Never wanting anything on my back, I started with a rear rack and panniers. Hard to imagine anything else would have enough capacity considering everything I carry..... change of clothes, towel, lunch, rain pant and jacket, gloves, hat, light weight fleece top, tights, headband, and helmet cover. Of course, the extra items are based on current weather, not summer. The extra tube, patch kit, tools etc. are in a seat bag.