YS_tirelabelUS

What you need to know about Class B RV tire pressure

YS_rubberdonutThe topic of Class B RV tire pressure comes up quite a bit. Tires all look like black rubber donuts, and we look at the tread, the advertising copy, and perhaps read some reviews and talk to friends when selecting a tire. Sometimes we let the tire guy tell us what we need.

As Class B owners, we need to go a little deeper. Our vans weigh in at about 5 tons, give or take. That’s a bit more than a ton per tire, and that translates to a lot of load on a black rubber donut. Not all rubber donuts are made the same, and not all rubber donuts are suitable for our Roadtreks.

The first stop when selecting the tire is the driver’s side door. Open the door, look at the pillar, and find the label that tells you the appropriate tire information. Don’t let anyone tell you that you need something different, or that you should use a lower tire pressure for a better ride. Remember all those Ford SUVs that rolled on the highway? That was due to low tire pressure.

YS_tirelabelUS

US tire label. There are separate lines for front, rear, and spare. Use these and never use less pressure than what is recommended.

YS_tirelableCA

Canadian tire label. Similar to the US label, except that it is in French as well as English.

Most of us on the heavy duty chasses will be looking for Load Range E tires.  Load range E tires are truck tires, they are not “extended range” passenger tires.  Those may be sometimes used on 1/2 ton chassis.  Roadtrek builds everything on either 3/4 ton or 1 ton chassis, and all of those need Load Range E tires.

Sometimes you may also see tires rated as a Load Index; the Load Index is a number with light duty tires having a load index in the 80s and heavier duty tires having a load index of over 100.  You can get yourself very confused by going between Load Index and Load Range; keep in mind that Load Index is typically used for passenger tires, and you need truck tires, so you need a tire with a Load Range E.

Some of the older Roadtreks used “Extended Range” passenger tires.  When in doubt, check the sticker on the driver’s side door.  If that’s not clear or the sticker is missing, you can usually find out by checking any of the tire websites, or with the chassis manuracturer, or Roadtrek.

http://www.tirerack.com is my favorite; you put in your model year and vehicle type and they provide the correct tire sizing.  Keep in mind when using these websites that your Roadtrek model is typically one model year newer than the chassis; my 2001 Chevy Roadtrek, for example, is built on a 2000 Chevy G35 chassis.

If bought your Roadtrek used, and you’re not sure of the tires, both US and Canadian law requires that every tire is imprinted with extensive information about the tire itself.  Once again, TireRack has a great explanation:

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=33

Sometimes you might hear people tell you that if you upgrade to a certain kind of tire, you can carry more load. Load carrying capacity is a function of tires, rims, brakes, bearings, axles, chasssis, frame, and ….. It’s determined by the manufacturer.  Nothing you can do as an owner will add to the load carrying capacity of your vehicle.

If you use heavier rated tires than you need, you will end up with less money in your pocket since they’re more expensive, a harsher ride due to the heavier duty construction of the tires, and quite possibly worse gas mileage. Go with the tires the manufacturer recommends, and stay within your load rating.

Lastly, many people recommend that you replace your tires every 5 years.  Firestone recommends a 7 year interval, and will not service tires older than that.  With the relatively low mileage most RV tires see, it’s likely that our tires will age out before they wear out, so keep an eye on the date of manufacture and the calendar, and schedule that expense accordingly.  Tires, like oil changes, are a maintenance item, especially with big, loaded, and expensive vehicles like our Roadtreks.  Chances are, with Roadtreks lasting more than 20 years, we will do 2-4 tire changes in the life of our Roadtrek.


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7 comments

  1. Pat

    i inflate my tires by checking the axle weights at a scale, and then inflating according to the manufacturer’s tire inflation chart for my model of tire at that weight. (In my case that is the Michelin chart, although I don’t know that here is any difference between manufacturers for a given tire size and load range). I thought this was the correct way, but here you are saying to go by the door sticker. However I don’t know how the door sticker would know what a given rig actually weighs? (They can know empty weight and GVWR, but not actual weight of an individual’s loaded rig.)

    Can you comment on this?

    Thanks – I enjoy the posts.

    Pat

    Reply
    • Graham

      Pat: The doorpost sticker on my new RT is specific for my vehicle — VIN is on it, as is the order number. It seems to take into account the options actually built on the rig. As to whether they actually put my rig on a scale, I can’t say.

      Reply
  2. Pat

    Sorry if this comes through twice – I seem to have a problem making a reply to a reply.

    ****
    I understand about the door post sticker being vehicle specific; it’s the same on my former Class B and my current Class C (but it’s a tiny Class C, so I still feel more comfortable hanging out with the “B” folks :)) But within a vehicles specs there can be a wide range of weights (everything from the empty weight as if you were driving it around solo, devoid of personal possessions ,and with empty tanks; on up to fully loaded right up the the GVWR. Within that range the optimum tire pressure would vary (as shown on, for example, the Michelin chart for my LT M/S 2 tires). So the idea is that you weigh your rig as loaded (which is important to know anyway) and inflate the tires accordingly.

    The max pressure is for the max load rating on the tire; but if you aren’t up at that weight level a lower pressure is appropriate.

    At least that is how I understand it.

    Pat

    Reply
  3. Pat nailed it: appropriate tire pressures are determined by the actual weight on each axle as you drive down the road. The maximum pressure molded into the tire’s side is NOT the pressure you want to use. If you inflate to 80 pounds, you’re going to have a heckuva rough ride, and your tires will be bald in the middle while there’s still lots of tread on the edges.

    Nor is the door sticker a good guide. As Pat pointed out, the numbers there were determined by the coach’s manufacturer without taking into account whatever possessions you load into the rig. What’s more, they only reflect the rig’s weight *as it left the factory*. That means they don’t include dealer-installed “options” such as solar panels, an air conditioner or generator, which can add hundreds of pounds of weight.

    Determining the correct pressures for your tires is not rocket science.

    1. Get your rig weighed when it’s fully loaded for travel. Truck stops, state weigh stations, and moving companies are all places to do this. You’ll need separate weights for the front and rear axles.

    2. Refer to the tire manufacturer’s inflation pressure chart for your your particular tires. For example, here’s the chart for Michelin truck and RTV tires:

    http://www.michelinrvtires.com/michelinrv/tires-retreads/load-inflation-tables.jsp

    3. Inflate both tires on each axle to the same pressure. Check all tires, either manually or with a tire pressure monitoring system, each morning before getting on the road.

    Do this, and you can be confident that your tiers are at the optimum pressures. Setting pressures by actual weight is the only correct way to do it. Any other way is just guesswork.

    Reply
  4. Judy

    I had my 1999 Dodge 190 Popular weighed at the last rally I attended. I was running 80 pounds in the back and 60 in the front. The guy told me I should increase the front to 80 as well. The sticker on the drivers door panel says 40 pounds, other Roadtrekers told me I should be running at least 60 pounds in the front, which I did, now they are at 80 pounds. Yea, there is a lot of controversy on the subject.

    Reply

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