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Friday, November 30, 2018

Can I change from LR-F to LR-G or H? (ply range change)

A motorhome owner needs to change his 245/70R19.5 LR-F  tires and asked some questions:

My questions are:
  1. Will the truck "H" rated tire give a much different ride than the recommended "F", or "G" rated tire?
  2. Some manufacturers claim UV protection. Does it make a difference?
  3. Are there any particular brands to steer clear of for RV tires?
  4. I qualify for veterans/AARP discounts. Are there other good discounts?
  5. What else should I be looking for/be concerned about?
My answer:

LR-F  vs LR-G  vs LR-H
You should never go lower. If you go up the only way you will get increased load capacity is by increasing the inflation. It is unlikely that you will get a different ride if all you change in the marking on the tire sidewall for what the Load Range is. Now if you also change brands then ride can change and if you change from a ribbed design to traction design then I would expect ride and noise to change. When you check the load/inflation tables you will note that the capacities for LR-H match the capacity for the LR-G at the LR-G inflations so it is OK to run an LR-H at less than the max inflation on the side of the tire as long as you know the actual load on each tire position and NEVER run lower inflation than what is needed to support the actual measured load.
Remember it is the air pressure, not the tire construction that actually supports the load.
I have a number of posts on my RV tire blog on Inflation as well as other tire topics so you can learn quite a bit there.
RE Brand. Yes, many to choose from. One thing to consider is how many and location of dealers."Billy-Jo-Bob cheap tire emporium and bait shop" may have the best price but with only one store how are you gonna get service if you travel?
Many of the "majors" also have alternate lines at lower cost, sometimes even made at the same plant with most of the same materials. For example in Warren Co TN Bridgestone truck tire plant also makes Firestone and Dayton brands which are less expensive. Do some research to see what other brands have.
Does the country or origin make a difference? If "Made-in-Canada" or where ever is important then be sure to read the tire sidewall as the country of origin is always listed. You can also look up the actual individual plant location by reading the first 2 characters of the DOT serial and checking HERE or HERE for actual plant location.  

UV protection:  All tires have some level of protection. There is no industry standard so it's impossible to get a meaningful comparison. Some will claim "more" or "better" but more than what isn't answered. Covering your tires will do a better job of extending tire life than simply depending on advertising.

Discounts. Yes, there are a number out there. Some might even vary depending on location as some large dealers can offer better discounts simply due to their volume.

If the price is a major concern you may be able to do a rolling change over a three year period as I suggested in THIS post.

Friday, November 16, 2018

Setting tire pressures on cold days?

Here was his post...
"I am looking for a formula for adjusting "cold inflation" pressures for large tires. I have read that for smaller (car) tires the recommendation is 1 psi per 10 degrees F.

What is also not clear is what the assumed "cold" temperature is. Is assumed to be 65 F, for example. So if we are sitting at 25 F, what is the adjustment?"

My reply
Here is my blog post that explains "Cold Inflation"
We are not in High school chem class so there is no adjustment need to get to "standard " temperature.

If you are running a TPMS, which you should be, you will soon recognize the normal range of temperatures and pressure variation in your tires.

I would not worry about adjusting inflation pressure is today's expected temperature is +/- 10F from yesterday. After all, you should be running +10% over the inflation you need to support the measured load.

Let's say your minimum needed is 90 psi. Adding 10% that means your cold inflation (cold meaning the tire was not driven on or in direct sunlight for the previous two hours)  should be 99 psi so you round to 100 psi. All is good.

The next day's weather is 20F colder. That would mean the tire inflation will drop 4%  ( 2% per 10F change)

So now your tires would be 96 psi but since you have to stay above 90 I would say there is no reason to worry about adding air. Just enjoy life and head out.

If the next day your weather went up 10F instead of down that means tour "cold" inflation would go up 2% from the 96 or to about 98psi. Again you don't need to do anything.

I would not worry about lowering the pressure until I saw pressures 10 psi above the pressure molded on the tire sidewall. When you get to that point you could bleed off a few psi but remember if the weather gets cold over the next couple of days you will be needing to add air again.

Don't get your shorts in a bunch about inflation. Just watch your TPMS and you will learn what is normal for your coach.

Friday, November 9, 2018

Remember: A tire is just a "tool" you use to get a job done

This in response to a report of tread cracking of some traction design tires placed on a custom heavy car hauler trailer. The owner was blaming the 4-year-old tires.

I do note that when there are tire problems, including actual "failure," it's common for some to say "My xxx brand tires failed, I will never buy xxx tires again".

Well, sorry to tell you but there is no such thing as "Fail-Proof" tire. This was even part of the testimony mentioned by DOT spokesperson during the Ford Explorer rollover fiasco of 2000.

Today's tires are amazingly robust. Even when they are made in Japan or Timbuktu, and we all remember how bad "Made In Japan" was when were growing up. As I pointed out in the thread, the subject tire an All season traction design was not at all appropriate for heavy trailer application. Both the tire type/size was wrong and the tread pattern was wrong.

Why is this the tire's fault?

If you put a truck tire with a heavy off-road mud traction tread design on the front of your 40' DP and had loud noise and vibration and harsh ride would that be the tire's fault? Would simply changing tire brands from say Bridgestone to Michelin solve the problems if you selected just another heavy off-road mud traction tread design? No of course not.
From my experiences as a tire engineer, I can tell you that I can probably "fail" any tire in under an hour and under 50 miles if you let me set the conditions.

A tire is just a tool you use to get a job done. If you don't select the correct tool that is appropriate for the job you want to be done why is it the fault of the tool manufacturer? Think of the absolute best tool company. Now select one of their flat blade screwdrivers.
 OK now start using it as a chisel and pound on it as you try and cut through some rusty bolts. After cutting through a few bolts would you blame SK or MAC or  Snap-On or ???? if the point of the screwdriver is dented and chipped?

Different tires are just tools with different intended usage.

Basically I would suggest "Rib" or "All position" designs for the front position and if you intend on occasional off-highway travel (a gravel road at a campground doesn't count) then you could select something with a bit more traction capability but I would consider any "Drive" position as not a great choice for Motorhomes or trailers.

Friday, November 2, 2018

Do you need your own air compressor? & Certified tire inspectors

Saw an RV forum post on this topic.  Here was my answer.

If you are running a TPMS (which you, of course, should be), you should have received plenty advance notice of needing to add 3 to 5 psi. This slight loss of pressure is due to normal air loss and pressure change due to change in ambient temperature. You can easily top off your tires at your next fuel stop.

If you don't have TPMS and discover you have been driving on a tire that needs more than 20% of it's required inflation, you should be calling road service and have the tire changed, as there is a good chance you may have done permanent internal structural damage. I consider this operation on the under-inflated tire made the tire unsafe to re-inflate until the tire has had a complete internal and external inspection by a trained tire service person, not just the guy that mounts tires who probably has not received the training.

AFTER the inspection, the tire should only be inflated in an approved safety cage as doing otherwise can lead to serious personal injury.

 Regarding how to find trained, certified tire inspectors...  Use THIS link    from Tire Industry Association.

There is a directory that you can search by zip code. Those listed are TIA Members, and those with the Certified Patch next to them have been TIA Certified.

I will suggest that folks with 19.5 or larger tires or with Load Range E, F, G or higher or with any steel body ply of any Load Range go to Certified,  Commercial inspection

People with Passenger, LT or ST type tires of lower load range, can use the "Automotive" link but a certified Commercial person should be able to inspect smaller tires too.

Remember as Sgt. Esterhaus said 'Let's be careful out there'