Who rides 28mm + tires on tarmac?

Discuss light weight issues concerning road bikes & parts.
zefs
Posts: 351
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

The lack of vibration is caused by the bigger contact patch. The same thing will happen if you reduce the air pressure on narrow tires, the lack of vibration will not make them faster though.

To make it easier, think of where does the air go when you are sitting on the bike vs when you are off the bike. The air moves away, so more tire is hitting the ground increasing the rolling resistance. The less the air pressure the more it will move.
Last edited by zefs on Wed Oct 03, 2018 7:33 am, edited 2 times in total.

by Weenie


2old4this
Posts: 366
Joined: Mon Jan 13, 2014 7:26 am

by 2old4this

Calnago wrote:
Tue Oct 02, 2018 4:36 pm
I'm of the belief that a fat tire at low pressure will indeed be harder to push up a hill, just based on my own experience, no data to support it, although I also believe that real life experience is a pretty good "data point" in itself.
Please no flames. Below is what I experience, and yours could be totally different...

I am consistently slower on climbs when I am on the wide tires. I really do not need to look the the data below since on the group rides I am generally in the front of the group with thinner tires, whereas I am generally in the back of the group when I am riding the bike with the wide tires.)

Real world data from the last weekend...
(Disclaimer: Both rides were loops. Steepness is very close but not the same. I was not using the same bike on both days. These were not races, so we weren't really pushing...)

Saturday (Willier Zero7, Enve 3.4 Tubular, Continental Competition 23s):
Total Climb: 2945 ft
Max Gradient: 17%
Distance: 34.7 miles
Total Time: 2:08:46

Sunday (Argonaut, Enve AR 4.5 Tubeless, Hutchinson Sector 28s):
Total Climb: 2718 ft
Max Gradient: 14%
Distance: 28.4 miles
Total Time: 1:49:23

Alexandrumarian
Posts: 324
Joined: Mon Mar 28, 2016 6:34 pm
Location: Romania

by Alexandrumarian

Calnago wrote:
Tue Oct 02, 2018 6:33 pm
The thing is, you don’t ride a high volume tire at the same pressure as a low volume tire. You could, but you’re defeating the purpose. For instance, at 200+ lbs I ride my Veloflex Arrenberg tubulars (25mm) at ~100psi rear and 90psi front. Using 27mm Veloflex Vlanderen tires I’d run closer to 80psi. Running the Vlanderens at 100psi would be akin to bouncing around like a pinball. But yes, they would roll fast I’m sure.
Interestingly this summer I have a Vlaanderen rear and 25 Corsa front (so similar to Arenberg) and used 100 (a hair under 7 bar) for both. With clothes I am 215-220 (97-98Kg) I can't say I feel noticeably more bouncy than with a 25 rear. Out of curiosity I just counted the number of pumps, 30 rear 21 front. I was really suprised. 21 pumps in the Vlaanderen make 75 psi 5.2 bar. I think I went out once at 6 bar and looking at the wheel climbing, it looked pretty flattened. I don't know if I was slower, but I felt kinda slow.

Hexsense
Posts: 766
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

zefs wrote:
Wed Oct 03, 2018 7:22 am
The lack of vibration is caused by the bigger contact patch. The same thing will happen if you reduce the air pressure on narrow tires, the lack of vibration will not make them faster though.

To make it easier, think of where does the air go when you are sitting on the bike vs when you are off the bike. The air moves away, so more tire is hitting the ground increasing the rolling resistance. The less the air pressure the more it will move.
It's side wall compression/deformation that cost watts, not moved air.
Increasing width -> less side wall compression as the contact patch is shorter and wider, hence less sidewall compression needed for the same weight/load.
Increasing pressure -> less side wall compression, less rolling resistance. Also induce extra vibration as the suspension effect is reduced (which increase rolling impedance).
Decreasing presure -> more side wall compression, more rolling resistance. Also reduce vibration as the suspension effect is enhanced (which reduce rolling impedance).
They aren't the same.

As i state in a few posts ago, vibration have to be absorbed somewhere, either rider (less efficient) or tire. Let the tire absorb rather than on human waste less energy, given everything else the same (which is the catch*). So lack of vibration make it faster.

*However, how to achieve the lack of vibration can cost watts, it isn't free. Reducing pressure on narrow tire cost more watts over reducing pressure on wider tire due to extra amount of tire sidewall compression needed.

JoO
Posts: 144
Joined: Thu May 04, 2017 7:30 am

by JoO

Hexsense wrote:
Wed Oct 03, 2018 4:38 pm
zefs wrote:
Wed Oct 03, 2018 7:22 am
The lack of vibration is caused by the bigger contact patch. The same thing will happen if you reduce the air pressure on narrow tires, the lack of vibration will not make them faster though.

To make it easier, think of where does the air go when you are sitting on the bike vs when you are off the bike. The air moves away, so more tire is hitting the ground increasing the rolling resistance. The less the air pressure the more it will move.
It's side wall compression/deformation that cost watts, not moved air.
Increasing width -> less side wall compression as the contact patch is shorter and wider, hence less sidewall compression needed for the same weight/load.
Increasing pressure -> less side wall compression, less rolling resistance. Also induce extra vibration as the suspension effect is reduced (which increase rolling impedance).
Decreasing presure -> more side wall compression, more rolling resistance. Also reduce vibration as the suspension effect is enhanced (which reduce rolling impedance).
They aren't the same.

As i state in a few posts ago, vibration have to be absorbed somewhere, either rider (less efficient) or tire. Let the tire absorb rather than on human waste less energy, given everything else the same (which is the catch*). So lack of vibration make it faster.

*However, how to achieve the lack of vibration can cost watts, it isn't free. Reducing pressure on narrow tire cost more watts over reducing pressure on wider tire due to extra amount of tire sidewall compression needed.
+1

Jan Heine gives a very good explaination:
"
1. Laboratory tests on steel drums eliminate the rider and thus the suspension losses. If you look at hysteretic losses alone, narrower tires run at higher pressures and thus flex less, meaning they absorb less energy.

We tested on real roads, with a rider on the bike, and found that the increased vibrations of the narrower tires caused energy losses that canceled out the gains from the reduced flex. These suspension losses are mostly absorbed in the rider’s body. Imagine a bean bag that drops on the ground without bouncing back – all the energy is absorbed by friction between the beans. The human body works similarly. Studies by the U.S. Army found that the more discomfort vibrations cause, the more energy is being absorbed.
"
https://janheine.wordpress.com/2018/01/ ... re-slower/

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Miller
Posts: 1559
Joined: Thu Sep 21, 2006 8:54 pm
Location: Reading, UK

by Miller

2old4this wrote:
Wed Oct 03, 2018 7:28 am
I am consistently slower on climbs when I am on the wide tires.
Saturday (Willier Zero7, Enve 3.4 Tubular, Continental Competition 23s):
Sunday (Argonaut, Enve AR 4.5 Tubeless, Hutchinson Sector 28s):
Kind of unfair comparison there. Conti Comp tub is widely used in pro level racing whereas a Sector 28 is for general riding/touring/commuting/gravel. I rode a pair of Sector 28s for a year. It's a robust durable tyre that works well as tubeless but it isn't a racing tyre.

2old4this
Posts: 366
Joined: Mon Jan 13, 2014 7:26 am

by 2old4this

Miller wrote:
Wed Oct 03, 2018 7:53 pm
2old4this wrote:
Wed Oct 03, 2018 7:28 am
I am consistently slower on climbs when I am on the wide tires.
Saturday (Willier Zero7, Enve 3.4 Tubular, Continental Competition 23s):
Sunday (Argonaut, Enve AR 4.5 Tubeless, Hutchinson Sector 28s):
Kind of unfair comparison there. Conti Comp tub is widely used in pro level racing whereas a Sector 28 is for general riding/touring/commuting/gravel. I rode a pair of Sector 28s for a year. It's a robust durable tyre that works well as tubeless but it isn't a racing tyre.
You are 100% right. The comparison is not apples to apples.

However, I am not quite sure if Continentals give that much speed advantage on short rides like these. :noidea:

I think the more important factor here might be the reduced pressure (increasing the contact area, and thus increasing the rolling resistance ???) One thing I can try is to reduce air pressure on the tubulars from 120 to ~85 psi for a few weeks to see the effect.

spud
Posts: 765
Joined: Sat Feb 07, 2009 5:52 am

by spud

not sure that you will achieve any clarity with this experiment. The bigger tire likely has a stiffer casing material, so it has higher rolling resistance (hysterisis), as well as higher suspension losses since it is less flexible. In addition, the Conti tubular makes you feel faster (aero and rolling resistance), so you ride the front more and feel better about your effort. Only way to compare these is with a powermeter on the same course, and even then, the Conti should be faster.

Mr.Gib
Posts: 3508
Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

2old4this wrote:
Wed Oct 03, 2018 7:28 am
Please no flames. Below is what I experience, and yours could be totally different...

I am consistently slower on climbs when I am on the wide tires. I really do not need to look the the data below since on the group rides I am generally in the front of the group with thinner tires, whereas I am generally in the back of the group when I am riding the bike with the wide tires.)

Real world data from the last weekend...
(Disclaimer: Both rides were loops. Steepness is very close but not the same. I was not using the same bike on both days. These were not races, so we weren't really pushing...)

Saturday (Willier Zero7, Enve 3.4 Tubular, Continental Competition 23s):
Total Climb: 2945 ft
Max Gradient: 17%
Distance: 34.7 miles
Total Time: 2:08:46

Sunday (Argonaut, Enve AR 4.5 Tubeless, Hutchinson Sector 28s):
Total Climb: 2718 ft
Max Gradient: 14%
Distance: 28.4 miles
Total Time: 1:49:23
Well that settles it then. We can end the thread...

Sorry bro' but you get flames. Different bike, different day, different route, different tire - seriously what will that tell you? Or tell us? Front of the group vs back of the group? Who's in the group? What tires are they riding that day? What did they do the day before? What did you do the day before? And how could you be faster on your Conti's vs your Hitchinsons, yet for someone else "it could be totally different". I guess it's never promising when it starts with "I don't need to look at the data".
Last edited by Mr.Gib on Thu Oct 04, 2018 3:18 am, edited 1 time in total.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

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MattMay
Posts: 54
Joined: Thu Apr 10, 2014 3:26 pm
Contact:

by MattMay

Schwalbe does a pretty good job of answering these types of questions (what exactly is rolling resistance? What factors affect rr? Why do wide tires roll better than narrow ones? Why do pros ride narrow tires if wide rolls better?).

https://www.schwalbetires.com/tech_info ... resistance

emotive
Posts: 143
Joined: Tue Nov 01, 2016 10:40 am
Location: Melbourne, Australia

by emotive

@2old4this look at any Strava segment you have ridden a lot. Look at the variation in results, even on the same bike with the same tyres. Two rides with different results is not evidence.

I have 3 bikes, one with 25's, one with 28's, one with 35's. Looking at a Strava segments with more than 20 results I can see when I ride harder, I go faster, no surprise there. When I look at which bike/tyres I was using, there is no clear result. I could share two results to prove the 25s are faster than the 28's, or I could choose two results to show the 35's are faster than the 25's. As MrGib says, there are too many variables.

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Frankie - B
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Location: Drenthe, Holland

by Frankie - B

My current bike is a bit against the grain of ww. :oops:
Alloy, Sram force disc (not even Etap) Effin' heavy alloy DT wheels, OEM seatpost and stem. Fizik cf bars and a heavy flite saddle. The tires are Challenge strada bianca vulcanised clinchers. Note vulcanised, not the beautyfully made open tubulars. They measure 33mm wide when mounted on a 19mm internal rim. I ride them at 43.5 PSI, a pressure gauge was also bought to check the air volume in the tires regularly. For instance, pump your tires to 43 PSI in the shade and then place your bike in the sun for 10 mins. Logic has it that the pressure has increased in that time. The trigger to buying the pressure gauge was one of the silca articles, they are a great read and are very interesting.
'Tape was made to wrap your GF's gifts, NOT hold a freakin tire on.'
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