100 miles and 10,000 feet of climbing.

My rule of thumb is that 200 feet of elevation is about like adding one more mile. But even a quite flat 100 mile route can easily have 3000 feet of elevation. So maybe this is more like an additional 7000 feet or 35 miles equivalent. That's a lot.

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For gearing, it's all about the steepest grades.

On this ride, see for example on the ridewithgps link, the climb at

**mile 80.5** (you can drag to select a section of the red elevation graph, then hover over the climb to see the grade at that point, and the Metrics tab shows the averages for the whole climb.) It's

**500 feet in 0.9 miles, for an average of 10.5%** and a max of 13%. There's a lot of 9% or steeper grades on the other climbs, too.

With your 11-28 cogs, switching to a 34 chainring from a 39 is just about exactly one more easier cog in the back.

**Here's your setup** in Mike Sherman's gear calculator, with a 53, 39, and 34 chainring to make it easy to compare. (the popup message when the page loads is just to let you know that you can save the URL in your bookmarks to repeat this setting.)

Scroll down to the bottom of the page to see, for steep hills, at 60 rpm,

39-28 is 6.5 mph.

**34**-24 is 6.6 mph,

**34**-28 is 5.7 mph.

(I would be riding that 500 foot/10.% climb at about 3.7 to 4.5 mph in my 34-29 low gear, standing up and doing 40-50 rpm, keeping my heart rate in a sustainable range. You are likely quite a bit stronger.)