Does weight have too much weight on downhills?

(Alan Hamilton - MRC) #1

Today I rode Zwift Island with a friend that I’ve ridden with in the real world hundreds of times for thousands of miles. He outweighs me by about 30-35 lbs which is not a problem in the real world. I never get dropped on downhills and if I do it takes very little extra effort to get back on his wheel. If I tuck in behind him on a downhill I can soft pedal and stay on his wheel. But on Zwift Island I have to work very very hard to avoid getting dropped on the downhills. I need to produce a whole lot more watts than he does. On the steeper parts he can be doing 150W to my 250-300W and we will stay even. (I’m estimating wattage based on w/kg reported by Zwift.) And if he pushes hard on the downhill I have to go all out and still might not be able to stay with him. The weight diff seems to be handled well enough on the flats an uphills, but on downhills I think there needs to be less of an advantage for heavier riders (or less of a disadvantage for lighter ones).

(Eric Min) #2

This is a known issue. There is another thread discussing this. It’s clear that the physics engine need to be tweaked. Are you on a Kickr or Computrainer?

(Christopher Pallotta) #3

I think the fact that on Zwift everyone has the same CdA now has got to be a big part of this. As I wrote on another post, in the real world, bigger riders have to displace more air and have greater air resistance.

This offsets to a degree the advantage of weight they may have on descents or the advantage of having (in many cases) more muscle mass.

If in the future Zwift uses our weight/height to calculate an appropriate CdA, things would be more realistic. Watts/kg just isn’t enough. The effects of wind resistance are substantial.

(Andrew Williams) #4

In real races I not only don’t get dropped on downhills, I actually use them to move up in the pack.

On Zwift I get shelled often and there’s nothing I can do about it. I’ve been whining about the fixed CdA for a while. I figure it’s a future development.

(Alan Hamilton - MRC) #5

Yes, I am on a KICKR, and was today, but so was my friend, so the only big difference between us today was our weight.

I knew there was another thread about this subject but wanted to start a new one based on a pretty good apples-to-apples comparison between real world and Zwift on downhills.

(Jeff Doughty PVC WBR (B)) #6

I was one of the people who created a thread about this a while back.  To be honest it is becoming more and more frustrating.  I have now become level 15 and logged over 1,200 miles on the island.  I love the software and will continue to use it.  That being said, I will not be looking to do any race type scenarios until the physics are refined. 

Having to bridge a gap caused by poor physics is super frustrating.  Watching a guy pull away from me while he puts out 90 watts and I’m doing 235 is way off.  

I am sure the team at Zwift will do something about it in the future.  They have certainly listened to feedback and made necessary adjustments in the past.  I hope they can solve issue sooner than later.

(Eric Min) #7

I think we might have resolved this issue in the next release. You might see changes this week. Would love to get your feedback. 

(Andrew Williams) #8

I’m eager to try out the new release!  Maybe the Orange jersey will be possible again!

(Jeff Doughty PVC WBR (B)) #9

I will be very happy to try the update.  Thanks for listening Zwift!

(Andrew Williams) #10

I LOVE LOVE LOVE the update!


I don’t feel like it gave me an advantage, but it finally took away a disadvantage.  My solo lap times are just a tiny bit faster than before, but I did the group ride today and never got shelled on the downhills.  Chasing groups on the flats was difficult (like it is in real life) but no longer impossible.  Also, the lap times that big rouleurs were setting were fast, but now they seemed much more realistic (except the zpower flyers and those who are using TR to make fake powermeters)


Before the update, groups would easily make 27mph or more on the flats.  Now, I feel that speeds like that are difficult for everyone (just as they are in real life).  You can make 27-28, but it takes a serious effort to do it.  It’s also actually possible for little guys like me to do it too (which I can in real life, but it takes a lot of w/kg to do)


Much more realistic.

(Andrew Williams) #11

One issue since the update is now the concept of “weight doping” or using incorrect weight in your profile is much more powerful as it gives a double gift to anyone who virtually drops an extra 10 or 20kg.  I am of the opinion that most people doing this are unaware that they need to go into in order to set their weight.


I have seen it a few times now, where people producing unlikely results (but not unrealistic enough to set off the yellow flag) aren’t found on strava at the island, but who might be found doing “trainer sessions” that day.  The most logical conclusion is that they simply never accessed their online account in order to link it to strava, and also never changed their weight from the default.


So I suggest something in-game to indicate rider weight.

(Joseph Bank [HPP] A) #12

I was going to post my own question and got forwarded here.  I’ve done a fair bit of solo riding on zwift with no real complaint about the physics, but over the last couple of weeks decided to try joining in on a few races.  The first race I did, I crested the reverse climb in first with another guy and then sat up to wait for the pack, which flew by us, making a huge gap.  Hmm, seemed a bit off my real world experience (I don’t typically get dropped on descents even if I sit up a bit).  Subsequent laps with a trailing group I had to hammer on the steep descent to stay with the group.  Similar thing happened when I tried another race today.  Was with another guy, crested the reverse KOM with him (slightly ahead), and then got dropped by a big margin on the descent.  This seems like a big mismatch from the real world where I would normally not even need to peddle to stay with a guy on a descent like that; I guess I will get used to it when racing on zwift, but some aspect of the physics seems off.  For what it is worth, in the real world I am on the relatively light and aero side of the spectrum (145 lbs, ~.2 CdA on a TT bike and ~.26 on the drops on a road bike),