Fredo76

May I ask your ages, years of riding experience, and whether you've ever raced, and when?

asgelle

Of course you may ask, but you know Max Testa never rode seriously (if at all).

Koyote

Nice attempt at the "appeal to authority" fallacy. But a person's cycling experience doesn't really impact the laws of physics.

PeteHski

I'm 54 and been riding consistently since I was about 4. I don't race, but I do ride timed endurance events with a view to being age-competitive.
But what makes me far more qualified to weigh in on this kind of thread is my engineering degree and several decades working in F1 motor racing development - where details (like tyre pressure) seriously matter.

GhostRider62

Mavic GEL280s with 15/16 spokes and Setas always seemed to jump out of corners better than GP4's with 14 straight gage with Wober tubies. I ain't never done the maths on it but I would guess a foot difference. Could someone do some of that physics stuff? Am I far off or was I just imagining it?

PeteHski

If we simplify the equation for Kinetic energy in the bike and wheels by assuming all the wheel mass is located at the rim, then it becomes:-

K = 1/2 M v^2 + 1/2 m v^2 where M is the total mass of the bike (including the wheels) and m is the wheel mass only.

So in terms of accelerating the bike to a velocity v, wheel rim mass requires double the kinetic energy as frame mass. Or put another way 100g wheel mass saving is roughly equivalent to 200g frame mass when accelerating (and only when accelerating).

In your real-world example, you could then use F=Ma and simply double the weight saving in those wheels when calculating the difference in acceleration. So if your lighter wheel set saves 0.5 kg, then simply substitute 1 kg into F=Ma and then calculate the distance required to accelerate from v1 to v2 out of the corner. It would get you pretty close. Is it going to make much difference when M = 80,90,100+ kg? I don't know about you, but my own bodyweight varies by +/- 1-2 kg throughout the day.

It's also worth noting that you only lose energy from the system when actively braking. If you are coasting, the extra kinetic energy it took to accelerate those heavier wheels is returned through momentum. Basically you have a couple of flywheels.

This kind of puts it all into perspective:-

https://pedalchile.com/blog/light-wheels

asgelle

Never mind. The linked article says it better than I can.

GhostRider62

So, racers can save another foot by taking a good one in the morning?

Similarly in terms of extreme marginal gains, the optimum tire pressure for racers depends on the tire, road surface, temperatures, and the rider's weight.

The only real mistake is going too high in pressure. I was running 90 psi on 25 mm GP5000 TR S yesterday on good roads. Then, I got to some nasty chip seal that was rattling my feeble brain. So, I recursively let out a little air until it felt comfortable. What a difference. I got home and measured 75 psi rear and 65 psi front. Normally on crappy roads, I just do 75 psi.

krakhaus 

I'm not going to argue physics, but I will argue aesthetics. Wide tires on a road bike are a lot like driving fast in a new model Mustang or Dodge Charger. You may go faster, but you look like a neanderthal doing it.

WhyFi

My poor caveman bike

70sSanO

Nice bike!

John

krakhaus 

Looks just like everyone else's bike. The only props you'll get is that it's not flat black.

WhyFi

If you say so.

krakhaus 

I'm sure it looks awesome on the rack on your Charger.

PeteHski

Entirely subjective of course, but I've got used to seeing 28 or 30 mm road tyres on nice wide carbon aero rims. Maybe would look out of place on a vintage bike, but horses for courses.

WhyFi

You'll have to try again; I have neither a Charger nor a rack (unless you're referencing man boobs, but I'm an A cup, at best).

seypat

Speaking of that picture, Here is an update on the Fall Line Trail. Some people voicing opposition.

https://www.virginiadot.org/projects...line-trail.asp

https://www.wric.com/news/local-news...tral-virginia/

tomato coupe

At the very least, you must now be an expert at celestial mechanics.

tomato coupe

Definitely a matte finish.

seypat

I thought that was a dying field. Once Ford ceased production of the Galaxie and GM did the same with the Saturn brand, there wasn't much use for celestial mechanics.

tomato coupe

The most puzzling part of the tire pressure debate is why so many cyclists can't seem to deal with "it depends." They want or need to believe that X is always better.

seypat

True.

70sSanO

When these threads start to go sideways and devolve into old vs new, I wonder what happened to those kids who used to drool over the latest showroom offerings.

Those kids weren't looking back when they saw their first Stingray or 911 Turbo or Viper, but somewhere along the way they became old and lost an appreciation for something new and cool.

It is truly an odd phenomenon.

John

seypat

Those Stingrays, 911s and Vipers weren't/aren't human powered.

Fredo76

Actually, I was hoping to get an idea if your lived experience may have included heavy vs light wheels in a competition setting.

I agree that a person's cycling experience does not influence the laws of physics. But we're not talking about the laws of physics. We're talking about the accuracy of a model, loaded with assumptions. If it contradicts decades, no, generations of lived experience and wisdom, then it is to be questioned. Models are not 'authorities'. I think those who parrot so-called 'scientists' going against such lived experience might not have that lived experience as a common-sense check on their opinions. When they assert "facts" as "proven", it looks really dumb, frankly. It reminds me of people on an audio forum who judge equipment by test results, quite literally without any listening. Their opinions are worthless.

When a current racer tells me he thinks his aero wheels make more difference than light ones in a criterium, I'll credit that opinion highly. However, my own explanation for his opinion is that he has not tried competing on heavy wheels, so has no experience to really make the comparison.

The model is too crude, with too many simplifying assumptions. That it can be used to "prove" that weight off the wheels is no better than weight off of anywhere else is evidence of its need for refinement, rather than evidence of its accuracy.