I'm talking high altitude of course. After seeing some of biker395's jawdroppingly spectacular photos of the Eastern Sierra. I signed up for the High Sierra Fall Century in September. I'll be traveling up from the sea level of the Bay Area on Friday, and doing the ride on Saturday. How much will the altitude impact the riding, and in what way? I saw a post from Dudelsack (and who wouldn't trust someone named Dudelsack) mentioning that altitude effects diminish with age. So, do I need to throw out the CO2 and Pack O2 instead or not?