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Bike tire rolling resistance and speed

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Bike tire rolling resistance and speed

Old 07-25-21, 06:13 AM
  #26  
rumrunn6
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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

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Old 07-25-21, 06:49 AM
  #27  
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Originally Posted by Branko D View Post
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.
10 watts? At what 200 mph?

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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Old 07-25-21, 07:58 AM
  #28  
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Originally Posted by Branko D View Post
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.
Figures I’ve seen from rolling resistance tests suggest those tyres are within 1-2W per tyre at around 30 kph. So I’m not surprised you are not seeing much difference.
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Old 07-25-21, 08:21 AM
  #29  
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Originally Posted by rumrunn6 View Post
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 arg speed
But arg speed only applies to pirate cyclists.
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Old 07-25-21, 08:28 AM
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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
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Old 07-25-21, 10:53 AM
  #31  
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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
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Old 07-25-21, 11:20 AM
  #32  
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Originally Posted by MattTheHat View Post
But arg speed only applies to pirate cyclists.

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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Old 07-25-21, 06:09 PM
  #33  
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Originally Posted by woodcraft View Post
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
aaaarg!
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Old 07-28-21, 12:53 PM
  #34  
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Originally Posted by MattTheHat View Post
But arg speed only applies to pirate cyclists.
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Old 07-28-21, 03:52 PM
  #35  
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Originally Posted by terrymorse View Post
Well, there’s also the “hands on the hoods, forearms horizontal” position.

Some say that’s even more aero than the “hands in drops” position.
As with most things in 'athletic cycling' = it Depends. Lots of variables about the human in question, bike fit and on the road conditions. Different positions may also greatly impact power output. Didn't Levi L. use an 'arms in front of face' position for time trials?, that the UCI outlawed for their racing events. L Armstrong never rode with a flat back.

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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Old 07-30-21, 05:12 PM
  #36  
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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.
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Old 07-30-21, 06:45 PM
  #37  
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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.
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Old 07-31-21, 01:16 AM
  #38  
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Originally Posted by Wildwood View Post
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.
I must speak with different racers than you.
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Old 07-31-21, 03:58 AM
  #39  
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Originally Posted by Wildwood View Post
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 )
I was amused reading of Eddie B putting helium in racer's tires and how they would do personal bests.

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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Old 07-31-21, 07:13 AM
  #40  
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Originally Posted by Wildwood View Post

But never the difference between Conti, Vittoria or Pirelli tires.
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.
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Old 07-31-21, 07:45 AM
  #41  
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Originally Posted by PeteHski View Post
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.
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.
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Old 07-31-21, 07:59 AM
  #42  
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Originally Posted by GhostRider62 View Post
I 3) Crr is not a constant, it increases with speed and lower temperatures-some tires are surprisingly better than others in that regard.
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

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Old 07-31-21, 08:35 AM
  #43  
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Originally Posted by GhostRider62 View Post
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.
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.
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Old 07-31-21, 11:54 AM
  #44  
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Originally Posted by PeteHski View Post
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.
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.
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Old 07-31-21, 03:11 PM
  #45  
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Originally Posted by GhostRider62 View Post
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.
I was kind of agreeing with you earlier in this thread about the magnitude of the OPs proposed tyre change. But now you are just derailing it with a totally different and irrelevant argument. Suddenly you are making it all about rim aero with varying tyre width and to be honest I hadn't noticed that you suddenly increased the speed to 30 mph! I'm not sure how that is relevant here.

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.

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Old 07-31-21, 09:39 PM
  #46  
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Originally Posted by nrsmd View Post
Assume tires with a rolling resistance of 20 watts. Now replace with tires with a rolling resistance of 10 watts. What speed increase, if any, can I expect all things being equal?
All things won't be equal as the "faster" tyres will be lighter and probably more supple and have a better road feel. Speed difference is a bit of a "piece of string" thing. What's your current speed? Or speed over a 25-mile time trial? Saving 10 watts over a time trial would certainly be noticeable! Just casually riding around or on a café club ride? Not so much. Still a worthy upgrade though.


Originally Posted by nrsmd View Post
Now, what if I purchase aero rims.? Will I get a measurable boost in speed adding carbon fiber rims (assume cost about $400-$500 for the pair of rims)?
Assume going from shallow box section rims to some 60mm deep aero rims, you'll definitely notice a difference! It's most noticeable in the ability to hold that higher speed and carry it for longer. In my testing over a 10-mile time trial, simply moving from shallow to deep wheels on the same road bike netted me about a minute over the course for the same power output.

Deep wheels won't make you fast, but they'll make faster easier.
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Old 08-01-21, 07:14 AM
  #47  
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Originally Posted by ofajen View Post
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
The greatest effect of decreased ambient temperature, swamping any deriving from increased tire stiffness, is the increase in air density.
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Old 08-01-21, 08:48 AM
  #48  
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Originally Posted by Trakhak View Post
The greatest effect of decreased ambient temperature, swamping any deriving from increased tire stiffness, is the increase in air density.
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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Old 08-01-21, 09:57 AM
  #49  
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Cold bad. Warm good.

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)."
The Recumbent Bicycle and Human Powered Vehicle Information Center

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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Old 08-01-21, 04:41 PM
  #50  
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Originally Posted by Trakhak View Post
The greatest effect of decreased ambient temperature, swamping any deriving from increased tire stiffness, is the increase in air density.
Ok you are thinking of effect on wind drag. If the temperature drops from 60F to 30F, the air is 6% more dense. Air drag varies linearly with density so 6% more wind drag at the same speed. In my case, winter riding is on frozen or saturated muddy trails. Lots of energy lost in deforming the trail surface, so speed and drag are less. Also I wonder if energy lost deforming rubber and casing at the colder temperature will start to increase more than linearly?

Otto

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