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Tuesday, June 23, 2015

Help It's hot and I need tires

That's the message I read on an RV forum.
Here is the pertinent background info.

   "I am having a real issue with Michelin tires.  I live in Las Vegas and there are 3 tire companies that carry Michelin tires.  The problem is they all tell me they are back ordered and have been for awhile.  They have no idea when they will get any.  I have a 40' 2008 RV that came with Goodyear tires and have serviced us well.  I just don't know what do do since I can't get Michelin tires which seems to be the tire to get. Should I settle for Goodyears that are in stock?  My other issue is we are going on a trip next week that we can't get out of and because of the extreme heat here in Vegas we are afraid that our old tires might just fly apart. What should I do?"


While I can't address tire availability from Michelin, you need to remember that there are generally considered to be 3 tiers of tire companies. Michelin, Bridgestone & Goodyear as #1 with the tires made & sold by these companies as being essentially the same  ie Firestone & Dayton ~ Bridgestone, Kelly & Dunlop~ Goodyear and Goodrich & Uniroyal ~ Michelin.

Now there are some minor differences within a corporation but many times the rubber compounds and reinforcement materials are identical or very similar. Tread designs may be a bit more advances in the Corporate brand and the top of the line tires may not have an equivalent in the 2nd brand  but for most people you will not see a difference in performance.

#1 tier have their own tire stores with many hundred nationwide.

Now Tier #2 would be tires made by corporations that have their own tire plants. These would be companies like Toyo, Pirelli, and others seen on this list. They may not have any company stores and jsut depend on large tire distributors to market their tires.

3rd tire would be companies that are not on the list above. These may actually be just sales companies the have other companies make lower cost product for them as "private brand" , Sometimes the same tire is made for a number of importers with only a name-plate change in the mold to differentiate the "brand" These companies seldom have their own stores but sell their products through wholesalers.

Check the tire warranty and I think you can get a good feeling for the real quality of the tires you might be considering. Are there lots of exceptions or if the warranty short could be a tip off that the seller isn't real willing to stand behind the products they are selling

Now to your concern about your current tires and the hot temperature.  It's kind of hard offering an opinion or suggestion on if you need new tires right away or not, but tires simply do not fail simply because it is hot outside. Excess heat is not good for long term durability but if the tires have always been properly inflated, never been punctures or run even a few psi low you should be OK for a while.

You didn't offer your actual age of your tires but they are probably 7 to 8 years old. You also failed to provide info on how you store your tires. Inside or out in the Sun? Do you have a lot or a little extra load capacity based on actual individual tire position weights? Do you run a TPMS and have never run lower than what is needed to carry your actual measured load. All of these items can contribute to making a suggestion to change your tires right away or suggesting that you can wait a few weeks or months.

If concerned about road or ambient temperature just drop the speed down. Don't run 70 when 60 will still get you there. Last Aug I drove Ohio to Oregon at 60 - 62 with no problem.

Can you increase your tire pressure without exceeding the tire or wheel max?

Where are you headed?  Have you checked to see if there is a large tire dealer at a future location that has tires for your RV in stock?

In the meantime I would suggest you go to a Goodyear truck tire dealer and have the tires inspected. Let them know your concern about the tire age and current hot temp in Vegas. Let them know your actual scale weights (Go to a local truck scale location first. There are a number around Vegas I'm sure)  and your normal cold inflation. WHile there ask if they would confirm the accuracy of your pressure gauge. If a stick type +/- 5 is about what I would expect. If digital (better) +/- 2 would be good. If outside these numbers you need a new gauge. Check my blog on tire gauges and how to have a reliable "Master Gauge" of your own for less than $15.
The tech should be familiar with the Goodyear tires you have so can offer first hand information on the condition of your tires.
Remember you can always get just the two fronts replaced as a failure there would be the greatest concern. With a TPM on the rear duals a failure would be less dramatic and you should get plenty of warning so you can safely pull over quickly before serious damage is done.

It would be nice to be able to offer more specific answer to his question but all to often people fail to provide important information that would allow more than a wild guess.

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Tuesday, June 16, 2015

Safety Recalls

The National Highway Traffic Safety Administration or NHTSA just made available a video to help people understand vehicle recalls.

Understanding Vehicle Recalls” gives a quick overview.

This website allows you to check if your vehicle or tires are under a recall.

If a safety recall is initiated, your manufacturer will notify you of the recall through first class mail and offer to fix it for free. If your vehicle is recalled, please call your local dealer as soon as possible to make an appointment for a free remedy. By fixing your safety recall, you have the power to save your life, and the lives of your passengers and other motorists.

Sign Up to Receive Recall Alerts via email alert.

Report Potential Safety Problem.  I have previously posted information on the importance of reporting tire failures to NHTSA. Just complaining while you sit around the campfire or venting on an RV forum may make you feel better but it will never result in action that could improve the quality of RVs or the tires that go on RVs. Reporting a vehicle or equipment safety problem to NHTSA is an important first step to get the situation remedied and make our roads safer. If we receive similar reports from a number of people about the same vehicle, this could indicate a safety-related defect may exist that would warrant opening an investigation. Report your vehicle safety complaints on

I am in the process of writing a post that will show that there is hope for RV owners. I am seeing an increase in load capacity  as well as an increase in speed ratings for trailer applications and will be covering this in depth next week.

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Thursday, June 11, 2015

80+ mph RV tires ?

Recently read a post on a forum where the question was asked about by-passing the speed limiter that was on the poster's Class-A unit as the poster wanted to drive faster than 80!

The general consensus was that this was not a reasonable speed in an RV and almost universally people knew that their tires were rated for 75mph or less.

On my trip from Ohio to Oregon last summer I noted that many interstates now had updated the posted speed limits from the old 55 to 65, 70 and as high as 80mph. While I "puttered" along in the right lane with my cruise set at 60-62 mph, I saw all manner of vehicles whiz past me, including many RVs, some of which were clearly exceeding the speed rating of their tires.

In March  I wrote about tire speed ratings, but this is a real safety issue with potentially both short- and long-term consequences. 



I wrote again in April on "How fast can I safely drive?"

First off, as a professional race car driver and police driving instructor, I think it would be unsafe and foolish to drive an RV in excess of 70 mph. A quick search of the internet finds numerous charts showing the effect of increased speed on stopping distance, with large RVs needing 40% to maybe 80% more distance to come to a stop as speed increases.

At 55 mph, you will "only" need 100 feet more than the length of a football field to stop; at 80 mph, it would take you the length of three football fields to come to a stop. While you might get lucky as you sit high above the traffic, have you asked yourself how you would feel after driving completely over a passenger car that can stop in maybe half the distance it takes you to stop?

BUT this blog isn't about general driving safety, as hopefully you have a good understanding of your vehicle capabilities, having done a practice emergency stop on a "closed course." I want to address the effect of speed on tire durability.

Tires have a speed rating. This is the speed at which a tire can be driven for a short time without failing immediately. For most ST type tires this is 65 mph. There are some special high load trailer tires that are only rated for 62 mph.  LT tires and TBR (Truck-Bus Radials) are rated for 75 mph in RV service. If you look at the side of passenger car tires you will see a "Speed Symbol" letter.
An example might be LT235/85R16 114/111 Q   with the 114/111 being the "Load Index" single and dual and the Letter "Q" being the speed symbol.

Many LT tires also have such a symbol but if you place a passenger tire or LT tire in RV service the manufacturer has lowered the speed rating to 75 max. If there is no Speed Symbol then the speed rating for LT tires should be considered to be 65 mph.

As I wrote previously, some ST tires may be rated with a speed number or symbol by the manufacturer. This number should be molded on the sidewall. I would not trust information that is just verbal from a tire salesman.

I just updated my "Links" post with information on an importer of ST type tires that has published the speed symbol for their tires as "L" which corresponds to 75 mph.
Here are some of the Speed Symbols and the corresponding max speed capability:
F = 50 mph              G = 55 mph        H = 60 mph        J = 62 mph     K = 68 mph     L = 75 mph

It is very important that you understand that all the above is based on a laboratory test done on new tires. If a tire has hit a pot hole or been repaired or been parked in the sun for months, then there has been some degradation to the tire's strength and I would not expect it to pass the same test requirements. In fact, if a tire has been repaired, it's in many pieces of literature that the tire looses its speed rating.

Another bit of information to remember is that running fast will increase the temperature of a tire and as I covered in depth in my post on tire covers: "Increased temperature causes continued and accelerated chemical reaction which "ages" a tire faster than when the tire is cool. A rule of thumb would be that the rate a tire ages doubles with every 18°F increase in temperature. We can see the result of old rubber on the surface. What we don't see is the more brittle rubber of the internal tire structure. As rubber gets more brittle with age it also looses strength." Running a tire at 70 rather than 60 will probably increase the internal temperature by about 18°F so every hour you are driving that fast is costing you two hours of tire life. Damage is cumulative and slowing down does not repair the damage you have already done.

Drive safe.  Slow down and enjoy the journey.

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Monday, June 1, 2015

Can't find your Tire Placard? Here is some help.

This post updated 1/5/19 to correct broken link.

As I review various RV forums I occasionally come across special problems. Here is an example:
Originally Posted by J View Post
"I'm new to motorhomes so bear with me. I don't have a sticker on the door jamb to tell what psi is recommended. The tires are 215-85-16, it's an 1988 ford E 350 20 ft. class c. The tires state max psi of 80 but I will have to replace them since I found out they are 10 years old. I wonder if someone could give a recommendation for pressures front & back? Also, a tire shop said I could use LT 245-75-16 instead since they are approximately the same diameter but slightly wider. Just have to make sure they are D or E load rated. I have seen that size on a 16 ft. moving truck before. What say you all?"
While J has the additional problem of not being the original owner so he doesn't have the manuals or original tire info from 1988 he still wants to do the right thing and to use the proper tire inflation for his application. While your size or RV may be different I think that you could follow the info here and resolve similar situation.
Here is what I suggest.
My Class-C is 21' that was also built on a "cut-away van" chassis so we probably have similar weights BUT just because I run xx psi is not the best way to learn what you should run.

I strongly suggest you read this page on tires from the Tire manufacturer's Association
I doubt you have a slide on your Class-C so you are probably reasonably balanced and probably within 48/52% side to side.

With your RV loaded as you would normally travel (Food, fuel, water, people, tools etc) get to a truck scale. Use these links to find nearest to you.

Truck Scales and Weigh Stations Locator for Truck Drivers and Trucking Companies at Truckstops

Locate truck scales, truckstops, truck service centers, and diesel prices

Get the individual axle loads then assume one side has 52% of the load. (NOTE if your RV has slides or is a Class-A you really need to confirm individual corner weights or assume a 45/55% side to side split if you only get individual axle weight readings) Using that load you can use the Load Inflation tables for your brand tire (list on THIS link)
You may be light enough to use LR-D but may find a better selection using LR-E. Either way, find the Minimum inflation that is rated to carry at least the load you calculated for your LT215/85R16 tires.

The LT245/75R16 tires suggested by the salesman needs 11.34" Dual Spacing which is a lot more than your OE LT215/75R16 that only need 9.88". This is the clearance between the center-line of duals and is controlled by the wheels. Tire to tire contact or "Kissing" can lead to tire failure so unless the tire store is willing to put in writing that the LT245's will not have dual spacing issues or they will replace the tires for free, I would stay with your current size.

I suggest your CIP - Cold Inflation Pressure) be the minimum inflation calculated above + 10% so you don't have to worry about the need to add air if there is a big temperature drop. Remember never exceed the "cold" inflation pressure rating for the wheel which should be stamped on the wheel or available from the wheel manufacturer.

For those that don't know "RMA" stands for the Rubber Manufacturers Association. This 100 year old organization represents tire manufacturers that produce tires in the U.S.A. RMA represents its members before federal, state and local government entities; develops safety standards for passenger, light truck and commercial truck tires; advocates for environmentally and economically sound scrap tire management polices aggregates data pertaining to U.S. tire shipments; and, educates consumers about proper tire care, among other activities. They have a number of informative publications available for free on their website.
I think the RMA RV tire guide gives a good overview on tire safety and proper practices.

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