Weight vs Speed
-
- Posts: 27
- Joined: Sat Jul 14, 2012 11:37 am
- Location: Templestowe, VIC
Weight vs Speed
Postby Cadel » Wed Jul 18, 2012 12:53 pm
Does anyone know if there's a way to calculate the speed gain by lowering the weight?
Let me explain... currently the bike is 12kg (it's heavy I know) and through some upgrades manage to get it down to 9kg say.
I weigh 75kg and avg speed is 25km/h (working on it...)
Would I notice a speed increase by applying the same force, considering the total weight 87kg dropped by 3.5% to 84kg?
Assume the bike geometry, tires profile etc remain the same.
...
Don't be fooled by my nickname... I have no idea.
-
- Posts: 86
- Joined: Tue May 17, 2011 10:23 am
Re: Weight vs Speed
Postby Lazyweek » Thu Jul 19, 2012 10:29 am
- The 2nd Womble
- Posts: 3058
- Joined: Wed Jul 27, 2011 1:21 pm
- Location: Brisbane
- Contact:
Re: Weight vs Speed
Postby The 2nd Womble » Thu Jul 19, 2012 10:35 am
Huge fan of booted RGers who just can't help themselves
- ldrcycles
- Posts: 9594
- Joined: Thu Oct 28, 2010 3:19 pm
- Location: Kin Kin, Queensland
Re: Weight vs Speed
Postby ldrcycles » Thu Jul 19, 2012 10:37 am
- Comedian
- Posts: 9166
- Joined: Mon Aug 09, 2010 7:35 pm
- Location: Brisbane
Weight vs Speed
Postby Comedian » Thu Jul 19, 2012 10:38 am
One thing I will say... Weight reduction generally goes hand in hand with other efficiency improvements that mean its quite hard to do a direct comparison.
Things like better frames, wheels, and tyres can make a massive difference.
-
- Posts: 5131
- Joined: Mon Apr 20, 2009 10:41 pm
-
- Posts: 364
- Joined: Tue Jul 10, 2012 12:43 pm
Weight vs Speed
Postby clydesmcdale » Thu Jul 19, 2012 10:56 am
If you can calculate your overall resistance relative to your mass then the reduction in mass will lead to a reduction in resistance.
This is most important when climbing as the other factors such as air resistance and rolling resistance are much less critical than resistance created by gravity.
I'd say that a simple overall calculation is not really practical as there are so many other factors to consider as pointed out above.
But if you can generate the same force with a lower resistance you will create a higher velocity. So it certainly can't hurt to reduce the mass of the machine.
-
- Posts: 985
- Joined: Thu Feb 25, 2010 10:31 pm
- Location: Sydney
Re: Weight vs Speed
Postby rogan » Thu Jul 19, 2012 11:08 am
-
- Posts: 27
- Joined: Sat Jul 14, 2012 11:37 am
- Location: Templestowe, VIC
Re: Weight vs Speed
Postby Cadel » Thu Jul 19, 2012 11:15 am
Thank you all for your comments and the link above.
Not afraid of hard work and I to train as hard as I can and even carry additional weight on the hills of Templestowe VIC to build up my muscles
Not trying to go super fast, but just wanting to know if there is a scientific explanation on the weight/speed ratio and also whether it makes sense to invest in an upgrade.
-
- Posts: 1346
- Joined: Thu Jul 28, 2011 12:35 am
- Location: Earlwood
- Contact:
Re: Weight vs Speed
Postby vander » Thu Jul 19, 2012 12:00 pm
I find 1kg loss to give you a lot more then 1sec/kmrogan wrote:I haven't looked at rkelsen's link, but the rough guide I use is that at ~20 km/h 1 kg adds about 1 second per km on a 4-5% hill.
- clackers
- Posts: 2065
- Joined: Mon May 16, 2011 10:48 am
- Location: Melbourne
Re: Weight vs Speed
Postby clackers » Thu Jul 19, 2012 12:17 pm
Climbing is where your power to weight ratio is the key player.
Of course, you could also want acceleration along the flat.
If you weigh 80kg, having a 10kg bike instead of a 15kg one will take you to your top speed about 6% quicker.
Not sure that's always worth the extra money for a recreational rider, but a 6% better kickoff in a bunch sprint would be appealing to someone who races.
- clackers
- Posts: 2065
- Joined: Mon May 16, 2011 10:48 am
- Location: Melbourne
Re: Weight vs Speed
Postby clackers » Thu Jul 19, 2012 12:24 pm
Do you even need to, with those Porter St and Williamson Rd climbs?Cadel wrote:
Not afraid of hard work and I to train as hard as I can and even carry additional weight on the hills of Templestowe VIC to build up my muscles
-
- Posts: 985
- Joined: Thu Feb 25, 2010 10:31 pm
- Location: Sydney
Re: Weight vs Speed
Postby rogan » Thu Jul 19, 2012 12:25 pm
http://www.kreuzotter.de/english/espeed.htmvander wrote:I find 1kg loss to give you a lot more then 1sec/kmrogan wrote:I haven't looked at rkelsen's link, but the rough guide I use is that at ~20 km/h 1 kg adds about 1 second per km on a 4-5% hill.
That website has some heroic assumptions around frontal area, road surface and so on, and thus can't be relied upon for power estimates. But putting in a 4 km hill at 4%, playing with only the weight of the bike and keeping everything else the same, gives me ~1 second per km per kg or less. There appears to be a bug on the site so it doesn't vary at all for a 1 kg change. But if you take the weight variance up to 6 or 10 kg, the pattern emerges.
A 1 kg drop in body weight can often be associated with improving fitness. To take out fitness as a factor, the relevant calculation should be the impact of adding a full bidon to your set up - which is pretty close to 1 kg.
The full impact of weight loss depends on you individually. My normal weight fluctuates through a 3 kg range of 79 kg to 82 kg, but find I actually climb best at the top of that range.
- grimbo
- Posts: 320
- Joined: Tue Oct 12, 2010 3:38 pm
- Location: Sydney
Re: Weight vs Speed
Postby grimbo » Thu Jul 19, 2012 1:41 pm
For me, it took riding from fun to exhilarating.
- B.Wiggins
- Posts: 1
- Joined: Thu Jul 19, 2012 2:47 pm
Re: Weight vs Speed
Postby B.Wiggins » Thu Jul 19, 2012 2:54 pm
Harden up Cadel. Stop blaming your bike. Col du Tourmalet wasn't that hard...Cadel wrote:Hi guys,
Does anyone know if there's a way to calculate the speed gain by lowering the weight?
Let me explain... currently the bike is 12kg (it's heavy I know) and through some upgrades manage to get it down to 9kg say.
I weigh 75kg and avg speed is 25km/h (working on it...)
Would I notice a speed increase by applying the same force, considering the total weight 87kg dropped by 3.5% to 84kg?
Assume the bike geometry, tires profile etc remain the same.
...
Don't be fooled by my nickname... I have no idea.
Brad.
MODERATOR NOTE: Sockpuppet? Almost certainly, naughty naughty.
Reason: Unravelling a sockpuppet...
- Alex Simmons/RST
- Expert
- Posts: 4997
- Joined: Fri May 02, 2008 3:51 pm
- Contact:
Re: Weight vs Speed
Postby Alex Simmons/RST » Thu Jul 19, 2012 5:36 pm
As the road tilts up beyond 4%, you will gain speed roughly in proportion to the overall change in mass, multiplied by the factor in orange in the chart below.
e.g. if you drop total system mass by 5%, then your speed gain (for same power output) on a +10% gradient will be ~ 5% x 90% = 4.5%.
-
- Posts: 536
- Joined: Wed May 26, 2010 2:54 pm
- Location: Macleod, Melbourne
- Contact:
Re: Weight vs Speed
Postby pawnii » Thu Jul 19, 2012 5:44 pm
2012 Scott Foil Premium
-
- Posts: 203
- Joined: Sun Nov 20, 2011 9:45 pm
Re: Weight vs Speed
Postby sdnelson19 » Thu Jul 19, 2012 7:54 pm
generally, whenever the bike/rider is accelerating there is a need for a NET force (speeding up, slowing down, changing direction), this net force needs to be increased when the mass increases (Newton's 2nd Law) If the bike/rider is not accelerating there is no need for an increase in effort. i.e. a heavy bike will be no slower than a light one; it's only the time it takes to reach that top speed that is different.
- DoogleDave
- Posts: 519
- Joined: Mon Mar 12, 2012 7:56 pm
- Location: Taylors Hill, Victoria
Re: Weight vs Speed
Postby DoogleDave » Thu Jul 19, 2012 8:03 pm
Just take the TDF as an example.
They're all riding great bikes and are all elite cyclists however some can break away, some can stay with the front of the peloton, some at the back and some can't keep up.
It's not the bike holding them back, it's the rider.
Dropping your bike's weight from 12kg to 9kg would make a difference but I don't think it would make a noticeable difference to your ave speed (on the flat).
You would likely find acceleration and handling is improved but once you're "up and rolling along" you still have to fight against the air resistance and the faster you go the more resistance you fight against. If you're not fit/strong enough to maintain the fight your average speed will drop.
I think improving your fitness, so you are stronger to fight against that air resistance along with your honing your riding technique will make a much bigger difference to your ave speed....along with helping your cycling overall.
Dave
- The 2nd Womble
- Posts: 3058
- Joined: Wed Jul 27, 2011 1:21 pm
- Location: Brisbane
- Contact:
Re: Weight vs Speed
Postby The 2nd Womble » Thu Jul 19, 2012 8:17 pm
Huge fan of booted RGers who just can't help themselves
-
- Posts: 27
- Joined: Sat Jul 14, 2012 11:37 am
- Location: Templestowe, VIC
Re: Weight vs Speed
Postby Cadel » Thu Jul 19, 2012 9:45 pm
The plan is to be able to climb moderate hills around 6-7% in a comfortable manner (read faster) by Nov-Dec.
This comes after my lungs nearly exploded on the way up a few months ago when I didn't know the importance of warming up or cadence...
Longer term plan is joining a club and enjoying 100km+ rides around hilly Melbourne not gasping for air like I normally do
- clackers
- Posts: 2065
- Joined: Mon May 16, 2011 10:48 am
- Location: Melbourne
Re: Weight vs Speed
Postby clackers » Fri Jul 20, 2012 1:46 pm
Well, I hope that everyone's comments have helped.Cadel wrote:I don't blame the bike at all , in fact I love it! Just looking for ways to save energy and/or increase speed, just like a truck uses less petrol if it carries no load.
The plan is to be able to climb moderate hills around 6-7% in a comfortable manner (read faster) by Nov-Dec.
This comes after my lungs nearly exploded on the way up a few months ago when I didn't know the importance of warming up or cadence...
Longer term plan is joining a club and enjoying 100km+ rides around hilly Melbourne not gasping for air like I normally do
It's been pointed out that, for instance, a 3kg lighter frame won't make you faster on the flat, but perhaps 3% faster up hills.
A UK doctor a couple of years ago kept meticulous records of alternating a long fast commute each day between a carbon and a steel bike, and published the results in Lancet, IIRC. Nothing between them.
But even for the different circumstances of climbing, he would suggest the best result would be the rider to lose 3kg of weight by November/December.
Benefits all round.
And you get to do it by the very activity you love.
- Alex Simmons/RST
- Expert
- Posts: 4997
- Joined: Fri May 02, 2008 3:51 pm
- Contact:
Re: Weight vs Speed
Postby Alex Simmons/RST » Fri Jul 20, 2012 3:58 pm
And it was a pretty ordinary piece of science writing too. I sure hope the same Doc doesn't do medical research.clackers wrote:A UK doctor a couple of years ago kept meticulous records of alternating a long fast commute each day between a carbon and a steel bike, and published the results in Lancet, IIRC. Nothing between them.
- PawPaw
- Posts: 1244
- Joined: Sat Dec 10, 2011 7:53 am
- Location: Brisbane
Re: Weight vs Speed
Postby PawPaw » Fri Jul 20, 2012 4:09 pm
Add 3kg in the form of 2x 1 litre water bottles to your bidons, and strap another to your top tube.
Then see if you can sustain the same average speed over 20 minutes, for roughly the same heart rate.
What would even be more accurate is to use a power meter before and after, and hold the watts at the same level for both intervals, and see what difference you get in average speed.
- Alex Simmons/RST
- Expert
- Posts: 4997
- Joined: Fri May 02, 2008 3:51 pm
- Contact:
Re: Weight vs Speed
Postby Alex Simmons/RST » Fri Jul 20, 2012 8:19 pm
There is so much slop in HR response that any speed difference would be less than the noise associated with such a variable.PawPaw wrote:Add 3kg in the form of 2x 1 litre water bottles to your bidons, and strap another to your top tube.
Then see if you can sustain the same average speed over 20 minutes, for roughly the same heart rate.
In order for it to be accurate, you will need to know, precisely, the environmental conditions in order to do such an analysis.PawPaw wrote:What would even be more accurate is to use a power meter before and after, and hold the watts at the same level for both intervals, and see what difference you get in average speed.
Even a minor change in wind undetectable to a human would be enough to mask such results.
- General Australian Cycling Topics
- Info / announcements
- Buying a bike / parts
- General Cycling Discussion
- The Bike Shed
- Cycling Health
- Cycling Safety and Advocacy
- Women's Cycling
- Bike & Gear Reviews
- Cycling Trade
- Stolen Bikes
- Bicycle FAQs
- The Market Place
- Member to Member Bike and Gear Sales
- Want to Buy, Group Buy, Swap
- My Bikes or Gear Elsewhere
- Serious Biking
- Audax / Randonneuring
- Retro biking
- Commuting
- MTB
- Recumbents
- Fixed Gear/ Single Speed
- Track
- Electric Bicycles
- Cyclocross and Gravel Grinding
- Dragsters / Lowriders / Cruisers
- Children's Bikes
- Cargo Bikes and Utility Cycling
- Road Racing
- Road Biking
- Training
- Time Trial
- Triathlon
- International and National Tours and Events
- Cycle Touring
- Touring Australia
- Touring Overseas
- Touring Bikes and Equipment
- Australia
- Western Australia
- New South Wales
- Queensland
- South Australia
- Victoria
- ACT
- Tasmania
- Northern Territory
- Country & Regional
Who is online
Users browsing this forum: No registered users
- All times are UTC+10:00
- Top
- Delete cookies
About the Australian Cycling Forums
The Australian Cycling Forums is a welcoming community where you can ask questions and talk about the type of bikes and cycling topics you like.
Bicycles Network Australia
Forum Information
Connect with BNA
This website uses affiliate links to retail platforms including ebay, amazon, proviz and ribble.