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Friday, September 20, 2019

Two front tire "Blowouts" in one day

There was a thread started by the owner of a Class-A motorhome who suffered two front-end "blowouts" on the same day. There was not a lot of data provided such as actula load on each front tire or the tire age or even when the last tire inspection was completed. But here is one of the replies in the thread:
 "The reason that your coach is equipped with a heavier axle and bigger tires is exactly that the axle and tires on the earlier model Aspires were too close to what the coach was carrying. The close limits on the Aspire as well as the tire choice on OEM tires have been a well-known concern for years and many Aspire, owners, that frequent this forum have shifted their tires to tires with higher weight tolerances and inflation load-carrying specs and overall better safety record.

My 15 Anthem was similar. With me fully loaded for travel (which was still well below the coach's maximum rated weight, and tanks all loaded and us sitting in our seats, I was also overloaded on my front axle by 140# which was deemed acceptable. It was that way the whole time we owned her. A whole lot of weight is borne by these front axles on coaches this big and heavy..... within tolerances and specs but close."

I can't address the accuracy of Gary's comments on the Aspire or Anthem motorhomes but I have heard of other cases where the OE tires and even front axle in one case, was in overload when the RV was shipped from the MFG. added the following:
Individual tires don't care about the load on the other tires on a coach or the average load on all the tires. Only on the load on that individual tire. This is why "4 corner weights" is strongly recommended for all RVs.

GAWR, not GVWR is what is important for each axle BUT that is assuming a perfect 50/50% side to side split in load which is almost never the case. Some coaches have been fount to be unbalanced by 500# to over 1,000# yet still close to GAWR.
Also having a reasonable "Reserve Load" is very desirable, especially in the more critical front position. A reserve load (tire capacity minus the measured load on that tire) of at least 5% with 15% being a good goal may require changing the amount of "stuff" you carry or moving "stuff" around or even getting higher rated tires.

You can also stagger tire replacement if you have the same size tires in all positions. I cover how to do that in my post on spreading out the replacement cycle.  My post has a 1-year cycle but you could easily change that to 2 years and never have tires over two years old on the front axle.


Friday, September 13, 2019

Truing tires. Is the tire properly mounted? Is the tire even to cause of vibration?

Had a question from "Fred" on "Truing Tires"
On a different subject, on the Escapee's forum, there was a conversation about tires, and someone mentioned truing new tires. IMO, truing of new tires today only covers up poor mounting procedure, vs 40-60 years ago when tire construction was not as advanced. What are your thoughts on this?

 First, let's be sure everyone knows what we are talking about.
The process of "Truing " a tire involves shaving part of the tread rubber off to make the mounted tire more round. HERE is a YouTube video showing the process.
I tend to agree with "Fred" that most out-of-round problems can be traced to a tire not being properly mounted and seated on the rim. It is also possible that the wheel itself may not have been properly mounted on the hub or it is even possible for the wheel itself to not be round.
 If you have a vibration problem you first need to ask "What has changed?" Did you just get new tires? Are the tires the same but the wheels were off the vehicle for something like a brake job? Have you been driving on especially rough roads with many large potholes? This is a "new to you" vehicle and you have no history with the tires and wheels on this vehicle. On some vehicles "Heat Set Flat-Spot" may be the cause. This happens when tires have been run, getting hot and you just stop and park the vehicle. Sometimes leaving the vehicle parked for weeks or months can also allow the tire to get a flat spot which could take a couple of hours running to work the flat spot out. High-Performance Passenger tires are more susceptible to this problem than large 22.5" size radials but even 22.5 tires can develop a flat spot.

The problem of vibration can usually be traced to either out of balance or the tire/wheel assembly being "Out-Of-round".
If you have vibration on a new tire, I would first confirm it was balanced. Next, I would measure the assembly on the vehicle and confirm it is in-tolerance. This usually means less than 0.030" radial runout goal with 0.125" the upper limit.
If you are exceeding the above, the next step would be to try and confirm which component is not "round". Ideally, you would confirm the wheel, with no tire mounted, was below the limit. If the wheel is "round" when measured on a mounting machine then we would need to confirm it is round when bolted to the hub. Some wheels are "Hub-Centric" and others are "Lug-Centric". Hub centric means the wheel centers on the ledge of the hub on the brake drum. Lug centric means it centers on the bolts holding the wheel to the hub. A lug-centric wheel can easily get "off-center" if one lug nut is fully tightened before the other lug nuts are snugged up. There are patterns for the sequence and steps of tightening lug nuts depending on the number of lug nuts. Here is the sequence as published by Chilton, a publisher of numerous automotive repair manuals.

 Image result for 10 lug nut tightening sequence
 In addition to the above sequence, it is advisable to tighten the nuts in three steps of 1/3rd of the torque level. Example: if your torque spec was 90 Ft-Lbs you would first do all the nuts to 30 ft-lbs then again following the sequence tighten to 60 Ft-Lbs. The finally to the 90 Ft lb spec, again following the pattern
If the pattern and amount of torque are not followed it is easy to end up with a round tire & wheel assembly to be mounted off-center to the hub which results in an out of the round situation and unacceptable vibration.

Before I resorted to shaving a new tire I would measure the out of round. If you have confirmed all the above yet still have vibration on new tires, I would work with the tire dealer to confirm there is nothing in the individual tire that might contribute to some vibration by simply switching tires around or trying a different set of tires.
In all probability, by now you would have found and fixed the cause of the vibration.

Friday, September 6, 2019

Are Hankook tires any good?

Read this question from an owner of a large RV

"Looking to replace the tires on my 33 MH. Was thinking about Hankook as I only put 3500-5000 miles per year on them, But I have seen a lot of negative reviews fo Hankook tires on cars but not seeing much on RV tires. Any suggestion?

My answer

While I can't address negative reports on some applications for some brands I do know that I can find negative posts on just about every brand tire I ever heard of.
A couple of points

No company that makes Passenger, Light Truck and Heavy truck (RV) tires make them with the same materials or on the same building machines. I doubt that you think that winning the Indy 500 means you can expect the same materials or process to be used in your 365/70R22.5 LR-J tire.
I have a couple of posts on my blog with links to videos of tire manufacturing process new and old, showing just how different the manufacturing process can be. The raw materials are different and the internal QA testing is different, so I don't feel it is reasonable to use a broad brush of "negative reviews" from some individuals to consider all the tires a company makes must also be bad especially given the well-documented cases of poor or non-existant tire maintenance for so many vehicle owners.

When people ask me for recommendations for tires I offer a couple of suggestions:
1. You can check with NHTSA and check for current recalls for the brand and type tire you are considering.
2. Visit the company web site and see if you can locate dealers or stores in the states you travel to. If there are hundreds of stores then it would follow that it should be easier to get service and that millions of consumers must be happy with the products that the company makes. When doing this check confirm that you have visited the appropriate company web site. Some companies separate passenger and Heavy Truck dealers and you should not expect to be able to get service for your 22.5" tires at a passenger tire dealer
3. Don't use purchase price as your primary yardstick
Things to think about. What was the complaint in the negative review? price? Service at a particular store? The tires didn't deliver 70,000 miles wear? The fact that the tire suffered a puncture? Maybe even a complaint about a tire failure but the failure was traced to a valve core leak. I have even heard some complaints about the style of lettering on a tire sidewall.

Bottom line I know of no reason to not include Hankook brand on your shortlist.