Bike tire rolling resistance and speed
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fwiw - biggest difference I ever felt was after changing rear wheel & hub. nearest I can tell, comparing ride notes, I've picked up 1mph on my avrg speed
Last edited by rumrunn6; 07-28-21 at 12:53 PM.
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You can just barely measure a speed difference between a pair of GP5000s and Vittoria Corsa Speed tires which is supposed to be about 10W difference or so. Given the difference in durability and puncture resistance and (especially wet) grip which all heavily fall in favour of the GP5000s, it's not a clear cut decision. I have a wheelset with one and one with the other.
Differences of a few watts between top shelf road tires would, by extension, be even harder to measure without applying more rigorous methods.
Aero wheelset is also a similar difference - detectable on segment times but barely - but it's a more clear cut decision to use one because there's literally no downside to using something like 45mm deep aero wheels except price.
Differences of a few watts between top shelf road tires would, by extension, be even harder to measure without applying more rigorous methods.
Aero wheelset is also a similar difference - detectable on segment times but barely - but it's a more clear cut decision to use one because there's literally no downside to using something like 45mm deep aero wheels except price.
On my half decent paved asphalt roads, I measure Crr of 0.004 and 0.0042 for The Speeds and GP5000 with latex tubes, respectively. We are fresh out of steel drum roads in my neck of the woods.
At 20 mph, the difference is about 1 watt.
The aerodynamic difference at 30 mph between the two tires is rather large.
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You can just barely measure a speed difference between a pair of GP5000s and Vittoria Corsa Speed tires which is supposed to be about 10W difference or so. Given the difference in durability and puncture resistance and (especially wet) grip which all heavily fall in favour of the GP5000s, it's not a clear cut decision. I have a wheelset with one and one with the other.
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To get the implied 50% reduction in Crr in the original post, one would have to compare a properly inflated GP5000 with latex tubes to an improperly inflated Gatorskins with butyl tubes. The speed to save 10 watts is around 11 mph. At 20 mph, cutting Crr in half (0.008 to 0.004) should save a little over 25 watts for a 200 pound rider on normal roads. CdA 0.36 and rHo of 0.122. Yes, some tires are really that bad on real roads.
At recreational cycling speeds, the difference would be very noticeable even without a power meter
At recreational cycling speeds, the difference would be very noticeable even without a power meter
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So much of this depends on where the OP is in his cycling journey.
It is easy to assume the OP has “not” already maxed himself out from a physical and positional perspective and is looking for whatever additional advantage that is still available.
If it were me, I’d probably make the changes if that is what I wanted to do. Regardless of the real life results, there is something psychological about making improvements on a bike that is motivational. There is something about making changes and being amped up to get out and ride.
If the OP has not looked in to getting fitted and doing exercises to possibly improve flexibility that would also be a good area to focus on.
John
It is easy to assume the OP has “not” already maxed himself out from a physical and positional perspective and is looking for whatever additional advantage that is still available.
If it were me, I’d probably make the changes if that is what I wanted to do. Regardless of the real life results, there is something psychological about making improvements on a bike that is motivational. There is something about making changes and being amped up to get out and ride.
If the OP has not looked in to getting fitted and doing exercises to possibly improve flexibility that would also be a good area to focus on.
John
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And they are primarily on gravel, so conversion factor needed for road speed.
The kit: https://www.voler.com/browse/cat2/?cat=grp&store=16095
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and they are primarily on gravel, so conversion factor needed for road speed.
The kit: https://www.voler.com/browse/cat2/?cat=grp&store=16095
The kit: https://www.voler.com/browse/cat2/?cat=grp&store=16095
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I ride narrow bars - and practice low body position with knees nearly brushing the top tube and elbows in. The low body position may be most aero but not most powerful or something I can maintain an entire ride. We all could benefit from a wind tunnel test with power through a range of fitments.
Any racer will tell you that tactics and power to finish strongly put one on the podium - usually. But never the difference between Conti, Vittoria or Pirelli tires.
(that's why i am amused , to some extent, with threads about 'in the lab' marginal performance gains - in General Cycling )
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10w is meaningful as a % of what the average Bikeforum user’s ftp likely is.
So if the risk reward of flats and cost of the setup is in your budget, have fun. Forget the haters.
Also, people train a lot extra to often net less than a 10w gain.
So if the risk reward of flats and cost of the setup is in your budget, have fun. Forget the haters.
Also, people train a lot extra to often net less than a 10w gain.
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I have no idea how many. I will assume 99% of cyclist don't understand wheel hub bearings and how QR plays a factor in that.
It is of no surprise that many dont see the difference in roll resistance in tires. Their QR is too tight to ever see the difference in tire performance anyways.
My opinion. Then again roll resistance is pointless, once you add in shoddy bike maintenance. Dirty chains, dirty cog wheels, cross chaining, worn out cassettes, etc...
People either understand it or they don't. If you feel the difference in roll resistance on tires, congrats on having a maintained bicycle.
It is of no surprise that many dont see the difference in roll resistance in tires. Their QR is too tight to ever see the difference in tire performance anyways.
My opinion. Then again roll resistance is pointless, once you add in shoddy bike maintenance. Dirty chains, dirty cog wheels, cross chaining, worn out cassettes, etc...
People either understand it or they don't. If you feel the difference in roll resistance on tires, congrats on having a maintained bicycle.
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As with most things in 'athletic cycling' = it Depends.........................
Any racer will tell you that tactics and power to finish strongly put one on the podium - usually. But never the difference between Conti, Vittoria or Pirelli tires.
(that's why i am amused , to some extent, with threads about 'in the lab' marginal performance gains - in General Cycling )
Any racer will tell you that tactics and power to finish strongly put one on the podium - usually. But never the difference between Conti, Vittoria or Pirelli tires.
(that's why i am amused , to some extent, with threads about 'in the lab' marginal performance gains - in General Cycling )
Racer's don't look for small advantages? Never. They don't go to the wind tunnel? Never. Team mechanics don't toss chains after 800km? They do not adjust tire pressure by rider and course down to 1 psi? Never
I am also amused.
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But yet they will go to the trouble of blacking out brand logos when they want to run an alternative tyre to their sponsor brand.
Not saying these marginal differences matter for the average club rider when similar tyres are all within a couple of Watts.
Puncture resilience and grip are my main criteria for choosing tyres - within any particular category. But I wouldn’t give away 10W per tyre at 30 kph in a competitive situation. But it wouldn’t bother me at all on a solo training ride. My current race tyres are about 5-6W faster than my training tyres. I can just about “feel” that kind of difference and it calculates out as a saving of several minutes over a 100 mile course according to BBS. A useful gain but not mind blowing.
Some guys I know do insist on using ultra-light fragile race tyres with minimal puncture protection to save a few grams and a few Watts of power. I don’t see the point in that unless racing professionally.
Not saying these marginal differences matter for the average club rider when similar tyres are all within a couple of Watts.
Puncture resilience and grip are my main criteria for choosing tyres - within any particular category. But I wouldn’t give away 10W per tyre at 30 kph in a competitive situation. But it wouldn’t bother me at all on a solo training ride. My current race tyres are about 5-6W faster than my training tyres. I can just about “feel” that kind of difference and it calculates out as a saving of several minutes over a 100 mile course according to BBS. A useful gain but not mind blowing.
Some guys I know do insist on using ultra-light fragile race tyres with minimal puncture protection to save a few grams and a few Watts of power. I don’t see the point in that unless racing professionally.
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But yet they will go to the trouble of blacking out brand logos when they want to run an alternative tyre to their sponsor brand.
Not saying these marginal differences matter for the average club rider when similar tyres are all within a couple of Watts.
Puncture resilience and grip are my main criteria for choosing tyres - within any particular category. But I wouldn’t give away 10W per tyre at 30 kph in a competitive situation. But it wouldn’t bother me at all on a solo training ride. My current race tyres are about 5-6W faster than my training tyres. I can just about “feel” that kind of difference and it calculates out as a saving of several minutes over a 100 mile course according to BBS. A useful gain but not mind blowing.
Some guys I know do insist on using ultra-light fragile race tyres with minimal puncture protection to save a few grams and a few Watts of power. I don’t see the point in that unless racing professionally.
Not saying these marginal differences matter for the average club rider when similar tyres are all within a couple of Watts.
Puncture resilience and grip are my main criteria for choosing tyres - within any particular category. But I wouldn’t give away 10W per tyre at 30 kph in a competitive situation. But it wouldn’t bother me at all on a solo training ride. My current race tyres are about 5-6W faster than my training tyres. I can just about “feel” that kind of difference and it calculates out as a saving of several minutes over a 100 mile course according to BBS. A useful gain but not mind blowing.
Some guys I know do insist on using ultra-light fragile race tyres with minimal puncture protection to save a few grams and a few Watts of power. I don’t see the point in that unless racing professionally.
What is probably not well appreciated is the actual wattage difference at speed from one tire to the next. To select the best tires for racing, you cannot simply use Crr values from steel drums at 18 mph for several reasons. 1) The aerodynamic influence of rim/tire is equally important. 2) Crr on real roads is much higher than drums and the differences are thus higher in absolute wattage 3) Crr is not a constant, it increases with speed and lower temperatures-some tires are surprisingly better than others in that regard. In other words, the rolling and aero differences at 30 mph can be over 20-30 watts total when comparing a good fit tire with lower rolling resistance at that speed vs a less than good fit to the rim. Not trivial. And yes, I have measured these effects.
I think amateur racers are also competitive.
Even Strava KoM chasers are competitive.
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Last edited by ofajen; 07-31-21 at 10:09 AM.
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I would not see the point to using fragile tires on training rides. I just use GP5000 tires, good enough. I rarely flat and with latex tubes, they roll very well and last a long time. There are faster tires for sure.
What is probably not well appreciated is the actual wattage difference at speed from one tire to the next. To select the best tires for racing, you cannot simply use Crr values from steel drums at 18 mph for several reasons. 1) The aerodynamic influence of rim/tire is equally important. 2) Crr on real roads is much higher than drums and the differences are thus higher in absolute wattage 3) Crr is not a constant, it increases with speed and lower temperatures-some tires are surprisingly better than others in that regard. In other words, the rolling and aero differences at 30 mph can be over 20-30 watts total when comparing a good fit tire with lower rolling resistance at that speed vs a less than good fit to the rim. Not trivial. And yes, I have measured these effects.
I think amateur racers are also competitive.
Even Strava KoM chasers are competitive.
What is probably not well appreciated is the actual wattage difference at speed from one tire to the next. To select the best tires for racing, you cannot simply use Crr values from steel drums at 18 mph for several reasons. 1) The aerodynamic influence of rim/tire is equally important. 2) Crr on real roads is much higher than drums and the differences are thus higher in absolute wattage 3) Crr is not a constant, it increases with speed and lower temperatures-some tires are surprisingly better than others in that regard. In other words, the rolling and aero differences at 30 mph can be over 20-30 watts total when comparing a good fit tire with lower rolling resistance at that speed vs a less than good fit to the rim. Not trivial. And yes, I have measured these effects.
I think amateur racers are also competitive.
Even Strava KoM chasers are competitive.
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There are not 20-30W differences between premium branded tyres of equivalent type. I haven't even seen that sort of difference between training and race tyres of the same brand. I use BBS for estimating times and that sort of difference would be a good 20 mins on a 5 hour ride. It would stand out like a sore thumb if it were actually true. If I put my actual average power over a course back into BBS, it's usually accurate to within a minute or two, so that sort of difference would be pretty dramatic. When I change from training to race tyres I alter the CRR by the same percentage as the drum tests for those tyres and that gives me accurate results. So they must be pretty accurate in relative terms.
BBS does not measure anything. They estimate based upon your input. Do you ride at 30 mph?
You either did not read what I wrote or you do not understand. Crr is not a static parameter.
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Put a 28 mm tire onto a 23 mm wide rim instead of a 23 mm tire. You will see over 20 watts at 30 mph just for the aero effects. If the 28 mm tire is a GP4000 with butyl vs a 23 mm Supersonic with latex, I assure you.....it is way over 20 watts at 30 mph.
BBS does not measure anything. They estimate based upon your input. Do you ride at 30 mph?
You either did not read what I wrote or you do not understand. Crr is not a static parameter.
BBS does not measure anything. They estimate based upon your input. Do you ride at 30 mph?
You either did not read what I wrote or you do not understand. Crr is not a static parameter.
I don't need a lecture from you about how BBS works either. You can calibrate CdA and Crr to match one of your reference rides and then look at the effects of changing Crr on your course time. I use the method BBS have developed for comparing different tyres:-
https://www.bestbikesplit.com/case-study-crr#
It isn't perfect, but it does work pretty well for the tyres I've used recently.
Last edited by PeteHski; 07-31-21 at 03:21 PM.
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I can definitely attest to this temperature effect. When I ride in winter, I can clearly feel the extra work needed to ride when it is low 30s F vs say 50 F due to the tires (Continental Race King) being stiffer. And those have their “Black Chili” rubber and are some of the faster rolling MTB tires around. Not a criticism of those particular tires, as all tires get stiff in the cold.
Otto
Otto
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For a decrease in ambient temperature of 1 deg. C., rho will typically increase by ~0.4% to 0.5%; it depends on the tire but typically we'll see Crr increase by maybe 1.2% to 1.5%. So we know the power needed to overcome aero drag dominates the power needed to overcome rolling drag at relatively low speeds; in colder temperatures, that crossover point gets moved up. For either rolling or aero drag, colder temps work in the same direction: drag increases.
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Cold bad. Warm good.
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The point I was making......some tires are worse than others. Some lose much much more than 1% per degree C. If yahoos like me know which tires are less slow in the cold, I suspect the professional teams do as well.
I wonder if the Pros still buy FMB and Ducast tubulars and black out the name.
This clearly shows the effect of temperature. David Wilson (one of the authors of Bicycling Science) sent me a quote by Jim Papadopoulos from the 3rd edition:
"Preliminary PowerTap measurements on the road and on a home ‘wind’ trainer have suggested significant effects on tire rolling resistance of temperature (with Crr dropping roughly one percent for each degree Celsius of temperature rise) and speed (with Crr doubling when wind-trainer speed reaches 5 m/s)."
"Preliminary PowerTap measurements on the road and on a home ‘wind’ trainer have suggested significant effects on tire rolling resistance of temperature (with Crr dropping roughly one percent for each degree Celsius of temperature rise) and speed (with Crr doubling when wind-trainer speed reaches 5 m/s)."
The point I was making......some tires are worse than others. Some lose much much more than 1% per degree C. If yahoos like me know which tires are less slow in the cold, I suspect the professional teams do as well.
I wonder if the Pros still buy FMB and Ducast tubulars and black out the name.
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Last edited by ofajen; 08-01-21 at 09:30 PM.