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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?

Max Ch
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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 '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 '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: http://bicycles.stackexchange.com/questions/9938/how-can-one-estimate-drag-for-a-bicycle/9947#9947 – R. Chung Jun 14 '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. – paparazzo Jun 14 '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. – paparazzo Jun 14 '14 at 14:16
  • Blam, he can't know why until he knows whether the issue is truly rolling resistance or aero resistance. Measurement will tell him that. – R. Chung Jun 14 '14 at 15:00
  • @R.Chung So if he switches tires and the results reverse he still doesn't know that is the cause because he did not measure? Based on "Revolt outruns in a matter of 5 sec significantly" I am going to go out on a limb here and state the Revolt has lower rolling resistance. – paparazzo Jun 14 '14 at 17:23
  • Most strangely is that when I turn them over and spin the wheels, the Anyroad's front wheel will outlast Revolt's. This is because I spent most time calibrating the cones for Anyroad. Also I realised I'd have troubles switching because the disk brake radius is different for two bikes. Finally, it seems that the Giant hub performs worse on load than the Formula hub. – Max Ch Jun 14 '14 at 19:22
  • As regards to the rolling resistance, the tyres are identical in all aspects (tread, material) except for the width. I tested both on pressure 70psi, although it didn't matter much.I will also try to lower the seatpost for Anyroad as it is higher than Revolt's right now. – Max Ch Jun 14 '14 at 19:30
  • Assuming that the bearings and brakes aren't dragging, any difference in rolling resistance would have to be due to the tires -- pressure, width, tread, and/or material. But with disk brakes there's a definite chance that brake drag is also a factor. Unless a bearing is overtightened or is actually defective, bearings could not be a factor. – Daniel R Hicks Oct 29 '14 at 11:19
  • But it's not clear that the difference being measured is not wind resistance or weight difference. – Daniel R Hicks Oct 29 '14 at 11:21

3 Answers3

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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.

John McGrath
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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 '14 at 07:33
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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

paparazzo
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  • Thank you for your answer. It totally makes sense, but the maximum pressure is equal for the both tyres. http://imgur.com/a/glY0J – Max Ch Jun 15 '14 at 09:11
  • 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. – paparazzo Jun 15 '14 at 13:28
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Weight distribution.

Bicycles have 2 tires, 2 wheels, 2 hubs, how is the weight split between the front and rear on both Bikes? I am going to guess that it makes a huge difference.

Tim Rice
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  • Welcome to [Bicycles.SE] Tim. This site is different - it's not a discussion (although you can use chat for that). It is a site where good answers should become definitive references. A guess doesn't really fit that description :-) – andy256 Oct 29 '14 at 03:54
  • Well then I'll have to go find an explanation to the above, as to why splitting the weight between front tire and back tire makes a difference. Then post that explain in a definitive answer, instead of a question layout, for reference reasons. – Tim Rice Oct 31 '14 at 18:58