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I have a gravel 1by bike with 42t and a 11-42 cassette. I also have a road bike with 50-34t and then 11-34 cassette. My question. When going uphill in easiest gear in both, they would both be a 1:1 ratio, but is one effectively an easier gear(i.e less effort) than the other because of the different number of teeth? cheers

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    There could be some small differences in efficiency depending on the number of teeth, even with the same gear ratio and development. For example small cogs tend to be less efficient. Having a big chain angle is also bad for efficiency. I’ve read that riding in the big chainring tends to be slightly more efficient, maybe because the chain is under more tension and loses less power to vibrations.
    – Michael
    Mar 24 at 10:21
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    @Michael For the same gear ratio, you're right, larger chainrings tend to be slightly more efficient but that's because the chain is under less tension. At the same cadence and speed, the power must be the same but the chain moves faster--so the force transferred through the chain (i.e., tension) is lower.
    – R. Chung
    Mar 24 at 18:09
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    Suggestion: Don't phrase the question oppositely in the title (are they the same?) versus in the body (are they different?). This makes it hard to write a clear "yes" or "no" answer.
    – nanoman
    Mar 26 at 19:07

5 Answers 5

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No, both gears will be identical. The absolute number of teeth does not matter, only the ratio does. Both bikes have a lowest gear ratio of 1:1, so from the gearing alone both will be equally "hard".

However, since the gravel bike's tires are probably bigger, the distance traveled in one wheel rotation is longer than on the road bike. This means that even in identical gear ratios (e.g. both 1:1), the gravel bike will be slightly "harder", particularly considering that the gravel bike is probably heavier.

You can use a tool like the bike gear calculator to compare effective gearing while factoring in tire size differences. For example see this comparison assuming 28mm and 40mm tires.

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  • thanks for that, hadn't really considered tyre size. cheers
    – Jubbly
    Mar 24 at 10:00
  • Just to highlight from the comparison you’ve linked: On the road bike in the lowest gear at 90rpm you’d be going 11.6km/h, with the gravel bike you’d be going 12km/h. That’s a 2.6% difference. If your total weight with the road bike is 77kg and with the gravel bike it’s 79kg that would be another 2.6% difference.
    – Michael
    Mar 24 at 10:17
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    Crank length will also make a difference Mar 24 at 15:12
  • Also, the gravel bike's tires may big bigger, in some cases that is offset by having a different size rim. My gravel bike has a 47mm tire on a 650B rim which by my calculations is very similar to a 28mm tire on a 700 rim.
    – Kibbee
    Mar 24 at 18:10
  • At 2.6%, geometry, bike fit etc will probably l make a bigger difference than wheel size to perceived effort if not real effort.
    – mattnz
    Mar 24 at 18:39
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Doesn't matter for easier pedaling, but matters for wear

Since nobody has mentioned it yet - with bigger gears,

  • the chain runs smoother as the gears are closer to circles,
  • the chain links have to bend for a smaller angle,
  • the force on the chain gets proportionally lower,

all effects that reduce wear. On the other hand, the chain travels over more teeth in the same amount of time, which might increase wear, but I'm pretty confident the wear-reducing effects dominate, and thus bigger = longer lifespan.

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    Larger rings also mean more teeth engaged, meaning that the force is spread over larger contact area, meaning less wear on the chainring and cog. Mar 25 at 0:37
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    The biggest factor for wear is the teeth count. Notice how chainrings are usually made out of aluminium and still last ages while the small sprockets are always made out of steel or titanium.
    – Michael
    Mar 25 at 5:42
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As said previously, the ratio is the important metric, not the number of teeth. Tires (tread and pressure) can be a important differentiating factor between the two bikes. The gravel probably has larger tires, which impact the outer diameter (as explained) and the surface in contact with the road.

They are also meant to be run at different pressures. Road bikes inflated are typically at high pressure (>6bars), while gravel bikes should be inflated at much lower pressure (2.5bars-4bars). That alone has an impact on the rolling resistance.

Gravel tires also have (deeper) treads, which improve traction on loose surfaces, at the cost of rolling resistance on hard surfaces. The effect of rolling resistance is more felt in uphill than on flat terrain, because it adds to an already existing effort.

So with that, the road bike should be easier on hard surfaces, while the gravel will be easier on loose surfaces because of the additional grip.

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Larger chain ring are slightly more efficient in transfer loses. But larger chainrings are heavier.

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  • I remember reading somewhere, possibly Bicycling Science (MIT Press) or a quarterly journal that ceased publication a couple of decades ago, that for a given ratio, the combination with the larger number of teeth is marginally more efficient, but I cannot put my finger on it. But I suspect that the difference is less than other factors, like whether the chain is lubricated.
    – ichabod
    Mar 25 at 15:50
  • The chain doesn't need to bend as much with a larger chainring (as noted by MaxD's answer), which results in a more efficient drivetrain.
    – Ealhmund
    Mar 25 at 18:21
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gear ratio is not the only factor affecting the force you apply on pedals on a given climb: put in account for pedal length and wheel radius !!

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