[300SLR]

Loctite isn't necessary (although it can be used as belt and braces if you really want to).

Some common causes of grub screws not being done up correctly are
Rounded off corners on the hex driver. Ordinary L shape allen keys are quite soft and wear out quite quickly in slot car use. A hardened hex driver is better, but even these will need a new tip after several years regular use.
Rounded off hex in the screw. Most commonly the screws are damaged by using a hex driver with rounded corners. The only solution is a replacement grub screw.
Debris in the bottom of the socket in the screw. The debris can be removed with a pin, thus allowing the hex driver to engage fully in the socket.

If you tighten the grub screw firmly with a hardened hex driver, having avoided the above list of problems, you'll have no trouble with wheels coming off.

QUOTE (stoner @ 23 Dec 2011, 10:26) <{POST_SNAPBACK}>as above low strengh thread lock and you could grind a small flat on each end of the axle ditto for the middle if you dont want the gear to move,you could grind the flats 120* apart but in all honesty it doesn,t really matter because the mass is so close to the centre you dont get unwanted vibration, john.
Unless you balance your wheels, that's not worth bothering about.
For high end racing it is normal practice to balance wheels, it does make a differance at the speed those cars are going. Lower down the performance spectrum hardly anybody balances wheels, it makes little differance at the much lower axle revs.
When balancing wheels, an allowance needs to be made for the grub screw being screwed further in on the flat.

 

[300SLR]

QUOTE (jonnynobber @ 25 Dec 2011, 10:36) <{POST_SNAPBACK}>I must be lucky, I,ve never had one come loose.

Negligible chance anybody can be that lucky all the time.
You must be doing something right.
Maybe you are tighten them up properly?
(It really isn't as difficult as some contributors seem to think!)

QUOTE (Screwneck @ 25 Dec 2011, 05:39) <{POST_SNAPBACK}>2mm screws undo because the thread is stripped, or you've stripped your grubscrew or allen key. These are sdaly too easy to do if you overtighten in fear of losing a wheel. All you need to do is:
Cannot say I've ever stripped a 2mm thread myself, but they are fairly delicate (particularly in ally).
If you do strip one, it's easy enough to repair by tapping out the hole to the next convenient thread size.
A convenient size for a lot of racers is 4/40 (that is the international standard size for grub screws in high performance slot cars - even in countries that otherwise use metric - so lots of racers already carry the hex wrench and a few spare grub screws that size).
M3 is slightly larger than 4/40.