So i've recently run into a dilemma. After converting an old road bike to a fixed gear, i turned lazy and kept the same crankset and i feel that it might be too high. I'm running 52:18.

After riding for a while i found it really hard to lock up the back wheel and i think it's because of my high gear. I still have a 39t chain ring but i'm afraid i'll spin out too easily on a 39:18.
Any tips to help lock up with the high gear ?