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i know the stock firestones are sheit, but they cant hold air for anything. i dont know if its the cold weather up here or the way im driving, but i have to put air in the tires once every 2 weeks or so. i will them to about 40 psi, i think the mark on the tire says no more than 44. when i get my oil changed they only fill them to 35, but i like the ride better at 40. yesterday when i filled them 3 of them were at 31 and one of them was at 20. i just cant wait til the summer when i can put my other rims back on, i didnt have this problem with those tires. anyone else have this problem?

 
Rep Power: 0

Sounds like you have a leak, you can put soap water in the tire valve to see if it is leaking. Check for nails ... etc

Few things to consider:
1. Street passenger tire pressure are rated at cold tire temperature (i.e. been rest for at least 5 hrs or been ran for less than 2km) Only race tire (r-compund) pressure are measured when hot. It is the common practice.
2. Having said above, every 10C drop will net you 1psi drop (PV=nRT). Watch weather.
3. It is normal to lose 1psi every month.