We were fortunate to have uphill headwinds on the downhill side of the Tien Shen mountains in Western China, or it could have been a problem. Our loaded tandem, including us, weighs around 400 pounds. That weight puts such pressure on standard brakes and brake pads that we risk an exploded tire from overheated rims, not a good thing at speed down a steep mountain.
When the nearest bicycle shop is hundreds, even thousands of miles away, we have to be prepared to fix most problems. I carry up to a kilo of tools and spare parts to fix most of the mechanical failures we might encounter after travel on bad roads, and dirt tracks.