Michelin make the heavy duty MFR/MGR tubes from a flexible butyl rubber compound. These tube are overlapped spliced together which is stronger than the more conventional butt splice process. They are a bit lighter than the V Rubber heavy duty tubes eg 110/90-19 rear weights 915 grams, the V Rubber weighs in at 1250 grams. Note Michelin dont know how to sell reinforced.
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