I carry one spare tube and a patch kit, that way I can just use the tube if needed, but if I have two flats I can patch a tube if needed.
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Bentbaggerlen
"When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." - Arthur Conan Doyle