Michelin ProTek Max Tube: Autopsy

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

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

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

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.


  1. #1 by scruss2 on 2018-11-24 - 20:09

    Those rubber fragments look like they’ve worn/corroded from the inside of the tube rather than been included in the sealant. Was the inside of the tube pitted?

    • #2 by Ed on 2018-11-24 - 20:14

      Nope, it was in fine shape all around the outside and in the sections I dissected. The lower picture shows the inside surface of the tube: it’s not shiny-smooth like the outside, but it’s not chewed up, either.

      Definitely a puzzlement. The other tubes seem OK so far and I hope I just got a manufacturing defect … but how would they get that much crud inside a tube?

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