Tire Engineer joines the forum

[Tireman9]

Hi all.
I am a retired Tire Design and Quality Engineer with 40 years experience. Am hoping to provide some answers to your tire questions based on science and facts and not so much on what some have heard while sitting around a campfire.

 

[hddecker]

Welome to the forum, Tireman.

It'll be nice to have the myths and BS about tires put to rest. If you don't mind my asking, which manufacturer did you work for?

 

[Tireman9]

Welome to the forum, Tireman.

It'll be nice to have the myths and BS about tires put to rest. If you don't mind my asking, which manufacturer did you work for?

I try and keep things as company neutral as possible. So lets say one of the "Big 3" in Akron

 

[lcv800]

Welcome aboard Tireman. Get ready for a restart of the Big Tire Debate again. I'll start off. Getting ready to get rid of my OEM Westlake tires. 6,000 miles on them so far. No problems and even wear (Check pressure every day, as well as temperature at every gas stop), however almost all on this forum have changed or recommended dumping them at first opportunity. 1,000 lb gross vehicle weight on a triple axle toy hauler currently running 16" wheels. Would you go to an LT or stick with trailer tire. Also, is it worth the expense to go to a 17" wheel? Thanks,
Rusty

 

[lcv800]

Tire Debate

Welcome aboard Tireman. Get ready for a restart of the Big Tire Debate again. I'll start off. Getting ready to get rid of my OEM Westlake tires. 6,000 miles on them so far. No problems and even wear (Check pressure every day, as well as temperature at every gas stop), however almost all on this forum have changed or recommended dumping them at first opportunity. 1,000 lb gross vehicle weight on a triple axle toy hauler currently running 16" wheels. Would you go to an LT or stick with trailer tire. Also, is it worth the expense to go to a 17" wheel? Thanks,
Rusty

21,000 GVW not 1,000! Damn keyboard.
Rusty

 

[Tireman9]

21,000 GVW not 1,000! Damn keyboard.
Rusty

No prob. Figured not 1k#

Now for a bit of a lesson for all asking questions on tire replacement or inflation. I do not know or have access to the few thousand of variations in RV's and tires over the last 15 years so I need some basic info.

As I posted on my blog Sept 14 2011
A quick review of some on-line RV forums show the problem of incomplete tire size information. Current posts mention:
225/75R-16E 235/80R 16s 275/70/22.5 215-15 LT235/85-16E 225/75R/16E 235/80R16E

None of these “sizes” provide what I consider the complete size nomenclature and certainly not enough for me to provide an informed answer. I would also need the measured load on the axles (better yet the load on each end of each axle) Have you bothered to read your RV certification label that has tire size, inflation and axle ratings?
Here are some facts from the Tire & Rim Association industry standards book that point out why having all the information is both helpful and important.

P235/75R15 105S (Standard Load -35 psi @ max load)
2028# 35 psi 112mph on a Passenger car
1844# 35 psi 112mph on a SUV or P/U (no Dual)

LT235/75R15 101/104Q LR-C
1985#single 1820# Dual 50 psi 99mph

LT235/75R15 LR-C
1512#single 1377# Dual 50 psi 85mph

ST235/75R15 LR-C
2340#single 2040# Dual 50 psi 65mph

To help understand the nomenclature the “P” or “LT” or “ST” is the type tire i.e. passenger, Light Truck and Special Trailer. The numbers are related to the physical dimensions of the tire with 235 being the overall width in mm. The 75 is the ratio of the height of the tire from rim to tread and the 15 is the nominal rim diameter. Hopefully everyone knows that the “R” means radial construction.

LR stands for Load Range with P type tires default to LR-B which usually means the max inflation is 35 psi but no one uses that designation as it is considered “standard”. P type tires can be rated XL for Extra Load or “Reinforced” if made to European Standards and tires with either of these identifications would have a max inflation of 41 psi marked on the tire. The rest of the letters C, D, E etc are related to the maximum inflation for that size. NOTE not all tires with the same Load Range letter are rated for the same max pressure.

An example would be the LT275/70R16 LR-C is rated for a max inflation of 50 psi while the LT305/70R16 LR-D is also rated for 50 psi max.
Now what about those numbers and letters such as 101/104Q? The “Q” is the maximum speed rating symbol and the numbers would correspond to the Load Index for Dual application and Single application. There is a table that identifies the load in pounds that correspond to the index. The simple way to think of why this is there and how it can be useful is to think of how you can decide if a different size tire can be used. If the Load Index number is equal to or higher than that would be an acceptable replacement.

All these examples relate to P, LT or ST type tires. I will provide another post focusing on larger Truck-Bus type tires some of which have a completely different dimension nomenclature.

BOTTOM LINE
Whenever you post a question here or in another forum or in an email or even when asking for replacement information at a tire store Please be sure to include the complete size description

Examples:
Most passenger tires will have this format
P235/70R16 104S

Extra Load passenger tire would look like this
P255/60R15 105Q XL

Most newer LT tires will have format like these two
LT235/85R16 116/120R LR-E
LT265/70R17 109/112S LR-C

This would be on some older non-speed rated LT tires
LT235/75R15 LR-C

Recently (Feb 2016) some ST type tires have been made with a Speed Symbol. No matter the speed rating I would consider 75 a MAX and in fact anything much above 60 to be questionable for general safety reasons.

 

[hddecker]

Recently (Feb 2016) some ST type tires have been made with a Speed Symbol. No matter the speed rating I would consider 75 a MAX and in fact anything much above 60 to be questionable for general safety reasons.

Tireman,

I'm pretty sure you had a hand in the manufacture of just about every tire I've bought in the last 50 years.


I agree 100% with you on safe speed, but some times I cheat. Once I'm cross the Rocky Mountains and on to the Great Plains, I'll push it to 65 on the Interstates. I have more faith in the tires running at speeds above 65, than I do in electric drum brakes bringing the rig down to zero.

 

[azdryheat-DUTCH]

Question: Why do Chinese made ST tires fail at such an alarming rate? I've seen these tires fail when not in use, they just pop while still mounted as a spare. Why don't ST's have higher levels of quality? Why would Good Year put their name on an ST tire when it is of such questionable quality. Why aren't ST tires made in the US?

I refuse to use an ST tire; my Voltage has Michelin XPS RIBS.

 

[hddecker]

Question: Why do Chinese made ST tires fail at such an alarming rate? I've seen these tires fail when not in use, they just pop while still mounted as a spare. Why don't ST's have higher levels of quality? Why would Good Year put their name on an ST tire when it is of such questionable quality. Why aren't ST tires made in the US?

I refuse to use an ST tire; my Voltage has Michelin XPS RIBS.

AZ,

Have you ever noted how many people pack up in the morning and go roaring out of the camp ground and not even looked at their tires, let alone chck the pressures.

In fifty years of driving, towing and motorcycling, I have have three flat tires and zero blow outs. Of the three flats, 2 were punctures on a job site and the third was on the bike and I have no idea how it got pinctured.

When I was a kid growing up in AB, there was an ad campain to reduce the number of speed related deaths. I couldn't have been more than 7 uears old at the time, but the tag line "slow down and live." I can see still see it in my minds eye. I was with my mother coming home from visiting relatives, I looked over and noticed the speedometer was creeping up. I said to mom, "slow down and live." About ten seconds later the right front tire blew. From that day forward, I have been a tire fanatic.

Everytime before I hook up, I check the pressures, run my hands over the sidewalls both inner and outer, feeling for abrasions and bulges. When I stop for fuel, I feel the tires for heat, yes feel, I can feel a tire that is running hot and I do a ping test. I know what the tire should sound like when I tap it with my 8 oz ball pein hammer, which is always under my seat. When I hear a thud, I know I have a low tire. If I hear the thud, I give the tire a hug, I check the sidewalls for defects. I have had one tire problem practice

I have had one "tire failure" on the old Airstream and it had nothing to do with. the fact that the Goodyear Marathon was made in China or the USA had no bearing on the failure and everything to do with the curb I bounced the right rear tire off of. I know exactly where I did it, I pulled over as soon as I could and put the spare on.

I hate Chinese Tires, but not because they are all "crap", but because of all the North American jobs that have been exported. When I was a kid, it was Japan that made all the "crap", then came India, now it's China?

 

[chily3]

AZ,


I hate Chinese Tires, but not because they are all "crap", but because of all the North American jobs that have been exported. When I was a kid, it was Japan that made all the "crap", then came India, now it's China?

Totally agree with this. We drive reasonable, usually around 58-60. We are on vacation and no need to speed. It does amaze me how many "trailers" pass us.

 

[Tireman9]

Question: Why do Chinese made ST tires fail at such an alarming rate? I've seen these tires fail when not in use, they just pop while still mounted as a spare. Why don't ST's have higher levels of quality? Why would Good Year put their name on an ST tire when it is of such questionable quality. Why aren't ST tires made in the US?

I refuse to use an ST tire; my Voltage has Michelin XPS RIBS.

I think you have fallen into the trap of confusing "Causation with Correlation"
With maybe 90% or more of TT come on tires made in China and when a majority of TT have one or more tires overloaded why would you expect anything but tires made in China to capture the headlines. Even if a tire made in Never-Never land failed at twice the rate the numbers would be so low that they would simply not register on your radar.

Tires suffer from cumulative damage. This damage does not repair itself. Damage also occurs from age and constant ongoing chemical reactions. The chemical reactions can cause a decrease in the strength of the rubber so tires are always getting weaker, running or not.

Heat from running overloaded, high speed or simply being in the sun accelerates the chemical reaction.

Your RV mfg made the selection of tires and it seems that the only criteria they use is finding the lowest possible cost tire possible. This also means the tires they use have the lowest margin possible. Since the RV mfg accepts no responsibility for their choice and suffers no financial penalty from putting low cost tires on their product why should they change?

Think of it this way. If you were selling tools and didn't have to worry about the durability of the tools but wanted to attract people with a low cost would you buy Craftsman wrench at $2.89 with a lifetime warranty or would you offer Harbor Freight wrench at $1.99 with a warranty that expired by the end of the month.

Auto mfg can make 12v electrical systems that are good for 3 or 5 years,and 50,000 miles maybe longer. Why can't the RV industry make a 12v system good for a couple thousand miles?

I can't answer for Goodyear marketing decisions.

There are some ST tires made in the US. There are also some made in China where the company appears to take quality seriously.

A couple things that would help.

1. If you have a tire failure take a few sharp, well lit pictures with the tire filling the frame.
2. Record and report the full DOT serial so we can identify who actually made the tire.
3. File a complaint with NHTSA.

 

[hddecker]

Tireman,

I have been of the opinion that the manufacturers play fast and loose with the numbers game.
It's a game that I don't play, when it's time to replace OEM equipement I believe in the go big or go home.

Dutchmens choice of tires gave me a 1000# margin for error. When I finally had enough of that game, I decided that I would replace the 10 ply with a 14 ply. I now have a 4000# margin for error or in other words three of the new tires will handle the total GVWR. Since going to the 14 ply I have noted there is less sidewall deflection and the tires seem to run cooler to the touch.

It's been a lot of years since I worked in the auto industry dealing with tires, but even with all of the advancements that have been made over the years, I can still feel the diference between the OEM econo tires and a better tire. Less sidewall deflection makes for less tire squirm and heat build up.

As you said there are some decent off shore ST tires out there, even coming out of China, you just have to look for them.

Causation or Correlation article sums it up nicely.

I'm curious to know if you had a part in the multi-zone tread design. That has got to be the coolest advance in tires in the last 50 years. There sure is a lot more to tires now, they're no longer just that round black thing the you put air in.

 

[MartyG]

Balancing?

Tireman, thank you for joining our forum! We are all hungry for the knowledge and insight you bring. I'd like your thoughts on my theory:
I recently changed my four ST205/75R14's for a U.S. name-brand (though made in China) set. They carry the RH (reduced heat) designator, the C designator, and are rated as 6-ply.
I was at my friend's tire shop when we mounted and balanced them. Clean wheels, no dents/bents, and pretty tires. But they shook like all heck on the balance machine. 3 out of 4 took 3-ounce weights ( the big ones) on both the inside and outside rim. My buddy at the shop said, "oh, yes, those trailer wheels and tires are way out of balance!"
Further investigation finds that wheels do not come from the manufacturer balanced, and many tire shops have said, "we normally don't balance trailer tires" As if, "nobody's riding back there, so why bother?"
My theory is, based on the terrible shaking I saw, that perhaps some of these tire/hub/wheel failures might be traced back to bad balancing issues. Your thoughts?

 

[calewjohnson]

Bad balancing will definitely put undue wear and tear on the suspension components. A few folks on here have replaced suspension bushings and they did not look good. Holes were elongated, possibly from the constant movement of an unbalanced tire.

Cale

 

[wahoonc]

Marty,
The unbalanced trailer running gear is a known issue that the industry chooses to ignore. Unbalanced tires wear thing out faster and run hotter. The trucking industry has spent millions on research on this very thing. One problem with trailers is that is not just the wheel that needs balancing but the entire running gear assembly. The spindle assemblies on most trailers are built to very low tolerance and can be out of round by quite a bit. On my Airstream I used to balance the entire hub and drum assembly. Hard to do anymore no one has the equipment, and it is a bit time consuming.

Aaron

 

[lcv800]

Wheel Balance

Marty,
The unbalanced trailer running gear is a known issue that the industry chooses to ignore. Unbalanced tires wear thing out faster and run hotter. The trucking industry has spent millions on research on this very thing. One problem with trailers is that is not just the wheel that needs balancing but the entire running gear assembly. The spindle assemblies on most trailers are built to very low tolerance and can be out of round by quite a bit. On my Airstream I used to balance the entire hub and drum assembly. Hard to do anymore no one has the equipment, and it is a bit time consuming.

Aaron

My best friend owns a front end shop. He still has an old machine that lets him balance wheels on the car. Maybe check with some "old school" shops.
Rusty

 

[wahoonc]

My best friend owns a front end shop. He still has an old machine that lets him balance wheels on the car. Maybe check with some "old school" shops.
Rusty

We have one too, called either a Spin Balancer or Dynamic Balancer. Ours is an old Hunter unit, probably 40+ years old. No repair parts available unless you luck up on them at an auction or on CL/eBay. We also have a bubble balancer that will take a whole wheel and hub. Problem is all of the current shops use the dummy ones, as in the dummy clamps the wheel on it, pushes a button and puts the weight on where it tells him to. Minimum skills required....

Aaron

 

[azdryheat-DUTCH]

I gotta disagree on some of tiremans comments. I've had Chinese-made Goodyear Marathons and had two blowouts. They were not over loaded and the pressures were checked before each outing but still they blew and damaged the trailer. There was nothing left to take a picture of and Good Year kicked my complaint to the curb. They've got a nice little racket going there - nothing left of the tire means they won't have to pay off.

I once saw an ST mounted on the rear bumper of a trailer with a fancy vinyl wheel cover protecting it. The ST tire blew a hole through the cover while still on the bumper. We've had people on various forums who have also had their spares blow without ever touching the ground. I've seen new trailers at the dealer with damage from blown ST tires while the trailer was enroute to the dealer from the manufacturer.

No, Chinese-made ST tires are complete and total junk and should be banned from use. We saw the public outcry with Firestones blowing up on cars. We have our own outcry about ST tires but nobody is listening, nothing on the media. Nobody cares. And then a supposed tire expert comes along and says it's our fault. Blah, blah, blah.

 

[hddecker]

Tireman, thank you for joining our forum! We are all hungry for the knowledge and insight you bring. I'd like your thoughts on my theory:
I recently changed my four ST205/75R14's for a U.S. name-brand (though made in China) set. They carry the RH (reduced heat) designator, the C designator, and are rated as 6-ply.
I was at my friend's tire shop when we mounted and balanced them. Clean wheels, no dents/bents, and pretty tires. But they shook like all heck on the balance machine. 3 out of 4 took 3-ounce weights ( the big ones) on both the inside and outside rim. My buddy at the shop said, "oh, yes, those trailer wheels and tires are way out of balance!"
Further investigation finds that wheels do not come from the manufacturer balanced, and many tire shops have said, "we normally don't balance trailer tires" As if, "nobody's riding back there, so why bother?"
My theory is, based on the terrible shaking I saw, that perhaps some of these tire/hub/wheel failures might be traced back to bad balancing issues. Your thoughts?

Marty,

I'll leave the technical bit for Tireman, but as a matter of curiosity, where the red and/or yellow dots used as the start point for balancing the tires.

Also some rims have a dot on them. The manufacturers place the dots on the tires and wheels to assist the installer in getting the tire balanced with the mimimal amount of weight.

I had a new set of tires installed this spring and the tire with the most weights has 2oz.

Bad balancing will definitely put undue wear and tear on the suspension components. A few folks on here have replaced suspension bushings and they did not look good. Holes were elongated, possibly from the constant movement of an unbalanced tire.

Cale

The suspension takes a pounding as it is, add to that tires that are out of balance that much the shackles and bolts won't last long.

One of the most important pieces in the suspension is also one that is easiest to overlook. I have to admit to overlooking the bolts and shackles when doing the annual bearing repack.
Won't happen again, greasable bolts mean they will be checked and maintained at least annually.

 

[wahoonc]

Jim,
You would not believe the quality of current manufacturing, especially on the low end, or maybe you would. I have been asked to leave more than a few places because I am going through stacks of items and looking for the best ones. I have the local Northern Tools pretty ticked at me. We needed some replacement rims for one of our work trailers, after the first go around with some of them so bent or out of round they couldn't be used they basically asked me to go somewhere else.

Me and a buddy got thrown out of a local Sears store quite a few years back, we needed some carpenter's framing squares. We had a quarter sheet of plywood and were checking the squares for accuracy, we had about 4 on the good pile and about a dozen in the ain't good enough pile. Had quite the crowd watching us too. Sales manager was not amused.

Aaron