I watched a video on this on GCN last night. Alex tested some really low grade tires and some Pirelli race tires, each with butyl, latex, or TPU tubes. With the crappy tires, the latex tubes made a 15w difference in rolling resistance, with TPU being a little less. But with the Pirellis the difference was only 6w. Lesson learned - don't buy crappy tires!!
I'm considering getting latex tubes for my 2 best bikes, where I'm running GP5000s, just as an experiment.
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