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Nitrimethane is not classified as an explosive.

FWIW, I am a physical chemist -- and I fear that you are under-informed: As you, yourself, noted in your final statement, nitromethane (properly catalyzed and/or highly shocked) is capable of detonation. In other workds, it is a high explosive.

For your enlightenment, I offer the following on-line technical papers as references:

http://www.cyberhost3.com/nitronic/research8/shelly.html

A great part of the considerable interest devoted to nitromethane, the simplest explosive nitro compound, is related to the understanding of the chemical mechanism of initiation of detonation. Experimental observations show that a careful study of the methyl group, in particular that of the highly excited [[nu]](CH) vibrational states, could bring some information to elucidate the initial chemical mechanism of decomposition, including the means by which intramolecular energy transfer processes can occur. Actually, one interesting peculiarity of the methyl group in nitromethane is the low value of the potential barrier to internal rotation, which is essentially free at normal temperature. Its coupling with the other vibrations, especially with the CH stretching modes, could affect the vibrational energy redistribution and thus the nitromethane reactivity.

and...

http://www.aps.org/BAPSSHOCK97/abs/S1700.html#SG1.005

Session G1 - Nitromethane.
MIXED session, Tuesday morning, July 29 CCA,

[G1.01] Mechanism of Chemical Decomposition in a Shocked Condensed Explosive

Based on these P-T Hugoniot data, we construct the detonation diagram of nitromethane, which consists of no-detonation, super-detonation, normal-detonation zones. In the super-detonation zone between 12 and 19 GPa, the shock-compressed nitromethane detonates with a significant induction time; whereas, the detonation occurs nearly instaneously in the normal-detonation zone above 19 GPa.

I should have checked those reference URLs before posting them. It looks like one of them has even been preempted by one of those nefarious "domain grabbers" who re-route traffic to undesirable locations.

Those papers were, indeed online when I used them as references a couple of years ago (while doing research on the compositon of the OKC truck bomb). However, like many things in this new medium, they obviously had a limited lifetime. (Webserver filespace is obviously considered to be more valuable and recyclable than printed journals...)

If you are truly interested in pursuing the nitromethane issue, FReepmail me, and I will dig out some current articles for you. Again, apologies for cutting-and-pasting old references without checking...

TXnMA,
I probably should have been a bit more specific in my statement. Pure nitromethane is shock sensitive, but not very. However, nitromethane as sold for racing fuel is diluted with a small amount of acetone (and maybe some other substances) and has a yellow indicator. The indicator turns purple (I think, never had this happen) in the presence of alkili. It is then considered shock sensitive and dangerous to use. I have seen cans banged and cars crashed rupturing the tank with out the nitro exploding.