3 chain ring V 2 chain ring.

[gavroche]

Many road bikes now come with 2 chain rings and I wonder if it is just as an economy measure or it is that there is no advantage to having a 3 chain ring? My Specialized Allez, bought in 2011 has 3 chain rings and I like the versatility it gives me on the road.
I am thinking of getting another road bike next year ( as a spare) and wonder if I will benefit in anyway by going 2 chain rings. Will if make much difference on hills?

 

[Robwiz]

The answer is - it depends. Historically, the classic road bike spec, known as 'standard' is for two chain rings, of 53 or 52 teeth and 39 teeth. Depending on rear cassette ratios, this set up may be a tad over-geared for a recreational cyclist (particularly up hills) as it's a set up used more for road racing. So going from a triple to a standard will make going up hills harder work, if you're used to dropping onto the inner ring.

The alternative is 'compact' - 50 and 34 teeth. It's argued that a compact gives the same wide choice of ratios as a triple with a reduction in weight. So, in theory, a compact shouldn't be much different on hills to a triple.

 

[Peteaud]

Depends on the cassette.

A 2012 Giant defy 2 has a compact 50/34 and a 12/30 cassette, so 34-30 gear, that may well be nearly the same as your ratio on a triple.

 

[black'n'yellow]

Many road bikes now come with 2 chain rings and I wonder if it is just as an economy measure or it is that there is no advantage to having a 3 chain ring?

For as long as there have been derailleurs, road bikes have always been available with 2x chainrings. It's not a 'new' phenomenon...

 

[lulubel]

The alternative is 'compact' - 50 and 34 teeth. It's argued that a compact gives the same wide choice of ratios as a triple with a reduction in weight. So, in theory, a compact shouldn't be much different on hills to a triple.

However, if you currently spend most of your time in the middle ring, which is probably 39 or 42 teeth, you might find yourself changing rings a lot more often with a compact, which some people find irritating.

 

[MattHB]

depends on the types of terrain you ride in and your levels of fitness.

If you ride in mountains and are a hardcore featherweight climber then a pro-compact (52-36), if youre a fit rider with an easy going cassette (28-11 or so) and you never get anything more than about 15% gradients then a run of the mill 50-34 will be all you ever need. If youre starting out, then you can either change the cassette to a 30-12 and run a normal compact or opt for a smaller 'granny' ring on the front to give you more spin options if you need it. For me, before I lost all my extra weight, I opted for a normal compact and upped the cassette to a 30-12 which did me fine.. I even managed (just) blissford hill in hampshire on it which is 23%.

Now adays I get frustrated with the gearing gaps on the 28-11 (which I currently run) as it interrupts my tempo HUGELY when zoned in and now I have the power to not worry so much Ill probably go for a 26 or 25 to try to even the ratio's out a bit in the spring.

 

[oldfatfool]

I have a triple on all my bikes and whilst it is rare I venture into the granny ring, it is even rarer I get off and push