Archive for November 24th, 2018
Michelin ProTek Max Tube: Autopsy
Posted by Ed in Machine Shop, Recumbent Bicycling on 2018-11-24
The Michelin ProTek Max tube I installed two years ago developed a slow leak this year, which I eventually ascribed to the valve stem, because the sealant should plug any other leak.
Cutting it open reveals the perfectly good greenish-yellow sealant:
Michelin ProTek tube – sealant
The sealant also carries black rubbery grit / shavings / dust, perhaps intended to jam inside larger gashes while the sealant coagulates and binds it together.
There’s a lot of rubber floating around in there:
Michelin ProTek tube – rubber fragments
Dismantling the Presta valve stem show the rubbery crud on and around the valve seal and seat:
Michelin ProTek tube – fouled valve seal
Whenever I pumped up the tires, I finger-tightened the nut to ensure a good seal, as you do with all Presta valves. Obviously, finger-tight can’t handle that much crud between the sealing surfaces.
I’m sorry to say I was right about the leaky valve stem, because I think all the ProTek tubes will fail in exactly the same way.
The valve has small wrench flats making it easy to remove, so I can at least attempt to de-gunk them when they develop slow leaks.
Color me unimpressed.
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