KH XC rim: which tyre doesn’t blow off?
My post is not exactly a tyre review, but a set of questions I thought I’d ask where people are knowledgeable about 29" tyres.
I bought a new uni with a Kris Holm Cross Country rim (37 mm wide) in July 2011. To my order, it had the Schwalbe Marathon Supreme 28 x 2.0" on it. After about two months and probably less than 1000 km, the tyre blew off the rim with a loud BANG, on an otherwise totally uneventful stretch of straight flat road. I had pumped it that morning to 4.8 bar, so well within the rated pressure of 5 bar as printed on the sidewall.
Fast forward to July this year. I finally bought a new tyre (again a Schwalbe Marathon Supreme 28 x 2.0") since I wasn’t sure the old tyre was undamaged, and a tube, and mounted them. Within a month (in fact, during the 100 km race at Unicon 
) it blew off again! Again, I had pumped it that morning, to exactly 5.0 bar this time.
Today I mounted a Schwalbe Big Apple 28 x 2.0" on the same rim. The Big Apple is a non-foldable tyre whereas the Marathon Supreme is a folding tyre. I assumed (admittedly with no basis at all) that a non-folding tyre might be stronger. On the tyre sidewall the print says pressure MIN 2.5 bar, MAX 5.0 bar. Confusingly, in the instruction leaflet is a picture of the tyre’s sidewall that stated MIN 2.5 bar, MAX 6.0 bar! Next to it is a drawing of a rim without an inner holding protrusion (I don’t know the name, it is apparently intended to “hook” the bead under it). In that picture it says MAX 5 bar. As if the protrusion makes for a higher max pressure, which makes some sence. Maybe on the XC rim (which does have this protrusion) the max is 6 bar? By way of precaution, though, I pumped it to no more than 4.5 bar.
I should add that both types of tyre mounted very easily on the rim. The Big Apple mounted even easier than the Marathon Supreme. No force at all, it just “flopped” in place. I found that actually disturbing, in light of my experiences.
Questions:
- Does easy mounting of a tyre indicate that the tyre is more prone to blowing off the rim?
- Is the Kris Holm Cross Country rim known to be a bad combination somehow with the Schwalbe Marathon Supreme 2.0"?
- Can it be true, as someone suggested to me, that the 37 mm wide rim is actually too wide for a 2.0 tyre?
- Pressure recommendation for the Big Apple, in light of the above?
- Suppose this combo fails again. Being stuck with the rim, would it be better to mount a wider tyre? I have some experience with the Big Apple 28 x 2.35 and did not like the sideways rolling effect on slanting roads. Any other tyre suggestions for road use that are more stable on this rim, both in terms of sideways roll, and in terms of not blowing off?