53, 54, 55 Front Chain Ring?

I second what The Bear said. I have the same setup with a 53 up front and an 11-23, and I've only spun out a handful of times. I don't see speeds in the 40+ range that often, and when I do I honestly don't worry all that much about pedaling all that hard.

Maybe if you go with a larger front chainring you'd want to get a slightly different cassette to help on some climbs.

Given you almost never drop into the 39, you shouldn't lose anything at all.

Here is a good calculator to help.

http://home.earthlink.net/~mike.sherman/shift.html

If it's not too expensive, go get a 54 or 55 and try it out... and report back what you find out...

This table is from the link I provided above.  It shows speed (mph) based on 90rpm's with a 172.5 crank and a 700x28 tire.

    |    11    12    13    14    15    17    17    19    21    23    25
----+------------------------------------------------------------------
 54 |  35.0  32.1  29.6  27.5  25.7  22.6  22.6  20.3  18.3  16.7  15.4
 53 |  34.3  31.5  29.1  27.0  25.2  22.2  22.2  19.9  18.0  16.4  15.1
 50 |  32.4  29.7  27.4  25.4  23.8  21.0  21.0  18.8  17.0  15.5  14.3

Do you have any idea what your Power Threshold is?  It takes considerable power to spin a 53x11 or 54x11 for any length of time.  If you dont know this, what is your Avg speed for a sprint or oly distance race?   Most people that upgrade to a 53 or 54 are usually averaging over 24-25mph and dont need the lower end range from the 34.

The main advantage of a 50 is that you can pair it with a 34 which helps most AG'ers in the hills.  If you run a 50/34 up front and a 11 in the rear, this is actually faster than a 53 or 54 with a 12, which is what many people run in the rear.  So it usually makes more sense to change the cassette to something that has an 11 (over a 12 or 13) than upgrade to a 53 or 54 upfront since this still gives options for hills.  It sounds like you already have an 11 in the rear.  The above chart and link I posted earlier can give you an idea of what it means to upgrade to a 53, 54 or 55. 

Ok...I'll help you do the math.

Several assumptions...you consider spinning out at 100 rpms.  At those RPMs, 53/11 = 38.1 mph, 54/11 = 38.9 mph, and 55/11 = 39.6 mph

Use a stop watch and start and stop the watch when you feel like you're spinning out in your 53/11 gear, or when you are exceeding 38.1 mph. 

Take that time, in seconds (X), and plug into the following formula to find out (approximately) how far you travelled while spinning out.  Granted, you could have been going faster than 38.1, this will skew the results a bit, but pretty much negligible.

X / 60 / 60 * 38.1 = total distance traveled while spinning out.

So lets say you were spinning out for 2 minutes total on a ride...or 120 seconds

120 / 60 / 60 * 38.1 = 1.27 miles

So for 1.27 miles, you could have been going faster with a 54 or 55 tooth chainring.

With a 54 tooth ring, you could have been going 38.9 mph instead of 38.1, or with a 55 tooth ring, you could have been going 39.6 mph..  So how much time would you have saved if you had those setups.  We already know it would take you 120 seconds to cover 1.27 miles with the 53 tooth ring.  So we just put in a variable for time and change the MPH in the above forumula

T / 60 / 60 * MPH = 1.27    Solve for T

T = 1.27 * 60 * 60 / 38.9   T = 117.53 seconds

T = 1.27 * 60 * 60 / 39.6   T = 115.45 seconds

So, assuming that you were spinning out at a speed of 38.1 mph for 2 minutes, you would save 2.47 seconds with a 54 tooth ring, and 4.55 seconds with a 55 tooth ring.

Again...this assumes that your MAX speed with a 53/11 is 38.1.  If you were going downhill faster than 38.1 with your 53/11 at any point...then the time savings would actually be less...because you would have been going at a speed you would still be spinning out in 54/11 or 55/11 anyway.