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Thursday, August 22, 2013

Who Do You Trust

When it comes to buying tires, who do you trust?

I recently read two posts on an RV forum about problems people had with their new tires. They were the wrong size! 

One person said:  I have an F250 4x4. I got new tires put on almost a year ago and just realized they are not the same as was originally on it. The tire store told me they were the same.  I took their word for it. The new tires have been inflated to 75 lbs since buying them eleven months ago. I just read the sidewall.  They are P265/70R17, where my original tires were LT265/70R17 LR-E. The truck door sticker says 75psi  for LT tires.

The other person said:  I replaced the crappy OEM P275/60R20 tires on our 2012 Ram 1500 4X4 w/ LTX AT2 tires at 10,000 miles. When buying a new set of tires last month I assumed the tire dealer would put LT tires on. But nope, they put P series tires on and I didn't catch it until I checked the tire pressures. Was I surprised and mad at myself 'cause I sure can't afford to get a new set and it wasn't the tire dealers fault at this point. I should have insisted on LT tires, but they will only put what the factory put on unless requested. I really wished I had been more attentive at the tire dealer and got what I wanted!

Quite frankly I was surprised by these two accounts but maybe I shouldn’t be considering how little interest some people take in their tires. Now I hope that these people are the exception and the readers of this blog actually do take more than a passing interest in their tires. 

For many people, tires are simply round black things that they are forced to buy every few years but I find it amazing that people would pay more attention to purchase of a pair of $20 pants than they do to getting the correct size, type and Load Range of a $400 -$800+ set of tire. When buying pants you probably know and confirm you are getting the size you want.

From the examples above, it is clear you cannot depend on all tire dealers to know what you want from your tires. At some dealerships I am sure the “order takers” know more about washing machines they were selling at their previous job last week than about the tires they are trying to push because of over stock. You need to be an informed, educated and demanding customer.
Do your research BEFORE you get to the store.

1.  Be sure you know the loads on your RV and tow vehicle. 
2. Be sure you select an appropriate tire that has load capability that exceeds your maximum loading.   
3. Know how to determine the tires you need.
4.  Ask about the warranty, if any 
5. Consider the ease of finding a replacement for the brand you are buying. 
6.   Read my post on “Best Tire


Wednesday, August 14, 2013

Autoguard LT245/75R16 being recalled

I have previously written about tire recalls. Here is what can happen when it is confirmed that some tires do not comply with DOT regulations. 

 Some Autoguard LT245/75R16 tires are being recalled by the manufacturer.

Tires manufactured June 25th, 2012, through November 11th, 2012. These tires failed the endurance test standards of FMVSS 139 and contain incorrect maximum load load data on the sidewall. Thus, these tires fail to to comply to the requirements of Federal Motor Vehicle Safety Standard No. 139, "New Pneumatic Radial Tires for Light Vehicles."

You can get more information at NHTSA Campaign ID Number: 13T007

Owners may contact Tire Group International, Inc., BCT's U.S. contact, at 1-305-696-0096 extension 5538.  



Thursday, August 8, 2013

Why did my engine "blowout"?

Why is it we almost never hear the above question on various RV forums?
Could it be that we don't hear this question because people know it is not wise to exceed the RPM limit or "Red-Line" specification of their engine so they simply don't run at and above the engine speed limit?

But I do see questions of what has to be done to run 75 mph with a standard ST type tire when the RV manufacture specifies the pressure on the tire which is one of the factors limiting the tire speed capability.


The interaction of tire types, load capacity, inflation and speed "rating" are complex, as are almost all topics about the various performance trade-offs with tire selection

I did a post just on the topic of "How fast is safe to drive on your tires?"   I have also pointed out that if you are going to deviate from US industry guidelines, such as published by Tire & Rim Association, you must follow the published guidelines for your specific size, type and brand. You cannot use Goodyear document to learn the appropriate load & inflation for your Maxis tires. It even means you cannot apply specifications, including speed, load & inflation from a Goodyear Marathon with a Goodyear G614.

Now as we all know, an ST type tire has a higher load capacity rating than a similar sized LT type tire.
ST235/75R15 LR-C is rated 2340# @ 50 psi (min) and 65 mph (max).
LT235/75R15 101/104Q LR-C is rated 1985# @ 50 psi (min) and 75 mph (max).

We have also established that load capacity is nominally a function of tire size (air volume) and its inflation pressure. If however we decrease the tread depth and the lower the maximum operating speed we can increase load capacity slightly. In my post of Oct 12, 2011 I identified a Michelin trailer tire with a higher load capacity but many want to ignore its max speed rating of 62 mph which is even lower than ST type tire rating of 65 mph.

Now to the specific question of how to operate a specific tire at 66 to 75 mph. This is accomplished by increasing the inflation pressure by 10psi according to a document published by the tire manufacturer. This is not as simple as many assume.

If you select the 65 mph max speed for an ST245/75R16 LR-C you will find a load capacity of 2,600# with a minimum of 50psi if you stick to 65 mph max. But if you want to drive at speeds up to 75 you need to increase the inflation pressure in the industry standards as published by Tire & Rim Association. So now to carry 2,600# you need an inflation of 60psi but this exceeds the max inflation rating for this size @ LR-C so you either need to get new LR-D so you can run 60psi or to limit your load to 2,270# and 60psi which is the published load capacity for 50 psi inflation of the subject size tire. This higher inflation may also exceed the rating of the wheel, but again many choose to simply ignore that rating too.

One obvious item many simply ignore is that the max speed for a tire is much like the red-line rev limit for their engine. It clearly is possible to run an engine with a 6,000 red-line at 6,300 RPM and possibly higher but what about long term engine life?

There are hundreds if not thousands of posts on RV forums from people complaining about tire failure but I have to wonder why they seem to understand the effects on engine life of high RPM operation but fail to understand that running a tire faster than its design specification will also contribute to shorter tire life.

Saturday, August 3, 2013

I read it on the Internet



With apologies to the "French Model" guy in the TV advertisement, I want to talk about the reliability of tire related information as seen in many RV forums.

 I subscribe to or monitor about 10 different RV forums. I know there are more but I do have other things to do than just read RV forum posts.
 Many times I use the "search" function to look for threads that are about tires. It appears to me that a significant percentage of the people asking questions, have not made an effort to seek out answers already posted before they ask a question. Too often what follows are answers from other RV owners who clearly do not have a good engineering background on the topic of tires. I would like to post a few examples and point out the problems I see in both the question and answers provided by others. 

An owner said “I have a 1992 Ford Four Winds motor home. 29 feet, I think. What kind of air pressure would I run in the tires. I have 60-70 but have read where some run around 100. Please help me decide".
Well first off the poster of the question left of much important information out of his post. What was his current tire size or the original tire size, including Load Range and what are the actual loads on the individual tires.
Clearly he had not noticed in numerous other threads that there is no “rule of thumb” for providing the proper inflation other than following the vehicle tire placard information. I would not be surprised to learn that this owner doesn’t even know he has a certification sticker.
What followed were 4 posts telling him the proper inflation for a motorhome, is a function of the real load and there are too many variables such as model, kind & size of tires to provide an answer. Another person replied that he should read other posts about tires and review the tire mfg “Load Charts”. Another asked for the tire loading but also mentioned the need to know the tire age by reading the DOT serial. Finally a more knowledgeable person suggested the tires need to be checked for sidewall cracking and pointed out the tire “birth date” is part of the DOT serial.
As of a week later the OP has not replied with any of the requested information. I think you can see that if he had made a little effort and read a few posts, or my blog :-) he would have been able to learn the answer to his question right off.

In another forum a person posted complaint about “blowout”.  Here we see the picture he posted.








 In this close-up you can see the tread on the right side is much more worn than on the left side.

 This is evidence of the detachment being in the tire for many hundreds of miles.
This thread has over 20 posts with lots of complaints about junk tires etc but not one properly identified that the subject tire did not have a blowout as it still held air. At that point I jumped in and provided a number of pictures of other tires showing the wear was not due to brake lock-up and the tire did not have a “blowout” but had a belt detachment and that if the tire had been more thoroughly inspected the failure and RV damage could have been avoided.
I suggested that if you have an RV, especially a multi axle trailer, an in the air rotation to look for tread wobble is something I would suggest at least once a year starting at year three.
This video  shows what a bad tire can look like.

Bottom Line.
If you have a question First spend a little time and see if the question has already been asked. Second, was the answer based on a lot of complaining and ranting or was the answer based on facts with pictures, links and hard data.
Remember that just because you read it on the Internet doesn't mean the information is correct.