kosmo886

I've noticed that my avg. speed on rides is down by anywhere from .5-1mph in the fall/spring vs. summer. I don't think this is a conditioning thing, but rather more likely a result of cooler air, which I think is denser and certainly wearing a somewhat loose fitting wind breaker...my guess is this is the biggest factor. Anyways, just curious if anyone has done more scientific tests on the topic (I am sure someone has)

RChung

One of the first field tests I did (after convincing myself that I had a relatively sensitive method and protocol worked out) was on clothing. Clothing can have a big effect, depending.

Actually, when I was first working out protocols, I did a couple of tests on a relatively cool day so I was wearing a Pearl Izumi cycling jacket, tight through the body but the sleeves were a little loose. My CdA was high but believably high, and it was cool, so I never tested without the jacket. A few months later, I was testing during the summer and it warm, so I lowered the zipper on my jersey. Then I had an idea and zipped it up all the way. When I analyzed the data I realized I could spot exactly when I raised the zipper. So I went back out the next day and repeated the field test, with jersey zipper fully up and partially down. The difference, if I recall, was almost .01 m^2 in CdA. Later, I figured out that it wasn't that my jersey was a parachute when the zipper was open, it was that it bunched up and got looser around my shoulders and neck, and when the zipper was up the shoulders smoothed out and there weren't any wrinkles around the neck.

So I decided to check out my cycling jacket again, and was appalled at how much drag it added. Those sleeves were like parachutes. So now I almost always keep my jersey zipper up, and I hardly ever wear a jacket except on bitterly cold winter days. The rest of the time, if possible, I wear two jerseys and two sets of arm warmers.

We discussed this briefly, at around the 42:25 mark here: https://cyclingtips.com/2019/07/nerd...s-made-simple/

If you want to know about a specific article of clothing and you have a power meter, you can do these tests pretty simply by yourself. If you don't have a power meter, it's a little more hassle but it's still possible. Ask if you're interested.

Kimmo

Clothing makes a huge difference - see how you go in street clothes; you barely make into the big ring if you're rocking 39/53.

rivers

Cooler air, as well as flappy clothing will make a difference. I did 2 x 10 mile TTs a week apart on the same course earlier this month. Wind conditions were the same. Temperature was about 8-10 degrees Celsius different. The colder week, I was 28 seconds slower for the same power output. Everyone who raced both weeks also had times between 25-35 seconds slower.

ls01

Colder air = higher air density. Now factor in the floppy clothes ( not really a hard fast factor. You can buy proper riding clothes that fit correctly and font flop.) With the thicker air.

popeye

Shaving is good for up to 10 watts.

RChung

Depends on how you rank on the Chewbacca scale but, yeah, it can be significant. Legs mostly, because they're cylinders that are moving around and around. The head is pretty static, so shaving your face appears not to have the same benefit as shaving your legs. i suspect, but don't know because I haven't tested this, that forearms are less important than upper arm so if you've got an arm fur issue, you should either shave or avoid sleeveless jerseys. Actually, speaking of arm and leg fur, let's keep this review for Veet in mind: https://www.amazon.com/gp/customer-r...R2QP56S5P2DEGA

Riveting

Extra clothing (even if non-flappy) will cause you to be slower because the body isn't dissipating heat as well with the extra layers on.

tomato coupe

I'll never be able to eat Brussel sprouts without laughing.

Jack Tone 

Best review ever.

RChung

Sometimes, but not always. I standardize for power output, so even if power output changes, I can measure the separate effect of clothing. But in other testing, it's clear that a full-sleeve skinsuit is lower drag and can be faster than, say, a sleeveless skinsuit. Likewise, properly designed socks can be faster than bare legs -- that's why the UCI is limiting sock height.

It's sort of like swimming -- it used to be thought that Olympic swim suits should be as minimally skimpy as possible (whence the brand name "Speedo") but it's now realized that well-designed higher coverage swim suits are faster. The same applies to cycling. So no riding in your thong, especially if you've got body fur. No one needs to see that. Unless they're into Furries. Not that there's anything wrong with that, but keep it to yourself.

That said, I have never been able to produce the same watts when my knees are covered. So on those occasions when I'm trying for speed (less and less common as the days pass) I never wear leggings, or even knee warmers.

hubcyclist

Since there's no racing and I want to wear nice kit sometimes, I've been doing some of my training rides in my long sleeve CX skinsuit (so no food and I throw my phone in the saddle bag since the kit has no pockets) and wearing a lazer bullet aero helmet. Seems that at around 260ish watts I'm around 21.5mph on flattish terrain I've ridden on in southern MA and the Cape recently. Normally I try to focus more on watts than speed but I'm getting awfully competitive on some segments, even with my bottom of the range Allez. The next step in low hanging fruit would be leg shaving (I've done it before but never really kept it up), and I'm certainly pretty high on the chewbacca scale so hoping the helps. And oddly enough I just realized today that my handlebars are 42cm, so I am thinking of going down to 40cm, any idea how much that would help? I've used 38cm in the past comfortably, but I'm kind of thinking of splitting the middle because I've got a good fit going and don't want to muck it up too much

RChung

It depends on how wide your shoulders are and where your elbows end up -- if your elbows stick out when your bars are too narrow, you could end up with worse drag. However, if that's not your problem, narrow bars are usually an aero drag win. Some riders who go to narrow bars and end up with flared elbows find they can salvage their position either with a slightly longer stem or slightly lower bars (either by removing a spacer or else changing the stem angle slightly).

colnago62

I ride 44cm Bontrager bars on the road and 38cm bars on the track the combination of narrow bars and less reach required me to add a longer stem on my track bike even though the reach is slightly longer on my track bike. It allows me to keep myself long and elbows more in front of me

canklecat

Yup, clothing fit matters.

RChung

That video gave enough information to make me wonder about the quality of measurement at that tunnel.

Tony P.

Climate has an effect on body temperature and body temperature has an effect on endurance. Of course, higher environmental temps. result in higher body temps. Significant studies have shown (not surprisingly) that increased body temp. reduces endurance. Beyond that, increased body temp. impacts the shift between aerobic and anaerobic breathing. So, in theory, riders should have more endurance in colder temps. However, adding layers negates the advantage gained from lower temps. Thus, adding clothing creates three negative impacts: weight and drag (mentioned in earlier posts) plus body heat.

RChung

Not necessarily. For endurance efforts, our metabolic efficiency is mostly constant (it appears possible that we can change it, slowly, over time, but not for any single ride). So at any work rate, we have to dump a lot of heat no matter what. But we can get rid of that excess heat either convectively or evaporatively. So it's not just temperature, it's heat flux. Plus, of course, as noted above, air density decreases with high temperature.

I've worked with a couple of record attempts where the rider could choose when to go, and we spent some time forecasting temperature, humidity, and air density to figure out what might be best. It's rarely as simple as "the cooler the better" or "the warmer the better."

Tony P.

I'm sorry for not being more specific. I didn't mean to suggest any change in temperature will always impact endurance irrespective of the individual. And it's clear that training mitigates the impact of climate. However, there have been numerous studies over a period of, perhaps, 20 years showing that body temperature impacts endurance and environmental conditions impact body temperature.

Here's one peer reviews study: Impact of Environmental Parameters on Marathon Running Performance,
Here's an analysis I believe is from that study that demonstrates the result:

RChung

Yes, I'm aware of that body of literature. The key is that there is an optimal range of temperature, and performance decreases when it's either too hot or too cold.

I looked at performance times for Ironman triathlons and, perhaps interestingly, the optimal conditions for the running leg appear different to the optimal conditions for the swimming and cycling legs. You can see that faster runs occur under slightly cooler conditions than faster swims and faster rides. That's why convective and evaporative cooling are important--water is a better heat conductor than air, and when riding you're typically going faster than when running so convection can be higher.

eduskator

Have you considered the wind in your equation? Spring and Fall are definitively the worst seasons for this.

Tight clothes helps being more aerodynamic for sure. In terms of air density, cold air is denser so it can explain why you move slower.

tomato coupe

I thought that was the whole point of waxing your ... chain.

terrymorse 

About cooler air being slower.

I just ran some numbers through bikecalculator.com:

Power: 150 watts, Temperature: 77 F, Speed: 19.11 mph

Power: 150 watts, Temperature: 55 F, Speed: 18.87 mph

Speed reduction: 1.3%