For those guessing the wattage penalty of gravel vs aero bike....

[mstateglfr]

I certainly wouldn't figure that large a difference for my riding.
...but my 2 main road bikes are steel tubing and my gravel bike is...steel tubing. No aero.

[rain dogs]

Originally Posted by rice rocket

Why though? Not only will you never ride them the same, there's already tons of data out there on how round tube bikes perform. The new data here is the pieces we've been missing.

Do cyclocross riders care about Watts and speed? Of course. Do they fret over tire selection and pressure? Of course. Do they care if an aero bike with deep dish aero wheels is faster than their cross bike in a wind tunnel when preparing for a cross race? Of course not.

Respose to the above in Bold: Isn't that what we should be saying about this "data". Which: uh, questionable motivations? It's a comparison between two not-really-comparable bikes. Roadie analysis can't see the trees, cause it doesn't go in 'em... it only sees the forest.

The "Data" is only important with sensible questions. Any bike designed solely to go fast on smooth roads and in wind tunnels (uhh TT Bike) will be faster on smooth roads and wind tunnels than a bike designed to be fast over multiple surfaces and varied terrain. Nobody needs to test just that. But people might want to know the influence of a component when on the road vs when off the road... and the estimation of TOTAL time. If your riding only demands an aero road bike... use an aero road bike - "horses for courses"

If you care about time/Watts/Gravel Bikes/Varied terrian etc., the question is: How much time/Watts am I losing/gaining by choosing applicable A vs B decisions. Like:

X measure of tire vs X+5mm or X+10mm of the same tire?
650B + wider tire vs 700c + narrower tire (at same system weight)?
Knobby vs Slick tires?
Tire Pressure?
etc. etc. and the difference, based on my experience, is very little... next to nothing when you've gotten out of "trees" and are looking just at the road parts of the above questions. But in the 'trees' to continue that analogy...big difference.

And, if what you care about above all else is speed, watts, and aero on smooth asphalt (not my thing, but fair enough) get yourself a TT bike (better a Tri TT bike or recumbent) ride that everywhere and argue for those wattage/Crr/CdA gains. That should be obvious.

[ripvanrando]

Originally Posted by rain dogs

Do cyclocross riders care about Watts and speed? Of course. Do they fret over tire selection and pressure? Of course. Do they care if an aero bike with deep dish aero wheels is faster than their cross bike in a wind tunnel when preparing for a cross race? Of course not.

Respose to the above in Bold: Isn't that what we should be saying about this "data". Which: uh, questionable motivations? It's a comparison between two not-really-comparable bikes. Roadie analysis can't see the trees, cause it doesn't go in 'em... it only sees the forest.

The "Data" is only important with sensible questions. Any bike designed solely to go fast on smooth roads and in wind tunnels (uhh TT Bike) will be faster on smooth roads and wind tunnels than a bike designed to be fast over multiple surfaces and varied terrain. Nobody needs to test just that. But people might want to know the influence of a component when on the road vs when off the road... and the estimation of TOTAL time. If your riding only demands an aero road bike... use an aero road bike - "horses for courses"

If you care about time/Watts/Gravel Bikes/Varied terrian etc., the question is: How much time/Watts am I losing/gaining by choosing applicable A vs B decisions. Like:

X measure of tire vs X+5mm or X+10mm of the same tire?
650B + wider tire vs 700c + narrower tire (at same system weight)?
Knobby vs Slick tires?
Tire Pressure?
etc. etc. and the difference, based on my experience, is very little... next to nothing when you've gotten out of "trees" and are looking just at the road parts of the above questions. But in the 'trees' to continue that analogy...big difference.

And, if what you care about above all else is speed, watts, and aero on smooth asphalt (not my thing, but fair enough) get yourself a TT bike (better a Tri TT bike or recumbent) ride that everywhere and argue for those wattage/Crr/CdA gains. That should be obvious.

SwissSide's simulation showed 8.5 minutes gain on a gravel race won by 1.5 minutes.

Slightly narrower tire on aero rim was something like 5-10 watts at 30-37.5 km/h. Not a little in my view.

[Davist]

Originally Posted by ripvanrando

SwissSide's simulation showed 8.5 minutes gain on a gravel race won by 1.5 minutes.

Slightly narrower tire on aero rim was something like 5-10 watts at 30-37.5 km/h. Not a little in my view.

If you're averaging over 20mph (30kph) on gravel, chances are you're not paying for your bike/wheels/tires anyway you use what the sponsor pays you to ride. For the rest of us, road bikes are faster than gravel bikes

[oldpotatoe]

Originally Posted by drewskey

The amount of variables in gravel racing are > the watt savings at this point (minus unbound and maybe BWR).

I’m sure that aero gravel bikes and optimization of the entire system will yield larger advantages in the near future that will get closer to road setups.

As more competition enters the gravel racing scene, more aero advantages will be sought out and we all will benefit.

[ripvanrando]

Originally Posted by Davist

If you're averaging over 20mph (30kph) on gravel, chances are you're not paying for your bike/wheels/tires anyway you use what the sponsor pays you to ride. For the rest of us, road bikes are faster than gravel bikes

If you read my other posts, you would see that I agree. I was responding to another who said there is little or no difference. Some of the comparisons to TT bikes is ridiculous when SwissSide was comparing an ordinary road bike to an ordinary gravel bike without a rider. On my local gravel, a road bike would also always be faster; however, on different gravel, my gravel bike is faster.

Horses for courses.

[spoonrobot]

Originally Posted by rain dogs

If you care about time/Watts/Gravel Bikes/Varied terrian etc., the question is: How much time/Watts am I losing/gaining by choosing applicable A vs B decisions. Like:

X measure of tire vs X+5mm or X+10mm of the same tire?
650B + wider tire vs 700c + narrower tire (at same system weight)?
Knobby vs Slick tires?
Tire Pressure?
etc. etc. and the difference, based on my experience, is very little... next to nothing when you've gotten out of "trees" and are looking just at the road parts of the above questions. But in the 'trees' to continue that analogy...big difference.

The differences are huge, and they get bigger the faster you go. This sort of equivocation is a holdover from mid-term gravel adjacent marketing where the goal was to sell product, not disseminate what is the fastest set-up for a given group of riders.

The Swiss Side study is fascinating and more relevant to off-road racers than anything other than Bicycle Rolling Resistance compendium of testing.

[rain dogs]

First, let's not kid ourselves that this is peer-reviewed science here... it;s an ad. As someone else said, the factors at play are greater than solely "aero".

You can gain 8,5 minutes (maximum... and 'real world debateable') using the "most aero setup tested in the wind tunnel" and you can lose HOURS if you are flatting, don't have appropraite traction, screw up tire pressure, and many more all those on-the-actual-surface-not-in-a-windtunnel considerations.

Even IF we take the numbers as reproducable truth, fine, you need to resist the red herring of the "aero bike vs gravel" because it's irrelevant. The important details, if we grant that, are things like 3,6W per 10mm of tire.

First, 3,6W might be huge to you, small to me, but it's certainly lesser consideration big picture. Second, "aero" only it ignores any benefit gained from +10mm width if applicable. If just you're using 10mm wider tires than you need jsut because, then you're screwing up component selection.

The numbers for the 2 Schwalbe's for example are 1,1W... but the grip (if needed) will provide a much larger advantage than those 1,1W of losses. But, hey, do what works for you. I'm not sure why I bother. If you think running tires that are pushing the envelope in the directio of being much less wide, thinner, and more slick, so that you can win 6W of aero resistance - good on you, but I'd hope you base it on experience vs some theoretical 'wind tunnel' on the internet.

[ripvanrando]

Not many peer reviewed wheel and bike tests out there. Even Tour Magazin isn't peer reviewed. (If it were, they would not get the data mixed up as often)

I wish Campy would publish any data to support their claims for the WTO wheels or at least support their assertion that 80% of road riding occurs at yaw angles of 10-20 degrees. The only other place I have seen that percentage of yaw figure.....Hambini

I thought Swissside broke it all down pretty well. A watt or two here and there is like finding a couple bucks here and there until eventually you have a free lunch, not three star dinner.....maybe a free Hoagie.

[mtechnica]

Originally Posted by rain dogs

First, let's not kid ourselves that this is peer-reviewed science here... it;s an ad. As someone else said, the factors at play are greater than solely "aero".

You can gain 8,5 minutes (maximum... and 'real world debateable') using the "most aero setup tested in the wind tunnel" and you can lose HOURS if you are flatting, don't have appropraite traction, screw up tire pressure, and many more all those on-the-actual-surface-not-in-a-windtunnel considerations.

Even IF we take the numbers as reproducable truth, fine, you need to resist the red herring of the "aero bike vs gravel" because it's irrelevant. The important details, if we grant that, are things like 3,6W per 10mm of tire.

First, 3,6W might be huge to you, small to me, but it's certainly lesser consideration big picture. Second, "aero" only it ignores any benefit gained from +10mm width if applicable. If just you're using 10mm wider tires than you need jsut because, then you're screwing up component selection.

The numbers for the 2 Schwalbe's for example are 1,1W... but the grip (if needed) will provide a much larger advantage than those 1,1W of losses. But, hey, do what works for you. I'm not sure why I bother. If you think running tires that are pushing the envelope in the directio of being much less wide, thinner, and more slick, so that you can win 6W of aero resistance - good on you, but I'd hope you base it on experience vs some theoretical 'wind tunnel' on the internet.

Have you noticed that gravel racers use the narrowest tires they can get away with? If it didn’t matter people would use a 2.1” MTB tire. Also “gravel” races are mixed surface usually so it’s interesting to see what you’re losing compared to a road bike, so the comparison isn’t completely invalid.

[yinzerniner]

Originally Posted by mtechnica

Have you noticed that gravel racers use the narrowest tires they can get away with? If it didn’t matter people would use a 2.1” MTB tire. Also “gravel” races are mixed surface usually so it’s interesting to see what you’re losing compared to a road bike, so the comparison isn’t completely invalid.

A couple things to consider:
-yes gravel racers know to choose the skinniest tire “they can get away with” bit again their skinniest tire at 150-165lbs weight / 68-75kg or so is a lot different than more average riders. And also puncture protection and grip need to be weighed against speed when making a tire choice - thats why recon rides exist.
-the swissside study is very beneficial because it put real aero numbers into different gravel tires choices, not just by size but also by tread pattern and manufacturer.
-the wattage savings for gravel racers isn’t also about speed, but it’s also about fueling. 10w saved per hour is ~ 40kcal, so that’s less food/weight you have to injest, and / or more fuel available for the race from your food or fuel storage. 400kcal for a race like Unbound isn’t a small difference.
-this study is probably not for the enthusiast with a deep knowledge base but for the competitive racer who wants to maximize performance, be it pro or amateur.

Again more data is important but hopefully it’s used correctly. Obviously skinnier faster tires mean bunk if you’re constantly getting punctures (cough-quickstep)

[rain dogs]

Originally Posted by mtechnica

Have you noticed that gravel racers use the narrowest tires they can get away with? If it didn’t matter people would use a 2.1” MTB tire. Also “gravel” races are mixed surface usually so it’s interesting to see what you’re losing compared to a road bike, so the comparison isn’t completely invalid.

Actually I haven't noticed that. I've noticed that gravel racers choose what they believe to be the fastest tire - including grip, puncture protection, ideal tire pressure, weight, and narrowness.

How bout this, rather than arguing and arguing and arguing. Why don't we crowd source a data pool. Get 30 of us together, or the more the better. Each person makes a local loop. Each of us gets our one bike. We buy the exact same tires in two sizes 10mm apart. We all TT the loops and we put together a big database. The more power meters the better, but not absolutely necessary.

Then we can put an end to the debate. We just set the "rules" to try and get the best data possible. I've done this (I bet lots of the people arguing have not)... so I am quite confident what the results will show, but I also like to prove myself wrong/learn/be surprised, so I'm happy to do more testing. Maybe something constructive and fun vs all the poop-slinging on the internet?

We don't need to "compare" who's the fastest rider.... just the difference/deviation in tires.

[fourflys]

maybe not as scientific, but far more entertaining and just as relevant I think...

GCN: How Much Is Your Winter Bike Slowing You Down? (They use a aero road bike vs a gravel bike with fenders, etc)

https://youtu.be/LntjNO9mVGY

[reuben]

Originally Posted by fourflys

maybe not as scientific, but far more entertaining and just as relevant I think...

GCN: How Much Is Your Winter Bike Slowing You Down? (They use a aero road bike vs a gravel bike with fenders, etc)

https://youtu.be/LntjNO9mVGY

Well. Toward the end they talked about a mudguard video they did, and spliced in a few clips.

It was freakly. And not in a good way, like Blue Man Group.

[fourflys]

the only way to get "real world" data is to have the same rider ride set-up A for xx number of miles/hours (ex. ride set-up A for 3 months) and then ride set-up B for that same miles/hours (either same course or varied, depending on preference)... this would alleviate an abnormally small sample size (the sample being miles/hours) and give a better end product IMHO... ideally, this would be done with several riders, but the end result will minimize variables such as rider position, weather, traffic, etc as the sample size gets larger (again, sample size being miles/hours).

BTW- I have no doubt a dedicated road bike (aero, tire choice, etc) will be faster on road rides and a dedicated gravel bike will be generally faster on all but a few gravel rides over several rides... as others have smartly said, horses for courses...

also, yes, I'll take a manufacture's article with the required skepticism it deserves...