*sigh* why do people keep recommending this? In many parts of the country this is simply not possible. I rode (slowly) on my heavy utility bike yesterday evening to the auto parts store and back, barely 4 miles round trip and I was absolutely DRENCHED when I got home.

I bathe every week, whether I need it or not. :)

Sounds like heavy utility bike is your issue.

Heavy utility bikes aren't a problem unless climbing steep hills. Leaning forward and not allowing for natural body cooling are the two primary causes of sweat. Most moderately fit people can ride an upright Dutch bike for several miles at 10-13 MPH and get no more sweaty than walking from their car to the building they work in. If the temp & dew point are not enough to cause you to sweat walking then they will not cause you to sweat riding upright at a moderate pace. In many cases riding upright will keep you cooler than walking. This is all assuming normal street/work clothes btw.

Helmets, and to some extent gloves, cause very considerable sweating as they keep your body from being able to cool itself properly. Your head is likely the number one heat radiator of your body and sticking a helmet on it prevents this just the same as covering the radiator on your car.

If you are doing a 25 mile training ride then go for the road bike, helmet, and all the other kit just as with any other sport or workout and plan to shower after. If you are riding for transportation then do so in a way that is much simpler, more comfortable, and does not produce excessive sweat.

Some people sweat at different rates than others, your bike has very little to do with it, your weather would definitely cause an issue too. If you are sweating a lot simply take some baby wipes with you and then wipe yourself down real well in the restroom at work and apply underarm deodorant, unless you sweat too while at work than apply a antiperspirant instead of deodorant so as not to get those wet stains on your shirts; but if you don't sweat while working use a deodorant instead because.

for the guys (and women I suppose) -- keeping the armpits trimmed (via any ole trimmer; I do a #2 length as part of overall general manscaping routine) helps keep the stank down.

To answer the question directly, personally, I prefer a shower after 10km. I sweat easily and muchly. Do I NEED it? Probably not, but it feels better to do it than change into work clothes all sweaty.

I commute 5 miles one way and I no longer "Race my bike" but instead "Ride my bike". On my commute to work I am showered that morning and take my ride slow even while sipping on coffee. Even on hot days I can make it to work with maybe a little sweat on my forehead, but not my entire body. I wear light, hi-wicking clothing on my commute then change into my uniform when I get there.

After work, I change back into my riding clothes and head home. I have to shower after work anyway so I get get as sweaty as I want ;)