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Comment by jackmott42 | Hacker News Reader

Why don't you actually do some math, or experiments, rather than just telling us you have doubts?

This is all really easy stuff to answer. For instance. 75kg rider + bike. Make the bike 1kg lighter. Go up a 8% grade for 1 kilometers at 300 watts Time saved by 1kg weight reduction? 30 seconds out of 40 minutes.

Or suppose we add 300grams to the frame to make it aero, which is typical. If that reduces the CdA by .02 out of .25, you are at about a breakeven point. JUST during the 1km climb. Then you save time on all the flats and non technical downhills.

Acceleration is even less affected by bike mass. People forget that bike mass is a tiny % of total system mass (our fat asses). And mass is only one of 4 major components that affect acceleration. I'm happy to run through some acceleration scenarios if you like.

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I'm a former racer too and this constant equipment arms race and arguing is just so fatiguing.

People can argue about analytics around equipment till pigs fly. It's all still just an order of magnitude smaller than the differences between being fit and not fit and a stronger rider versus a weaker rider or a coached rider versus un-coached rider.

The sport has separated into riding enthusiasts and equipment enthusiasts and the bike companies have completely brainwashed equipment enthusiasts.

Your times don't make any sense either... 8% for 1km takes vastly less time than you're talking about at the power levels you're talking about. You're probably off an order of magnitude there. A rider with an FTP of around 300 will probably climb closer to 10km @ 8% in 40 minutes.

Nothing is more tiring than being at the start of a race and there's someone with a $10k+ bike and a gut talking smack about bikes to someone everyone else knows is going to win the race and the guy with the $10k bike is getting dropped & pulled from the race. One person spent all their time on training and the other spent all their time researching & buying equipment.

You are right I had the gradient off by 10x, sorry that should have been obvious, it has been a while

Actual time savings of 1kg of weight reduction: 1 second

And personally I've used aeroweenieing to podium in a cat 3 road race, and my wife has set state records and won pro races. You can make fun of fat guys doing a professional job if you like but it isn't just them.

If spending lots of money to win a Cat 3 race and knowing you did it with money and equipment instead of fitness and smarts is OK with you more power to you. But if it means thousands of dollars spent on a race that likely paid < $50 to the winner the whole thing can also look ridiculous too depending on perspective.

This isn't really funny, it's a fundamental problem with cycling as a sport that limits who participates in the sport and hurts the sports ability to find and develop the best riders. It seems particularly bad in the US. Rules which helped control the equipment arms race would be good for the sport at the competitive level. Many promising athletes never try the sport because the costs are so prohibitive. On top of that in road racing if expensive equipment raises the speed of everyone in the field it accomplishes nothing other than increasing the risk of severe injury as speeds go up.

If someone made $10k shoes that gave a competitive advantage in soccer or basketball, or a $10k baseball bat that offered significant advantages, etc.. that equipment would very likely be outlawed right away. Cycling has let everything get very out of control. Baseball obviously has already banned lots of bats that offer competitive advantage, whether it's banning metal bats after a certain level or limiting the power of metal bats below that level.

In almost every hobby there are people who get enjoyment from choosing and buying equipment and others who just want to do the thing. Look at people with massive collections of beard games they never play, people with any cameras and lenses but little output, etc. It's fine. Let people enjoy their hobby however they like.

Keirin bikes need to be built out of approved frames and parts, I’m surprised there isn’t a road racing category with similar rules

> The sport has separated into riding enthusiasts and equipment enthusiasts and the bike companies have completely brainwashed equipment enthusiasts.

I'm NOT a former racer but I've cycled recreationally (probably an average of about 30 miles a week, give or take) for over 20 years.

When I first got into road cycling I nerded out on gear. Back then that meant skinny tires, carbon fiber, big bucks. I felt reallllly cool.

As I've gotten older I stopped caring about what's cool. Like, in cycling, but in pretty much everything else too.

I had to move recently, and ditched my road bike but kept my "cyclocross" (as it was called at the time I bought it) bike, since I wanted something more flexible and comfortable. It ways weigh more, and I ride on big honking tires with hefty tread.

I tracked my (solo, non-drafting) rides and I'm slower... by like, .5 mph.

I have no doubt that all the gear nerds out there know what they're talking about, and these data driven fads are real improvements, but the margins have gotta be smaller than most of us weekend warriors should realistically ever care about.

At a certain point you gotta ask yourself why you're even into the sport - either you think you're gonna win something, and then this is your life (and every advantage is worth it), or you're in it to ride with buddies and enjoy the feeling of moving through space. If you're in the latter category, and you aren't getting dropped, obsessively optimizing gear isn't actually gonna make your experience any more fulfilling.

Its always easier to try to buy your way up the chain than putting in the work. And when you are not actually a pro it often becomes a social novelty of its own (and within reason one I often enjoy myself). The end game for me in all things like this is that when I actually become a sort of expert in the gear choices I realize that often the middle ground items are sometimes the best - pricier things are often better but there are huge diminishing returns and sometimes the simplest item of decent quality is actually the most functional.

You are correct on the watt, weight computes but I think the aerodynamic saving is worthless on a gravel race. People are not going that fast on gravel to gain anything from aerodynamical optimisations. You need to keep going at least 40 km/h to have any advancement without up-down movement which is obviously not something that you can achieve on gravel.

Aero also helps at 25 or 30kph.

It is quite easy to check out actually on a road bike. Ride at a steady pace without pushing hard, hands on top, then put your hands in the hoods of the brake lever, elbows at 90° without pushing more, you will gain easily 1kph just by changing position. More if it is windy.

I assume the poster meant aerodynamic optimisation of the bike itself (eg. aero wheels, aero saddle post, etc).

Riding position obviously makes a huge difference.

I know nothing about typical bike timings, but I was struck by that. Does it really take 40 minutes to go 1 km at an 8% grade? Would it be faster to get off the bike and walk? When you're not rolling, you don't have to output power to fight your own weight trying to roll back - the friction between your shoes and the ground counteracts that. (I assume a real race doesn't allow you to walk, just batting around thoughts hypothetically here.)

One racecourse I know about that has both running and bicycle races is the Mt Washington Auto Road in New Hampshire USA. It is the tallest mountain east of the continent. The top is at 6288ft/1917m above sea level. The road is 7.6 miles / 12.2 km long and the climb is 4650 vertical feet / 1420m.

The footrace has been run since 1936 and the bicycle race since 1973. The road used to be paved only half way and gravel the rest, but it is now largely paved.

Now, the Men's bicycle record is 0:50:38 (2022) and the women's record is 58:14 (2000). The running race records are 0:56:41 (2004) and 1:09:25 (2012).

So, pretty clearly, even at a 12% grade, the bicycle still has an advantage. I'd say this is still true even though the bicycle race consistently attracts US Cycling Team and other international class competitors, and the running race seems to less frequently attract that caliber.

[0] https://en.wikipedia.org/wiki/Mount_Washington_Road_Race

[1] https://en.wikipedia.org/wiki/Mount_Washington_Auto_Road_Bic...

Very interesting information, thanks. The sibling comment pointed out that the parent probably meant 40 minutes for 1km of elevation gain, not linear distance, which makes sense too.

Maybe I'm just trying to justify my own struggles where it's faster to walk the bike up any significant grade :)

YW. You might be using too high a gear, so pushing too hard, which will definitely slow you down going uphills.

In general for reasonably flat riding, you want to be spinning at 80-90RPM. Most cyclists I see are spinning much slower, so pushing much harder. Think in terms of lifting a weight. You might be able to lift 10kg only six times on some motion, but you can likely lift 1kg far more than 60 times with the same motion.

I also have a lesson from Mt Washington. I was an unranked teenage amateur bicycle racer doing ok, but only using bicycle racing as training for ski racing. I'd won a couple regional-level hillclimbs and was looking for another race and someone said "call this guy". I did, and got told about the first Mt Washington bike race. I had no idea what gearing to use, so got the lowest granny-geal cluster I could find in a day. I got to the race and among the small crowd were four guys from the US Cycling Team. I wound up finishing 3rd, only 4min behind John Allis (3-time Olympian) 1h:15m time and 4sec behind 2nd place. I had by mostly dumb luck out-guessed everyone on the gears (neither my conditioning nor my bike was close to their class). The next year Allis came back and won again knocking 14min off his time, presumably with a lower gear cluster.

So, I'd definitely take a look and see about using lower gears...

I suspect the parent is referring to elevation, not distance. 1km in distance would only take a few minutes.

You're forgetting the effect of exertion on the rider under heavy loads like climbing.

I've ridden heavy bikes, and I've ridden light bikes. Light bikes feel better, rotational weight mattering more than anything else.

I am not sure this is true - I actually prefer a heavier bike for general use. If I was racing up hills or still doing cyclocross then light as possible would be best (and of course also me being light as possible being the biggest factor). I have ridden a lot of bikes and the ones that "feel" the best have a moderately "heavy" frame designed to be fairly stiff but not crazy stiff (heavy meaning at most the light end of a steel framed road bike) with extra sturdy rims that are also as light as possible. By far the biggest effects on "feel" however tend to be tires (skinny tires suck) as you can fine tune the pressure to the surface. And of course quality bearings in the BB and hubs can make a huge difference but once you get to a certain middle level they are all good enough.

When the bike gets too light you feel the effect of bumps and terrain much more and it throws the bike around more (especially if you are "getting light" over said bumps). The lightest bikes also tend to be made for racing and can sometimes be on the ultra super stiff end of the spectrum.

I'm not that old, or have a super long history with cycling. But out of the handful of bikes I've ridden, I def prefer double-butted steel (over straight-gauge Hi-Ten, straight-gauge 4130, 90's aluminum, modern aluminum, modern steel gravel bikes) whether I'm going all-out, or cruisin. And even between 2 double-butted steel frames from different tubing manufacturers made for the same use-case more or less, they've felt different enough to me. At least that's how I felt after having put the same components on two steel framesets, and putting them both through about 2k miles each. One frameset was definitely more enjoyable, while the other felt lacking to the point where I wished it were the other bike.

I have two relatives who have raced bikes in the past at high levels, and both owned stores. One of them was a stronger racer who didn't care about gear as much. The other was still a heavy hitter, but wasn't as naturally talented, and enjoyed the nuances between components way more. He and I seem to agree on things.

I do know that tire pressure and width make a huge difference in plushness, but I still prefer a springier ride-feel from the steel I like, vs. even a modern steel gravel bike with 42's with lower PSI. I had such high hopes for that ride, but man, it just felt kinda muted and leaden, and I missed my steel road bike.

But yeah everyone will have their personal prefs, subjective interpretations, and theories about what works for them and doesn't. Gimme that springy lightweight steel any day.

You would probably love late 1980s high end touring bikes then - they are basically the best of the best of steel

They’re not- 300W of effort is 300W of effort, it doesn’t have a bigger impact if the bike is heavier or not.

I wonder if that's really true on hills. Most people ride hills with more effort, pushing down on one pedal at a time. The bike speeds up and slows down much more with each pedal stroke. Compare to the flats where you have a smooth stroke and very consistent output.

I could see all the mini accelerations adding up to a much larger energy expenditure than would be indicated by a spherical cow in a vacuum.

Eh, it's really quite small, unless you have stupid heavy wheels (meaning, that the wheels are a significant percentage of the mass of the entire system).

If the mass of the wheel is 100% located at the rim, the energy goes 1/2 into straight line energy and half into rotational. But -- if you slow down, you don't lose that energy, it just redistributes to gravitational potential. The flywheel effect from heavy wheels may actually help, as it tends to smooth out pedal strokes.

The energy to go up a hill is just mgh - friction. Some cadences are less efficient than others (e.g. for me, standing is more power but lower efficiency), and bikes that are too stiff may not help you get the best rhythm.

In a totally unscientific test -- I've got a 12kg Aluminum gravel bike, wide tires, rack, fenders. I've also got an 8kg carbon racing bike, skinny tires, aero rims, etc. They have similar riding positions (reach/drop), though the gravel bike has a wider seat, which is better for one climbing cadence. I usually ride the gravel bike these days, because comfort.

Two weekends in a row, I did a 12x rep climbing workout (2.5 hours), one on each bike. First weekend, Road bike. It felt _fast_. Quick, lively, accelerated from the stoplights on the way to the hill. Second week, back on the gravel bike, grinding up the hill. Total ET difference: 5 seconds.

Sure there are differences.

Rotational inertia matters extremely little for bike feel compared to the overall weight of rider+bike. The torque required to accelerate a wheel by itself without any resistance is minimal.

You have any sources for this? Not trying to call you out but I am generally curious. We know on a car that rotational mass makes a huge difference but a car is continually accelerating and has a constant type of locomotion that is very different than a person riding a bike. In addition the rotational mass of a bicycle wheel is much, much larger diameter comparatively to the total weight of the vehicle (compared to a car) and provides a gyroscopic effect that is critical to the way a bicycle rides and stays upright. I would expect if we could make impossible light bicycle rims and tires the bike would have trouble balancing and feel like shit and also decelerate much faster. But surely there is some middle ground that is ideal?

It's first year kinematics. The (first order) math is pretty easy to work out. 1/2 I w^2 is the rotational potential energy, Assuming all the mass of the wheel is at the rim (worst case) I = mr^2, w=v/r, so that works out to 1/2 mv^2, which is the same as the translational kinetic energy. So the 'energy penalty' of rotating mass is 2x. So, a 10kg bike with 2kg of wheels and 100kg of rider is approximately equal a non-rotating mass of 112kg. However, that rotating mass gives you 2% more kinetic energy to trade for wind drag, gravitational potential, or other friction. So, not much.

A bike's does not require gyroscopic effects to stay up -- there was an experiment with counter rotating wheels (to cancel the gyroscopic moment) that was ridable. The actual stability depends on the geometric and pneumatic trail, flop, weight distribution on the steering axis, and a few other things.

There is a middle ground that people have converged to -- Somewhere in the range of around 600mm bead seat diameter and an inch or two of tire. (26"->700c, 25->50mm width covers most of the biking world.)

Sounds like those crazy 650B people then have been right all along!

You can test this yourself. Flip your bike upside down, shift it into a gear that you use to accelerate, take a torque wrench with hex socket and put it in the left pedal socket on the backside of the crank like you would when installing it. Then test the torque required to get the wheel moving. You would find that these numbers are minimal.

Also gyroscopic effect has very little to do with the bike staying upright. The reason a bike stays upright is because of the trail interaction and camber thrust. When the bike leans left, camber thrust of the tire makes it turn left, which moves bottom of the bike to the left, correcting the initial lean, while the geometric trail prevents the tire from turning left completely.

Interesting!

The issue is that a lot of the aerodynamic frame advances only work in ideal laminar conditions. However wind is gusty, there are trees and other obstacles next to the course etc. In those cases the advantages largely disappear as Hambini has shown.

I'm not sure what testing Hambini has been up to, last I saw him he was calling for the death of Damon Rinard (who is a really nice guy, by the way! and great cycling engineer)

However I have plenty of first hand field testing data showing that this is very obviously not true, as do hundreds of other people. We ride in the real world with power meters and timers and we can detect these things even in gusty real world conditions.

Just two examples:

http://www.trainingandracingwithapowermeter.com/2010/10/chal...

and

https://betterbicycles.org/science/speed/validation-of-bicyc...

You are assuming that rider can output X watts continuously. This is not how humans work. Riders have different profiles in terms of torque vs rpm from their legs. A lighter bike means that a rider is outputing less torque, which he/she can sustain without downshifting to a lower gear, leading to overall increase in time not only during the climb, but also how much energy the rider has left in the tank after the climb for the rest of the course.

> I'm happy to run through some acceleration scenarios if you like.

Yes, please continue! I'm digging your analysis.

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