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triathlete

Math is Illuminating

In my last post, I mentioned that I was going to have to make some upgrades to my bike due to how hard hill climbing is with the current 1 x 11 gearing. For those wondering, 1 x 11 means one front ring (instead of the usual 2 or 3) and 11 cogs on the rear cassette. Simpler. Fewer parts to break or rely on. But gives up some flexibility.

Here’s the quote:

Key realization made: the 1×11 drive train may be the new hotness and all the rage in the cyclocross world, but if I’m going to do more gravel races (and I will!) then I’m going to be adding a front derailler and enjoying the gearing with a 2×11 setup.

I decided that before I start spending money, I should check that assertion a little more closely.

My road bike’s lowest hill climbing gear is with the 34 tooth ring up front and a 28 tooth cog in the rear. Checking a handy gear ratio calculator, that gives me a ratio of 1.21. I have climbed some big ass hills with this combo. A 32 in the rear would be nice, but my current rear derailleur won’t support such madness.

The gravel bike’s front ring is a 40 and the lowest hill climbing gear is 36. That’s a 1.11 ratio — which is dang close to the road bike but a bit better. Kind of like getting one more lower gear, in fact.

So… why is hill climbing so much harder on the gravel bike even though the gear ratio is actually more favorable? I have no idea, but as always, I have guesses:

  1. More rolling resistance due to riding on loose gravel or dirt (I feel this HAS to be the issue but not sure how to quantify it)
  2. More rolling resistance due to riding on wider tires [and at a lower air pressure].
  3. For some perverse reason, some of the gravel route hills are just plain steeper.

Where do I go from here? Not sure yet. One option would be to just drop my gravel bike’s front ring from the 40 down to a 38 or 36. I would give up some top speed but gain more bottom.

Another option would be to replace the gravel bike’s rear derailleur with something that could support larger cogs in the rear. I could keep the 40 up front but go 40+ in the rear. That has a lot of appeal, but costs more. I keep the benefits of the “1 by” and get more oomph for the hills.

Or I stick with my original idea and replace the single ring up front with a double and add a front derailleur into the mix. The most expensive option, but gives the most flexibility.

Right now I’m firmly in the “analysis paralysis” zone.

One reply on “Math is Illuminating”

Great explanation, was math your favorite class? The rolling resistance could be what you hit on, but, need a work around. You have four bikes, is anything interchangeable ? Your time is cheap, when it comes to your hobby. Their must be some gravel forums ?

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