06 keystone Raptor

The best answer will be based on measuring your RV:
1) How much clearance do you have between the existing top of the tire and the deck of the rv?
2) How much clearance do you have between the wheels?

We can go from there...
How much does your rig weigh?

we used to own a 2006 Keystone Raptor 3612DS that we purchased new. It came from the factory w/15" D rated tires. In 2007 or 2008 we put Maxxis E rated/10ply on...I think M8008. The neighbors own the toyhauler now and still have the original tires on it. It sits outside too. I'd recommend Maxxis for a 15" E rated tire.

If you want 16" you will need to upgrade your rims.

this topic should probably be moved to the toyhauler forum, since the OP is asking specific about a toyhauler.

Moved to Toy Hauler forum from 5th wheels.

Tire diameter is the figure you want to keep in mind. All MFR's list that on the tire specs on their website. ANd you can easily measure from the ground to the top of your tire to see what yours are today.

You will find that a ST225/75R15 has a smaller diameter than a ST225/75R16 most of the time. My trailer had the axles flipped and over 7" between the tires (wheel to wheel) so I was able to go up in diameter.

Good Luck.

I have an 07 Raptor 3612...i too went with the Maxxis 15' M8008 E rated tires. Definately a beefier tire than the stock Ds, more square shouldered, really happy with them. Just an option if you dont want to buy new wheels

I had an 08 changed to 16 inch rims and tires makes the gate about 3 inches higher but made a diff in towing and i felt allot safer with e rated tires

Have an 07 DS 3612,put xps ribs on it.Had to buy 16in rims for the 215/75r16.Weight is ok since rig axles are 5500lbs.No rub,no touch,no FLATS,in 6 years.Just replaced them last summer before trip to Texas,on 2nd set.Pull great!!!

When I had my Raptor I got 16" rims and ran LT225/75-16 Michelin XPS Ribs. Fit fine and no more worries.