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Why does one bike climb better than another?

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Why does one bike climb better than another?

Old 09-10-21, 02:38 PM
  #26  
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Assuming that all else is equal, it's not necessarily the total weights of each wheelset that matters. What counts most is the locations of the weight. If the 700c wheels have lighter hubs, but heavier rims+tires, than the 650b bike, all of those little accelerations will take more force to accomplish. If the 700c rims+tires weigh exactly the same as the 650b, but have a larger diameter, those little accelerations will take more force. If the 700c rims+tires weigh more than the 650b, and they have a larger diameter, they'll need even more force.
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Old 09-10-21, 03:33 PM
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There are about a hundred different factors as to why one bike would ride better than another for any stretch of ground. Pick one.
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Old 09-10-21, 04:00 PM
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Originally Posted by seypat
It might be the color also. That's really important, maybe.
Yes. Red is the fastest. Except when black is around.
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Old 09-10-21, 06:36 PM
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Originally Posted by BadgerOne
Dammit, I knew buying a matte gray bike was a bad idea. It's just so....ordinary. Maybe I should try painting it a fluorescent yellow/hot pink fade and see what that does. Clearly the electric blue metallic is working for the Doppler. Krylon rattle cans, here I come!
Don’t be ridiculous. Everyone knows red bikes are faster.
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Old 09-11-21, 05:31 PM
  #30  
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The Breezer planes.

https://www.renehersecycles.com/what-is-planing/
https://www.renehersecycles.com/the-...cs-of-planing/
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Old 09-12-21, 10:10 AM
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Originally Posted by Frank S
Assuming that all else is equal, it's not necessarily the total weights of each wheelset that matters. What counts most is the locations of the weight. If the 700c wheels have lighter hubs, but heavier rims+tires, than the 650b bike, all of those little accelerations will take more force to accomplish. If the 700c rims+tires weigh exactly the same as the 650b, but have a larger diameter, those little accelerations will take more force. If the 700c rims+tires weigh more than the 650b, and they have a larger diameter, they'll need even more force.
Heavier rims/tires mean more inertia and it does require more force/torque to accelerate them, but that energy is not lost - it's stored in the wheel and assists the rider in between strokes.

There may be some efficiency difference in the biomechanics, like how quickly it tires out the muscles to accelerate slowly on each pedal stroke, or perhaps differences in the flexing of the tire (and frictional losses from that, if the tire flexes more during more of the downstroke, like especially if the rider is out of the saddle), but in terms of rotation of the wheel itself, there is probably relatively little energy lost regardless of wheel weight or weight distribution.
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Old 09-12-21, 08:09 PM
  #32  
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In this case, I expect it’s the tires. WTB Horizon is fairly fast rolling for its size and probably some fair number of watts less work to move than the Kenda K-1024 which looks to be a hefty touring tire. It’s the sort of thing that really gets noticed when you are climbing and have to also deal with the work against gravity.

Otto
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Old 09-13-21, 06:25 AM
  #33  
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Has the OP stated what tires he is using? the post above indicates WTB Horizon vs Kenda K-1024. If that is the case, that alone would make a pretty big difference.
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Old 09-13-21, 06:38 AM
  #34  
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Originally Posted by Kapusta
Has the OP stated what tires he is using? the post above indicates WTB Horizon vs Kenda K-1024. If that is the case, that alone would make a pretty big difference.
That’s just a guess, based on what appears to have been the tires supplied with the two bikes.

Otto
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Old 09-13-21, 07:00 AM
  #35  
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Originally Posted by ofajen
That’s just a guess, based on what appears to have been the tires supplied with the two bikes.

Otto
Well then this is the best guess I have seen so far in this thread.

Trying to answer the OPs question without knowing what tires he is running is like trying to figure out why a house is cold without checking to see if the windows are all open.
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Old 09-13-21, 07:09 AM
  #36  
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Originally Posted by ofajen
In this case, I expect it’s the tires. WTB Horizon is fairly fast rolling for its size and probably some fair number of watts less work to move than the Kenda K-1024 which looks to be a hefty touring tire. It’s the sort of thing that really gets noticed when you are climbing and have to also deal with the work against gravity.

Otto
Perhaps, but the 47c Horizons which came on my Doppler were 697g each (actual)! That’s heavy AF! Rode like the proverbial Cadillac, but was slow. I replaced them with Herse Switchback Hill 48c standards, claimed at 441g, dropping over a pound in rubber and bringing the ride alive. It’s still a heavy bike, though, so I dunno if it made any meaningful difference to climbing speed, but I find the bike a blast to ride, so I don’t care!
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Old 09-13-21, 08:10 AM
  #37  
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Originally Posted by chaadster
Perhaps, but the 47c Horizons which came on my Doppler were 697g each (actual)! That’s heavy AF! Rode like the proverbial Cadillac, but was slow. I replaced them with Herse Switchback Hill 48c standards, claimed at 441g, dropping over a pound in rubber and bringing the ride alive. It’s still a heavy bike, though, so I dunno if it made any meaningful difference to climbing speed, but I find the bike a blast to ride, so I don’t care!
But in the OP’s case the WTB Horizons are not being compared to $80 high performance RH tires, they are being compared to $16 garden hoses.
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Old 09-13-21, 09:06 AM
  #38  
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Originally Posted by jayp410
Heavier rims/tires mean more inertia and it does require more force/torque to accelerate them, but that energy is not lost - it's stored in the wheel and assists the rider in between strokes.

There may be some efficiency difference in the biomechanics, like how quickly it tires out the muscles to accelerate slowly on each pedal stroke, or perhaps differences in the flexing of the tire (and frictional losses from that, if the tire flexes more during more of the downstroke, like especially if the rider is out of the saddle), but in terms of rotation of the wheel itself, there is probably relatively little energy lost regardless of wheel weight or weight distribution.
OK, let's put this to rest quickly...
Yes, there is some inertial energy/momentum which keep a bike in motion... (and let's just say, in this case, roll resist, 'drag' and overall mass is the same for flat & uphill)
so, once gravity is added in, things change.... quickly demonstrated - given an equal velocity, stopped pedaling will carry you further (momentum/inertia) on the flat as opposed to any level of uphill.
so, for any degree of upslope, you will have to add more energy (pedaling) to cover an equal distance.
Depending on the slope/gravity, that inertia will dissipate quite rapidly, so the 'work' you will need to do will be greatly increased.
'Work' over time is 'Power'...
Graviity creates 'Acceleration' - base jump w/o a chute and you will experience acceleration until you hit terminal velocity OR stop...
riding uphill, is the same in reverse, except is deceleration ...
every pedal stroke requires acceleration to counter the deceleration.
I'm not gonna go into the limitations of our human pedaling power, cadence, gear selection, mass, rolling resistance - we all know the real world of that....
so things we can improve/change for climbing...
POWER (tough, not a money thing, except what is spent to create more of it... LOL !!!)
overall mass of the object being accelerated
rolling resistance (tire, pressure AND road/riding surface)
rotating mass (which will add acceleration requirements)
the last three elements are what the OP is asking... most often a money thing...
so heavier rims/tires will require more force in acceleration.
Thx
Yuri

Last edited by cyclezen; 09-13-21 at 09:13 AM.
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Old 09-13-21, 10:08 AM
  #39  
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Originally Posted by Kapusta
But in the OP’s case the WTB Horizons are not being compared to $80 high performance RH tires, they are being compared to $16 garden hoses.
I dunno anything about the Kenda at issue, only that a 697g tire is very heavy…to the point that I’d be surprised if the Kenda 700x40c were significantly heavier than that.
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Old 09-13-21, 10:09 AM
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Originally Posted by chaadster
I dunno anything about the Kenda at issue, only that a 697g tire is very heavy…to the point that I’d be surprised if the Kenda 700x40c were significantly heavier than that.
How heavy the tire is is much less important that how well it rolls.
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Old 09-13-21, 10:12 AM
  #41  
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Would be interesting to try and put the 650b wheelset onto the other bike and see how it feels then.
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Old 09-13-21, 10:27 AM
  #42  
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Originally Posted by Kapusta
How heavy the tire is is much less important that how well it rolls.
Well we are talking about climbing, so I guess that would depend on how steep, how fast, and how far we’re measuring. In any case, a 650b tire weighing nearly 700g is not constructed for low rolling resistance; it’s probably a coarse, stiff, low thread count casing with a lot of rubber making it it even less supple.
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Old 09-13-21, 11:19 AM
  #43  
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Originally Posted by chaadster
Well we are talking about climbing, so I guess that would depend on how steep, how fast, and how far we’re measuring. In any case, a 650b tire weighing nearly 700g is not constructed for low rolling resistance; it’s probably a coarse, stiff, low thread count casing with a lot of rubber making it it even less supple.
You are making a lot of assumptions, here, based solely on weight.

WTB Horizon is 60 or 120 tpi, depending on the model. Kenda in question is 30tpi.

There are many reasons why a tire can be heavy, some correlate to rolling resistance, others do not. The WTB in question costs ~4x what the Kenda does. It is reasonable to assume that in addition to the higher tpi casing, it may also use higher quality (more supple) casing material. Also, it matters a lot WHERE the extra casing material and stiffness is. It matters less in the middle of the tread than in the sidewalls.

I am curious about the nearly 700g weight you are claiming. BikeRumor, Gravel Cyclist, Riding Gravel all show actual weights around 510-520g a tire.

Last edited by Kapusta; 09-13-21 at 11:47 AM.
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Old 09-13-21, 12:43 PM
  #44  
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Originally Posted by cyclezen
OK, let's put this to rest quickly...
Yes, there is some inertial energy/momentum which keep a bike in motion... (and let's just say, in this case, roll resist, 'drag' and overall mass is the same for flat & uphill)
so, once gravity is added in, things change.... quickly demonstrated - given an equal velocity, stopped pedaling will carry you further (momentum/inertia) on the flat as opposed to any level of uphill.
so, for any degree of upslope, you will have to add more energy (pedaling) to cover an equal distance.
Depending on the slope/gravity, that inertia will dissipate quite rapidly, so the 'work' you will need to do will be greatly increased.
'Work' over time is 'Power'...
Graviity creates 'Acceleration' - base jump w/o a chute and you will experience acceleration until you hit terminal velocity OR stop...
riding uphill, is the same in reverse, except is deceleration ...
every pedal stroke requires acceleration to counter the deceleration.
I'm not gonna go into the limitations of our human pedaling power, cadence, gear selection, mass, rolling resistance - we all know the real world of that....
so things we can improve/change for climbing...
POWER (tough, not a money thing, except what is spent to create more of it... LOL !!!)
overall mass of the object being accelerated
rolling resistance (tire, pressure AND road/riding surface)
rotating mass (which will add acceleration requirements)
the last three elements are what the OP is asking... most often a money thing...
so heavier rims/tires will require more force in acceleration.
Thx
Yuri
The fact that some of the mass is rotating is not even worth talking about in respect of climbing performance. Only the total mass makes any real difference on a slope, governed by trivial Newtonian physics. Whether or not it is rotating is almost irrelevant in this respect.

If you are riding at a constant speed up the hill then the inertial energy stored in the wheels is also a constant (since they are spinning at a constant speed). So it's all really just about the total mass and gravity acting on it vs the pedal force. Lighter wheels help climbing simply because they are lighter, regardless of their rotational inertia.
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Old 09-13-21, 01:28 PM
  #45  
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Originally Posted by Kapusta
You are making a lot of assumptions, here, based solely on weight.

WTB Horizon is 60 or 120 tpi, depending on the model. Kenda in question is 30tpi.

There are many reasons why a tire can be heavy, some correlate to rolling resistance, others do not. The WTB in question costs ~4x what the Kenda does. It is reasonable to assume that in addition to the higher tpi casing, it may also use higher quality (more supple) casing material. Also, it matters a lot WHERE the extra casing material and stiffness is. It matters less in the middle of the tread than in the sidewalls.

I am curious about the nearly 700g weight you are claiming. BikeRumor, Gravel Cyclist, Riding Gravel all show actual weights around 510-520g a tire.
yeah, I’m making assumptions precisely for the reason that it seems to be a special OE Horizon that’s not sold retail, based on the weight. They’re hanging in my garage, wire bead, and very rigid sidewalls. I don’t think this OE Horizon has much in common with commercial options, but I don’t anything about it other than what I can observe; casing, compound, and stuff like that are unknowns, suggested only by weight and texture.
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Old 09-13-21, 01:33 PM
  #46  
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Originally Posted by chaadster
yeah, I’m making assumptions precisely for the reason that it seems to be a special OE Horizon that’s not sold retail, based on the weight. They’re hanging in my garage, wire bead, and very rigid sidewalls. I don’t think this OE Horizon has much in common with commercial options, but I don’t anything about it other than what I can observe; casing, compound, and stuff like that are unknowns, suggested only by weight and texture.
Yeah, wire bead would indicate a different tire.

Considering the OP has not even bothered to say what tires he has, I think we have already invested way too much time in this corner of the discussion.

Last edited by Kapusta; 09-14-21 at 06:56 AM.
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Old 09-13-21, 10:17 PM
  #47  
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Originally Posted by PeteHski
The fact that some of the mass is rotating is not even worth talking about in respect of climbing performance. Only the total mass makes any real difference on a slope, governed by trivial Newtonian physics. Whether or not it is rotating is almost irrelevant in this respect.

If you are riding at a constant speed up the hill then the inertial energy stored in the wheels is also a constant (since they are spinning at a constant speed). So it's all really just about the total mass and gravity acting on it vs the pedal force. Lighter wheels help climbing simply because they are lighter, regardless of their rotational inertia.
Yes, Inertial energy is determined by the velocity (and mass) of the entire mass, but not a 'constant'...
why ? By Definition 'climbing' is a change in vector, hence 'Acceleration'
Mind Experiment (which could be done in 'reality).
So, maintaining same air and rolling resistance, same equipment/rider, you ride to a set velocity (speed) , on 'flat', stop pedaling, you will coast a certain time/distance...
same air and rolling resistance, same equipment/rider, you go on an up-slope and stop pedaling at the same velocity, you will coast a shorter time/distance...
going upslope is 'acceleration' - the inertial energy is dissipated/used faster, over a shorter time, which also determines distance... Gravitational acceleration.
The pull (acceleration) of gravity is a 'Constant' during all this, but when you 'climb' you are changing the 'vector' and now needing to overcome the 'acceleration of gravity'.
an example of calculation of this - lifting a 35kg object 1/2 meter... I'm lazy and the calculations are all done here:
How much work does it take to lift a 35 kg weight 1/2 m ?
I expect measurement or calculation of inertial stored energy will be spectacularly well below what is needed to climb 1 meter of road elevation.
rotational mass... is then also affected by gravity, - "the rotational inertia of an object depends on its mass. It also depends on the distribution of that mass relative to the axis of rotation." more on this here: What is rotational inertia?
Anyway, differences in rotating masses are also involved in the gravitational effect.
Th
Yuri

Last edited by cyclezen; 09-13-21 at 10:32 PM.
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Old 09-14-21, 03:01 AM
  #48  
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Originally Posted by cyclezen
Yes, Inertial energy is determined by the velocity (and mass) of the entire mass, but not a 'constant'...
why ? By Definition 'climbing' is a change in vector, hence 'Acceleration'
Mind Experiment (which could be done in 'reality).
So, maintaining same air and rolling resistance, same equipment/rider, you ride to a set velocity (speed) , on 'flat', stop pedaling, you will coast a certain time/distance...
same air and rolling resistance, same equipment/rider, you go on an up-slope and stop pedaling at the same velocity, you will coast a shorter time/distance...
going upslope is 'acceleration' - the inertial energy is dissipated/used faster, over a shorter time, which also determines distance... Gravitational acceleration.
The pull (acceleration) of gravity is a 'Constant' during all this, but when you 'climb' you are changing the 'vector' and now needing to overcome the 'acceleration of gravity'.
an example of calculation of this - lifting a 35kg object 1/2 meter... I'm lazy and the calculations are all done here:
How much work does it take to lift a 35 kg weight 1/2 m ?
I expect measurement or calculation of inertial stored energy will be spectacularly well below what is needed to climb 1 meter of road elevation.
rotational mass... is then also affected by gravity, - "the rotational inertia of an object depends on its mass. It also depends on the distribution of that mass relative to the axis of rotation." more on this here: What is rotational inertia?
Anyway, differences in rotating masses are also involved in the gravitational effect.
Th
Yuri
You are confusing the issue between force and acceleration here. You are not overcoming "acceleration of gravity", you are overcoming the "Force" of gravity. Gravity only causes the mass to actually accelerate if you don't apply an opposing force. All that matters as far as the mass is concerned is the net force acting on the body. The body can be accelerating, decelerating or moving at a constant speed depending on the net balance of those opposing forces.

If you want to accurately predict how fast a rider will climb up a hill, all you need to know is:-

1. Total mass of the bike + rider
2. Gradient of the hill
3. Rolling resistance of the tyres
4. Aerodynamic drag
5. Rider power output

The distribution of wheel mass is, to all intents and purposes, irrelevant to the result. I can't think of a model that even includes it as a parameter in such a calculation. Can you?

I'm not questioning the concept of rotational inertia and being an engineering grad I'm well aware of how to calculate it, but it is simply not relevant to your climbing speed. Lightweight wheels with low inertia feel nimble, accelerate more easily etc, etc. but none of this matters (except their overall weight) when you are plodding at a steady 5 mph up a steep hill.

Last edited by PeteHski; 09-14-21 at 03:09 AM.
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Old 09-14-21, 03:24 AM
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Originally Posted by cyclezen
By Definition 'climbing' is a change in vector, hence 'Acceleration'
This is incorrect. When you are climbing up a constant slope (eg. 10% gradient) the only thing that changes compared to riding on the flat is the direction (vector) in which the Force of Gravity is acting relative to the body and ground. Whether or not you accelerate depends entirely on how much force you apply in the opposite direction. When you are climbing at a constant speed your mass is not accelerating. It is moving through space at a constant speed, just in a different direction i.e. forward and upward.
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Old 09-14-21, 03:59 AM
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Originally Posted by cyclezen
Graviity creates 'Acceleration' - base jump w/o a chute and you will experience acceleration until you hit terminal velocity OR stop...
riding uphill, is the same in reverse, except is deceleration ...
every pedal stroke requires acceleration to counter the deceleration.
Again you are confusing "Acceleration" and "Force" here.
This gets a lot easier to understand if you think in terms of applied forces rather than accelerations. Every pedal stroke requires a force. In physics/engineering we don't talk about applying accelerations do we? Accelerations are the result of net forces acting on bodies.
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