i've always ran 40 in the front and never had a problem. good tread life and traction. i put my third front tire on at 25,000. it runs very straight and smooth
I had this a few weeks ago and it drove me nuts. Since it couldn't hurt anything I put the grease gun on the neck and started giving it a few squeezes. 15 squeezes of the handle before I noticed any movement at the lower seal. Once I cleaned it up I took it for a spin and no more shake. I watch that a bit closer now since I do my own service so either the last service I forgot to add grease or it has been squeezing out a bit more than I thought. I doubt that since there was no added grease on the front of the bike.