also need a triple front shifter.
Inside of the chainset rubs it bit against the chainstay, a spacer eliminates any rub. Thanks for the tip @ratz .
My first impressions are that I'm pleased with my new rig. Even though I fitted the Q rings last night, I have rode with round rings for the last month or so. And a few weeks ago I went on a hilly bike ride, coming out of Brighton there is a fairly long sustained climb at about 6% overall average with bits at 8-9%. Looking at my data just now, I was at a far more sustainable 175w with a much more knee friendly 84rpm.
And one might say that this gearing is low, but a 40*11 at 95rpm still gives around 27mph. The way the bike is I'll probably run it as a straight 40*11/32 only going into the granny ring when going up some serious 'bergs.
The only reservation I have is that going down a hill I'll maybe spin out faster. But the majority of downhills that I've gone down you don't really need to pedal to go fast. As I'm sure you are all aware!
Anyways, feel free to make comments or questions.
With this in mind and with some rather hilly rando's coming up, I've reviewed my choice of gearing and here he is:
Changes that I've made are:-
Installed a 104/64 BCD XT chainset with 40/25 Q rings.
Installed a triple front mech and shifter.
Installed a 11/32 cassette.
Problems I had and solutions:-
As you can see form the pic the front mech arm allows a front mech to go down only so far. This made shifting with a double shifter a bit of a mare. You can probably buy or get a shim from somewhere which allows the front mech to be placed nearer to the chainset. As it is, I went with a triple to solve this problem and it shifts just fine. Needless to say you also need a triple front shifter.
Inside of the chainset rubs it bit against the chainstay, a spacer eliminates any rub. Thanks for the tip @ratz .
My first impressions are that I'm pleased with my new rig. Even though I fitted the Q rings last night, I have rode with round rings for the last month or so. And a few weeks ago I went on a hilly bike ride, coming out of Brighton there is a fairly long sustained climb at about 6% overall average with bits at 8-9%. Looking at my data just now, I was at a far more sustainable 175w with a much more knee friendly 84rpm.
And one might say that this gearing is low, but a 40*11 at 95rpm still gives around 27mph. The way the bike is I'll probably run it as a straight 40*11/32 only going into the granny ring when going up some serious 'bergs.
The only reservation I have is that going down a hill I'll maybe spin out faster. But the majority of downhills that I've gone down you don't really need to pedal to go fast. As I'm sure you are all aware!
Anyways, feel free to make comments or questions.
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