[sfriesen5]

I bought a Pirelli MT 43 for my 250L to replace the stock rear tire. My local bike shop said I should have a rim lock if I plan on running around 8lbs of pressure. I have heard of others running this tire, but haven't heard mention if they use a rim lock. Thoughts?

[Aussiecrf230]

Why are you only running 8 psi? Did you mean 18 psi? What sort of terrain are you riding on? Lowest I have used was 15 psi in mud.
A rim lock is used so the tyre does not move around the rim as you accelerate or brake. If it did you will rip the valve stem out of the tube, especially when running lower pressures.
Does your bike rims have a hole drilled for the stud, usually opposite the valve stem hole. Depending on your pressures, terrain and riding style you can get away without a rim lock. You really need to dismount the tyre to drill it and deburr the hole. Hope this helps answers your questions.