going double to triple

[wnyrider]

...Just changing your cassette will make a big difference. ... You might want to do one or the other at first. I'm not sure how badly you're struggling with your current setup. ...If you go compact, do that with your current cassette first. Then see if maybe you'd want a 12-25, 12-26, 12-27, 12-28, 13-29, etc.

The best example of what I need may be reflected in my ride the day before. I was going up an escarpment. I down shifted to the 39 and 23-- my lowest gearing. I couldn't spin at this point and I felt like I was mashing big time. I was bearing down and the chain actually skipped several times (another issue) and I thought I was going to do some damage. If I could have just had a bit of lower gearing than it would have been more pleasurable. I've priced compact cranks and cassettes, and for the most part the prices are close. The newer compact Tru cranks seem to be mostly 50-36. I have spotted some old new stock 50-34 though. So with that, just to gain some lower gearing, which would I swap out if I had to choose just one, crank or cassette?

[silver]

switching your cassette:

53/39 - 13-29 2.6%

switching your chainrings:

50/34 - 12-23 2.9%

lower ratio is obtained with just switching the cassette

(BTW if you decide to do the chainrings....50/36 - 12-23 3.1% recommending the 50/34 if you can get it)

[wnyrider]

Thanks for you patience doing the math silver. I am glad you find it fun! Well, I am thisclose on making the switch. Saw this posted in a thread on another forum and it does appear interesting. Is anyone here familiar with this crank? It looks to be a 52-24 crank:
http://www.whiteind.com/cranks/roadcranks.html

[SadieKate]

Is anyone recommending that you use a 24-52 combo?????? That is an incredibly wide range to pair.

The size rings WI lists are just the different size rings they sell which are compatible with that crank.

There are a whole host of things that go into a properly functioning drivetrain. For instance, the front dérailleur must match ring curvature (determined by the ring diameter) and the rear dérailleur must be able to take up chain slack (calculating by chain wrap). Do some research on dérailleur capacity for your brand of component.

[Eden]

hmmmmmm it looks like you could possibly order that crank with a 52 outer and 24 inner, but I would think that would not be such a good idea. With a difference that great in the rings shifting would be a real bear... you'd really be pulling hard to get the chain up from the small ring to the big one and when you shifted down the drop would be so big that you'd probably drop your chain a lot... I'm looking around for the biggest suggested difference between inner and outer rings.

[SadieKate]

The rule of thumb I've been given is 10-12 tooth max difference between rings for the snappiest shifting. This is part of the reason there was a real lapse in the performance of shifting on compact doubles, the 16 tooth jump. Until recently many front derailleurs just weren't designed for this gap, hence the intro of derailleurs designed for compact doubles.

[Eden]

I have doubts that a 28 tooth difference would shift at all.... on my old bike with a triple it was *hard* to shift from the 30 to the 42 and that's only a 12 tooth difference.

[SadieKate]

I went back and noticed that the drivetrain is Campy. Definitely stick with 10-12 tooth gaps max.

Look at a nice polished Sugino triple with 46-36-26. This should give you a nice set of climbing gears while still maintaining the tight cogs set for flat land riding. You will need a new bottom bracket but you can get some nice quality JIS taper BB's for a reasonable price.
http://www.sheldonbrown.com/harris/cranks/11074.html

For upscale cranks, you can look at TA cranks from Peter White and customize the ring choices even more.
http://www.peterwhitecycles.com/carmina.asp

Here is info on calculating your derailleur capacity
Chain Capacity and Cage Length
http://branfordbike.com/page.cfm?pageID=62

[SadieKate]

I have doubts that a 28 tooth difference would shift at all.... on my old bike with a triple it was *hard* to shift from the 30 to the 42 and that's only a 12 tooth difference.

Yeah, typically the smallest ring to the middle ring should only be 10 while you can go to a 12T gap between middle and big.