Theoretical watts lost due to too wide a tire

[Alumen]

I don't care about the theoretics tbh...

On 28 I am faster than 25. Period.

Given the fact that the biggest aero impact is you, your position on your bike and your helmet, going from 25 to 28 has probably the same aero impact of your loose fitting jersey you were wearing yesterday vs your tight fitting jersey you have been wearing today.

[spartacus]

I don't care about the theoretics tbh...

On 28 I am faster than 25. Period.

Given the fact that the biggest aero impact is you, your position on your bike and your helmet, going from 25 to 28 has probably the same aero impact of your loose fitting jersey you were wearing yesterday vs your tight fitting jersey you have been wearing today.

So what you're saying is it can make a big difference?

[Alumen]

I don't care about the theoretics tbh...

On 28 I am faster than 25. Period.

Given the fact that the biggest aero impact is you, your position on your bike and your helmet, going from 25 to 28 has probably the same aero impact of your loose fitting jersey you were wearing yesterday vs your tight fitting jersey you have been wearing today.

So what you're saying is it can make a big difference?

Not exactly. But yes, wider is faster vs aero impact.

I have said on 28 I am faster than 25.

And I do ride smooth tarmac / dedicated bike lanes. So it is not that bad roads will give the benefit to the 28.

But you have a point, if you want to look at aerodynamic gains, you'll have to look at the whole system and the total of gains you can make.

[C36]

I have said on 28 I am faster than 25.

And I do ride smooth tarmac / dedicated bike lanes. So it is not that bad roads will give the benefit to the 28.

Curious, What makes you think you are faster?
All things equal there is no science behind being faster on wider tires, particularly on good roads.

[Alumen]

I have said on 28 I am faster than 25.

And I do ride smooth tarmac / dedicated bike lanes. So it is not that bad roads will give the benefit to the 28.

Curious, What makes you think you are faster?
All things equal there is no science behind being faster on wider tires, particularly on good roads.

If you think I am overthinking things here... trust me, I am not that smart at all.

But my numbers don't lie, simple as that.

And that is the beauty with our sport, sometimes the reality overtakes science on paper. From that perspective, I am just smart enough to understand that.

[cajer]

If you're using outdoor rides, there's so much noise that you can't draw any conclusions espically with a ~1W resolution.

[C36]

And that is the beauty with our sport, sometimes the reality overtakes science on paper. From that perspective, I am just smart enough to understand that.

Hum that’s not really how it works… physics do mimic very well performance… if we understand what physical properties are at play.

I remain curious how did you compare both setups to drive this conclusion? Time? Power?

[smokva]

Hum that’s not really how it works… physics do mimic very well performance… if we understand what physical properties are at play.

I remain curious how did you compare both setups to drive this conclusion? Time? Power?

Hum that’s not really how it works… physics do mimic very well performance… if we understand what physical properties are at play.
I remain curious how did you compare both setups to drive this conclusion? Time? Power?

When it comes to road bike tyre width, there’s a balance to be struck between comfort, rolling resistance and aerodynamics. Where the balance lies will depend on road bike, road conditions, riding style and rider power output.
For someone who averages 20 km/h on a flat, wider is probably faster because rolling resistance outweights aero gains. For someone else who goes 35 km/h on the same route wider is slower because aero penalty is much bigger for wider tires. There is no doubt about that....wider frontal area means bigger aero drag.
So to generalize...faster you get narrow becomes better, slower you are wider is better.
My measurements show that for me WIDER IS SLOWER at this moment if I use watts that are available in my legs. For someone else conclusion might be different, even I might change my preference in the future.

[Hexsense]

Wider is slower, no doubt at high speed straightline for me.
But wide rim reduce the penalty so much that I'm taking the trade.
Speed wise, 27mm (measured) tire on 28mm rim > 29mm tire on 32mm rim >>> 30mm tire on 28mm rim.
It feel particularly slow when tire is wider than the rim. But I don't notice much when the rim is widen to exceed tire width.
And I corner with more confidence on 29mm tire on 32mm rim. So, I somewhat gain some speed back there.

[Alumen]

And that is the beauty with our sport, sometimes the reality overtakes science on paper. From that perspective, I am just smart enough to understand that.

Hum that’s not really how it works… physics do mimic very well performance… if we understand what physical properties are at play.

I remain curious how did you compare both setups to drive this conclusion? Time? Power?

If you take a one dimensional look only, at physics, then yes, you can mimic performance on paper. Quite safe right ?

But..., there is also my physical biology of the performance of my own body. You know, that thing that operates your bike.

I look at average speed and power output on distances from 25 miles and up. 28mm is faster than 25mm. Not by a whole lot, but faster. What I notice is that I can maintain my absolute speed better at the end of the ride. Again, I look at average speed only. Though at the end of the ride I also look at absolute speed, which drops less compared with a 25mm tire and contributes to the higher average speed. So that says to me that a 28mm causes less fatique to my body and increases my performance on longer rides and thus increases my average speed. I am talking speeds in the range of 21 - 25 miles an hour (or 33 - 40 km/h).

Yes, all things being equal and I ride a straight line of one mile from A to B, with both a 25mm and a 28mm the difference will be neglectable. But with 25 miles / 40km rides and up ? Yes, please give me the 28mm tire.

[choochoo46]

Gotcha, Alumen. You're not saying that 28mm tires are categorically faster than 25mm tires, but for you personally and from what you can deduce from your ride data, 28s are faster for you. And you're not saying that you've done any scientific testing since you can't control all the variables across all your rides (rim to tire width, road surface, temperature, barometric pressure, elevation, hydration & calorie intake during the ride, sleep the night before, body position, etc). Good on you. What matters most is that you feel confident on your bike and you enjoy the ride.

All: just came across this comparison of the aerodynamics of racing tires by AeroCoach showing that watts attributable to aero drag are as much as 15X higher than the watts associated with rolling resistance. https://www.aero-coach.co.uk/aerodynami ... cing-tyres

As mentioned before this difference increases with speed. The test was done at 45kph / 28 mph, so race pace.

I wonder, though, how they isolated the tire in their wind tunnel test vs. frame, cockpit, seat, etc. Across all tires in the test it took about 340 watts at 45kph. How much more watts did the rest of the system consume?

[xav]

I wonder, though, how they isolated the tire in their wind tunnel test vs. frame, cockpit, seat, etc. Across all tires in the test it took about 340 watts at 45kph. How much more watts did the rest of the system consume?

As it says on the page (click on the "Wind tunnel and velodrome testing" tab) the data presented is a combination of wind tunnel and velodrome testing. We can split Crr by using wind tunnel, velodrome and roller Crr data to allow us to measure the drag contributions from the various areas.

[smokva]

All: just came across this comparison of the aerodynamics of racing tires by AeroCoach showing that watts attributable to aero drag are as much as 15X higher than the watts associated with rolling resistance. https://www.aero-coach.co.uk/aerodynami ... cing-tyres

I would like to see graph of aero drag vs speed (basically this comparison for various speeds in increment of 5km/h), so that we can finally conclude what is the speed where aero drag becomes bigger than rolling resistance. That would put to end many "wider is faster" debates. Than we could say...ok your avg speed is so and so, you are better on these tires... I don't average 45 km/h so test on that speed doesn't do much for me.

[kervelo]

I would like to see graph of aero drag vs speed...

Swiss side has a great comparison of gravel tyre widths, I wonder if similar tests exist for road tyres.
https://www.swissside.com/blogs/news/gr ... ?locale=en

[LedZeppelin007]

For me, there are so many outside uncontrollable factors, it’s difficult to determine whether different wheel depths, tire widths, etc. actually make much of a difference at all in my actual riding.

I can tell and measure a difference between my road bike and gravel bike on tarmac regardless of conditions. Beyond that, it’s been a bit of a minefield.

One exception: I can say that the Canyon Aeroad with the 62mm deep DT Swiss ARC 1100 wheels, GP5000s and latex tubes is fast AF. Unfortunately, it was also incredibly unreliable and somewhat I’ll suited for the riding I do.


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