I only descended about 236,000 feet but I never had the first problem with mine stopping me. They slowed me down from speeds approaching 60 mph on several occasions. I'm generally in the 170 - 175 pound range. However, right now I am 185 pounds, I rode with them yesterday down five pretty good downhills, never even gave them a second thought.
I'm using 07 0G's.
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I may be fat but I'm slow enough to make up for it.