IMO, the key is a proper fitting mousse, and keeping it very well lubed (and only with the correct silicon lubricant). The issue is that as the tire flexes, and rubs against the mousse, it creates heat (see James' pic!). Lube lessens this effect, as does a correct fit.
With those conditions met, you can get a lot of trouble free mileage from a mousse. A few considerations:
- Michelin Mousses don't fit very well in non Michelin tires. The profile and internal size of a Michelin is quite different to others (Bridgestone/ Dunlop).
A solution to this is the new Mefo Mousse from MX1West
. They come in appropriate sizes for non Michelin tires and seem to have a nicer profile as well. I've also found them to be much more durable than even the latest M16 Michelin.
For DS use on the front, I'd get the 21-Big, that's what I'm running in Dakar. The rear will of course depend on the width of your rim as well as what tire you choose.
- As the mousse is used, it shrinks somewhat. There are a few solutions to deal with this.
First, you can go to a smaller profile tire. My favorite front, the Bridgestone M403, comes in both an 80 and 90 width. I prefer the 90, but order a few 80s so that I can get one last tire out of a mousse.
Second, you can wrap the mousse in an old tube- cut around the inside, set the mousse inside, and install. Lube everything, it's a bit of a mess, but you'll get another tire.
Finally, you can cut extra sections of an old mousse and just shove them in. So, instead of 21", you can put in 26" of mousse, if that makes sense. By the time the mousse is this shagged, you'll know how it should feel and be able to judge accordingly.
I ride them pretty much exclusively on my small bikes, it's great to be able to charge stuff without concern of a flat, they protect the rims much better than a tube since the air can't squish out of the way, and I can leave my tire tools at home. I've done a lot of exploring that includes both trail and 70-80mph dual sporting on them and have found them very reliable... but I lube them religiously and they are rarely installed in a single tire for longer than a few weeks.