Any hard data on rotational weight?

[veggieburger]

I usually ride to work on 32w Panaracer tires, which are great and flat-free...but slow and heavy. This morning I replaced my rear tire with a 25w 240 gram tire and the difference was remarkable. I felt like I had lost 20lbs.

Any charts that show what is gained and lost by lighter/heavier tires?

Thx!

[oldpotatoe]

Originally Posted by veggieburger

I usually ride to work on 32w Panaracer tires, which are great and flat-free...but slow and heavy. This morning I replaced my rear tire with a 25w 240 gram tire and the difference was remarkable. I felt like I had lost 20lbs.

Any charts that show what is gained and lost by lighter/heavier tires?

Thx!

Wish I could find the article. On Bike.com just before dot.bomb bust. They doubled the weight of a rim and measured the additional energy to accel to a specific rpm. Difference was something like .1 of 1% additional energy.
I think you are feeling the tire characteristics, not the weight. Like carbon wheels, 'spin up fast', the stiffness, not the weight. Imho of course.
Some physics guy will chime in hopefully. I can't even spell fisics.

[Gummee]

I know the plural of anecdote isn't data, but my Mavic Cosmics (first gen) were sloooooow to accelerate.

Great once you got em up to speed, but they weren't fast getting there.

HTH

M

[fiamme red]

I changed the rear rim on my commuter from a Velocity Synergy to an Atlas, which is over 100 grams heavier. I can't tell the difference when I'm at speed on the flats, but I can easily tell the difference when I'm accelerating.

[Mark McM]

Originally Posted by veggieburger

I usually ride to work on 32w Panaracer tires, which are great and flat-free...but slow and heavy. This morning I replaced my rear tire with a 25w 240 gram tire and the difference was remarkable. I felt like I had lost 20lbs.

The biggest performance difference between light and heavy tires usually isn't due to the change in mass - its due to the difference in rolling resistance. Tire rolling resistance comes primarily from the energy lost in flexing the tread and casing. A lighter tire will have less tread and casing to flex, and a tire that has less tread and casing to flex will create less rolling resistance.

Here's a chart of road tire rolling resistance that shows a difference of up to 18 watts between the best and worst 25mm wide tires - depending on how hard you are going, that could easily be a 10% difference in total power.

[54ny77]

heavier rolls just fine.

[John H.]

I have noticed that speed increases with going up to 25-28 (if they are fast tires)- but they get exponentially slower as they get bigger than that.

I found 700x28mm Conti 4seasons to be slightly slower (than 25)- 32mm was like towing a boat.

[veggieburger]

Part of the issue might be that the Panaracer was squared off pretty badly. So the footprint was much wider than when I first mounted them.

[Mark McM]

Yes. It is true that wider tires roll faster, all else being equal. But all else is generally not equal when comparing tires of different widths. Wider tires are typically built more with durability in mind, so they usually have thicker treads, deeper tread patterns, and heavier casings, all of which increase rolling resistance.

The lowest rolling resistance tires have thin, compliant casings, paper thin slick treads, and no puncture protection layers. They are also very fragile and wear out quickly. If you increased the width of the tires to 32mm or more, they'd have even lower rolling resistance - but good luck finding a tire like this, as there is no demand for very wide, but fragile and short wearing tires.

[Mark McM]

Originally Posted by veggieburger

Part of the issue might be that the Panaracer was squared off pretty badly. So the footprint was much wider than when I first mounted them.

Tire resistance decreases as tires wear down and square off. This has been measured and confirmed many times. The reason is two-fold: There is less material to be flexed at the ground contact point; and a flat profile needs to flex less to conform to the road surface. As tire flexing is the primary cause of rolling resistance, this results in less rolling resistance.

And this isn't just for bicycle tires - this affect is well known for automobile tires as well:

https://www.tirerack.com/tires/tiret...jsp?techid=177

[veggieburger]

Originally Posted by Mark McM

Tire resistance decreases as tires wear down and square off. This has been measured and confirmed many times. The reason is two-fold: There is less material to be flexed at the ground contact point; and a flat profile needs to flex less to conform to the road surface. As tire flexing is the primary cause of rolling resistance, this results in less rolling resistance.

For sale: about a half dozen old, squared off tires. Perfect for time trials. Best offer, or will trade for new tires.

[MaraudingWalrus]

Sure there's some. Check out this article on Wheelfanatyk Blog. Check out the referenced links in there, too.

I'll go use the device I built and grab some numbers I've been dawdling on doing. Same wheelset with Gatorskin vs Corsa tire.

I'll report back.

[MaraudingWalrus]

I threw one wheel on my trifilar pendulum, and used the formulas described on the above mentioned wheelfanatyk blog post to calculate final results.

I used the same wheel, my ENVE Classic 45 laced with ACE3 spokes to a Paul High Flange front hub, using ENVE rim tape. I used the same tube with each different tire, and none of the tires were inflated to any pressure, they were just installed onto the rim.


I did three runs with each tire option and averaged the results.

I show results with no tire and tube (that'd be just the wheel with rim tape), a 23mm Open Corsa EVO CX, a 25mm wire bead Schwalbe Lugano, a 23mm Continental Gatorskin, and a 37mm Michelin Protek.




So, here's some background information/ comments/critiques on the "experiment" :



The end result, the watts column, is watts of energy required to spin that wheel up to 30km/hr in 10seconds. These numbers do not account for friction in any way - not bearing friction, not friction between the tire and the ground. These are just looking at overcoming inertia to spin the wheel in a theoretical situation in which all we are doing is spinning the wheel. It also doesn't really account for aerodynamic drag in any real way - given this test is done, in my case, in a garage and not a vacuum, I suppose there is some wind resistance, happening, but we're probably not achieving speeds of 30km/hr so that would obviously ramp up more at speed.

This also is obviously only the amount of energy required to spin that wheel by itself up to speed. The wheel, in the real world, is part of the whole bicycle rider system, so % variance between these wheels is lessened when taking the whole system into account, but it's worth noting the actual watts variance is not changed.





Results show that every time you go to spin that wheel up to 30km/hr in 10seconds the wheel by itself requires 3.1 watts of energy. The 23mm Corsa tire (and tube) require an additional 2.6watts of energy of the wheel by itself; the Lugano requires 3.4 watts additional; the Gatorskin requires 4 watts additional; the Protek requires an additional 10.3 watts to spin up to speed.

These are HUGE % variance between each other when just looking at the wheels by themselves. They're a considerably smaller % variance when taking into account the whole bike/rider system...but perhaps not an insignificant amount of actual watts. How many times in the course of your ride to you accelerate and decelerate? Saving two watts per wheel (so 4 watts total) every time I go to speed up is worth it to me to run Corsas over Gatorskins....and I'd wager it's something you and I can feel.


You can also check here for a spreadsheet of mine I'm updating with wheels I test to give data. It's not currently a very good spreadsheet and I haven't yet figured out a formatting that I like to show it in a way that makes clear obvious sense.



Also attached is a a photo of a Michelin Protek mounted to an Enve wheel...


in case anyone wanted to see that sacrilege

[zap]

Originally Posted by Gummee

I know the plural of anecdote isn't data, but my Mavic Cosmics (first gen) were sloooooow to accelerate.

Great once you got em up to speed, but they weren't fast getting there.

HTH

M

Agreed. I think this wheelset weighed around 2000g.

On the other side, I built a 1070g wheelset and that just accelerated like snap......but you had to stay on top of it cruising at 25-30mph.

[veggieburger]

Originally Posted by MaraudingWalrus

I threw one wheel on my trifilar pendulum, and used the formulas described on the above mentioned wheelfanatyk blog post to calculate final results........

Marauding Walrus is one smart dude/dudette..