Affect of bike on lower power riders

I sent this originally to Eric but wondered if anyone has any answer. I started Zwifting last November as an alternative to the gym, which was shut due to Covid. I’m 63, 68Kg and hadn’t been on a bike for 20 years. My FTP started at 99 now 139, or just 2w/kg. I’ve been wondering for a while that my choice of bike makes a bigger difference to my times than would be expected from your speed tests. Using the Cannondale Evo with the Inve wheels my climbing times are so much better. Today I did the Watopia flat route for the first time in a couple of months using the Zipp 808 wheels which I’ve recently acquired as opposed to the DT Swiss last time, both with the Canyon Aeroad. Despite averaging 146w this time compared to 121w last time I only improved my time by 2 seconds. The only reason I can think of is that on the climbing sections, although not particularly long or steep, I’m losing time due to the heavier wheels. I’m wondering if this fits with the game mechanics and how much your speed tests are applicable to someone like me. Does it make sense that the choice makes a bigger difference for back of the peloton riders like me?!

I don’t think it’s the bike/wheels. What was your average power on the long climb compared to on the flat route? I suspect you’re getting better at pushing against higher resistance (on the climbs), and aren’t pushing as hard when there’s less resistance.

Also, the average power doesn’t tell you the whole story. How much you drafted (or didn’t) can be a very large factor, for example.

Hi @Gary_James1 ,

Have you looked through the pages on ZwiftInsider, which detail many tests they’ve done on the subject of wheel and bike combinations?

Or do you mean you’ve asked Eric from ZwiftInsider if he’s thought about repeating these kind of tests at lower powers?

I’ve seen all the bike and wheel tests that Eric has done on Zwiftinsider. I wonder what the tests would show if they were done at 2W/Kg rather than 4W/Kg but I don’t really expect them to be done again, I suspect Eric has better things to do with his life!

Unless you were riding by yourself, the comparisons do not mean much. As was alluded to by @Steve_Hammatt drafting is the biggest factor on flat courses. Try on a tri-bike with different wheels to get the comparison. No drafting on a tri-bike.

I wouldn’t say that on a course of over 6 miles that you can say bike choice is the defining factor.

That’s such a small time gap I would put it down to variations in your bodies performance. We have good days and bad days. The are so many factors that can lead to a variation in performance and 2 seconds could literally be the difference of 10 minutes extra sleep the night before for example.

The thing I meant was that with the average watts being so much higher I would have thought the time improvement would be higher.

This is very interesting. Eric’s tests suggest that in Zwift, the bike weight is proportional to the rider weight, so if you go to a lighter bike, that advantage is a certain % of total weight, rather than being a larger fraction of a lighter rider’s weight. Ashleigh Moolman-Pasio, the women’s world champion, made similar comments. But Eric would have better info.

I recommend this article, which shows how strongly pacing strategy can affect time on a course with mixed climbing and flats, even without drafting: How to Pace Your Best Zwift Bologna TT Race - Zwift Insider

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In other words you would have thought 20 per cent increase in average power from 121 to 146W would have led to a greater improvement in time than 2 seconds over a nearly 20 minute ride.

I find my ride times on any specific route excluding long climbs varies much more on drafting opportunities than on which bike/wheel combo I’m using. The larger the group you are riding with, the faster your times will be at any given power output, and this dynamic plays a much larger role than equipment choice. My guess is that if you repeated the same flat route with a time trial bike to eliminate any drafting effect, once with the Enve wheels at 121w and once with the Zipp 808 wheels at 146w, you would see a much larger difference. Cheers.