Are watts and RPM correct?


(Man) #1

Since I don’t have a power meter or any other device to actually measure my watts, I decided to record a short video of my regular RPMs during a race.

So essentially, at the beginning of the race, I ride hard, and then for the rest of the race I settle at the speed in the video hoping to remain in the current position. The issue is that once I settle at this speed, literally everyone passes me. By minute 10, I’m 120th place of 135.

The race is a WBR 4 Classique flat race.

Do the numbers in the video look correct?


(Daren) #2

Can’t see the video, it’s a 404. Maybe set to private?


(Paul Allen (Watopia Wayfinder)) #3

It would be close to impossible to know if the data is correct using just a video.

If you are going to race on Zwift it might be worth looking into a trainer that at a minimum broadcasts watts or a power meter. A Tacx Satori Smart is a trainer that broadcast watts but does not adjust to meet virtual elevation changes. A 4iiii single sided power meter is also sold at a reasonable price.


(Man) #4

I’ve edited the settings. You should be able to see the video.


(Man) #5

HI Paul,

I understand your point, but a smart trainer or a power meter will easily cost me over $600.

I started this year with zwift by buying a cycleops mag trainer with all the accessories so that everything would work. Then I moved up to the Road Warrior with inride. Add to that the bike, the membership, the time to set everything up, and the dollars pile up.

I appreciate your suggestion of buying more expensive stuff, and I applaud the people that can just buy the smart trainer and the power meter without giving it a second thought. But I can’t do that and even if I could, I won’t. I’ll find a solution to what I have, and that’s why I posted the video.

In any case, I’m not looking for the perfect answer. I just want to get an idea of what’s going on.


(Paul Allen (Watopia Wayfinder)) #6

A 4iiii power meter is $400: https://4iiii-innovations.myshopify.com/collections/power-meters

The video does not show much, just watts and cadence. I can produce the same watts with varying cadences (different gears). I really don’t think they is anyone that can say without a doubt that your setup is correct or not. Without a HRM there is no way of knowing if you are pushing hard or just cruising. Even with the HR info I still don’t think anyone could say for sure that everything is correct.

I was just making a suggestion about upgrading.

I don’t know what Cat you were in, but if it was C or above those watts would not allow you to hold your position very long. I don’t race so maybe I’m wrong.

What is your FTP and how much do you ride per week? That could give us a better shot at assisting you.


(Tim Camden (B)) #7

I see an issue but I will leave it to the more knowledgeable users to explain the significance.
I assume the course is flat since it appears that you are in a urban area but at 160 watts, I think that 8-10 mph is low.


(Paul Allen (Watopia Wayfinder)) #8

If you watch the entire video you will notice the speed raise, so I would assume he was climbing for most of the video a crested the hill at the end. It’s only an assumption since we don’t see the virtual elevation changes and the watts stay about the same.


(Man) #9

When I made the video, my goal was to ride between 70-85 rpm, regardless of the course.

I would like to know if the watts look right for the rpm.


(Paul Allen (Watopia Wayfinder)) #10

There’s no way to tell. I can ride at 80RPM and produce different watts depending on what gear my bike is in.


(Devin Knickerbocker2522) #11

Yeah you basically said, even if you could buy a power meter, you wouldn’t do it. Well, it’s all about priorities: If you really want to know if the watts are right, you need to have a device to measure them. It sounds like it wouldn’t be a priority for you, and that’s totally fine, but there’s really no other way to know.

For what it’s worth, consider periodically checking ebay for used or overstock single sided crank based power meters like 4iii or Stages. I picked up a left-only stages crank arm on ebay for about $150, and it wasn’t the same model crankset but because it was the same BB standard and the same bolt pattern, it still fit on just fine. Overall, a low cost, easy way to measure power that is accurate in most situations.


(Devin Knickerbocker2522) #12

And to follow up with what i mean about priorities: The cost of my power meter was the same as the cost of roughly 15 drinks at bars where i live in NYC. Would I drink 15 fewer drinks over the course of say, a month or two, in exchange for a power mter? Abso freakin lutely. Would, and did.


(Ward Brady) #13

Watts are not solely related to cadence…

If they were, power meters would be $20 instead of $500+

It’s an impossible question the OP asked, Paul is exactly right, I can pedal at 85 rpm and produce 80 Watts or 800 watts


(i van) #14

Cadence does not determine the speed you are traveling at. Speed in Zwift is mainly determined by your speed and weight. Make sure you choose the correct category when entering races. You’re probably in the D category.


(Danny Boyd) #15

you should have no concern for power or numbers with what you are currently doing - you are just fantasizing. get a proper trainer and this story is then irrelevant.


(Dave) #16

My Tacx/Neo1 is notorious for inaccurate cadence… none the less, the power meter is 99.9% accurate IMHO. Sometimes I get strange cadence readings, and that’s because the Neo1 only estimates the cadence (Neo2 has a real cadence meter). To correct this, I installed a Wahoo ANT+/BL cadence meter on my crank, and I pair to that instead.


(Man) #17

Thanks to all. After contacting kinetic support, the issue was that the trainer knob was too tight.

In any case, I was able to calibrate it using the kinetic app and now everything’s well.