The following information is posted for your general information. I am not an expert on tires (or anything else!), but tires, and safety, are my hot spots. So, please continue and read my advice.
If you go look and see what tires are on your Discovery, you will likely find that the are Michelin XRV. This tire is designed specifically for motorhome use, and contains ultraviolet sidewall protection. Unfortunately, your D (short for Discovery) does not carry a spare, and if you ever get stuck in the boonies and need a new tire, you may find it difficult to find another XRV. However, do not settle for anyhing other than an XRV. Sometimes, the dealer may try to sell you another line Michelin tire to get you back on the road. Oftentimes, this may be a tire such as the Michelin XZE. Don't settle for anything other than an XRV! As an example, the XZE is only rated for a max 65 mph (more on this later), contains no sidewall uv protection, and is 0.4" difference in diameter, which can cause you other problems.
I will bet that many motorhome owners are running their tire at the 100 psi maximum pressure that is stated on the tire sidewall. THIS IS MOST LIKELY A BIG MISTAKE! You really need to match your tire pressure to the load it is carrying! I travel full-time, and based on my actual weight, the front tires are inflated to 85 psi nd the rears are inflated to 80 psi. If I had 100 psi in each of the tires, they would be overinflated and would wear out prematurely.
If you have not weighed your motorhome, you really should have it weighed - and weigh each "corner" individually. If you have a significant imbalance from side to side on an axle, then you really should readjust your cargo to even out the load side-to-side on each axle. BE SURE TO WEIGH YOUR COACH LOADED AS YOU NORMALLY TRAVEL, WITH PASSENGERS ND FLUID CAPACITIES FULL.
For best handling of your coach, Freightliner advises that each axle be loaded to approx the same percentage of the gross axle weight rating. I have found that filling the water tank significantly improves the handling of my 98 36T, compared to travelling with it empty. Of course, my tire pressures are adjusted for this added weight.
You can weigh your D (and toad) at a variety of places. Oftentimes, highway weigh stations will leave their scales turned on when they are closed. Alternatively, you can try the scales at a truck stop, gravel pit or moving company. John Anderson's Aweigh-We-Go service attends many of the larger RV rallies and he will give you a custom report with a lot of information that is worth well beyond the $35 charge.
It is very important to regularly check your tire pressures, both on your motorhome and toad. You really should check the tire pressure BEFORE EVERY TRIP!. Be sure you check it before you travel one mile, and ideally, your tires will also not be in direct sunlight.
ALSO it is very important that you check your tires pressures at fuel and rest stops. Since the tires will have heated up and you will not get an accurate reading with a tire pressure gauge, you can either check it with a "tire thumper" or just by placing your hand on the tread of each tire and comparing the tread temperature with the other tire(s) on the same axle.
Finally, you should also be aware that the inside dual is the tire that takes the most abuse, due to crowned roads. Personaly, I always put about 3-5 more pounds of pressure in this tire because of the extra weight that it is usually subjected to.
I have known folks that claimed they routinely drove at high speeds. One guy, a former cop, tried to maintain 80 mph, pulling his Jeep Durango that did not have supplemental braking! Other than the usual reasons for not travelling this fast, your tires are not rated for these speeds. As your speed INCREASES, your tire's load-carrying capacity DECREASES. Go to the Michelin site if you want details. The maximum load-carrying capacity is usually at 55 mph for a truck tire. For me, 62 mph is plenty fast, and some states limit a motorhome to 55 mph. The Michelin Tire Guide, for the Discovery tire, says that cold tire pressure should be increased by 10 psi for sustained speeds between 60 and 70 mph. For speeds between 70 and 75 mph, the load carrying capacity is also derated by 10%. Note that our tires are only speed rated for 75 mph and are not safe for higher speeds! As speed increases, tire temperatures increase dramatically which causes blowouts.
Most tire blowouts are caused by improperly inflated/loaded tires, aging or ultraviolet effects, or damage caused to the tire from potholes, curbs, or road debris. Note that the effects of hitting potholes or curbs is cumulative. The tire cannot heal itself. If you are careful, you can minimize your chances of having a blowout. You also need to periodically check the sidewall of your tire for cracking, and refer to the manufacturer's guidelines to determine if you should replace your tire due to age. However, if you do have a blowout, do you know what to do? Most people would probably automatically either slam on the brakes or at least get off the accelerator. What you should do is actually FLOOR the accelerator! Now, this doesn't mean speed up drastically, just floor it long enough to help you regain control, then you can decide where it is safest to get off the road and pull over. John Anderson has a great video on blowouts. They actually took at 1997 D and purposely blew out 16 tires one day and took a movie of it. Granted, the driver knew that a blowout was coming, but it was amazing how he was able to maintain control. Let's pray that none of us ever have to experience this!
-Submitted by Bob Cook
The DISCOVERY OWNERS ASSOCIATION, INC, was formed to promote the sharing of information and the camraderie of fellow Discovery motorhome owners. Membership in the club is limited to owners of Fleetwood Discovery motorhomes.