You should have a marking on the wheel to tell you the size somewhere. My need to take the tire off though. Also, if your traveling 35 next to your laptop, get out of your car man
, but I would pull the battery and let it reset it self or maybe try a new battery. I had to replace the batteries in my brand new Garmin when I got it last year. If that does not work I would take it back the shop. I have a 8i on my wife's bike and it has been flawless, but you might have just gotten a dud.