Just got my bike back from the shop, I had a new rear tire put on. How long should it take to brake in? how long till it is not so slippery?

 

you can look at it and tell, the whole point of taking it easy is that the release compound on the tire (you know the crap that makes it look shiny) is slippery and needs to be scrubbed off. Technically you can get some sandpaper and scrup it off (fine grit of course). anyway you can look at the tire and see the where there is still release compound and where its been scrubbed off. Actual mileage depends completely on your riding, a tire can be completely scrubbed in within one lap at barber (2.3 miles) but if you don't lean much it can take a lot longer on the street. just take it easy until the tire doesn't look so shiny

 

+1 you'll be able to tell. Know alot of people that scrub it with sandpaper. I always just rode carefully for the first few good turns.

 

take it easy for the first 100 miles
and try to break in the sides too