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Friday, July 31, 2020

Can't "Balance" your tires? Bad ride?

Can't remember the number of times I have seen someone post about the "bad ride" they had in their Motorhome and that they took the vehicle to their RV dealer but was told they could not "Balance" the tires or that they were balanced and the ride was 'What it is".

The ride can be affected by a number of different contributing factors.

1. One or more tires may be out of balance
2. The tire may not be properly mounted to the wheel
3. The wheel could be out of round
4. The brake drum/rotor may be out of balance
5. The wheel may not be mounted to the hub correctly
6. The tire may be out of round
7. The tire may have internal structural "uniformity" problems.

Many times people jump to the conclusion that the tire must be "Out Of Balance" and they want to ignore all the other possibilities.

Back in Nov 2011 I covered a number of possible contributing factors when I answered the question of Do You Need To Balance Your Tires? Obviously, those that just focus on "balance" did not review this blog post.
In that old post, I said it was possible to balance a cinder block. You might consider reviewing this post as it has some good pictures of the other conditions that can give poor ride.

I have used this comment a few times in my RV Tire Seminars but I bet few believed me. Well here is the proof.
This first shot is of my "Bubble" Balancer and my test cinder block. Yes, the balancer is old ( from the 70's) but I have balanced hundreds of tires.








Even those used on my Camaro race car

where high speed (125+) would quickly show up if the tire was out of balance.

Now first I confirm the balancer is adjusted to a near-zero level of out of balance itself. We can see the bubble is very near to perfect balance with it right at the center point.

Next, I loaded the cinder block onto the balancer. I chose to not try and pile standard wheel weights on the block, so just grabbed some hand wrenches. After some moving these "balance weights" around I ended up with a
very acceptable level of balance.

I do hope this clears up some of the confusion on Ride vs Tire Balance.


Friday, July 24, 2020

One tire fails. What about it's "mate"?

Had a question from a friend about replacing both tires when one failed on the same side of the RV. 

 In Motorhomes with "Dual" tires (side by side) in the rear and you do not get the early warning from TPMS of air loss, you need to seriously consider replacing the "un-failed tire" because when it's "mate" failed the un-failed tire was overloaded by 100% for some unknown number of miles. 
You can always take the un-failed tire to a dealer, for that brand of tire, and have it inspected inside & out, and if ruled OK, in writing, by the dealer, you could keep the tire as a spare.
However, if it ran some unknown number of miles at 100% overload, I would not even trust it as a spare. 

 Now in the case of a multi-axle RV trailer (tandem axle) and one tire failed and again you were not running a TPMS to get an advanced warning, we need to consider what happened to the load on that side of the trailer. Wouldn't all the load from that end of the axle with the failed tire transfer to the un-failed tire on that side of the trailer? This transfer would be transferred through the springs and the link between the axles. The load supported by the "failed" tire doesn't simply evaporate, does it? It has to be taken up by the un-failed tire on that side of the trailer.

So again that tire should be removed, inspected, and replaced as with the Motorhome example. It might be OK to keep as an emergency spare but only used with great caution and only if inspected and judged OK by a dealer of that brand of tire.


This is one of the things people do not think of when considering running TPMS. If you get advance warning of air loss in one tire in a "Dual" or "Tandem" location you not only might save the cost of the punctured tire if it was caught soon enough to be repaired but you might even have saved enough by not losing the 2nd tire not to mention avoiding the $Thousands of possible damage to the RV.

Friday, July 17, 2020

Shield your tires from exhaust heat

Some folks are noticing the inner dual on one side seems to always run hotter than the outer dual or the inner on the other side of their coach.
IMO it is the radiant heat from your exhaust system that is causing your tire to always run a bit hotter.

Remember that the "aging rate" of tires doubles with each increase of 18°. This means you are potentially cutting the life in half.

I suggest you take a look underneath your coach. You do not need to wrap your exhaust. This can cause problems and may shorten the life of your exhaust system. A simple metal shield can shield the tires from the IR heat.

Here is what GM installed on my C4500 for my Class-C. Simple sheet metal with a bottom lip to provide some stiffness and to prevent cuts I guess. Just some galvanized 16 to 20 Ga steel can do the job. I bet if you check with a Home heating shop that does ductwork they can cut and bend a piece for not much $.  My shields were welded (1" every foot or so) and show no signs of failing after 17,000 miles. Could also drill and use some heavy metal screws too.



Friday, July 10, 2020

Why doesn't Bridgestone, Michelin, Hankook, or Continental make ST type tires?

I was asked by a fellow RV owner if I could recommend a tire for their trailer.

We have asked why the major tire companies other than Goodyear (Bridgestone, Michelin, Hankook, and Continental) don't carry ST tires, but they didn’t really provide a direct answer.  Just sort of danced around it.  I have been reaching out and trying to find an ST provider, but have not had any luck so far.  

My reply:  In My Opinion,

None of the "major" tire companies are interested in the RV trailer market (ST type tires) because of the documented poor level of weight and inflation management. Goodyear tire company pushed for the introduction of Special Trailer tires back in the late 60's & early 70's at a time when 20' single axle trailers pulled with bumper hitches were the norm. a 1/2 ton truck was rarely an option for average family use vehicles. ST tires were offered with increased load capacity i.e. lower cost to the RV company and to compensate for this the 65 mph max speed and reduced tread depth was presented as required and sufficient to allow the bias tires of the day to run to wear out in maybe 10 to 15,000 miles. Many times P-type passenger tires were applied to these smaller RV Trailers but a -10% load capacity adjustment to the P-Type load capacity was required.

The 1974 National 55 mph speed limit kept operating speeds down so tire failures were still at a lower level but with the introduction of steel-belted radials to the tire marked coupled with the growth of trailers to 35'+ and tire mileage theoretically increased to the 30 or 40,000-mile range the tires no longer wore out but started to fail at an unacceptably high rate.

The annual tire market in the US is 200 Million a year for Passenger type tires and about 37 Million LT type. Annual sales of all types RV is very volatile and ranges from 160,000 to 500,000 a year for all types, from Class-A down to teardrop,  Some industry information suggests only 20% of the RV market are "conventional RV Trailers so that would translate to a market of 400,000 tires in the best years  When looking at the tire market I think we can see little incentive for a company to go to the effort and expense of developing tires for a market that is only 0.5% of the P- and LT-type tire market. Especially considering the high level of warranty claims and problems due to the extremely poor maintenance record seen from RV owners.

BUT   back to the original question. The only ST tire that I was able to look at a section of recently was a Goodyear Endurance. It looked like it might perform better than some other ST tires I have looked at.  BUT  the only performance data I have is just the reports on various RV Forums where customers seem happy with the Endurance.

Sorry to say that your choice is relatively limited if you have to stay with St type tires. While Maxxis and Cooper have supporters you might be better off switching to LT type as long as you make the required adjustments for load capacity by increasing physical size and or Load Range. If you follow my blog you should have already see THIS post of the topic of lT vs St type tires..


Friday, July 3, 2020

Valve Stems and TPMS Part 2

As a follow up to last week's post of why I recommend people NOT use rubber valve stems with their external TPMS sensors I decided to show some of the "guts" of valve stems.

Standard "rubber snap-in" stems like the TR413. If you look down the hole you can see the end of the brass part of the stem. More on this later.












These have been used for decades on hundreds of millions of tires. These can be installed by hand using a "puller" that stretches the rubber which makes the diameter of the stem small enough to "snap into place in the wheel hole.








Once installed the wheel "pinches" the rubber part of the stem to seal the air in. The arrows show the location of the wheel relative to the metal part of the stem.  Note the part of the valve stem that goes into the air chamber was cur off before I took this picture.










You can see that the brass stops before it gets past the edge of the wheel. This makes installation easier.





Next, we have the "High Pressure" stems such as the HP-500.


 Here you can see the brass part extends almost to the bottom of the valve and into the air chamber.








When the rubber is buffed off you can see that the brass part extends through the wheel hole (location shown with the arrows.)








Now when we look at a "bolt-in" stem, like this TR416s
we see the location of the wheel hole at the arrows. We can also see the much larger brass body (nickel-plated in this piece) that goes inside the air chamber and expands to a broad base. This type of stem needs to be installed through the wheel hole with the rubber grommet sealing the air. An external washer is used and the nut is to be tightened to specification to prevent air loss.















I am also including pages from the US Tire & Rim Association yearbook which publishes the "interchange and fitment" specs so all tire companies and valve manufacturers know what dimensions are required. This is the book where all the Load & inflation tables come from and might be considered the Tire Engineer's "Bible" and is used by tire engineers around the world when they are making tires that are intended to be used in the US.

Here we find the details of valve stem designs as specified by TRA.


















Finally to show the attention to detail here is the spec for the little pin that sticks out of the valve stem. Not meeting this specification could be the reason your TPMS does not register your tire pressure. (Yes I have run into that problem)

 I just wanted to try and give you a little understanding of the attention to detail tire engineers go-to when designing tires and when trying to understand the "why" for a tire to lose air.


##RVT956