What Size Melbourne? What's its Wheelbase? Have you Weighed it? And as noted, Which Chassis?
It seems that many C's, even on Ford E450 are front-light/rear-heavy. If you have weighed it, get a tire weight/load chart. Doesn't have to be your Brand, but you need to match Tire Size, Load Range, and Axle Position (Single and Dual have different ratings). If it's an E450 (and E350 too, I believe) Front Tires should be at no more than 65PSI. That's 65 (works out to max load on front axle) or Less, given that most C's are front-light. That's 65 or less, even though tire sidewall for Load Range E is 80. On a fully loaded E450 REAR axle, the Dual part of the chart comes out to 80, the sidewall pressure. Having no more pressure than required by load will ease the ride a little. Having correct FRONT pressure will also help tracking.
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If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB