UPDATE I ended up removing the spare and got a lighter mattress. I had an incident at the junction of I-40 W and I-75 N where the road was rough, and my MH literally bounced. It almost bounced off the road. I decided to lower the tire pressure to 55 all the way around. This has cured all my handling issues. I have added a TPMS with temperature gauge. The tire temperature is in the 90s.
65 psi is the lowest pressure on the tire chart, but as I state earlier in the thread, my weight is way under the 65 psi chart weight.
My hypothesis is that Winnebago made a decision to standardize tires and wheels on the entire Sightseer line and due to liability issues could not specify a pressure lower than the lowest pressure on the chart. I have the smallest Sightseer. If you extrapolate an additional 10 psi load increase downward, I still have a margin of safety. I will need to keep tabs on my weight. I think removing the spare and getting a lighter mattress (I also removed several heavy items) helped put more weight on the front. That also improved the handling. I just wish it hadn't taken me 7 years to figure it out.
