Fleetwood Excursion Tire Upgrade Guide: 255 to 275 Width Conversion

Bottom Line Up Front

For your 2015 Fleetwood Excursion M-35B, I recommend sticking with the stock 255/70R22.5 tire size rather than upsizing to 275/70R 22.5. Your motorhome was specifically engineered for the 255 width tires, and changing to 275s could create clearance issues, affect handling, and potentially void warranties. The stock size provides the correct load rating and performance characteristics for your 35-foot Class A motorhome. Focus on getting high-quality tires in the original size rather than going wider - you'll get better performance and avoid potential problems.

Root Causes

Many new RV owners assume that wider tires automatically mean better performance, but motorhomes are different from passenger vehicles. Your Excursion M-35B has specific wheel wells, suspension geometry, and weight distribution designed around the 255/70R22.5 specification. The "255" indicates a 255mm width, while "70" is the aspect ratio (sidewall height as a percentage of width), and "22.5" is the wheel diameter in inches.

Upsizing to 275/70R 22.5 adds 20mm (about 25/32 inch) of total width to each tire. While this might seem minor, it can cause rubbing against wheel wells during turns, especially when the suspension compresses over bumps. Additionally, wider tires create more rolling resistance, which reduces fuel economy - a significant concern with a large motorhome like yours.

The load index and speed rating on your current tire sidewall are calibrated for your RV's gross vehicle weight rating (GVWR). Changing tire sizes without consulting load tables could result in inadequate load capacity, even if the tires physically fit.

Before You Start

Before purchasing any tires, check your current tire's sidewall for the complete specification including load index and speed rating (it will look something like 255/70R22.5 121/118N). Write down the DOT date code (4-digit week/year code on the tire sidewall) on your existing tires - if they're over 6-7 years old, replacement is definitely needed regardless of tread depth. RV tires age out from UV exposure and ozone damage even with minimal mileage.

Measure the clearance between your current tires and the wheel wells, both at full steering lock and with the suspension compressed. You'll need at least 2 inches of clearance on all sides to safely accommodate the wider 275 tires. Also check your owner's manual or the placard inside your driver's door for the recommended tire pressure - this is crucial for proper load carrying capacity.

Consider your actual needs versus wants. If you're experiencing handling issues, poor ride quality, or premature tire wear, the solution likely isn't wider tires but rather proper inflation pressure, wheel alignment, or suspension maintenance. Quality 255/70R22.5 tires from brands like Michelin, Bridgestone, or Continental will serve you much better than wider budget tires.

The Repair Process

Start by getting quotes for premium 255/70R22.5 tires from RV-specific tire dealers. Expect to pay $400-600 per tire for quality RV-rated tires like Michelin XRV or Bridgestone R250F. Many dealers offer mobile installation, which is convenient for large motorhomes. Always replace all tires at once on a motorhome to ensure even wear and handling characteristics.

When shopping, specify that you need tires rated for motorhome use, not truck tires. RV tires have stiffer sidewalls to handle sustained highway speeds with heavy loads. Look for tires with a load range G or H rating. The load index should match or exceed your original tires - typically around 121/118 for your size motorhome.

During installation, request that the technician inspect your wheels for cracks or corrosion, check valve stems (replace if over 5 years old), and properly balance each wheel. Have them set the pressure according to your RV's weight distribution - this often requires weighing your loaded motorhome at each wheel position to determine optimal pressures.

After installation, drive conservatively for the first 50 miles to allow the tires to seat properly. Check pressures weekly for the first month, then monthly thereafter. Keep a tire pressure monitoring system (TPMS) to alert you to pressure or temperature issues while driving.

Professional Help Needed

Contact a commercial tire dealer that specializes in RV tires rather than a regular auto shop. They'll have the proper equipment to handle 22.5-inch wheels and understand the specific requirements of motorhome applications. Many Camping World locations offer tire services, or search for "commercial tire dealer" in your area.

If you're determined to explore the 275 size option, have a qualified RV service center physically inspect your wheel wells and suspension to verify clearance. They should also confirm that your wheels can handle the wider tire and that your GVWR allows for the change. This inspection typically costs $100-150 but could save you from expensive damage later.

Consider having your motorhome weighed at a truck scale or RV rally to determine your actual loaded weight at each wheel position. This information is crucial for setting proper tire pressures and ensuring you're not exceeding load ratings. Many RV dealers and some tire shops offer this service for around $50-75.