kjc9640

Some interesting test on wide tires vs narrow

https://www.bikeradar.com/news/articl...he-myths-29245

BlazingPedals

This subject was discussed - again - on BROL, ad nauseum. Not that you'd have any reason to go there. None of this is new and there were no new converts in either direction. Fat tires have lower losses from casing deflection, but have more frontal area and higher weight. Also, the results are somewhat skewed, because these comparisons always compare tires at equal pressures, which means one of the ones being compared is at the wrong inflation.

It's a no-brainer that fat can absorb more road shock, too. So Fat is better at low speeds and flat/rough ground, while skinny is better at higher speeds and hills. The trade-off that's best for you depends on how you ride.

StephenH

If you're having problems getting passed by people on Puggsleys and Large Marge tires, this could explain it, though.

Phil85207

Yes this has been around for a while and the posts at the end of the article are interesting as to putting the percentages in perspective.

alcanoe

There's no data in the article, just opinions and pictures.

The data that I'm aware of does show much lower energy required to pedal a wider tire at 31 km/hour on a rough surface than a narrow tire. The energy generated by the rough surface and absorbed by the rider is not available for forward motion.

On a smooth surface, they are all about the same at that speed . That's for all losses including air drag.

Years ago I found a calculator on the web that showed that a 40 mm tire had a square foot of frontal area more than a 23 mm. However, in still air the frontal area of the bike does not change IMO as the down-tube and seat tube cover the same frontal area of the tires. The bikes drag coefficient may change due to different tire sizes causing different turbulence characteristics, but not it's frontal area.

Some representative data from a trial reported in Bicycle Quarterly, August 2009 issue:

Tires evaluated: Pasela 35mm (P35) @ 50 psi; Grand Boise 25mm (GB25) @ 75psi; GB25 @ 95 psi; Bontrager 27mm (B27) @95 psi.

They were tested on a bike with 4 forks ranging from stiff to one that had suspension. The tests were on a smooth road along side a road side rumble strip and over the rumble strip. The r. strip grooves were 8 to 10 mm deep.

The power to propel the bike at 31 km (19.4 mph) :

Road: P35 @ 50 = 198 watts, GB25 @ 75 = 209, GB25 @ 95 = 237 and B27 = 232.

R strip: P35 @ 50 = 313 watts, GB25 @ 75 = 386, GB25 @ 95 = 468 and B27 = 479.

There's no real statistical difference for either the smooth road or the between the 4 forks used.

Bicycle Quarterly (https://www.bikequarterly.com/vbqindex.html ) is a classic bike and Randonneur focused publication. They preach and demonstrate as well that wider tires are faster, corner better and are a heck of a lot more comfortable. They just aren't as cool.

They do a lot of tire testing.

They have some articles on the site. I've been buying back issues as I really enjoy their tech articles, bike reviews and articles on bike history.

An article on tire inflation: https://www.bikequarterly.com/images/TireDrop.pdf

Al

xizangstan

All I know is I got into some off-road mud yesterday afternoon, and I wished I still had my big, fat Continental 2.5" wide knobbies on, instead of my 1.5" Schwalbe Marathon road tires.

Problem with thin tires in mud = they cut deep down, fast.

stapfam

One of the effects of a good mud tyre. Cuts through the mud to the good surface below instead of skating around on top of the gloop.

I use the Panaracer Mud tyre in 1.8 in mud and snow. Another good one is the conti cross countryt in 1.5.

AzTallRider

Those are all low pressures that will have a lot of deflection. Any test where the tires are pumped up to where roadies actually use them? 120-130 psi on 23s or 25s? I'll try to find the tests I read with higher pressures. It showed lower rolling resistance if you reduce the deflection.

Robert Foster

How would we escape the idea that is "no one" that races road bikes for a living uses wide or fat tires? We could debate it all we want but from experience we know what is harder to push past 25 MPH on the flat and we know what wins races. But this topic comes up anyway. Comfort is a different issue.

from a personal observation I have had a Masi Cafe Solo that came with 700X28s and I rode it for a few weeks with that tire set up. Switched to 700x23s and picked up 3 MPH cruising speed. Nothing that can be posted would convince me the 28s were faster.

bobthib

Ok, referring to the article above, let me see if I got this.

Lets assume:
"Racing" Bike so load distribution is 60/40 (R/F)
23 mm tires
200 lb load (combined weight of rider, bike, etc)

Then:
Wheel loads are Rear = 120 lbs, Front = 80 lbs.

Referring to the chart on the 23 mm inflation line, the rear tire should be about 127 psi
and the front about 83 psi if I'm reading it right. That seems a bit low, exp compaired to Shedon' Brown's rule of thumb which is approx Rear - 10% = Front.

The rear at 127 compares favorably with Shedon's recommended 125 for my total load, but the front by his formula would be about 113.

If I can remember, I'm going to try the 80 lbs in the front on my next ride and see if I can tell any difference. There are some washboard roads on my typical route that can provide a good test of comfort. With out a power meter I don't think I'll be able to give an unbiased assessment of the effort difference, if any.

Please review my assumptions and let me know if I made any errors. That 80 psi for the front really seems low!

bobthib

Wow, that really explains why riding out on the levee with the gravel (R strip) is so much harder and slower than a paved road! No wonder I only averaged 12 mph!

alcanoe

[QUOTE=Robert Foster;12251984]How would we escape the idea that is "no one" that races road bikes for a living uses wide or fat tires? We could debate it all we want but from experience we know what is harder to push past 25 MPH on the flat and we know what wins races. But this topic comes up anyway. Comfort is a different issue.

QUOTE]

I think it's easy to explain. They ride faster/longer where both aerodynamics and weight play a big role in winning. Those bigger tires are heavy and the weight is at a long lever-arm which really eats up energy in acceleration. Then at higher speed, bigger tires/rims (and more spokes) likely cause more air drag especially from off-angle wind.

I've never averaged more than about 15 mph on a 70 mile ride. That's far lower than even the 2200 mile TDF. Air resistance is not a big factor for me except in a wind.

Another interesting tidbit about bike technology and racing from Bicycle Quarterly Summer 210: regression analysis shows that the average speed increase of the TDF (Tour de France) matches the increase in Average speed trend of runners from 1950 through 2010. In other words it's not the bike, but the riders. Training/nutrition drives the improvements.

There was a big improvement in cycling in the '30s as they paved those roads in the mountains and the more modern frame geometry was locked in to about what's used today. They checked the data against one classic, Milan-San Remo and saw the same trend for that one day race.

Al

rydabent

Another aspect of wider tires is safety. I think we can all agree that the condition of roads these days is terrible. There are areas of cracks and broken pavement. The wider larger tires will span cracks, and roll over sharp edged bumps without give you snakebite flats. The Primo Comets on my Rans bent roll extremely easy with their 100psi rating. Bottom line you are not very fast laying in bed with a broken collar bone due to being dumped due to bad pavement.

alcanoe

Yes but, the culture here is one of the Rondenneur. They ride like 1200 km in less than 80, 84, or 90 hours and most don't ride like it's a race. They likely prefer not to vibrate down the road as fatigue is a big issue and there's a premium on comfort. They use lights, bags and many use fenders as well: like my road bike.

A friend of mine has done Paris-Brest 3 times. He often trained by riding his bike to work (about 30 miles), then after work on a Friday he would ride until 8-hours before he needed to go to work on Monday. Probably a factor in the divorce.

It was interesting to hear how he and his co-riders often hallucinate.

Al

jppe

All I know that the tires on the bikes ahead of me in a pack are all 23's.............except for maybe a tandem.

Robert Foster

[QUOTE=alcanoe;12252759]True and the Faster longer part ends the debate on what is faster. If there were a speed advantage then even TT bikes would have fat/wide tires. A quick study of what the teams do with computer modeling would convince most of us that they are riding the equipment that gives them as much of an advantage as is legal.

It is hard to accept the contention that fat/wide and heavy will give you a speed advantage when in real life we can't see it. We aren't saying they are not comfortable or safe but faster? Bench racing is always nice but on race day the one finishing first, second and third is proof of a theory.

jppe

If wider tires are faster why are the new generation of TT tires the exact width of the Aero wheel rims?

XR2

I don't see anyone recommending using fat tires on a TT bike,or any racing bike for that matter. I see it as more a "what is the advantage of using skinny racing tires on our non-racing bikes?" Comfort and flat resistance enter into the equation when practicality enters the room. None of the tires referenced in the BQ test are racing tires are they? Striking that balance is not an easy task and I commend them for looking into why the constructeur bikes used the tires they used.

ThatBritBloke

The article really describes the difference between 23mm and 25mm tyres, not 23mm to 28mm. I don't think it's suggesting that 28s are superior to 23s.

However, over the past year or so I've migrated from a 23mm tyre / tube combination to 25mm tubeless - not tubular - running 10psi less than I used to with tubes and have a more comfortable ride and now coast ahead of my colleagues with their 23mm tyres on descents.

late

When I got my wife a 650b I had to fiddle with it a bit.

I sat on it and rolled down the driveway.

The drive was suddenly paved with silk.

Ok, maybe an exaggeration.

But my wife doesn't watch for bumps anymore. They don't bother her.

Everyone once in a while she finds a pothole and I hear a loud Oooph.

I'll be posting a pic of my new 650b frame soon, hopefully within the week.

It'll be here..

https://ruedatropical.com/

The Keep Riding video is nice, you'll like it.

Oh, I forgot, I think for a lot of people the greater comfort
is a big improvement. Being bounced around is tiring, and
that is an energy loss.

It's like in planing. It prob doesn't make the bike more efficient,
but the end result is the same as if it was.

Robert Foster

Already we have reached the same point we always do in this particular discussion. Two diametrically opposed points of view with no possible solution.
The people that get paid to go “faster” seem to think high pressure skinny tires are faster. People that ride for comfort aren’t so sure. No opinions are changed and no one will pick different tires because of it.

stapfam

There are places where a wider tyre will be faster-but that is not down to Less Friction or rolling resistance.

It is down to comfort. A rough surface and a bit of suspension is wanted to ease the body from slowing down through pain. You can only take so many "Knocks" without the terrain affecting you.

Surprised they haven't come up with a Tyre called "Roubaix" by now. (Paris Roubaix where many of the riders will run 25 tyres to ease the pain over the cobblesas well as modified frames and forks)

ThatBritBloke

You were saying?

Metric Man

Yep...seen that coming.

Robert Foster

One thing I have observed and will testify to is the thinner and narrower “you” get the faster you are.