# Speed drops dramatically

**URL:** <https://forums.zwift.com/t/speed-drops-dramatically/553933>\
**Category:** General Discussion\
**Created:** [July 29, 2021, 5:35pm UTC](https://forums.zwift.com/t/speed-drops-dramatically/553933 "2021-07-29T17:35:16Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![David\_Turner5](https://sea2.discourse-cdn.com/gozwift/user_avatar/forums.zwift.com/david_turner5/32/503202_2.png) [@David\_Turner5](https://forums.zwift.com/u/David_Turner5)\
**Post date:** [July 29, 2021, 5:35pm UTC](https://forums.zwift.com/t/speed-drops-dramatically/553933/1 "2021-07-29T17:35:16Z")

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I’m cycling along at 35kph then suddenly I drop to like 3kph, I’m new to Zwift using a dumb trainer, Cycleops Fluid 2 with Speed Sensors on the rear hub, also I can only connect via 4g as using outside so no WiFi connection.  
Does Zwift assume my speed and if I go uphill it will automatically drop my speed based on Watts output or something or am I losing connection even though it doesn’t say so  
All help welcome

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**Author:** ![Mike\_Rowe1](https://sea2.discourse-cdn.com/gozwift/user_avatar/forums.zwift.com/mike_rowe1/32/530428_2.png) [@Mike\_Rowe1](https://forums.zwift.com/u/Mike_Rowe1)\
**Post date:** [July 29, 2021, 5:39pm UTC](https://forums.zwift.com/t/speed-drops-dramatically/553933/2 "2021-07-29T17:39:08Z")

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Hi @David_Turner5, please read this thread about how your speed is determined. If you are on a hill you will need to put out more power to hold a steady speed.

> [@How Does Zwift Determine My Speed?](https://forums.zwift.com/t/how-does-zwift-determine-my-speed/427729):
>
> How Does Zwift Determine My Speed? For Wheel-on Classic Trainers: Zwift takes the wheel speed broadcast by your speed sensor and the power curve (see example below) of the trainer you select on the Pairing Screen and converts that to virtual watts, also known as “zPower”. Your in-game speed is de…