Short answer: No. Please don't.
There are a few reasons why we do not recommend wearing underwear inside while cycling.
1) Chafing. or rather abrasion.
When you cycle, your body (in this aspect, your lower body) will move hence the seams of your underwear will cause abrasion. You will leave your ride with rash marks and contribute to even painful saddle sores!
2) The tights are designed to fit perfectly for you. Not too tight. Not too loose. This is to ensure the chamois/padding fit nicely to you and your bum. The padding should not move around when you ride. Hence, if you wear underwear, it will be a more tighter fit, making you feel more uncomfortable while riding.
3) The chamois/padding is designed to absorb sweat and helps create airflow in the tights so it becomes more cooling when you ride. Wearing underwear inside will reduce this effect.
Having said this, some of us are still very cautious or not used to going 'commando' yet, you can try wearing underwear first, but wear those seamless type ones. but then as you get more comfortable, you can try not wearing one!
It takes a bit of time to get used to it. No worries! We will be there to 'jia you' you!
