Compact vs Standard Ratios

Today I came across a nice app called Bike Gear Calculator, www.BikeGearCalculator.com I had the same dilemma to get compact or not. this gear calculator gave me the answers I needed. Switching to compact now. As it turned out there are so many things to take into consideration.
http://itunes.apple.com/app/bike-gear-calculator/id505985340?ls=1&mt=8

andy - it really sounds like you want a standard chainset for aesthetic reasons but are trying to mitigate it's unsuitability for you by adding bigger sprockets or worrying about crank lengths. I reckon you should just get a compact with the right length arms for your legs and stop fretting.

The effects of crank arms length are not clear in terms of efficiency. I think it comes down to personal preference to be honest.

If you want a standard chainset for image rather than practicality, you'll need a straight through 11-23 block. Prepare for the club riders to snigger and mock you if not

Having two separate wheels and cassettes is a good option but just be aware of chain length - particularly over-stressing a chain on 53-29. It'll also have to be taught enough for 39-11 - even if that's bad form in terms of crossing the chain, it'll need to cope.

I had the same problem last year, so in the end I bought 2 bikes, 1 with 53/39 chainset for weekend riding and a bike with the compact 50/34 chainset on the cyclescheme for comuting. I much prefer the compact set-up as I am no pro-cyclist and I am not getting any younger. I get up the hills much better on the compact chainset.

also consider that with a compact you can always put a 52 / 39 chainring combo if you choose to later, you can't put smaller than a 38 on a standard.

I think it's easy to over estimate the size of large chainring you need. Just before my left hand lever broke and I went to a single chainring I had a 48/36 12-27 compact setup which had more than adequate top and bottom end for most riding and a much less awkward jump between chainrings. I'm now just using the 36 and it's fine for the commute and cxing, only tend to spin out over 25mph.

Basically, if you'd need a 29 on the back with a standard double; go with a compact.

Rob

I'm sure someone on here pointed out that a 50-34 compact with an 11-23 cassette offered a higher top gear and lower bottom gear than 53-39 and 12-25 whilst keeping (with campag 11 speed, I think) the same jumps between gears on the cassette.

I'm normally dead against compacts purely from an aesthetics point of view (vain, I know), but it's given me food for thought.

Rob

Difference between the compact's 50 teeth and a standard 52 or 53T big ring is minimal and 50x11 is a pretty high gear. Unless you're a big gear rouleur I'd stick with the compact and spend the money on upgrading your tyres or even wheels - you're likely to feel the benefit there more than anywhere else on the bike.

Here's a graph of my triple 52/42/30 (solid) against compact 50/34 (dashed) with a 12-25 9 speed cassette. 39T ring is only slightly lower than 42T shown. Ratios are based on Sheldon's calculator, linked above.

If you were set on the bigger chainrings you could look at Apex-style wide range cassette. New 10 speed Tiagra has 12-28 and 12-30, though you should check your rear mech has adequate capacity.

I have the same dilemma at the moment. The key I think is whether you believe you can push the 39-29 up the steepest hill you are likely to encounter on a typical ride.

Try a gear calculator, e.g. http://sheldonbrown.com/gears/ - to get an idea of the difference between your different options at various cadences.

Cheers!