Give it to me straight /n/, does weight matter aside from hills and acceleration/braking? It shouldn't matter for riding on flat ground, since you aren't trying to change speed or elevation, what matters then should be rolling resistance and aerodynamics. Why do people spend a lot to shave grams off bikes?
Because it matters on hills and acceleration/braking.
A heavier rider at the same height generally means they're stronger (unless they're just fat) so the increased strength helps to offset the extra weight for climbing and accelerating, however if you're larger you could have more aerodynamic drag. Extra weight on a bike doesn't necessarily contribute anything (can sometimes be greater strength, better aerodynamics, or greater efficiency due to being stiffer) so dropping weight there may be better than dropping rider weight (unless they're fat).
In addition to climbing and accelerating less weight can also improve handling, those three areas are more important than the two where it doesn't really matter (maintaining speed on flat ground and downhill).
Braking does affect how fast you go can on the downhills. The faster you can brake before a corner, the more time you spend at higher speed. Being heavier will also decrease your cornering limits somewhat, although you do have a higher top speed, all else being equal.
>>944802
>Why do people spend a lot to shave grams off bikes?
Because for most cyclists (aside from people who live in super flat areas) climbing hills and going back down them is one of the greatest pleasures on a bike. Less grams helps that.
That said aero is very important too, and you see on TT bikes and such, they're a 1-2 kg heavier than equivalent spec road bikes.
>>944843
Aero is the most important thing after the rider being fit. People want light bikes because they are sexy and feel nice when lifted. People may also think that couple of hundread grams means something on ascends. People want also spend their money somewhere expensive to feel more like pro.
I ride my road rides with 12 kg bike and I'm pretty sure I couldn't measure any statistically meaningful difference between that and equivalent bike with lets say 4 kg less weight.
Obviously things change if one is racing (seriously). Then there's no excuse giving any help for opponents even if it would get expensive.
friction causes bikes to slow down, friction also applies on flat ground, friction is the bike being pulled towards the ground and slowing it down when it is moving. pulling towards ground is calculated with m * g wherein m = mass so, yes mass of a bike does matter on flat ground
>>944872
>friction is the bike being pulled towards the ground
burger education detected
>>944873
friction is the resistance while being pulled against ground* and not burger just bad at english explanations
>>944872
You don't slide your bike on roads. It rolls. And please show me some reports showing the amount of slowing effect on flat sections.
>>944802
Because not everyone lives in flatlandia, and low effort acceleration is nice when you're riding in a city with lots of stoplights.
>>945033
so >>944872 is bad at english, but rolling resistance *does* go up with mass. The top equation is power lost to rolling resistance.
Crr1 is the rolling resistance coefficient of your tires (dimensionless), Crr2 is a coefficient related to bearing losses (awful units of kg/s) and is effectively zero unless your bike is in shit shape, m is the mass of the bike + rider, g is acceleration due to gravity, V is velocity. Ignore N...
So mechanical rolling resistance goes up roughly linearly with velocity (or with the square of velocity if your bike is in shit shape and Crr2 is non-negligible). Meanwhile, aero drag goes up with the cube of velocity and therefor is the wildly dominant resisting force at any reasonable speed.
For those playing along at home, the lower equation is power lost to air resistance. ρ (rho) is air density, V_g is groundspeed, V_a is airspeed, Cd is coefficient of drag, and A is characteristic area.
>>945066
Whoops, "V" in the second equation is groundspeed (not explicitly noted as V_g)
>>944802
>It shouldn't matter for riding on flat ground
Try running with a backpack carrying 2 pounds.
Try running with a backpack carrying 50 pounds.
Shouldn't make a difference as long as you're on flat ground :^)
Of course with cycling getting lighter components doesn't matter too much if you're not racing.
Weight matters on hills because of potential energy.
Weight matters on the flats because of rolling resistance.
>>945066
neat. I always thought riding 20 km/h into a 20 km/h headwind produced the same amount of drag as riding 40 km/h into 0 km/h wind, but apparently that's not true? Any chance you could elaborate on that?
>>945162
Wait I just realized my interpretation makes no sense. Is V_a measured relative to the ground or the rider?
>>945162
The aerodynamic drag in the two cases would be the same, but I believe your drag due to rolling resistance is going to be about double when you're riding 40 km/h.
>>945066
I stand corrected. But without doing any calculations I guess that difference of something like 5 kg isn't going to mean too many second's difference on something like 40 km flatland route?.
And how haven't I found this website before? http://www.bicyclerollingresistance.com/
I wonder if that's thrustworthy unbiased site. So according to them Contis 4kGPs take about 12 W per tire at 29 km/h at 45 kg load. So 24 for two tires and 90 kg (altough I know the tires arent loaded equally in real world). Removing 5 kg would mean 85/90*24 W = 22,7 W wich is just 1,3 W saving. Sounds like nothing. Of course the difference would be bigger with slower tires but even Marathon Plus doesn't take more than double compared to 4kGPs so it would still be just 2,6 W saving.
>>945162
Airspeed (V_a) is the speed of the rider relative to the air. So if there's a 20 km/h wind and you're riding 20km/h facing it, airspeed is 40 km/h. If you're riding away from it, airspeed is zero.
>I always thought riding 20 km/h into a 20 km/h headwind produced the same amount of drag as riding 40 km/h into 0 km/h wind
It produces the same amount of drag FORCE, but does not require the same amount of POWER to overcome. For example, consider the extreme case: The same force is applied wether you're riding 40km/h with no wind, or sitting still facing into a 40km/h headwind. But in the second case, no work is being performed so no power is expended.
(Before some aspie starts arguing about how it takes work to stand still while facing a headwind, look up the physics concept of "work".)
>>945192
Depends on a bunch of factors! 5kg is a lot.
Depending on your tires, it could add anywhere from 2.5 to 5 Watts when cruising at 30 kph - that's probably 1-2% of your average power output? Probably more 2-4 *minutes* over a 40km route, not seconds.
I've seen that website before. I'm *slightly* suspicious of the methodology, but it's lightyears more scientific than anyone else reviewing tires out there.
Weight matters if you're racing. If you're not, try having a shit.
Wheel weight is the most important for a responsive bike. Frame and groupset weight only matters if you like wasting money or are a dentist.
This thread is a classical example of complete and utter pointless bullshit posting. You answered the question you wanted to know the answer to before you even asked the question. Between that you throw a completely pointless and bizzare statement that clearly acts as bait.
>Why do people spend a lot to shave grams off bikes?
Because of.
>hills and acceleration/braking
Please get out.
>>945651
And you are a classical example of illetarate doofus who doesn't even read the thread. Next time try to be a little more specific with your claims and not just shout "muh hills/acceleration".
Please get ou- wait, why did you even come in?
>>945832
What claims? Are you saying that a lighterbike does not make any sense to you?
Do you think that there is not a noticable difference between a 21kg bike and a 13kg bike?
>>945853
OP talked about spending a lot for shaving grams. You dont have to pay much to get aa 13 kg bike instead of 21 kg ride. What is lot of money depends on situation. What is a noticeable difference in speed or ride quality is subject you can discuss here. Lets talk about seconds, watts, endirance etc and less about some pseudo or placeboeffects.
>>945073
But every step or stride uses a portion of upwards motion essentially lesping between. ... where in cycling your bike holds your weight vertically making you only work horizontally. Biggest difference would be in accelerating out of corners.
>>944802
A lighter bike will feel more nimble, turn and brake better. You'll also be able to shave time on climbs and descents, since you can brake faster.
In my own experience, once you start dropping below 8kg every weight saving becomes less and less noticeable. For example, The difference in feel, handling and out-of-saddle ride quality is huge between a 10kg and 8kg bike, but it's way less noticeable when going from a 8kg bike to a 6kg bike. The lightest bike I've ridden is a 6.05kg Berria, and at this point you really have to spend crazy amounts of cash on components to shave some grams that you really can't feel anymore.
Almost every bike under 8kg will feel light (unless it has some retarded geometry/heavy wheels), and a bike under 7kg feels seriously light.
Like someone else said, weight savings are absolutely nothing compared to aero savings. Unless you're literally climbing at 10km/h half the time, a heavier but more aero bike will give you better times. But of course, that says nothing about bike handling or ride quality.
>>945860
I think that people spend a lot of money mainly because of their feelings. I doubt it has too much to do with actual reasoning.
This is why this conversation is not worth having in my opinion. Someone might spend tons on lighter parts like bottleholders, because they like the look of ex. carbon fibre.
>>945899
>people spend lots of money for a lighter bike
That is true. Another thing that's true is that you can build a bike under the uci weight limit for less than $2000
But people will always love their name brands, spending thousands more than they need to
Chinese carbon frame+fork - $589,1065g
SRAM force - $633, 2100g
Campy zonda - $300, 1550g
Finishing kit - $300?, 900g?
Tires and tubes- $90 500g
Shimano pedals- $90 250g
Some other shit/error in g- 500g
Whatever you get the point it can be done without being a dentist
>>945964
Funny that you mention campy zondas, I have been considering replacing my wheelset for my roadie and guess what is at the top of my list at the moment now?
>>945073
>with cycling getting lighter components doesn't matter too much if you're not racing.
Since most of us are riding for fitness or fun, yeah, a lighter bike is like ""hollowing out the dumbbells" when lifting weights.
But the free market drives innovation even when none is required, so... lighter bikes.
>>945964
Just build a chinkarello with like microtech shifters and a chinkk wheelsets and watch all the dentist fucks get pissy
>>946176
Zondas?
Ride is a bit harsh if you're light
If you can get flo 30s or dura ace c24
Otherwise they're cheap and light enough
>>946299
Bingo.
I have to look into those too, as this would be my wheelset replacement.
Thanks for the extra info dyyd.
