Aero vs Lightweight when the rider is neither

rollingscone

This question came up in the process of deciding I didn't need to /couldn't justify replacing my decent Alu roadbike using my BTW.

My general impression was that for anyone not TTing lightweight bikes are the way to go.

But what about riders who for reasons of build, work or other sporting commitments are always going to have to weigh more even if it's all "good" muscle which maybe "outweighs" any advantage of a light bike ( as opposed to light wheels).

Whereas if aero advantages are minute but constant do aero bikes not have more to offer to the (theoretical) muscular rider?

Weepsie

Surely if the bikes properly built regardless of weight it should be good for any rider if geometry is good.

Unless it's that super light dedacai aluminium that was used to make some wiliers about 10-15 years ago.

I saw one for sale but it had a strict weight limit saw had to let it go

Tenzor07

From what I gather based on your post, i'd go for something like a Giant Defy, Cannondale Synapse, Canyon Endurace..

Non-aero bike will be more compliant and suit most people...

fat bloke

I've never ridden an aero road bike so I can't comment on those, but I've done a bit of TT'ing, and there's no doubt whatsoever but that the difference that getting a bit more aero makes is quite astonishing.

But having said that it's hard to beat that little smile elicited every time you lift a properly light bike to take it out for a spin.

Lumen

Assuming this is not a "for racing" question.

If you have an aero frame you must have deep section wheels. It's the law.

So the question is: do you want to ride deep section wheels all of the time?

I do not. Therefore I do not want an aero frame.

joey100

Cannondale super six is sold as a semi aero bike. No idea's how aero it is but it's light as well. Old scott foil is the same, a light-ish, compliant aero road bie.

Have read a bit on wheels and most recommend going for aero over lightweight, I think best bike split and flo did some work and found aero wheels nearly always faster than light weight, no matter what the course really. They are a wheel company though so I'm sure they were pushing for that result.

nordicb

As an owner of aero Felt AR5 and Giant Defy1, both 105, I think aero bike doesn't bring too much to the table on its own. Both bikes shared same wheels (Campy Zondas) at some point and speeds were very comparable. What made real difference in speed for me is the aero position on the bike and comfort, ability staying in those positions for prolonged periods and I find Felt being more comfortable (road and position wise) despite more aggressive shape in the end gives better performance. Personally I find aero bikes (but not TT bikes) look better too. Just me 2c.

smacl

With regards weight versus aero, I'm quite fond of this chart posted by Lumen some years back, which highlights that aero isn't going to help you so much on the hills where weight will. For both aero advantage and climbing, it also comes down to the engine. e.g. easier for a leisure rider to lose a couple of kg on the body than the bike, and aero advantage comes from spending a fair amount of your time in the drops which comes back to core strength and flexibility.

Alek

Aero advantages start to be somehow important if going over 30kph - but think of your own aero profile vs the bike!
Weight-wise, 1kg off the bike won't mean much if your own weight is lets say 90kg.
Lighter wheel/tyre combination will give you nicer feeling when accelerating, but that's it, your average speed will be more or less the same.

I'd go for comfort (as in endurance type bike + fitting) and perhaps lighter wheels.

Thud

you won't be able to get (decent) mudguards on most aero bikes if you ever intend using it in the wet

Lumen

Thud wrote: »

you won't be able to get (decent) mudguards on most aero bikes if you ever intend using it in the wet

Proper order!

fat bloke

Alek wrote: »

Weight-wise, 1kg off the bike won't mean much if your own weight is lets say 90kg.

Well wouldn't it make the same difference (thereabouts) to a rider who is 70kg?

Re the aero thing, I do my FTP tests on the same climb all the time (Cruagh Road) and the last time, for the laugh (it wasn't) I did the test on a TT bike in the tuck position and I was quite surprised that I ended up a good bit higher up the road at the finish than I thought, given that my power is a good bit lower in the tuck position than sitting up.

GCN have a vid as well where they test out aero advantage on a climb and -while not massive, it's not inconsequential either.

Lumen

fat bloke wrote: »

Well wouldn't it make the same difference (thereabouts) to a rider who is 70kg?

The time saving is identical, as that depends on the time taken to move 1kg to the top of the hill with a given power output, but the speed difference is much less for a heavier rider.

If you're counting success as the number of seconds fewer that your mates are waiting for you at the top, a light bike has the same benefit for everyone.

edit: think of moving each kilogram of the bike and rider to the top of the climb with a winch of fixed power, one after the other.

Lose 1kg from the rider or bike and you can stop sooner. That amount of time is precisely the amount of time taken to move that 1kg up the climb.

Alek

Well wouldn't it make the same difference (thereabouts) to a rider who is 70kg?

To my understanding, its all about the total weight, except the rotating mass - so the difference is smaller the heavier you are. And its very hard to take 1kg off rotating mass.

But as far as understand OP is not racing or even preparing to do so, we are talking about rather leisure riding here and not bursting your legs and lungs in FTP tests Marginal advantages don't really apply here, and if so you can always leave that second water bottle home :P

Tenzor07

fat bloke wrote: »

GCN have a vid as well where they test out aero advantage on a climb and -while not massive, it's not inconsequential either.

This is the vid:

Alek

Also, I have two roadish bikes: one 10kg CX racer, the other 14kg steel tourer with racks and mudguards.

If I go for a longer ride on a flattish terrain, the average speeds are comparable, even if the racer feels nimble and the tourer like a pregnant pig.

In fairness though, I rather don't take the tourer to the hills, so can't compare this scenario.

magicbastarder

smacl wrote: »

With regards weight versus aero, I'm quite fond of this chart posted by Lumen some years back, which highlights that aero isn't going to help you so much on the hills where weight will. For both aero advantage and climbing, it also comes down to the engine. e.g. easier for a leisure rider to lose a couple of kg on the body than the bike, and aero advantage comes from spending a fair amount of your time in the drops which comes back to core strength and flexibility.

i've often wondered if the difference is down to that (very generally) lighter bikes are more expensive. and more expensive means the frames are (very generally) better, and i don't just mean lighter; so they may be less likely to absorb the energy of the rider, and be a more efficient ride.
thus the fact that you perform better on such a bike is correlated to the weight, rather than cause by the weight.
someone who actually knows what they're talking about might be able to tell me if i'm talking ****e.

equivariant

Lumen wrote: »

The time saving is identical, as that depends on the time taken to move 1kg to the top of the hill with a given power output, but the speed difference is much less for a heavier rider.

If you're counting success as the number of seconds fewer that your mates are waiting for you at the top, a light bike has the same benefit for everyone.

edit: think of moving each kilogram of the bike and rider to the top of the climb with a winch of fixed power, one after the other.

Lose 1kg from the rider or bike and you can stop sooner. That amount of time is precisely the amount of time taken to move that 1kg up the climb.

Nice post - you should be a maths/physics teacher

Crocked

Tenzor07 wrote: »

This is the vid:

They have another one where they compare climbing in a regular position versus an aero position. Aero was faster, all be it only slightly but also for less watts.

https://www.youtube.com/watch?v=e9BSPZtjJuc

smacl

Lumen wrote: »

edit: think of moving each kilogram of the bike and rider to the top of the climb with a winch of fixed power, one after the other.

But given the winch is actually powered by the riders leg muscles, if our 70kg rider and 90kg rider have the same relative body fat ratio, the 90kg rider has more leg muscle to do the lifting (as well as having more to lift). The bike is dead weight in both cases, but as a function of total muscle mass a heavier bike means a greater percentage of dead weight for the lighter rider and I would have thought therefore would be more of an issue. I'd say the 1kg off the bike is more beneficial to the lighter rider.

Lumen

smacl wrote: »

But given the winch is actually powered by the riders leg muscles, if our 70kg rider and 90kg rider have the same relative body fat ratio, the 90kg rider has more leg muscle to do the lifting (as well as having more to lift). The bike is dead weight in both cases, but as a function of total muscle mass a heavier bike means a greater percentage of dead weight for the lighter rider and I would have thought therefore would be more of an issue. I'd say the 1kg off the bike is more beneficial to the lighter rider.

I think you're mixing up power and weight factors there, though it's true that a lighter rider will gain more speed from losing 1kg, but gain the same number of seconds.

I think the argument that muscle mass helps with climbing is a bit weak. Alberto Contador weighs 62kg. Those extra 28kg of your 90kg rider aren't Contador-quality slow-twitch muscle fibres. :pac:

smacl

Lumen wrote: »

I think you're mixing up power and weight factors there, though it's true that a lighter rider will gain more speed from losing 1kg, but gain the same number of seconds.

Problem is that with your winch analogy, you're using different winches in each case, where for equally fit riders, the heavier rider will be more powerful. Not sure how for a fixed distance / elevation gain, extra speed doesn't directly translate into seconds?

I think the argument that muscle mass helps with climbing is a bit weak. Alberto Contador weighs 62kg. Those extra 28kg of your 90kg rider aren't Contador-quality slow-twitch muscle fibres. :pac:

I take your point regarding slow vs fast twitch muscles, and that the more massive muscles on a sprinter are more likely to be fast twitch suited to short bursts. That said, all other things being equal, muscle mass provides power and when climbing, weight adds resistance. I think when considering dead weight, it makes sense to do as a function of available power and hence muscle mass rather than as a constant.

fat bloke

Arguing with the teacher is a fast track to detention!

Anyway, boil it down to a succinct W per Kilo and there's no arguing against the benefits of weight loss, whether you pay 7 grand to lose it off your bike or do it the hard way and lose it off your love handles.

Macy0161

The conclusion I'm reading here rollingscone, is to get both...

I have been reading up on this a bit, trying to decide if n+1 would be a TT or a new road bike and stick with clip on's , and my understanding is that it's more your position and rider aero profile than the frame itself in that comparison. The TT bike will get you in a better position and potentially one you can hold for longer. So obviously my conclusion for myself was also I needed both! Bike fit person reckoned aero/ better wheels should be my next upgrade though.

rollingscone

It's pretty clear that no one read the OP.

This is a purely theoretical thread about a hypothetical (sadly) fat free heavy rider

fat bloke

rollingscone wrote: »

It's pretty clear that no one read the OP.

This is a purely theoretical thread about a hypothetical (sadly) fat free heavy rider

Sir Hoy comes pretty close (or used to).:)

smacl

fat bloke wrote: »

Arguing with the teacher is a fast track to detention!

Wouldn't be the first time...

My take on it is you need to consider power to weight ratio. Give we're talking about a ratio, extra dead weight needs to be considered as part of that, so an extra kilo on the bike will be felt more acutely by a light rider than a heavier one. If you look at bikecalculator.com you see speed for a fixed gradient and distance is directly dependent on power. If you're in any doubt about this, maybe ask yourself why competitive weightlifting is broken down into categories by the lifters weight, where a 62kg lifter is not expected to be able to lift the same amount as a 105kg lifter.

Lumen

smacl wrote: »

Problem is that with your winch analogy, you're using different winches in each case, where for equally fit riders, the heavier rider will be more powerful. Not sure how for a fixed distance / elevation gain, extra speed doesn't directly translate into seconds?

In my example of riders with same power but equal weight, the extra speed handed to the lighter rider gives the same amount of seconds over a shorter time.

Anyway, lets run the numbers.

First, two riders with the same power, say 300W.

Rider 1: 60kg, 300W, 8kg bike vs 60kg, 7kg bike.
Rider 2: 90kg, 300W, 8kg bike vs 90kg, 7kg bike.

Height: 100m, gravity: 10, distance: 1km. Ignore aero.

Rider 1 @ 68kg takes 68x10x100/300=226.67 seconds, speed 15.88kph.
Rider 1 @ 67kg takes 67x10x100/300=223.33 seconds, speed 16.12kph

Benefit from losing 1kg: 3.33 seconds, 0.24kph.

Rider 2 @ 98kg takes 98x10x100/300=326.67 seconds, 11.02kph
Rider 2 @ 97kg takes 97x10x100/300=323.33 seconds, 11.13kph

Benefit from losing 1kg: 3.33 seconds, 0.11kph.

So, the lost kg gives the same number of seconds for riders of the same power but different weights, but the lighter rider gains more speed (and in reality will be still faster because he can produce more power over a shorter time).

Second, two riders with the same power/weight, say 4W/kg.

Rider 1: 60kg, 240W, 8kg bike vs 60kg, 7kg bike.
Rider 2: 90kg, 360W, 8kg bike vs 90kg, 7kg bike.

Height: 100m, gravity: 10, distance: 1km. Ignore aero.

Rider 1 @ 68kg takes 68x10x100/240=283.33 seconds, speed 12.7kph.
Rider 1 @ 67kg takes 67x10x100/240=279.16 seconds, speed 12.9kph

Benefit from losing 1kg: 4.17 seconds, 0.19kph.

Rider 2 @ 98kg takes 98x10x100/360=272.22 seconds, 13.2kph
Rider 2 @ 97kg takes 97x10x100/360=269.44 seconds, 13.4kph

Benefit from losing 1kg: 2.78 seconds, 0.14kph.

So, the lighter rider gains more seconds and more speed.

I think there is an issue with your argument that muscle mass is proportionate to aerobic power, which is that muscle power is proportionate to cross-sectional area, whereas mass is proportionate to volume. So muscles gain mass faster than they gain power, if you're scaling the rider up.

This is possibly why smaller riders climb better even though the bike is more of a burden.

I'm also not sure that aerobic power is highly related to muscle size.

smacl

I was taking the second case as being more typical as anything else would make nonsense of power to weight ratio. Not that it is ever likely to be an issue in my case, where the extra weight there as strategically stored fuel for future cycling efforts :P

RayCun

smacl wrote: »

But given the winch is actually powered by the riders leg muscles, if our 70kg rider and 90kg rider have the same relative body fat ratio

that's a big assumption

magicbastarder

Lumen wrote: »

Rider 1 @ 68kg takes 68x10x100/240=283.33 seconds, speed 12.7kph.
Rider 1 @ 67kg takes 67x10x100/240=279.16 seconds, speed 12.9kph

Benefit from losing 1kg: 4.17 seconds, 0.19kph.

i think that's pretty much in line with what people are saying though - a 1KG loss in bike weight (which is probably a costly jump in price) makes a difference of less than 2% to climbing performance.
so maybe it depends on how you value your time.