Red Line Auto Sports

I just went there because I thought I had a nail/hole in my tire or something because it went flat last night. I went there with the doughnut on. They took the doughnut off, checked the regular tire, but couldn't seem to find a hole to patch. So they refilled the tire, put it back on and told me to periodically check the pressure over the next few hours. It seemed to still be dropping, and I heard a faint noise from the valve. I took it back and asked them to check the valve. Surely it was the valve, and they replaced the screw thing inside the valve to fix the problem. The people I dealt with were really nice, and at the end I asked them how much I owed them...and they said nothing!