You will pull out!
I am sure that these are grea for conventional MTB but i used these fixed and I would constantly pull out of these at starts on the lift motion. I do not like hitting my knees on my handle bars at all. I constantly would come out when i didn't want to. I changed to the Time Atac sx and tryed as hard as i could to duplicate this issue. I could not! Times are far better. Don't waist your money on the shimanos.