Weight - effect on speed
Weight - effect on speed
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Discussion

Gargamel

Original Poster:

16,355 posts

290 months

Friday 10th August 2012
quotequote all

Morning,

I am still being nagged by my failure to complete my commute to work in under an hour.

Extreme measures are required. I am presently 90kgs, or 14 stone, which is probably too many. When I was a runner I was around 12 st 10lbs or 80 kgs.

My question would be what is 10 kg costing me in time per hour ? assume an average speed of 20 mph.

Any rough guides ?


davepoth

29,395 posts

228 months

Friday 10th August 2012
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Depends if you are 90kgs of fat or muscle really.

TonyHetherington

32,091 posts

279 months

Friday 10th August 2012
quotequote all
Weight doesn't effect top speed, don't forget, it only effects acceleration (ignoring the fact that you may be bigger when heavier).

So it depends how much stopping and starting you're doing (and therefore how much accelerating from 0) that your weight will effect.

I've recently lost 5.5kg simply by eating slightly less. Same foods, just not quite as big portions. And I started off at 76kg, so it's not like I was big. Try that, you may see your times tumble smile

okgo

42,127 posts

227 months

Friday 10th August 2012
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"Numerous studies have been performed to show just how much weight effects a cyclist. Bicycling Magazine published the results of a study from James C. Martin, Ph.D., assistant professor in the department of exercise and sport science at the University of Utah. Using the calculations from a 160-lb. rider on a 5 kilometer, 7 percent grade, he concluded that for every 5 lbs. added to a rider, it would take him an additional 30 seconds to ascend a steep climb."

So you can see from that roughly what it might cost you up hill...However on the flat your weight is much less relevant. Which is why many TT riders can afford to be a bit bigger compared to road riders.

It will be more effort to get your weight moving each time, but when at speed, to hold the speed will be no different really.

How far is the commute?

Uriel

3,244 posts

280 months

Friday 10th August 2012
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Stick 10kg of books/weights/baked beans in a back pack for one commute and see how you find it. Imagine the reverse.

davepoth

29,395 posts

228 months

Friday 10th August 2012
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Surely air resistance comes into play here if you're really bulky?

Gargamel

Original Poster:

16,355 posts

290 months

Friday 10th August 2012
quotequote all
okgo said:
How far is the commute?
Commute is 21.3 milesone way - and around 600 ft ascending on the way in, about double that on the way home...

So the effect on climbing speed is pretty significant.

I should imagine the aero effect of the size of my (expensively acquired, beer gut) to be relatively small ?

daz3210

5,000 posts

269 months

Friday 10th August 2012
quotequote all
Gargamel said:
Commute is 21.3 milesone way - and around 600 ft ascending on the way in, about double that on the way home...

So the effect on climbing speed is pretty significant.

I should imagine the aero effect of the size of my (expensively acquired, beer gut) to be relatively small ?
Could the beer gut have aero advantage? I mean a slab front as opposed to a nicely rounded front must be less aero.

crisisjez

9,209 posts

234 months

Friday 10th August 2012
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I would be very very happy to get that in under an hour.

Gargamel

Original Poster:

16,355 posts

290 months

Friday 10th August 2012
quotequote all
daz3210 said:
Could the beer gut have aero advantage? I mean a slab front as opposed to a nicely rounded front must be less aero.
I always assumed greater mass meant faster top end speed when descending

okgo

42,127 posts

227 months

Friday 10th August 2012
quotequote all
How rural is the route? Many start stop points?


daz3210

5,000 posts

269 months

Friday 10th August 2012
quotequote all
Gargamel said:
daz3210 said:
Could the beer gut have aero advantage? I mean a slab front as opposed to a nicely rounded front must be less aero.
I always assumed greater mass meant faster top end speed when descending
Nope, from what I remember from physics at school, mass has no bearing on acceleration due to gravity, only aerodynamics and drag affect this.

dangerousB

1,701 posts

219 months

Friday 10th August 2012
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Forget the minutiae - for one reason or another, you're basically not working hard enough (putting out enough power) to achieve your target.

What's your current limiting factor - your lungs or your legs?

Justin Cyder

12,624 posts

178 months

Friday 10th August 2012
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davepoth said:
Surely air resistance comes into play here if you're really bulky?
Boardman was on the Olympics the other night saying that 80% of a cyclist's effort was spent punching a hole through the air. I tend to believe Chris Boardman, I think he knows a thing or two about cycling.

Gargamel

Original Poster:

16,355 posts

290 months

Friday 10th August 2012
quotequote all
okgo said:
How rural is the route? Many start stop points?
No I am lucky in this respect, I live out in the surry hills not far from Hindhead, so commute into Woking on the back roads.

Only four sets of Traffic lights (all in the last 500 yards) I stop timing at the railway bridge in Woking as I don't want to take big risks through town.

Only two junctioned right turns - one in Elstead and one in Normandy

I often cycle the whole thing without unclipping.

My feelingis I lose the times on the climbs, I really burn the house down on the long straights into Woking (Normandy to Worplesden) There it is definitly legs - on the climbs it is lungs !

deeen

6,403 posts

274 months

Friday 10th August 2012
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Gargamel said:
daz3210 said:
Could the beer gut have aero advantage? I mean a slab front as opposed to a nicely rounded front must be less aero.
I always assumed greater mass meant faster top end speed when descending
Hammer and feather...

Anyway weight has a slight EFFECT on top speed, because it AFFECTS the rolling resistance. I would think the effect on your climbs is far more relevant though. Look how much effort people go to knock 1kg off the weight of their bikes, never mind 10! I like the above idea of sticking 10kg in a ruacksack, and see how much time it adds to your route.

Also as above, I would be very happy with 20 miles in an hour on the flat, never mind a hilly route!

Gargamel

Original Poster:

16,355 posts

290 months

Friday 10th August 2012
quotequote all
daz3210 said:
Nope, from what I remember from physics at school, mass has no bearing on acceleration due to gravity, only aerodynamics and drag affect this.
Sorry I missed my wink from the end - yes I know it doesn't really. Speed is often confused with energy.

okgo

42,127 posts

227 months

Friday 10th August 2012
quotequote all
What boardman said it right. But at these speeds c/da (drag) is not such an issue. And 10kg won't change your body shape that vastly really, especially not if its all in your belly.

Hmm, should be possible? Would you mind posting the route? I used to live in Tilford, and would be interested to see which way you go. Very lucky to ride around there, bugger all traffic and a great mix of terrain.

As dangerous said, its likely that you just need to improve fitness and power.

okgo

42,127 posts

227 months

Friday 10th August 2012
quotequote all
swerni said:
You used to be a fat knacker, you're much faster now you've lost weight wink
haha, its one of those things, if I had a powermeter back then I could tell you how much was due to improving power/fitness and how much was down to weightloss, but sadly I didn't have it back then.

Gargamel

Original Poster:

16,355 posts

290 months

Friday 10th August 2012
quotequote all
okgo said:
Hmm, should be possible? Would you mind posting the route? I used to live in Tilford, and would be interested to see which way you go. Very lucky to ride around there, bugger all traffic and a great mix of terrain.
I think this should work

http://maps.google.com/maps/ms?ie=UTF&msa=0&am...

Route comes up a little shorter as I have only put the start line as The Crossways in Churt

Doesn't feel lucky when you are slogging up the hill to Hindhead ......