Dave Mayer

The end result of not paying attention to weight on the bike is that you'll make a series of decisions that results in you having a 25 pound road rig, which is nowhere competitive on fast rides.

For 15 years I commuted daily on the same route which involved a 3 block long hill climb at a 8% grade. I often rode with a pal who was the same size as me, and similar fitness, and we did this on a variety of different bikes. We used to swap bikes back and forth between us.

THE LIGHT BIKE WON THE HILL CLIMB EVERY TIME. A 5 pound bike weight difference translated into a half block distance penalty regardless of anything else. We did this test innumerable times. In a race situation, this would mean you'd be shelled off of the back of the group, possibly never to reattach.

So buy the right bike for your riding, and get something that fits, but always try and get the weight down.

Disc brakes: prime example. Do you really need that 2 pound weight penalty? Do you ride with panniers in the rain? If so, they're great, but otherwise, heavy, fussy and unnecessary.

tomato coupe

As other posters have pointed out on numerous occasions, disc brakes do not incur a 2 pound weight penalty. Please stop repeating the same old BS -- everyone is tired of it.

rm -rf

On a 3 block long, 8% race up a hill, the 5 pound weight penalty was 16% slower? (that's "half a block" in 3 blocks).
150 pound rider + 15 pound bike vs 150 rider + 20 pound bike that is 3% heavier. What causes the huge climbing speed differences?

tomato coupe

Are you implying his claims aren't consistent with physics? That would be ... shocking.

Eric F 

I've passed lots of people on my 26" MTB...and it's a singlespeed!! 29" wheel bikes, full suspension bikes, and even e-bikes. However, we were going uphill were it wasn't significantly technical, making it more a matter of fitness.

Jughed

Interesting.

#5's of difference up an 8 mile 8% climb (Alpe dHuez) = a .97% total time difference for the lighter bike, about 2-3 min total depending on rider weight and power.

It's the same .97% for a 1/4 mile climb, or a 50 mile climb. The time difference is about 8 seconds for that 1/4 mile climb. (Im not sure how long your "blocks" are, but you could figure out the real difference.)

Your claim is = to a 16% difference. Basic math (or cheating using online calculators) says you need to add about 35#'s to make a 16% difference.

Real life talk - for me to take 5#'s off my bike that is just shy of 18#'s would probably cost in the region of $4-5000 dollar bucks. To save 8+/- seconds on your 3 block climb. Or, about $600 per second.

Those 8 seconds would only really matter if I was going full gas in a race and wasn't stronger than the other rider of equal weight that was on a slightly lighter bike.

Those 8 seconds = about 5 watts+/-. So the 8 seconds would really only matter with all of the above qualifications, and if I was at my absolute peak fitness and couldn't gain 5 more watts for a few min effort.

3alarmer

...I have heard from other sources it's approximately a pound difference, once you consider the frame mounts, hardware, etc. Is about a pound heavier accurate ?

PeteHski

It’s all just bs.

base2 

I've heard "about a pound" repeated many times. I recently compared the published frame and fork weights of a rim brake size 55 Richey Road Logic vs the actual weights of my disc brake Rodriguez. The total difference in frame/fork amounts to about 300 grams ~12 ounces or 3/4 pound in a size 57. ~200 grams frame, 100 grams fork. These are both top spec machines. Factoring proper selection of calipers, hoses/cables (actuation) and levers...It wouldn't be hard to come up as a draw on that front.

All things considered "About a pound" sounds about right enough for more middling ground equipment.

GCN recently did a video comparing the weights of this year's TDF riders bikes. My steel disc Rodriguez would slot into 5th place. Granted all the bikes were way over the UCI limit. The conclusion is the teams all prioritized something else than weight in component selection. More aero and disc? It seems so.

Eric F 

The shocking truth...There are more factors than just weight that make one bike faster/slower than another.

tomato coupe

It's not easy to make a direct comparison these days, since there aren't many frames made in both rim and disc formats. When I bought my Factor O2, however, the difference between the two brake setups was about 230 g for an O2 built with SR EPS components. (The weight difference was only 5 g for the frame, so virtually all of the half-pound difference was in the wheels or the brake components.)

SoSmellyAir

This thread has inspired me to forego weight-weenieism; I am still going to keep the light-weight CF parts I already have. My next performance gain is going to come from Chef Hannah Grant: Watch Eat. Race. Win. - Season 1 | Prime Video (amazon.com)

Koyote

Exactly.

Let's consider that (roughly) one pound weight difference between a disc and rim brake bike. Rim brakes and cf rims don't work very well together, but disc brakes and cf rims are fine together. Decent cf rims can easily shave a good portion of that one pound differential off the disc bike, and they can also be more aero -- which will likely have a bigger effect on speed anyway - even on climbs. So, if (like Dave Mayer ) you're really concerned about not getting spit off the back of the pack, disc brakes are probably the way to go. If like most riders, you're not concerned about that, then just ride what you like.

Eric F 

Additionally...Disc brakes allow for wider tires. Wider tires are proving to be faster than the narrow tires required to fit under a rim brake caliper, or inside the tight clearances that were typical for high-end rim brake frames. Therefore, disc brake bikes are faster.

FWIW, there are some CF wheels that function acceptably well with rim brakes. The Enve 3.4s on my rim brake road bike are an example. That said, disc brakes might have kept me from denting the door of the mini-van that turned left in front of me with my shoulder.

79pmooney

My prediction: (I have no guess as to how soon, but ...) the day will come that techies in the bike world develop a narrow (25c or less?) tire that is near as low Crr as the wide tires and a narrow aero rim to go with it and come up with a combo of the same Cd that the wide tires and matching rims get. Put these wheels on a bike and wind tunnel test it. Wow! Lower drag despite the same Cd. How did that happen? (Hint - aerodynamic drag is a product of Cd and area. Narrow tires and rims have less area.)

They give these wheels to racers. And - the racers love 'em because they are lighter. They feel faster! Now it will take a good long time before these skinny tires make to a good team and winning rider. Their sponsors have WAY too much invested in this wide stuff. But sharp observers will start noticing bikes being put away immediately after wins and perhaps even a wheel that is properly decaled but looks awfully skinny on so-and-so's bike.

Again. I make no prediction of how soon we will see this. Mantras die hard. But simple physics. Aero trumps rolling resistance at race speeds. For the same Cd, less areodyamic area trumps more area. And as a byproduct, smaller almost always means lighter. And best of all, this trend to be belongs in weight weenies!

SoSmellyAir

79pmooney I understand what you said above re: narrower vs. wider with the same CD. But the comparison is not just for the wheel and tire combo. It is for the entire frontal profile, i.e., wheel and tire, downtube, cranks, pedals, shoes, shaved legs, etc. So it seems at least potentially possible that a wider tire and wheel may better interact with components located further aft to present an overall more aerodynamic profile.

PeteHski

Seems highly improbable to me considering how tyres and rims have evolved over the last decade. It’s more a question of whether or not they will go even wider. You might have noticed that pro racers are not into weight-weenie wheels these days.

3alarmer

...I went from 235# to 232# while participating in this thread. So it had the opposite effect on me.

squirtdad

aero is to say the least is complicated and not intuitive take a look at this discussion for gravel bikes https://www.renehersecycles.com/aero...-gravel-bikes/

Maelochs

I agree that for the same rolling resistance, or what is much more important to most riders, a combination of comfort and control, a lighter wheel is better. A narrower wheel/tire which weighs less and rides just as well should be much better, offering two benefits. Just now, the industry hasn't figured out the "best" way to deliver that ("best" in quotes because there will always be folks imagining better ways.)

I also understand @squirtdad 's point ... a slightly wider tire/wheel might offer better overall aero. Aero is a package of all the area, but also the vortices and such .... I recall back when designers realized that a big source wheel drag was the transition from tire to rim---tires ballooning off of skinny rims created whirlpools of drag. A wider tire matched to a skinny rim was less drag than a skinny tire on a skinnier rim.

Still ... lighter is better with wheels after the aero is worked out. Or rather, lighter wheels/tires "feel" better to most riders (even though the aero gain is marginally greater on anything but stiff climbs (as has been debated and demonstrated by all the math wizards and physicists in other threads.) The pros might not care since they are more focused on competing than enjoying the ride, but day-to-day riders generally (based on anecdotes only) seem to like light wheels. And if the aero is equal, racers will take the lighter wheels I am sure, even if the bikes need ballast .... less energy expended even if is in the "marginal gains" category.

Dave Mayer

Unless you are riding on third world roads, narrow high-pressure tires have the lowest rolling resistance. Check the Silca curves. A 32mm tire may have a (slightly) lower rolling resistance than a 23 at 100psi, but you don't inflate the 32 to 100, but more like 60psi. Then the RR for the bigger tire is higher than the 23. The bigger tire also is much heavier and less aero.

Regardless, RR is only a handful of watts difference, insignificant in the grand scheme of things. In pack riding conditions, so is aero, as you are drafting 95% of the time.

In hard group riding, rotating weight is absolutely the most critical factor, as you cannot allow yourself to lose the wheel in front of you. You lose the wheel on surges, climbs and accelerations out of corners. When you lose the wheel, you're probably done for the day, limping to the finish minutes to hours after the leaders.

indyfabz

Do they also spin in the opposite direction in the southern hemisphere? And have you ever ridden somewhere like NE Ohio? Talk about some 3rd world roads.

PeteHski

This is simply not true. Complete bs

elcruxio

I wonder if a professional cycling team could use your wisdom... Just do the opposite you're suggesting and they'd be winning the yellow jersey in no time

I suppose a narrow high pressure tire might be fastest if you can curate your road selections in such a way that they only consist of brand new asphalt. Personally I'd rather spend my time just riding roads instead of scouting them out but each to their own.

I tried looking at the silca curves and I didn't find a chart comparison between 32mm and 23mm tires. Perhaps you may be able to post a link?

However a crucial point you've missed in the Silca data is the breaking point, ie. after the tire has too much pressure for a give road surface the rolling resistance shoots up like a rocket. And honestly there doesn't seem to be enough openly available data out there to definitely state that a 23mm tire has significant break point advantages against a 32mm tire or vice versa. The silca data does suggest however that with a rough enough road surface and narrow enough a tire it might be unfeasible to use a tire pressure that is below the break point.

But even after trawling the net for more info on the subject I haven't found definite evidence one way or the other. Professional teams use wider tires these days so there's that. I doubt pro tour teams would use losing tech just because their sponsors dictated that stuff to them. Losing races isn't exactly what the sponsors want either.

How much heavier a bigger tire is depends on how much bigger a tire we're talking about. But a jump from 23mm to say 28mm is still insignificant enough to have no practical effect.

Aerodynamics is what you make of them. Granted, getting a 32mm tire to function propely with a rim is pretty difficult, because the rim would have to be rather deep and wide. However no such issues are present with a 28mm tire. Also the aero difference between 23mm and 28mm isn't exactly huge. If the 28mm allows for the rider to remain fresher due to fewer vibration losses and more comfort, it might be the winner overall.

I don't know what sort of packs you're riding in but drafting 95 % of the time seems pretty moochy. No wonder you're always writing about losing a wheel and getting dropped. You're clearly riding with people who are out of your league.

However RR can be quite a bit more than just a few watts especially if you go over the breaking point.

Alas rotating weight is in the grand scheme of things just as detrimental as static weight. You can calculate it really easily.
We can handily rule out any air resistance or friction losses for the calculation as they don't matter. Only weight does.

Let's take a cyclist + bike + water of 90kg and assume they're accelerating to 32,4 km/h or 9 m/s. It's a pretty darn stiff acceleration so it takes them three seconds. The energy required for such effort is 270 watts (I know it seems low, but no friction, air resistacne etc. remember?). Also remember watts is a per time thing so the actual energy would be in joules, but for cycling that's a bit impractical.

If we take the same cyclist and swap their 25mm* tires for marathon plusses and add half a kilo of sand to each tire just for the fun of it, the same cyclist would need 288 watts to reach the speed of 32,4 km/h in three seconds. That's 18 watts of difference for 3kg weight addition to the tires.

Rotating mass only has an amplified negative effect during accelerations. However when you coast that added rotating weight helps you ride further along, so it's not just a net negative. When one is riding at a steady pace, rotating weight is just weight. If you believe in the "micro accelerations" -idea, you should also be aware of the "micro decelerations" idea where rotating weight actually helps.

But let's say our example rider doesn't swap to marathon plusses and sand but rather goes from 23mm GP5000's to 32mm GP5000's. Tubeless of course because why would anyone ride something slow and inefficient like tubulars or tubes (teehee).
Again, energy required for the 25mm tires = 270 watts
Energy required for the 32mm tires = 270,66 watts.

I mean... 0,66 watts doesn't seem that big to me...

*I tried calculating this against 23mm tires, but GP5000's aren't made that narrow...

PeteHski

This is the part where the myths about rotating weight get blown out of the water. But it never seems to convince some people. The physics is trivial and easy to plug real world values into the equations. The results clearly show that rotating weight (within a realistic weight range for comparable bicycle wheels) has very minimal effect and can be treated simply as a component of the total static weight.