bm0p700f wrote: ↑
Thu Feb 14, 2019 10:01 pm
They work by essentially creating two chambers in the tyre. The air chamber at low pressure has a low spring rate and the insert has a higher spring rate. The way spring constants add in series means the air chamber dominates just keeping more of the tyre in contact with the ground. The volume of the insert though stops the tyre bottoming out and burping.
There are inserts that are separate air chambers, but these are foam. They decrease the volume of the tire but protect the rim (and the tire from the rim) as a tradeoff.
They will keep the tire on the rim and keep it from going completely flat, which is crucial in XCO racing because they just have to get to where there's a fresh wheel and tire waiting. But just because "pros do it," it doesn't automatically mean it transfers over for the reasons people wish it would, sometimes it's not for ultimate speed, it's as a fail safe measure that only applies to them.
Unless they literally take up the entire space of an inflated tire and are pretty rigid on their own (and heavy), they are going to allow the tire to squirm, a lot, if pushed in a corner at lower pressures. There's just no other way about it.
This is a full on 330g mousse for gravity racing, meaning pressure is higher because bashing through rocks is part of the game, and they're just able to drop down to normal xc tire pressure. https://www.pinkbike.com/news/mr-wolf-b ... -ride.html
If you cut a tire, it still only allows the bike to be limped home, despite the size and weight.
Is that smaller 107g noodle going to do that? Those (XCO) guys aren't getting flats from thorns, they're cutting tires and sealant won't save them, so they're going with something that allows them to minimize their losses.