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I own two bikes:

Experimentally Revolt has a better roll than Anyroad. This really bugs me because:

  • Anyroad has a stiffer fork.
  • Anyroad tyre width 32, Revolt - 35.
  • Revolt weights slightly more.

I've perfectly adjusted cones for Anyroad, experimented with tyre pressure, switched riders.

The only thing I didn't change is the hubs. Revolt has Formula [F] DC20 [R] DC22, alloy disc hub, double-sealed, Loose Ball Bearing, 32H. Anyroad has sort of noname Giant, [F]24h, [R]28h.

Does anyone know anything about this mysterious Giant hub? Could it be a culprit as the Formula hub gives better roll? Are there any other suggestions how to make Anyroad roll better?

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Interesting. I would suggest swapping the wheels and comparing again (if possible). The two bikes have slightly different geometries which would give you a slightly different ride position. Also, check the seat heights. Seat height also gives a different position. How large is the difference in speed? –  andy256 Jun 14 at 10:28
    
I've tested both bikes primarily on road on hills of various steepness. The bikes were rolling beside each other. Revolt outruns in a matter of 5 sec significantly. Thank you for an idea - I will try to change the wheels to see if it makes any difference. –  Max Ch Jun 14 at 11:12
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If you truly want to know, you'll have to measure the difference between the two bikes in both rolling resistance and in aerodynamic drag. The most precise way to do that requires having a device that will record your second-by-second speed as was described in this bicycles.stackexchange answer: bicycles.stackexchange.com/questions/9938/… –  R. Chung Jun 14 at 13:17
    
@R.Chung He is not asking how to measure he is asking why. He has tested on various hills and switched riders. –  Blam Jun 14 at 13:43
    
When you say experimented with tyre pressure you are not by any chance running them both at the same pressure? Run both at the max for that tire. Significant in 5 seconds is a lot. If you turn em over and spin the tires how do they compare? If swapping wheels makes a difference then swap tires to determine if it is the wheel or hub. –  Blam Jun 14 at 14:16

2 Answers 2

up vote 1 down vote accepted

Running both tires at the same PSI could be your problem. In a comment you stated you are running both at 70 PSI.

Tires of different width will typically have different design pressures. Larger tires run at lower pressure. Run both tires at the max pressure for that tire. On the sidewall will be an operating pressure range for that tire. Run both tires at the maximum for that tire.

If you are running both tires at the same pressure you are penalizing the smaller tire that is designed to run at a higher pressure.

The size of the contact patch is PSI times weight. So if you have 140 lbs on the tire at 70 psi the contact patch is 2 square inches. The more narrow tires must have a longer contact path to achieve that same 2 square inches. The more narrow tire must deform more. That deformation is rolling resistance. More deformation is more rolling resistance.

This link discusses resistance, deformation, and pressure Rolling Resistance

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Thank you for your answer. It totally makes sense, but the maximum pressure is equal for the both tyres. imgur.com/a/glY0J –  Max Ch Jun 15 at 9:11
    
I would swap tires to test if it is tires. If you want to even things out run the larger tire about 8 psi less. –  Blam Jun 15 at 13:28

If you're measuring on downhills, the Revolt will roll better because it weighs more, not despite it. While objects of different mass will free-fall at the same rate (all else being equal), the mechanics of coasting are different due to the effect of air resistance. A great explanation is available here.

There are better ways than roll to measure a bike's efficiency--like given the same energy input, same speed, and same wind profile (for the rider at least), which one goes farther on a flat surface? Or, given the same energy expenditure and the same flat distance, which one arrives first?

If you're concerned with efficiency, hunching over a bit more for aerodynamics will have much more of an effect than minor differences in rolling resistance, or slight differences in the weight of the bike.

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Interesting insight, thank you. I've noticed that if I bend deeper over the handle bars, I outrun Revolt. –  Max Ch Jul 16 at 7:33

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