Head injuries are the leading cause of mortality in cycling. Helmet technology and safety has really improved over the years, and there a few helmets on the market that are specially designed to protect both your head and brain. A properly fitted helmet is most certainly the preferred option, but if you can get him to wear yours until he buys his own, go for it! Today’s options for helmets look better, are lighter, and more cost-effective than ever before. Tell your friend to use his head and protect his head! Also, I recommend wearing sunglasses or protective eyewear while biking.