Effectively rim-locks are there to stop the tyre spinning on the rim when running very low pressures. I run about 13psi in the GasGas, and that pressure isn't enough to stop the tyre from spinning. If the tyre spins it can rip the valve out of the tube.
However, the GasGas weighs about half as much as an XT. If you run pressures that low on a heavy bike you are running the risk of either getting a lot of pinch punctures or potentially denting your rims by completely flattening the tyre.
If you are running 25psi or more to avoid this, it should also prevent the tyre spinning.
That's Ricky's point, and personally I do the same, running 25-30psi. It's not entirely clear cut of course...
- Our resident Heroes and Legends have run XTs with mousses in, which I beleive are supposed to be equivalent to about 15psi, without (AFAIK) knackering rims. Of course those weren't OE Yamaha rims either.
- rim locks would allow you to limp a few miles on a puncture before stopping to change the tube. You would be limping to avoid damaging the rim, but might be useful in some circumstances.
Your choice
