How much faster are shaved legs for cycling? Should you shave your arms too?

Froze is correct - all these ways & means of "saving watts" for racing folk amount to cheating, for the same reason that using an electric motor is cheating: technology gives you a watt-advantage over your racing rivals, which they don't have. If cycle racing is to be a true sport (measuring the relative abilities of the riders rather than the tech of their bikes and clothing) then the racers should all have exactly the same bike and clothing with the only difference being the size and fit to suit the size and body configurations of the racers.

But "sport" is now really a circus for advertising gew-gaws, innit? 

For we non-racer cyclists, all means to save energy may be used without anyone cheating anyone else, since there's no competition. But this begs the question: when cycling, why do you want to "save" watts? Asked another way: why do you want to always go faster for the same power output?

Personally I like the feel of a bicycle that's efficient, comfortable and safe to ride (not too twitchy, too heavy for the brakes, etc.). I also want to be able to go anywhere on it, including steep hills on rough roads in the wet, etc.. I want it to be easily fixable and maintainable.

But I don't necessarily always want to go faster. I just want to enjoy the ride and not have it shortened by devoting a large percentage of my power output to heating up the bike or otherwise squandering energy rather than using it for going forwards. But it has to remain comfortable, affordable, fixable et al which might mean I won't have to care if it isn't as aero as possible or complete with exotic carbon wheelset costing twice the price of the rest of the bike.

Also, I don't want to have to contort and disfigure my body just to be a faster cyclist. Those hairs grow on your body for a good reason. Just ask Mr Darwin!

Sorry, but I having troubles believing all this saving watts stuff if you do this and buy that.  I once figured it up calculating total watts saved if you buy all the gear, the bicycle, clothes, set in a particular position, etc and according to these companies watts claims a person could save about 100 watts...of course where they get you, especially on products, is that they say up to X number of watts, but I digress.

100 is a huge number, which means saving that kind of wattage would definitely be a noticeable improvement, this is about the same sort of wattage that the Vivax Assist hidden motor did for female pro racer Van de Driessche who won the race but lost due to the motor being discovered, and Froome was suspected of doing so the way he attacked and passed riders climbing like they were standing still up a steep grade.  100 watts is a huge deal, but there is a problem.

Since 1958 till now, the average speed of the TDF has only gone up about 3 1/2 mph, but the "biggest" change in speed came in 1985 with the introduction of the clipless pedals and since then the average speed has only gone up about 1 1/2 mph, a far less increase than 100 watts of saving would have seen. 

But the story doesn't end there for in 158 the total distance of the TDF was 2,648 mile, in 1985 that figure drops a little to 2,553, not a big deal there, but in 2023 the miles raced was 2,115, and since 2018 the average miles raced was 2,107, modern races are running at least 400 miles less than they did just 35 years ago.  Why did I bring up the mileage raced?  Because the 1.5 mph gains we're seeing since 1985 is a direct result of the racers not being as tired because they are racing less miles, it has nothing at all to do with watts gained by technology.  This is all marketing hype to get us to buy stuff, of course shaving there isn't anything to buy, but the point is the watts thing is nowhere near as big of a deal as marketing forces want you to believe...either that, or man is getting weaker over time, especially considering that in 1923 the TDF was on mostly gravel with some cobblestones, and those monsters raced like that for 3,570 miles!  Even going back to the first mostly paved race in 1948 the riders road 3,058 miles.  Since 1995 the average speed has been virtually flatlined, with some up and down times per year, the biggest spike was from doping, and of course grades climbed will alter that to some degree, but we're seeing 20 years of nothing happening to warrant saying technology is working.

So all the mph gains we have seen have been from clipless pedals, doping, and from less miles raced.

The unbearded have an obvious aerodynamic advantage. I expect to see more clean shaven roadies in the future and all those inefficient beardies will be left in the past where they belong!

Just the legs, you say?

If I can't break the 25 minute barrier on my club 10 next year I may have to resort to this...

I fear that, at the speeds I ride, wind in my unshaven legs is more of an assistance than a hindrance. Even in a headwind, I benefit from the some ricochet effect of the wind on its way back again.

I started racing and shaving when I was 12 and did that for 15 years. I got laughed at as a teenager a lot for that but non-cyclist know $h!t about life anyway so I never cared. 33 years on I only shave (my legs) for holidays and events but it feels kind of liberating every time as hairy legs still look and feel awful to me.

After a bit of a stack a few month's back I'm convinced a hairless leg faired better for convalescence... 🤷

You believe that you believe anything.

My wife has been clear for years that if I start shaving my legs our marriage is over. So they stay hairy...for now.