I know nothing about you or the way you ride, but I think if you're concerned enough to consider it you should probably swap it. The first few rides are relatively flat so you have a few weeks to decide, but the later rides have a lot of climbing with some steep sections. I think most A-19 and A-Classic SIG leaders and participants are riding at least a compact, some a triple.

Hopefully others will chime in here.

As Nick started to allude to, cassettes have changed a great deal in the last few years, with the largest cog in the back frequently counting 28t (where 25t used to be the max for stock setup). If the former describes your new setup, you may find that a standard crankset can more than handle the challenges you will face together. 

Either way, you will notice a much greater ability to face those hills later in the season, the sooner you start doing hill repeats. I suggest now. ;]

I rode a cyclocross (48/38) crankset (with a 12-25 cassette) for last year's A Classic, and found it did alright for me. I do wish I hadn't waited until the good weather of the 4th week to start getting my hills in during the week, though!

Those early/pre-season workouts can really pay off quickly. Especially the hill workouts. Might as well embrace the pain now. :)

I fell in love with my compact (after riding a triple) within days. The recommendation here is go compact... you'll appreciate it on the hills; all of them!

George Arcarola

I did the A19 last year with a 53/39 12-26, so it's doable, but I was standing many of the hills. This year I'm going back to 50-34 11-25.

If you purchase a compact and sell your brand new 53/39 (ebay) you shouldn't be out more than $50-75.

Why suffer more than necesary on hills?  I have a compact with 11-28 gearing.

Adrienne

I encourage the OP to use an online calculator and do the math:

http://www.unwiredaviation.com/biking/

[Not working in Safari.  OK in Firefox]

The point of having any gears at all is to allow a cyclist to maintain optimum cadence (say 85 RPM) under varying conditions: flats-climbs-descents; head/tailwinds-paceline; smooth-rough-slippery road surface.  Otherwise, we could all by with single speeds.

In that regard, the two operative characteristics of any gear range is "wide" and "close":

"wide" refers to the lowest and highest gears that enable us to spin up steep hills yet pedal with resistance on 30+ mph descents.  Ie, the "extremes".

Yet "close" is what we care about in the vast majority of situations: moderate grades, headwinds, close proximity pacelines, etc.   Otherwise, we could all have three-speeds with just a low-middle-high.

The key is to first determine the level of rider; A-B-C, as well as the types of rides; SIG, club rides, touring, etc.  

In that context, review the three most common setups sold on contemporary road bikes:

(1) A 53/39 "standard" road double is common to most racing bikes of the last few decades.  With an 11-23 cassette, you get excellent nuance ("close") in a 21-32 mph range in the 53T; and an 11-18 mph climbing range in the 39T.  But to stay at your target cadence, you're going to have to attack every hill of every ride or limit yourself to flat or rolling terrain.  Ie, the "tail is wagging the dog".

[Remember you can't use all ten rear cogs with each chainring.  To avoid "cross chaining", you want to limit to the nearest 6-7 cogs with each ring.]

(2) The more modern 50/36 "compact" double, paired with a 12-26 cassette, works out well for the "A-Classic" rider: 18-28 mph cruising range in the 50T ring and a 9-16 mph climbing range in the 36T.  

- But compact doubles get tricky for B16-A19 rider.  Their cruising speed fall s into the gap of 50T and the 36T.  So their rowing back and forth between 50T-36T chainrings trying to find a comfort zone that just frankly isn't there.  I see this a LOT on the B-SIG.  Further, trying to maintain 9 mph on rides with extended climbing will be less than pleasureable.

- Counterintuitively, the 50-36T is an acceptable (though not ideal) choice for the "C" rider.  For relatively flat routes, they can just stay in the climbing range afforded by the 36T.  But there's not much to get them up Walnut let alone a succession of "Dead Presidents".

(3) A 50/40/30 "road" triple with a 12-25 cassette works out to a 14-20 mph cruising range in the middle 40T; an 8-12 mph climbing range in the 30T; and an additional cruising range of 20-28 mph in the 50T.  In this setup, a B16-A19 can spend 90% of the day in the middle ring, just by tweaking the rear cogs.  And for rides wth extended climbing, it's cheap and easy to swap out the 30T for a 24-26T "granny".

Now there are modifications and compromises possible within all three setups, (adding a modified "mountain" cassette to a road or compact double, etc.) but they involve some expense (long cage derailleurs) and a willingness to tradeoff one virtue for another ("wide" vs. "close").  

But to the extent you know what kind of rider you are-hope-to-be and the kind of rides you plan to do, you can save $$$ later by getting it right at the outset.

Finally, if everything above just makes your head hurt.  Go for the triple.  Inherently, it's the optimum between "close" and "wide"; it doesn't add to the cost on initial purchase; it's the least expensive to modify; doesn't really add much weight; If properly setup shouldn't provide any more mechanical difficulties than a two-ring set up; one can always choose to remove or "block off" a redundant ring; and a knowledgeable rider who scouts the terrain can preset alternate ratios, wheelsets.  

"Their legs, like giant levers, will power onwards for sixty hours; their muscles will grind up the kilometers; their broad chests will heave with the effort of the struggle; their hands will clench onto their handlebars; with their eyes they will observe each other ferociously; their backs will bend foward in unison for barbaric breakaways; their stomachs will fight against hunger; their brains against sleep. And at night a peasant waiting for them by a deserted road will see four demons passing by, and the noise of their desperate panting will freeze his heart and fill it with terror." - Henri Desgrange

I used to ride a 50/34 and 11-28 cassette and had the problem Neile describes - at 18-20 miles/hr I was always cross-chaining.  I switched the 34 for a 38 small ring and it solved the problem.  I did the A19 and part of the A Classic on that setup.

Have you done any of the favorite climbs on the new bike yet? River Road, Bradley, the Presidents? If so, how did it feel?