I never had this problem with my Chevrolet R3500 until now. I didn't have to pay attention to the steering of the vehicle before, but now, I see myself always adjusting or turning the steering wheel just to make sure that the vehicle will go at the right direction. My Chevy seems to wander. This problem becomes even worse when I drive at high speeds. Any hint on what could possibly be the problem here and how I could fix this?
This problem may seem manageable, but if you let this go on, over time, it can only get worse. Steering can become unpredictable and unstable. You have to consider a number of factors leading to this issue. For instance, this may happen when the vehicle is overloaded. The added weight or load excess is causing trouble with steering. Find out if the weight is distributed evenly. You'll also have to inspect the wheels. The front wheel bearings may already need adjustments or they may already be broken and need replacement. Make sure that the wheels are aligned properly. Also check if the springs are already brittle or worn out or if any component of the steering linkage needs to be tightened or fixed.
Is it still safe to re-inflate a tire that's been severely underinflated and run on? What causes progressive air loss?
It won't be highly advised to re-inflate a tire or tires that have been run on. It's risky. When tires lose air progressively, this can be due to punctures and cuts. Curbing and other impacts can also lead to severe under inflation. Another thing to consider here is partial bead unseating. Make sure that the beat seating is complete. The bead may be torn by a machine all because of improper adjustment and lack of lubrication. Leaky valve cores and other valve components can cause air loss as well. Check these components and have them replaced as needed. Do this every time the tires are replaced or when you notice a drop in air pressure.
How will I know if the tires can still be repaired or if they should be replaced already? What are the guidelines? What are the things I should do in case the tire loses air pressure or becomes flat?
You can't simply tell through a glance if the tires are up for replacement or can still be salvaged through repair. When the tire loses air pressure significantly, it would be best to remove them for inspection so that you can look at the inner portions. Don't drive on a flat tire even for just a short distance or trip. This will only increase the wear. Instead, have the tire changed or fixed right away. If the tire is punctured due to impact, nails, or other things, they can be repaired as long as the cut or damage is just up to 1/4 in. This can be sealed through a patch. Tires can be repaired if the damage is on the tread only. Don't push for repair if the sidewall or tread damage or puncture is over 1/4 in. in size or over 0.64 cm. It won't be safe and practical. Also, tires that have worn down below 1/16 in. or 0.16 cm. couldn't be salvaged anymore and should already be replaced.