Gradient Lag (3 secs)

Hi all,
I’m experiencing about a 3 second delay between the gradient I can see on the route (including the percentage shown in the map at the top right corner) and what I feel from the trainer.
To explain a little more, the gradients feel right they are just delayed by about 3 seconds. For example, on Downton Dolphin on the ‘Prime’ climb, when I first hit the bottom of the climb I don’t feel any increase in trainer resistance till I’m 3 secs in to it. When the climb has finished and goes back to flat, I still feel the resistance for another 3 seconds.
The trainer difficulty setting in the Zwift settings menu is set at default 50% if that makes a difference.

My spec;
Windows 10 (64 bit)
Intel i3-4130 @ 3.40ghz
8GB Ram
50mbps Ethernet Wired Fibre Broadband
Garmin ANT+ Dongle with 2m USB shielded extension cable (placed under bottom bracket)
Saris H3 Trainer (Ant+)
iPhone companion app (12 Pro / iOS14.7.1)
Taope Heart Rate Monitor (Ant+)
32” Celcus TV @ 1080p via HDMI (60hz)

My previous setup used the Zwift iOS game app on my phone, connecting everything via Bluetooth. There was never any gradient lag on this setup with the same trainer, so I guess it’s unlikely it’s a trainer issue.
Any ideas please?

In my experience bluetooth reacts quicker than ant+ are you able to connect to the PC via bluetooth and see if it is any different?

It shouldn’t really be an issue but that isn’t the most powerful of PCs so maybe it is struggling a little? I’ve used 4th gen i5s with 8GB ram without any lag though so unlikely to be the cause.

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Thanks for the response.
One reason I changed platforms was due to Bluetooth dropouts, so I was hoping to avoid using it… but I’ll give it a shot, just need to get a Bluetooth dongle for the PC.
I realise the PC isn’t the best, it’s just built specifically for Zwift use on a full hd tv. Runs a solid 60fps on Ultra detail settings on everything but the known areas that tank. Nothing in the logs or in Zwiftalizer to suggest it’s struggling but I’ll keep an open mind on this if Bluetooth doesn’t sort the issue, thanks.

It is weird that some get a delay while others with the same setup Don’t.

I have a similar setup win 10 ant + fe-c and saris h3.

Do you pair the ant+ as fe-c for both power and controllable.

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Yea power, cadence and controllable all paired via fe-c.
Do you get any lag with your setup?

Any recommendations for a Bluetooth dongle please?

No lag on my setup.

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I use a cheap one from amazon I have found the Bluetooth V4 ones work and V5 don’t (at least for me anyway)

this is the one I use and it works fine for me

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Can confirm: issues when using ANT+ are more common. Having a dongle closer to the bike solved for me. I then went about lessening RF noise and have happily used Bluetooth ever since.

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Thanks for the input. I moved the Ant+ dongle right next to the trainer without improvement unfortunately.
The Bluetooth dongle should be here today, so I’ll check that when it arrives and see if I can also lessen the RF noise if needs be.

Yikes. What a conundrum. What kind of wifi do you have? Are you close to your router?

It’s a wired connection now, so I’m not using WiFi…. This should help cut out some of the RF noise that caused BT dropouts on my old setup.

I’m not sure if it is still the case as I haven’t used bluetooth but initially the trainer wouldn’t show up as controllable but if you pair it as power source first then search for controllable again it’ll show up (same for cadence)

if you have a separate power meter you can then pair this but after the above steps.

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Just tried the Bluetooth dongle briefly and it worked perfectly with no lag at all.
I need to test it more to see whether I’m going to have BT dropout issues but initial signs are good. Thanks for all the advice guys.

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glad it seems to be working for you.

Not sure why bluetooth seems to act quicker but it does in my experience and that is using different PCs and trainers so don’t think it is specific to my set up.

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I have had the same experience. Using a (very cheap) Ant+ dongle sitting right next to my Saris H3 trainer, I felt a 2 or 3 second delay. Especially noticed riding Titans Grove with all the rollers. Using Bluetooth, no delays at all. I wonder if it because I was using a super cheap $8 eBay Ant dongle…. For folks who do not feel any delay with Ant, are you using a more reputable/expensive dongle or a cheap one?

I have used super cheap ant+ dongles, Tacx ant+ dongles, garmin ones and various others in between and the lag is always the same for me.
This is using different PCs (never very high spec but more than fine for zwift), different trainers, different positions of the dongle etc.

I think bluetooth just locks in a bit better which is good until it drops out when i find it doesn’t reconnect as well as ant+ does.

Three seconds to change is ages, that doesn’t seem right irrespective of the protocol used. On parts of Titans Grove for example it would never catch up. I’m on the same £9 Anself ANT+ stick I bought over three years ago and it’s never been a problem on any of my trainers. Can’t say I’ve ever timed the delay but it’s never felt unreasonable. This isn’t the first time I’ve seen people say Bluetooth seems faster but I don’t really understand how/why this would be. I probably need to test it again. :wink:

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PS: Can’t remember the last time I actually paired my trainer manually. On a completely clean install of Windows and Zwift, upon launching the game for the very first time it pairs itself for controllable, power and cadence without me doing anything at all. I have a Neo 2T on which legacy ANT+ can be disabled, so I guess because Zwift sees only one trainer on only one protocol (FE-C), it just pairs everything for me. I just add my HRM after that.

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I did another 90 min activity last night using the Bluetooth dongle, it worked great, with no lag.
Zwift did freeze briefly, enough time for me to say ‘what the Fu…’ and then unfroze. I noticed the light on the trainer had gone from solid blue to flashing blue, so looks like the BT did drop out and then reconnected. Zwiftalizer didn’t analyse the Bluetooth though when I put the log file into it. I can live with that as long as it reconnects quickly.
Re the 3 lag on ANT+, maybe it wasn’t quite that but more than 2 secs for sure. If I did the ‘two bridges’ route in Watopia, after about 1km when I hit the rolling up and down sections ranging from about -6% to +6%, I wouldn’t feel the +6% until I was at the top of the climb and it would continue at this resistance until I’d descended a fair bit as well.
I have used an Anself and a Garmin ANT+ dongle, both had the same lag.