Weight difference
09-04-14, 05:54 PM
#26
The Recumbent Quant
Wrong. I noticed a world of difference swapping tires on my bikes. In one case I went from 1.95" Crossroads to 2" Marathon Supremes,in another I went from 45mm Borough XC's to 42mm Contact Lites;both were much more pleasant to ride in stop-and-go traffic,and were easier to climb up steep hills.
09-04-14, 06:03 PM
#27
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No,in both cases the tire size and tread pattern didn't change significantly,just the weight of the tires.
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09-04-14, 06:31 PM
#28
The Recumbent Quant
Neither tread nor tire size have necessarily large effects on rolling resistance. If you can the difference, it was rolling resistance. The weight difference between tires is miniscule compared to the weight of the rider and the bike.
09-05-14, 04:54 AM
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Oh - and I doubt you understand width: wider = LOWER RR; you probably think the opposite.
Last edited by meanwhile; 09-05-14 at 05:01 AM.
09-05-14, 04:56 AM
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Useful links on rolling resistance:
MTB Tire analysis - rolling resistance and snakebite resistance
Bicycle Quarterly rolling resistance tests: Spring 2013 - Weight Weenies
Technical Q&A with Lennard Zinn - Rolling resistance redux - VeloNews.com
Fast Tires 2013 - Part 2 - Slowtwitch.com
JV's Cycling Blog: The latest tire rolling resistance data is out!!
wide is fast for road
Tech FAQ: Seriously, wider tires have lower rolling resistance than their narrower brethren - VeloNews.com
lower psi can be faster
Technical Q&A with Lennard Zinn - Rolling resistance redux - VeloNews.com
Tyres can make 25% difference on road, drum testing wrong:
Bicycle Quarterly: Performance of Tires | Off The Beaten Path
Rolling Resistance and Tire Pressure | Velochimp
Charts
Tyre Rolling Resistance Data
Mountain Bike Tyre Rolling Resitance
Tire test results from german "bike" magazine
MTB Tire analysis - rolling resistance and snakebite resistance
Bicycle Quarterly rolling resistance tests: Spring 2013 - Weight Weenies
Technical Q&A with Lennard Zinn - Rolling resistance redux - VeloNews.com
Fast Tires 2013 - Part 2 - Slowtwitch.com
JV's Cycling Blog: The latest tire rolling resistance data is out!!
wide is fast for road
Tech FAQ: Seriously, wider tires have lower rolling resistance than their narrower brethren - VeloNews.com
lower psi can be faster
Technical Q&A with Lennard Zinn - Rolling resistance redux - VeloNews.com
Tyres can make 25% difference on road, drum testing wrong:
Bicycle Quarterly: Performance of Tires | Off The Beaten Path
Rolling Resistance and Tire Pressure | Velochimp
Charts
Tyre Rolling Resistance Data
Mountain Bike Tyre Rolling Resitance
Tire test results from german "bike" magazine
09-05-14, 05:09 AM
#31
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Yes. There was a difference but you didn't understand the cause.
I'm sorry: I thought that experiment was idiot proof. But you seem to believe that the energy stored in two identical wheels spinning at the same RPM can be enormously different: I honestly thought this was too absurd to need addressing. Energy stored in the wheel is 0.5 x mass x radius x the square of spin rate; the energy stored in the wheel is the same whether the bike is rolling down an alpine mountain with Lance The Liar onboard or upside down with a 12 year flicking the pedals around.
Which, to be honest, should have been explained in high school physics when you were about 12.
What it does it that it shows that contribution of THE WHEEL MASS to the above is minuscule. Which is what we were discussing. The process you are struggling with is called "coherent logical argument"...
Huh? First,you just proved yourself wrong. You actually had to put effort into spinning that wheel up,while hitting the brake required almost none.Second,what does this have to do with riding the bike?
Which, to be honest, should have been explained in high school physics when you were about 12.
Second,what does this have to do with riding the bike? In that example,there's only the momentum of the wheel spinning,when riding the bike you have the weight of the bike+rider,plus gravity if going down hill to deal with.
09-05-14, 01:49 PM
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You can ignore the laws of physics but you can't repeal them.
09-05-14, 05:12 PM
#33
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Sure. A 160 pound rider would be nearly 8% faster up the steepest hills on a 20 pound bike than a 34 pound one. On hills where he could only manage 10 MPH before he could go 10.8 MPH, and he'd be nearly 4.5 minutes faster to the summit of a hill that used to take an hour to climb.
09-05-14, 05:36 PM
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Sure. A 160 pound rider would be nearly 8% faster up the steepest hills on a 20 pound bike than a 34 pound one. On hills where he could only manage 10 MPH before he could go 10.8 MPH, and he'd be nearly 4.5 minutes faster to the summit of a hill that used to take an hour to climb.
Weight of a Steel BikeGeorgena Terry
In this issue, Jan tested a titanium bike against a steel randonneur bike. It was a real world test: two guys racing each other up the same hill, one on the ti bike, one on the steel. They swapped out the bikes several times. Both were evenly matched in terms of strength, endurance and weight.
The weight of a steel bike is always of interest. This steel bike was 9.6 lbs heavier than the ti bike, but it climbed as well. It sounds implausible, but as Jan explained, when the weight of the riders was taken into account, the steel bike plus rider was only 5% heavier than the ti bike plus rider, but the steel bike “planed”, helping the rider generate the extra power needed to overcome the weight difference.
Fans of Jan’s bike testing will know there is an advantage to a bike that “planes”. This is a bike that is in synch with the rider and flexes in a way that “gives back” some of the rider’s energy to the drivetrain.
In this issue, Jan tested a titanium bike against a steel randonneur bike. It was a real world test: two guys racing each other up the same hill, one on the ti bike, one on the steel. They swapped out the bikes several times. Both were evenly matched in terms of strength, endurance and weight.
The weight of a steel bike is always of interest. This steel bike was 9.6 lbs heavier than the ti bike, but it climbed as well. It sounds implausible, but as Jan explained, when the weight of the riders was taken into account, the steel bike plus rider was only 5% heavier than the ti bike plus rider, but the steel bike “planed”, helping the rider generate the extra power needed to overcome the weight difference.
Fans of Jan’s bike testing will know there is an advantage to a bike that “planes”. This is a bike that is in synch with the rider and flexes in a way that “gives back” some of the rider’s energy to the drivetrain.
..What planing is about is the energy from the pedal stroke that torsions the frame. Some frames are especially efficient at returning it; some are especially bad. Confusingly, the ideal frame for one rider may be different to another because of the interactions between pedaling style, bodyweight, etc, and this behaviour.
Last edited by meanwhile; 09-05-14 at 05:42 PM.
09-05-14, 06:04 PM
#35
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Ah,that's my problem. I was 15 when I started high school(10th grade for SAHS). If you were in high school at age 12,you must've been a genius. I bow to your knowledge,and will leave the thread.
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09-06-14, 04:06 AM
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Ah,that's my problem. I was 15 when I started high school(10th grade for SAHS). If you were in high school at age 12,you must've been a genius.
09-06-14, 07:25 AM
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There's an excellent wikipedia article - I already sent the link to Mr Fantasy Physcis - on bicycle performance here:
Bicycle performance - Wikipedia, the free encyclopedia
Bicycle performance - Wikipedia, the free encyclopedia
09-06-14, 07:28 AM
#38
The Recumbent Quant
Sure. A 160 pound rider would be nearly 8% faster up the steepest hills on a 20 pound bike than a 34 pound one. On hills where he could only manage 10 MPH before he could go 10.8 MPH, and he'd be nearly 4.5 minutes faster to the summit of a hill that used to take an hour to climb.
It's not that weight is irrelevant. It's that it is exactly as important as it is, and most people overestimate it.
Bike calculator web pages are great for answering these questions.
09-06-14, 07:37 AM
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You shouldn't take the particular values in that graph as gospel - just that AR is a curve and that RR and gravity are linear.
It's important to understand this, because when you do then you understand that what is optimal for TDF racing speed is not necessarily relevant to Audax or commute speed. A TDF team uses narrower tyres with higher RR for their low aero drag, but at the speed of an Audax or commute then a wider tyre with higher AR but lower RR will be faster.
09-06-14, 07:42 AM
#40
The Recumbent Quant
No, you're wrong now. The guy specified a steep hill where the cyclist could only make 10mph and at this speed aero is NOT important. Power needed for work against gravity and RR is LINEAR with speed, but aero is SQUARED. Which means that aero dominates at speed but drops away to be trivial at lower speeds.
You shouldn't take the particular values in that graph as gospel - just that AR is a curve and that RR and gravity are linear.
It's important to understand this, because when you do then you understand that what is optimal for TDF racing speed is not necessarily relevant to Audax or commute speed. A TDF team uses narrower tyres with higher RR for their low aero drag, but at the speed of an Audax or commute then a wider tyre with higher AR but lower RR will be faster.
You shouldn't take the particular values in that graph as gospel - just that AR is a curve and that RR and gravity are linear.
It's important to understand this, because when you do then you understand that what is optimal for TDF racing speed is not necessarily relevant to Audax or commute speed. A TDF team uses narrower tyres with higher RR for their low aero drag, but at the speed of an Audax or commute then a wider tyre with higher AR but lower RR will be faster.
09-06-14, 07:44 AM
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There's a terrific article on rolling resistance and aero here:
As a general rule, most riders who try to get higher performance at commute speeds put exactly the wrong tyres on their bikes, almost everyone worries about weight too much, and some people believe quite insane things about wheels. (These beliefs have been stoked by years of marketing and pressure on cycling magazines to write absurd things, the aim being of course to extract money from people.)
Tire Rolling Resistance | Roues Artisanales
In general terms, the total drag of a cyclist will consist of 80% tire rolling resistance and 20% wind resistance at 10 km/h or 6 mph. At 40 km/h or 25 mph the numbers will reverse, with total drag consisting of 80% wind resistance and 20% tire rolling resistance.
In general terms, the total drag of a cyclist will consist of 80% tire rolling resistance and 20% wind resistance at 10 km/h or 6 mph. At 40 km/h or 25 mph the numbers will reverse, with total drag consisting of 80% wind resistance and 20% tire rolling resistance.
09-06-14, 07:56 AM
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Because
1. When aero starts to become important wont be the same, even on the flat, for different types of bike and different tyres
2. It becomes important later going uphill because the other forces - gravity! - are greater. And the guy specified a STEEP hill
You mentioned online calculators, but you obviously don't use them! Here's a reasonable example for a rider on a steep hill at the speed you gave:
[TABLE]
[TR]
[TD="align: left"]Frontal Area[/TD]
[TD="align: right"] 0.50[/TD]
[TD]m[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Coefficient Wind Drag[/TD]
[TD="align: right"] 0.50[/TD]
[TD]dimensionless[/TD]
[/TR]
[TR]
[TD="align: left"]Air Density[/TD]
[TD="align: right"] 1.226[/TD]
[TD]kg/m[SUP]3[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Weight[/TD]
[TD="align: right"] 75.0[/TD]
[TD]kg[/TD]
[/TR]
[TR]
[TD="align: left"]Coefficient of Rolling[/TD]
[TD="align: right"] 0.008[/TD]
[TD]dimensionless[/TD]
[/TR]
[TR]
[TD="align: left"]Grade[/TD]
[TD="align: right"] 0.050[/TD]
[TD]decimal[/TD]
[/TR]
[TR]
[TD="align: left"]Wind Resistance[/TD]
[TD="align: right"] 2.5[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Rolling Resistance[/TD]
[TD="align: right"] 5.9[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Slope Force[/TD]
[TD="align: right"] 36.8[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Cadence[/TD]
[TD="align: right"] 100.[/TD]
[TD]rev/min[/TD]
[/TR]
[TR]
[TD="align: left"]Crank Length[/TD]
[TD="align: right"] 170.[/TD]
[TD]mm[/TD]
[/TR]
[TR]
[TD="align: left"]Pedal Speed[/TD]
[TD="align: right"] 1.78[/TD]
[TD]m/s[/TD]
[/TR]
[TR]
[TD="align: left"]Average Pedal Force[/TD]
[TD="align: right"] 101.4[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Effective Pedaling Range[/TD]
[TD="align: right"] 70.[/TD]
[TD]degree[/TD]
[/TR]
[TR]
[TD="align: left"]Effective Pedal Force[/TD]
[TD="align: right"] 260.6[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Speed[/TD]
[TD="align: right"] 4.00[/TD]
[TD]m/s[/TD]
[/TR]
[TR]
[TD="align: left"]Power[/TD]
[TD="align: right"] 180.4[/TD]
[TD]watts[/TD]
[/TR]
[/TABLE]
So at the speed you specifed, work against weight will be FIFTEEN TIMES work against air resistance! And this is with only a 5% gradient.
...Bike performance calculators: knowing about them doesn't make you any smarter if you're not smart enough to freaking USE THEM!
09-06-14, 11:51 AM
#43
The Recumbent Quant
This is stupid.
Because
1. When aero starts to become important wont be the same, even on the flat, for different types of bike and different tyres
2. It becomes important later going uphill because the other forces - gravity! - are greater. And the guy specified a STEEP hill
You mentioned online calculators, but you obviously don't use them! Here's a reasonable example for a rider on a steep hill at the speed you gave:
[TABLE]
[TR]
[TD="align: left"]Frontal Area[/TD]
[TD="align: right"] 0.50[/TD]
[TD]m[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Coefficient Wind Drag[/TD]
[TD="align: right"] 0.50[/TD]
[TD]dimensionless[/TD]
[/TR]
[TR]
[TD="align: left"]Air Density[/TD]
[TD="align: right"] 1.226[/TD]
[TD]kg/m[SUP]3[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Weight[/TD]
[TD="align: right"] 75.0[/TD]
[TD]kg[/TD]
[/TR]
[TR]
[TD="align: left"]Coefficient of Rolling[/TD]
[TD="align: right"] 0.008[/TD]
[TD]dimensionless[/TD]
[/TR]
[TR]
[TD="align: left"]Grade[/TD]
[TD="align: right"] 0.050[/TD]
[TD]decimal[/TD]
[/TR]
[TR]
[TD="align: left"]Wind Resistance[/TD]
[TD="align: right"] 2.5[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Rolling Resistance[/TD]
[TD="align: right"] 5.9[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Slope Force[/TD]
[TD="align: right"] 36.8[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Cadence[/TD]
[TD="align: right"] 100.[/TD]
[TD]rev/min[/TD]
[/TR]
[TR]
[TD="align: left"]Crank Length[/TD]
[TD="align: right"] 170.[/TD]
[TD]mm[/TD]
[/TR]
[TR]
[TD="align: left"]Pedal Speed[/TD]
[TD="align: right"] 1.78[/TD]
[TD]m/s[/TD]
[/TR]
[TR]
[TD="align: left"]Average Pedal Force[/TD]
[TD="align: right"] 101.4[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Effective Pedaling Range[/TD]
[TD="align: right"] 70.[/TD]
[TD]degree[/TD]
[/TR]
[TR]
[TD="align: left"]Effective Pedal Force[/TD]
[TD="align: right"] 260.6[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Speed[/TD]
[TD="align: right"] 4.00[/TD]
[TD]m/s[/TD]
[/TR]
[TR]
[TD="align: left"]Power[/TD]
[TD="align: right"] 180.4[/TD]
[TD]watts[/TD]
[/TR]
[/TABLE]
So at the speed you specifed, work against weight will be FIFTEEN TIMES work against air resistance! And this is with only a 5% gradient.
...Bike performance calculators: knowing about them doesn't make you any smarter if you're not smart enough to freaking USE THEM!
Because
1. When aero starts to become important wont be the same, even on the flat, for different types of bike and different tyres
2. It becomes important later going uphill because the other forces - gravity! - are greater. And the guy specified a STEEP hill
You mentioned online calculators, but you obviously don't use them! Here's a reasonable example for a rider on a steep hill at the speed you gave:
[TABLE]
[TR]
[TD="align: left"]Frontal Area[/TD]
[TD="align: right"] 0.50[/TD]
[TD]m[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Coefficient Wind Drag[/TD]
[TD="align: right"] 0.50[/TD]
[TD]dimensionless[/TD]
[/TR]
[TR]
[TD="align: left"]Air Density[/TD]
[TD="align: right"] 1.226[/TD]
[TD]kg/m[SUP]3[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Weight[/TD]
[TD="align: right"] 75.0[/TD]
[TD]kg[/TD]
[/TR]
[TR]
[TD="align: left"]Coefficient of Rolling[/TD]
[TD="align: right"] 0.008[/TD]
[TD]dimensionless[/TD]
[/TR]
[TR]
[TD="align: left"]Grade[/TD]
[TD="align: right"] 0.050[/TD]
[TD]decimal[/TD]
[/TR]
[TR]
[TD="align: left"]Wind Resistance[/TD]
[TD="align: right"] 2.5[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Rolling Resistance[/TD]
[TD="align: right"] 5.9[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Slope Force[/TD]
[TD="align: right"] 36.8[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Cadence[/TD]
[TD="align: right"] 100.[/TD]
[TD]rev/min[/TD]
[/TR]
[TR]
[TD="align: left"]Crank Length[/TD]
[TD="align: right"] 170.[/TD]
[TD]mm[/TD]
[/TR]
[TR]
[TD="align: left"]Pedal Speed[/TD]
[TD="align: right"] 1.78[/TD]
[TD]m/s[/TD]
[/TR]
[TR]
[TD="align: left"]Average Pedal Force[/TD]
[TD="align: right"] 101.4[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Effective Pedaling Range[/TD]
[TD="align: right"] 70.[/TD]
[TD]degree[/TD]
[/TR]
[TR]
[TD="align: left"]Effective Pedal Force[/TD]
[TD="align: right"] 260.6[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Speed[/TD]
[TD="align: right"] 4.00[/TD]
[TD]m/s[/TD]
[/TR]
[TR]
[TD="align: left"]Power[/TD]
[TD="align: right"] 180.4[/TD]
[TD]watts[/TD]
[/TR]
[/TABLE]
So at the speed you specifed, work against weight will be FIFTEEN TIMES work against air resistance! And this is with only a 5% gradient.
...Bike performance calculators: knowing about them doesn't make you any smarter if you're not smart enough to freaking USE THEM!
When climbing hills, your average rider is going to be, in general, less aero than usual.
But, yes, it all depends.
And even with the example here, the effect with the given rider weight is 7.7% at most, and this only for climbing very step hills.
There are other effects that will make a bigger difference sooner for most types of riding (changing the tires could on most 34lbs bikes will make a bigger effect that will be noticed everywhere, not just on hills).
09-06-14, 12:48 PM
#44
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4 m/s is 9 mph, not the 11 mph of the faster bike.
But, yes, it all depends.
[TABLE]
[TR]
[TD="align: left"]Wind Resistance[/TD]
[TD="align: right"] 5.5[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Rolling Resistance[/TD]
[TD="align: right"] 5.9[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Slope Force[/TD]
[TD="align: right"] 73.5[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[/TABLE]
..So wind resistance won't even noticeable.
(Forces on Rider)
Going over to SF, I once delivered a package on a street with something like a .27 gradient. (Cars can only park at right angles to the road and my bikes front wheel went light!) Imagining that I could climb it at 10mph ( which would take about 1500Watts, and I have to admit is a little beyond my sustained personal best) then
[TABLE]
[TR]
[TD="align: left"]Wind Resistance[/TD]
[TD="align: right"] 5.5[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Rolling Resistance[/TD]
[TD="align: right"] 5.9[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Slope Force[/TD]
[TD="align: right"] 198.6[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[/TABLE]
Last edited by meanwhile; 09-06-14 at 12:54 PM.
09-06-14, 01:22 PM
#45
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But of course, your muscles will make the maximum difference. You could ride a bike that weighs 10lb but if you just don't have the power to pedal, you're not going to see any difference...
09-06-14, 03:03 PM
#46
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Now I know why I prefer to bike alone.
09-07-14, 05:47 PM
#48
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By all means go look at the links but before you do, look at this article on bicycle drag. It clearly shows how little importance rolling resistance of the tires has on the over all drag on a bicycle. The whole discussion above has been about how to reduce a tiny fraction of drag. The whole discussion is mostly a tempest in a teapot and, in reality, has only an marginal effect for the commuting cyclist. Reducing rolling resistance is important at a professional level where tenths of a second make a difference but for the bicycle commuter, rolling resistance makes little difference.
Weight, on the other hand, can make a huge difference for a bicycle commuter. We are constantly slowing, stopping, starting and accelerating. Adding more weight to the wheels of the bicycle means that we have to put more energy into riding to get back up to speed and then, once at speed, we have to keep putting more energy into the system to keep it at speed due to air resistance which is a power curve vs a linear curve for rolling resistance. Going to heavier, wider tires may give a cushy ride but you have to pay a penalty for it.
Weight, on the other hand, can make a huge difference for a bicycle commuter. We are constantly slowing, stopping, starting and accelerating. Adding more weight to the wheels of the bicycle means that we have to put more energy into riding to get back up to speed and then, once at speed, we have to keep putting more energy into the system to keep it at speed due to air resistance which is a power curve vs a linear curve for rolling resistance. Going to heavier, wider tires may give a cushy ride but you have to pay a penalty for it.
And now I'm done. I will not come back to this thread,and keep your PM's to yourself.
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C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L/S2E-X
C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L/S2E-X
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