Rider Weight Impact

It is very clear and rightly so that heavier riders have to produce more watts when climbing to summit a hill than a rider of lower bodyweight with all else being equal. However, is there any benefit whatsoever – for example on the descent – to equalize things a bit and to give heavier riders so payback with a speed advantage? IRL heavier riders even have an advantage on the flats … As it stands now, especially as there is no wind effect (which is a IRL advantage to heavier riders), it seems as though ALL of the advantages go to the lighter rider and none to the heavie rider.  Is that the case or just my perception after riding yet another ZTR-EB where I am the only person with BMI body size 2 on Zwift racing against these skinnier guys?   Please advise as we do want Zwift to be somewhat equitable and that means that sometimes the heavier rider should get an advantage too … THANKS.  

Hi KC, heavy riders get the same advantage in Zwift as they do in real life.  They’ll be faster on the descents.  This wasn’t coded specifically for, it’s just how the physics math works out.


Thanks Jon. Can you please share some stats on that? There are some stats on Facebook that show that heavier rider are in fact slower on the descents and flats at equal wattages to the light folks. What I can tell you from Zwift race experience is that the 50-60 kilo guys have it WAY too easy to stay with a heavy rider on a descent or a flat. It is just not realistic vs IRL.  We know that the draft algo was quite changeable and in need of change. Why couldn’t the algo that simulates rider weight impact be just as much in need of change as the draft algo was previously? The Zwift climbs are not that long nor steep, I am absolutely certain that the light riders are benefitting too much. Just wait until longer climbs are introduced (especially if heavy riders do not get a better descending benefit) as you are going to destroy the ability of light and less ight riders to ride, let alone race together.  Please remember that I was one of the voices that said the large group draft benefit was too beneficial and it took a long time for ZwiftHQ to agree. I believe we have a very similar issue here with race weight impact. Please be open minded that something needs a tweak. A lot of smart, experienced racers agree. THANKS! #Rideon #zwiftΔriding 

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+1 I also test riders 75kg vs 90kg with bikecalculator, the calculations are good for the guy 75 kg but not for the guy 90kg too high penalty.

So what impact or change takes place when I weight 206 lbs and loose 6 pounds is it imperative to update my weight GeForce faster climbs?

The TT Bike not bad for calculation = best bike for people heavier.

The normal bike more penalizing for overweight people.

Test Rider 90KG: TT BIKE

Richmond 2015 UCI Worlds Lap 0% { 16,2km Speed 33,2km/h Watts 250W Time 29:28 }
Zwift TT flatout (3rd Str) 0% { 07,5km Speed 36.6km/h Watts 250W Time 12:28 }
Downtown Downhill Stretch -3% { 01,3km Speed 50.8km/h Watts 250W time 01:34 }
3 Hill Climb 1% { 04,3km Speed 24.3km/h Watts 250W time 10:45 }
23rd Street Climb. 10% { 00,2km Speed 13.1km/h Watts 250W Time 01:13 }

Test Rider 75KG: TT BIKE

Richmond 2015 UCI Worlds Lap 0% { 16,2km Speed 35,3km/h Watts 250W Time 27:43 }
Zwift TT flatout (3rd Str) 0% { 07,5km Speed 38.2km/h Watts 250W Time 11:56 }
Downtown Downhill Stretch -3% { 01,3km Speed 49.9km/h Watts 250W time 01:35 }
3 Hill Climb 1% { 04,3km Speed 26.8km/h Watts 250W time 09:45 }
23rd Street Climb. 10% { 00,2km Speed 15.0km/h Watts 250W Time 01:04 }

So could the reason that I am slower be based on riding the steel bike? I am still trying to find out the best way to get my best bang and fastest effort. Does the TT bike have any other benefits?

I Agree,… The flat and descends aren’t even close to IRL experience…

Yesterday I cycled with someone that is half my weight I Had to produce 350 watts to stay in her wheel,… She wasn’t even breaking a sweat. 

Feels like something is left out of the equasion

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I agree, heavier riders do seem to get unfairly penalised. One example of many… I rode with a friend the other night around London classic flat course 3 laps on TT bikes, and 68kg rider @ 240 w avg 39.9kmh and 84kg rider @ 293 w avg 39.8kmh. Real life and online calcs would indicate 293w rider should have averaged around 42kmh. Is this something Zwift is looking to improve?  

Heh, I’m finding the same. In real life, I’m a somewhat lightweight rider, at 75kg and 186cm. Most guys I ride with, including the really fast ones, are heavier. Not so in Zwift - looking at zwiftpower, the majority of A and B racers are sub-70kg (that’s assuming they are accurately reporting their weight).

I’m not yet able to compare to real life accurately, because zPower with Fluid2 trainer appears to be grossly underestimating my wattage, making me come in with the dregs of the C racers averaging well under 200W while my previous experience (before power meter was wiped out by a car accident) says I easily average 280W over an hour on a hard ride. Looking forward to getting a replacement power meter so that I can at least somewhat compete…

200 W @ 50kg with 44,5 km/h @ Volcano Flat …

380 W @ 80 kg @ 44,5 km/h @ Volcano Flat …


any Questions? What are you doing in your Zwiftlabs? That is absoluty unfair and *ull*hit… you have Aero Bikes which are faster which doesnt even make sense in a world without any wind resistance … LOL?

BUT if anatomy of people should count it doesn’t appropriate - in other word it does absolutely not!

Just put in some advanced coding which allows heavier rider to get their REAL advantage in the FLAT. I can easily outclass the lighter riders in the flats but in zwift i’m in z5 and the lighter ones in z2/3 … that is ridiculous!

Just put this code into yours:


JUST DO IT! Everything would be great! …:slight_smile:

First of all, of course Zwift has wind (=air) resistance. There is no wind, but that doesn’t mean you’re not fighting air resistance.

The stats you showed do seem odd. If these are real race results, they may be influenced to some extent by efficient vs. non-efficient riding: the 50-kg rider may have been better at hiding in the pack, always being in the draft.

I would expect there to be some penalty for heavier riders on the flats, because presumably heavier riders face higher air resistance. That’s too bad for the heavy-boned segment of the population :slight_smile:


Try it out for yourself. It doesnt make fun to race under these circumstances …

I expect the speed is more likely to use w/kg rather then the raw watt data in the code… Solo (London) flat course results:

80 kg - 220 Watt ~37 km/h

60 kg - 220 Watt ~40 km/h

sorry but thats just ridiculous!!!

Something is just wrong for a heavy rider on the upgrades.  There are plenty of us heavies that are serious about fitness and or weight loss.  But really is that difficult to calibrate the watts for upgrade.  Testing by producing max effort on a flat section vs a upgrade should produce the same peak watts, at my weight upgrades are half of flat, what is with that?  Kinetic Smart trainer purchased 2017.  

Had this issue been fixed or addressed? I’m a heavier rider at 113kg. I’m seeing no benefit to my weight and power on flats and descents. I am all for penalizing me on climbs, but give us our advantages on flats and descents please.

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Steel bike does take more work to ride. I know in real life, I have no move over and let heavier friends lead on downhill’s. It should be noticeable in Zwift.

May I suggest you try pure coasting tests? Slow roll through the KOM and let gravity take effect.

I’m a 105 kg rider that mashes the pedals on sprints but I get nowhere. The watts and speed don’t make any sense. I know what I do on the road in real life; not seeing it on Zwift. All I know is that it’s not making sense; I understand why peeps may weight dope. Especially bigger guys.