Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

Bike tire rolling resistance and speed

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

Bike tire rolling resistance and speed

Old 07-24-21, 09:09 AM
  #1  
nrsmd
Senior Member
Thread Starter
 
Join Date: Dec 2010
Posts: 79
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 29 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Bike tire rolling resistance and speed

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?
nrsmd is offline  
Old 07-24-21, 09:26 AM
  #2  
cxwrench
Senior Member
 
cxwrench's Avatar
 
Join Date: Jul 2013
Location: Nor-Cal
Posts: 3,767

Bikes: lots

Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1958 Post(s)
Liked 2,932 Times in 1,489 Posts
Depends on speed, frontal area, Cd.
cxwrench is offline  
Old 07-24-21, 09:28 AM
  #3  
nrsmd
Senior Member
Thread Starter
 
Join Date: Dec 2010
Posts: 79
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 29 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
All things being equal. Is there a speed increase that is measurable?
nrsmd is offline  
Old 07-24-21, 09:35 AM
  #4  
Iride01 
I'm good to go!
 
Iride01's Avatar
 
Join Date: Jul 2017
Location: Mississippi
Posts: 14,809

Bikes: Tarmac Disc Comp Di2 - 2020

Mentioned: 50 Post(s)
Tagged: 0 Thread(s)
Quoted: 6100 Post(s)
Liked 4,732 Times in 3,262 Posts
What will be more measurable is how less tired your legs will be. Why don't you just try them and see what you get. Average the best 6 out of 12 of the same rides with one tire set against 6 best of 12 on the other tire set. Then you'll know.

I'd bet similar to my experience most of the positive will be how much better your legs feel and how much more energy you feel like you have left. Maybe you'll get an 1/2 to 1 mph average on a 30 mile ride.
Iride01 is offline  
Old 07-24-21, 09:36 AM
  #5  
HTupolev
Senior Member
 
Join Date: Apr 2015
Location: Seattle
Posts: 4,261
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 1971 Post(s)
Liked 1,297 Times in 629 Posts
Originally Posted by nrsmd
All things being equal.
The amount of speed increase will still depend on those things even if they're held equal across the two cases.

If you're talking about rolling resistance per-tire, and we spitball a bike+rider with a CdA of .32 previously doing 20mph on level ground, you'd see somewhere in the neighborhood of a .8mph increase in speed at the same power.

Is there a speed increase that is measurable?
Yes, if your measurement is precise enough.
HTupolev is online now  
Likes For HTupolev:
Old 07-24-21, 10:16 AM
  #6  
nrsmd
Senior Member
Thread Starter
 
Join Date: Dec 2010
Posts: 79
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 29 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
So, that is helpful and a Go.

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)?
nrsmd is offline  
Old 07-24-21, 10:28 AM
  #7  
Racing Dan
Senior Member
 
Racing Dan's Avatar
 
Join Date: Aug 2015
Posts: 2,224
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 1332 Post(s)
Liked 316 Times in 214 Posts
Originally Posted by nrsmd
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?
Not a lot. Less than 1/2 mph, depending on initial speed and power input.

Bike Calculator
Racing Dan is offline  
Old 07-24-21, 10:37 AM
  #8  
Wildwood 
Veteran, Pacifist
 
Wildwood's Avatar
 
Join Date: Dec 2004
Location: Seattle area
Posts: 13,303

Bikes: Bikes??? Thought this was social media?!?

Mentioned: 284 Post(s)
Tagged: 0 Thread(s)
Quoted: 3875 Post(s)
Liked 4,780 Times in 2,205 Posts
One can only wonder... don't be disappointed if you make changes and still finish mid-pack. Changes that suggest minimal performance improvements 'in the lab', do not always translate to measurable improvements 'on the road'. So many, many variables. Overcoming air resistance is the primary solution to greater speed.

Eddy is attributed with saying - 'Don't buy upgrades, ride up grades.'
That said, the best place spend $$$ to improve ride quality is tires and wheels.

What you may need most after the wheels is a more aero position on the bike, skinsuit, shoe covers. Assuming a high level of fitness and low body fat measurement.

When splitting hairs, be sure to shave those legs, too.
__________________
Vintage, modern, e-road. It is a big cycling universe.

Last edited by Wildwood; 07-24-21 at 10:42 AM.
Wildwood is offline  
Old 07-24-21, 10:55 AM
  #9  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 8,174
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 4273 Post(s)
Liked 4,710 Times in 2,910 Posts
Is that 10W per tyre or for both tyres? Also what speed is that 10W saving quoted at? If you know the CRR coefficients for both tyres I could give you a fairly accurate estimate of their relative performance. I recently did this exercise myself. The gains were pretty marginal, not something I really noticed out on the road.
PeteHski is offline  
Old 07-24-21, 11:01 AM
  #10  
Outrider1
Full Member
 
Outrider1's Avatar
 
Join Date: Jun 2020
Location: Central Florida
Posts: 402

Bikes: Trek Emonda ALR 5

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 155 Post(s)
Liked 296 Times in 137 Posts
Originally Posted by nrsmd
So, that is helpful and a Go.

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)?
You will notice a difference.
Outrider1 is offline  
Old 07-24-21, 11:36 AM
  #11  
Retro Grouch 
Senior Member
 
Retro Grouch's Avatar
 
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 30,225

Bikes: Catrike 559 I own some others but they don't get ridden very much.

Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1572 Post(s)
Liked 642 Times in 363 Posts
The break even point is around 15 MPH. That's the speed at which aero drag passes all other factors combined that are typically holding you back. As you accelerate beyond 15 MPH, aero drag becomes progressively more and more significant.

If you typically ride 10 MPH or less, you might be able to sense a speed difference in low drag tires. If you are able to ride in the middle to upper 20's on the flat, the rolling resistance factor, while still present, will become such a small fraction of the drag factors holding you back as to become insignificant.
__________________
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
Retro Grouch is offline  
Likes For Retro Grouch:
Old 07-24-21, 12:16 PM
  #12  
GhostRider62
Senior Member
 
Join Date: Apr 2021
Posts: 4,083
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2332 Post(s)
Liked 2,094 Times in 1,311 Posts
Going from 20 watts to 10 watts implies a 50% reduction in Crr. This would be a massively noticeable change.

You'd go from 11 mph to around 13 mph if everything else is "normal"

On my recumbent at 30 mph, I need 300 watts of which about 55 watts are rolling resistance. Cutting the rolling resistance in half would increase my speed by just around 1 mph.

Last edited by GhostRider62; 07-24-21 at 12:19 PM.
GhostRider62 is offline  
Old 07-24-21, 12:20 PM
  #13  
GhostRider62
Senior Member
 
Join Date: Apr 2021
Posts: 4,083
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2332 Post(s)
Liked 2,094 Times in 1,311 Posts
Originally Posted by nrsmd
All things being equal. Is there a speed increase that is measurable?
Yes
GhostRider62 is offline  
Old 07-24-21, 12:36 PM
  #14  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 8,174
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 4273 Post(s)
Liked 4,710 Times in 2,910 Posts
Originally Posted by GhostRider62
Going from 20 watts to 10 watts implies a 50% reduction in Crr. This would be a massively noticeable change.
This is true. If this change is per tyre then you are talking about the difference between a dedicated road race tyre and the slowest of armoured commuter tyres. Would be quite an obvious difference.
PeteHski is offline  
Old 07-24-21, 03:57 PM
  #15  
Pratt
Senior Member
 
Join Date: Aug 2019
Posts: 1,092
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 409 Post(s)
Liked 488 Times in 291 Posts
I just changed from 50mm Schwalbe Super Marathons to smaller width, smoother, softer compound tires. I doubt I'm going to do the two dozen rides prescribed by Iride, but I'll be happy to report back here. Probably just muddy the waters.
Pratt is offline  
Old 07-24-21, 05:47 PM
  #16  
Rolla
Guest
 
Join Date: Sep 2020
Posts: 2,888
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 1346 Post(s)
Liked 3,269 Times in 1,439 Posts
Originally Posted by nrsmd
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?
Originally Posted by HTupolev
a bike+rider with a CdA of .32 previously doing 20mph on level ground, you'd see somewhere in the neighborhood of a .8mph increase in speed at the same power.
Originally Posted by PeteHski
If you know the CRR coefficients for both tyres I could give you a fairly accurate estimate of their relative performance.
Originally Posted by GhostRider62
Going from 20 watts to 10 watts implies a 50% reduction in Crr.

You all have no idea how comforting it is to know that these are matters which I will never spend a single second of my life considering.

Seriously -- and this isn't snark -- I thank you for reminding me of the sheer, simple pleasure of just going for a bike ride!
Rolla is offline  
Likes For Rolla:
Old 07-24-21, 06:14 PM
  #17  
Trakhak
Senior Member
 
Trakhak's Avatar
 
Join Date: Jan 2005
Location: Baltimore, MD
Posts: 5,337
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 2428 Post(s)
Liked 2,883 Times in 1,645 Posts
Originally Posted by Rolla
You all have no idea how comforting it is to know that these are matters which I will never spend a single second of my life considering.

Seriously -- and this isn't snark -- I thank you for reminding me of the sheer, simple pleasure of just going for a bike ride!
Notification: you must further assert that you have never worn and will never wear Lycra/spandex for official authentication of your post.
Trakhak is online now  
Likes For Trakhak:
Old 07-24-21, 06:17 PM
  #18  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 8,174
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 4273 Post(s)
Liked 4,710 Times in 2,910 Posts
Originally Posted by Rolla
You all have no idea how comforting it is to know that these are matters which I will never spend a single second of my life considering.
!
Except you just did!
PeteHski is offline  
Likes For PeteHski:
Old 07-24-21, 06:52 PM
  #19  
MattTheHat 
Senior Member
 
MattTheHat's Avatar
 
Join Date: Aug 2018
Location: Allen, TX
Posts: 2,624

Bikes: 2021 S-Works Turbo Creo SL, 2020 Specialized Roubaix Expert

Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 762 Post(s)
Liked 3,982 Times in 1,415 Posts
Originally Posted by GhostRider62
Going from 20 watts to 10 watts implies a 50% reduction in Crr. This would be a massively noticeable change.

You'd go from 11 mph to around 13 mph if everything else is "normal"

On my recumbent at 30 mph, I need 300 watts of which about 55 watts are rolling resistance. Cutting the rolling resistance in half would increase my speed by just around 1 mph.
Using bike calculator a 20 watt (10 per tire) difference with a 170 pound rider putting out 200 watts on the flat looks more like a .7 MPH difference.
MattTheHat is offline  
Likes For MattTheHat:
Old 07-24-21, 07:44 PM
  #20  
GhostRider62
Senior Member
 
Join Date: Apr 2021
Posts: 4,083
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2332 Post(s)
Liked 2,094 Times in 1,311 Posts
Originally Posted by MattTheHat
Using bike calculator a 20 watt (10 per tire) difference with a 170 pound rider putting out 200 watts on the flat looks more like a .7 MPH difference.
Except I listed 11 mph to 13 mph and not 200 watts in the first example. In the second, my CdA is under 0.150 m^2.

I have no idea what your assumptions were.

The bottom line....a 50% reduction in Crr would be huge. At 200 watts, the reduction would be more like 40 watts down to 20 watts. OP formulated the question very poorly
GhostRider62 is offline  
Old 07-24-21, 07:48 PM
  #21  
GhostRider62
Senior Member
 
Join Date: Apr 2021
Posts: 4,083
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2332 Post(s)
Liked 2,094 Times in 1,311 Posts
Originally Posted by Rolla
You all have no idea how comforting it is to know that these are matters which I will never spend a single second of my life considering.

Seriously -- and this isn't snark -- I thank you for reminding me of the sheer, simple pleasure of just going for a bike ride!
Seriously-and this isn't snark-I thank you for reminding me of the sheer, simple pleasure of just not going for a ride with people like you.
GhostRider62 is offline  
Likes For GhostRider62:
Old 07-24-21, 08:27 PM
  #22  
70sSanO
Senior Member
 
70sSanO's Avatar
 
Join Date: Feb 2015
Location: Mission Viejo
Posts: 5,771

Bikes: 1986 Cannondale SR400 (Flat bar commuter), 1988 Cannondale Criterium XTR, 1992 Serotta T-Max, 1995 Trek 970

Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 1935 Post(s)
Liked 2,149 Times in 1,313 Posts
Originally Posted by nrsmd
All things being equal. Is there a speed increase that is measurable?
If you are not riding in the drops the majority of the time, you are losing speed.

Everything you do will help, but aero rims will not overcome a non-aero you.

John
70sSanO is online now  
Likes For 70sSanO:
Old 07-24-21, 11:34 PM
  #23  
terrymorse 
climber has-been
 
terrymorse's Avatar
 
Join Date: Dec 2004
Location: Palo Alto, CA
Posts: 7,002

Bikes: Scott Addict R1, Felt Z1

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 3335 Post(s)
Liked 3,436 Times in 1,737 Posts
Originally Posted by 70sSanO
If you are not riding in the drops the majority of the time, you are losing speed.
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.
__________________
Ride, Rest, Repeat. ROUVY: terrymorse


terrymorse is offline  
Old 07-24-21, 11:40 PM
  #24  
canklecat
Me duelen las nalgas
 
canklecat's Avatar
 
Join Date: Aug 2015
Location: Texas
Posts: 13,522

Bikes: Centurion Ironman, Trek 5900, Univega Via Carisma, Globe Carmel

Mentioned: 199 Post(s)
Tagged: 0 Thread(s)
Quoted: 4559 Post(s)
Liked 2,798 Times in 1,798 Posts
You'll notice the difference, although as other folks noted above around 15 mph wind drag becomes a more important factor.

It'll be a nicer ride too. Tires with lower rolling resistance are usually more supple and comfortable, especially at slightly lower pressures without sacrificing much rolling resistance. The rolling resistance tire test site has plenty of data. Tires differ in how much the resistance changes with pressure.

Thinner, lighter butyl tubes will help a bit too. So will latex tubes. Ditto newer tubes like the Tubolito and Aerothan. Or going tubeless.

Aero rims help a bit in some conditions. In cross winds high profile rims can make handling tricky.

Regarding position, riding the hoods rather than drops, with forearms parallel with the ground, is more aero than using the drops, per wind tunnel tests. But it's physically taxing and harder to hold for extended periods. Plan on doing some pushups, planks and core strengthening to hold the hoods/parallel forearms position for long stretches. Riding the drops can be fast if we keep our heads down, but as soon as we look up to check the road ahead it's like unfurling a sail. Everything is a tradeoff between efficiency, comfort and safety.
canklecat is offline  
Old 07-25-21, 01:11 AM
  #25  
Branko D
Senior Member
 
Join Date: Feb 2018
Posts: 786
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 338 Post(s)
Liked 408 Times in 252 Posts
Originally Posted by nrsmd
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?
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.
Branko D is offline  
Likes For Branko D:

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.