How much effect does losing weight have on speed?

MozBiker

In my personal experience dropping a few kg's makes a notable difference. I was around 80kgs and in the past few months it has come down to around 75-76kgs. Before I lost the weight I was reasonable on the hills and had a few top 10's on strava on the hill segments. But I can definitely feel I can cycle uphill much more easily and I can see my average times on the hills decrease by quite a lot. I can feel a big difference. I can now drop a few of my mates I ride with that I couldn't drop before.

But like it has been mentioned there is a sweet spot. Too little weight and you lose power. Too much and it holds you back. On the flats it isn't as important. But if you spend a lot of time heading for the hills losing one or two kg's will make a noticeable difference. especially on the longer climbs.

One thing that could help those struggling to decide to lose weight or not. 95% of us amateur cyclists are not at our genetic maximum performance or close to the best form we could ever be in. Riders in the pro peleton are very close to their, if not at, their maximum muscular and endurance ability.

For example. Suppose Froome, who is 67.5kg, weighs 72kg. And suppose his FTP is as high as he can get it by training alone. For him the only option to gain speed on the hills is by losing weight.

Most of our FTP's aren't at the highest we can get by training alone. SO we don't need to lose weight to get faster. We can by training alone make up the time we would've gained by losing weight. If we are at our training limit and still need more speed, then it would be necessary to lose some blubber.

In my case I am nowhere near my full physical capability. So I prefer to gain power over losing weight(even though I lost weight without consciously making an effort to do so), cause to be honest those chopstick arms and skinny upperbody image doesn't appeal to me. I prefer to keep some muscle mass up top and in the arms and just increase my power to make up for the extra weight.

Quite a tricky balancing act this one.

Good thread

okgo

Train to be powerful, eat to be lean. Its not hard when put like that.

Either way, the more you cycle the more you'll lose muscle mass where its not needed. Though it will never totally go, I've never managed to get cyclist arms

itboffin

HaydenM wrote:

It's doubly inefficient for me to lose 2kg over buying a new bike as the weight is from being a borderline alcoholic, cutting out the beer would mean being unpleasantly sober for extended periods of time and that is a sacrifice I am just not willing to take.

^this^

yiannism

Assuming that we are talking for adults 35-50+ if our not built is physically slender we have some extra weight and if you like beers like me some belly too. In that case if you improve your body and your eating habits will improve you much more than a little lighter bike thats a fact. A fact also is that if you shed some of that extra height you will be healthier and at the same time you will improve your aerodynamics too. Not so important on climbing but important enough on flat.

Bike is not more than 15% of the performance, so my advice is to improve your self 1st before spend 4-5000 for that shiny masterpiece with the idea that suddenly you will be the champ

davidof

Lets say you are climbing l'Alpe d'Huez. You weigh 85kg and put out 235 watts. You'll take about 1h11. Now you lose 5kg you'll cross the line around 1h06, assuming you can still put out 235 watts. So that's about 5 minutes for 1 hour climb over 1000 vertical meters.

With less fat in your muscles they will be more efficient.

fat daddy

5 minutes is enough time to cool back down, get your breath back, turn a normal colour, order a cold beer with condensation down the glass and be sat drinking it when your mates turn up and make some comment about it being a pleasant bimble, do you guys need a stop or shall we head on back down ?

definitely worth the effort

mind you, 2kg lighter bike means you can get it back on the roof of your car that evening without having a hernia

dannbodge

I've recently dropped 2/3kg from my body and also from the weight of my bike (10ish kg ally to 7.5kg Carbon)

I've not noticed any real difference in my riding....yet, however I may be slightly faster but as I've done lots more riding already this year compared to last, it could just be that I'm more prepared.
Also going up hills is slightly easier now but again too many things have changed for me not including the weight of me + bike.

I suppose the real test could be september when I get to Brands again for revolve 24.

davidof

fat daddy wrote:

mind you, 2kg lighter bike means you can get it back on the roof of your car that evening without having a hernia

Not to be neglected - or even putting it in the back without slipping a disk.

burnthesheep

GCN has a short youtube on just this:
https://www.youtube.com/watch?v=iW47gb01FeA

For yourself? Do the experiment. Find a short hill, maybe 100 feet over 1/2 mile. Do it. Grab a backpack and weigh it on the scale to 15 or 20 lbs. Put it on and do it again. How did that feel?

No bike you can buy will give you that much difference. Weight weenies do help but unless you're getting to the point of losing so much body fat that an illness would hurt you......body weight and power. Once you're eating to avoid losing muscle, you're at the sweet spot.

It's a lot easier to "cheat" on flat land if you need to lose weight. Your extra weight isn't penalizing. You can cruise at 16 mph effortlessly for a few hours. Find a hill, no hiding from that bad boy. There's only so many teeth you can put on a cassette.

For me: about 12 to 13 lbs weight loss, a 2 lb lighter bike, and a gain in power of 50 to 60 watts from 150 to 210 was the difference in 9 minutes up a Cat III climb. Not just that, but it made the difference in doing the same climb 3x in a row with no feet down. Before training, I had the feet down 3x on the climb.

onyourright

For a decently steep hill (i.e. one where you ride slow enough that aerodynamics don’t matter much), climbing time is proportional to weight. It’s that simple.

That’s total weight, of course. It makes no difference if the weight is on you, your bicycle, or your bicycle’s wheels. It’s all weight that has to be lifted against gravity to the top of the hill.

If you weigh 75 kg (in your clothes and shoes and helmet, with your mobile phone and wallet and toolkit …) and your bicycle weighs 10 kg (including bottles and pumps and computers strapped to it …), the total is 85 kg. If you then lose 5 kg, your new climbing time will be your old time ÷ 85 × 80. So a 20 minute climb will now take 18 minutes and 49 seconds.

That’s assuming your power stays the same. For pro athletes near their performance limit, losing weight tends to slightly hurt their power. For the rest of us, the riding needed to lose weight makes us stronger. So you’ll probably be not only lighter but stronger.

Alex_Simmons/RST

Craig0657 wrote:

Thanks for your replies guys, it was just 1 particular GCN video that mentioned "if an 80kg rider lost just 5kg they could improve their time on a course by upto 4 minutes" that got me wondering if there was an exact formula for this.

Yes there is, however it requires is that you flip this equation around to solve for speed and to calculate the value for every moment for each of your two ride scenarios (e.g. heavier and lighter):



The complexity is that you need to know all of the relevant variables for each moment of the ride (e.g. gradient, wind velocity, CdA, Crr and power output) and be able to solve the resulting cubic equation which depending on the gradient doesn't always have a closed form solution (making it not so easy to do in a regular spreadsheet).

I have done that, although not for every second but for slightly longer segments, as part of pacing optimisation model I built about a decade ago.