Help - Trailer Tires - who is lying???

I have a very small 18.5 foot fleetwood 5th wheel and have full-timed in it now for 3 years. Day before yesterday on a trip from S CA to Utah and Salt Lake City I stopped for fuel and noticed one of my trailer tires looked a little low, a Goodyear store on premise at the truckstop told me to pull over and they would air it up...upon close inspection the tires are wearing funny and of course the guy tried to sell me a full set of 4 tires at a hugely inflated price and also told me the tires on there were the wrong tires...

The tires on there are 2 years old, I replaced all 4 about a year after I bought the trailer - I purchased them through a good friend at Les Schwab in Montana and he assured me they were good tires, but now having my doubts...they are a slightly smaller size than the label on the trailer calls for....and they are radial tires - the guy yesterday said I needed bias ply tires for strength.

Here is what is on there: Dynatrail Radial ST - ST 175/80 R-13 - these tires have under 20K miles but the inner and outer edges are worn down past the warning strips??? This does include a round trip to Alaska last summer!

Trailer tag recommends: B78/13B - 13 X 5

So who is right, I will be buying 4 new tires soon and want to get what is correct...

Tire experts and experienced please help...

Jim

With 13inch wheels you are basically stuck with junk for tires.  B is such an old tire designation i doubt most dont evenmknow anout it any longer.  If possible you would be wise to upgrade to 14 inch wheels then your tire choices go up some.  Radial tires are a perfectly acceptably alternative to obsolete bias ply tires.

Let me see if I have this right. You drove to Alaska and back and you are now wondering if you will need to replace the tires? And the inner and outer edges are worn down past the warning strips? How soon can you drive to the tire store?

Hmmmm...... I guess this means I'm old, but I used to sell tires at my service station when we still used the alpha sizes, before we went to p-metric designations.

So what you want to do IMHO is look at a conversion chart and see if what people are telling you is true. On this chart ( http://www.tirerack.com/tires/tiretech/45_conversionchart.html ) we see that "B" in a 13" size is equivalent to a 175-80-R13. Looking at that, it looks like Les Schwab sold you exactly what the trailer calls for, except radial instead of bias ply.

Next look at the weight classification on the tires you have and compare to the actual weight of the trailer. Make sure you aren't overloaded. The outside edges wearing before the center is a classic sign of under-inflation. So you'll also want to look at whatever brand tires you haves inflation chart and compare your trailers actual weight to the pressure recommended.

If you're worn past the wear bars you'll be getting new tires, drive thru a scale before you do and get a weight so you can get a copy of the inflation chart from the dealer, and get tires rated for the actual weight and get the tires properly inflated when they're installed.

I don't have extensive experience with trailers so I have no strong opinion on radial vs bias ply on them.

Ken

Won't the inner and outer edges wear down if they don't have enough air in the tires? Cathy

SeilerBird said:

Let me see if I have this right. You drove to Alaska and back and you are now wondering if you will need to replace the tires? And the inner and outer edges are worn down past the warning strips? How soon can you drive to the tire store?

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Tom not wondering if I need to buy new tires wondering what kind I should be buying....I am a little surprised at only having about 16K Miles on them, but know they took a bunch of abuse going to Alaska!

bucks2 said:

Hmmmm...... I guess this means I'm old, but I used to sell tires at my service station when we still used the alpha sizes, before we went to p-metric designations.

So what you want to do IMHO is look at a conversion chart and see if what people are telling you is true. On this chart ( http://www.tirerack.com/tires/tiretech/45_conversionchart.html ) we see that "B" in a 13" size is equivalent to a 175-80-R13. Looking at that, it looks like Les Schwab sold you exactly what the trailer calls for, except radial instead of bias ply.

Next look at the weight classification on the tires you have and compare to the actual weight of the trailer. Make sure you aren't overloaded. The outside edges wearing before the center is a classic sign of under-inflation. So you'll also want to look at whatever brand tires you haves inflation chart and compare your trailers actual weight to the pressure recommended.

If you're worn past the wear bars you'll be getting new tires, drive thru a scale before you do and get a weight so you can get a copy of the inflation chart from the dealer, and get tires rated for the actual weight and get the tires properly inflated when they're installed.

I don't have extensive experience with trailers so I have no strong opinion on radial vs bias ply on them.

Ken

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Thanks Ken for the informative reply - I am going to upgrade to the next higher weight rating - like a class C and think maybe I will see about trying a set of bias ply vs the radials and see if it makes a huge difference. The guy at the Goodyear store pulled two same size one, radial and one bias ply and pushed down on the unmounted tire and it was significantly stronger than the radial version and he said he always recommends using a bias ply on trailers vs a radial! If I can find a scale around here, I will weigh the truck and trailer, should not be a problem here in Salt Lake!

BTW - All the tires were at 40 pounds and the tire recommendation was 50 pounds - so all lost about 10 pounds since leaving California, I checked them all before I left and they were at 50!

So that will be my plan unless in my research I find something else out, thanks for the replies people, this is a couple weeks away, I am parked now for at least three weeks here in Salt Lake, so no issues on traveling, there will be 5 new tires on when I leave 4 plus an identical spare. The spare on the trailer now is a passenger tire and older than sin...

Thanks again, keep adding more info and opinions please...

Jim

Maybe this chart will help you.

http://www.trailerwheel.com/accessories_tireswheels1.html

FastEagle

You got st rated tires. Which have a 6ply construction. Verses 4 ply.  So they are trailer tires.    Do you have them inflated to 50 lbs.    I'm with you.  Never trust the high psi sales pitch with loom and gulm. And a bit of fear mongering. You have gone 20 k. Your doing something riht

I'd much prefer the radials over bias ply. The bias ply will wear faster than radial ply and provide a stiffer ride (all else being equal ). It sounds as if you got the right tires and replacing them would be appropriate.

Note that you need to check the pressure more often, particularly when it gets colder (going North) as pressure drops with temperature (also be sure you set the pressure when the tires are cold - before driving on them).  As to wear, 13 inch is a small tire and may well have softer rubber.  Radials will last much longer if they have the same tread compound.

Ernie

The guy at the Goodyear store pulled two same size one, radial and one bias ply and pushed down on the unmounted tire and it was significantly stronger than the radial version and he said he always recommends using a bias ply on trailers vs a radial!

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Stronger in what way? How did he show that? Bias ply isn't inherently stronger than radial, but the bias construction tends to have stiffer sidewalls. However, ST (trailer) tires are always constructed with stiffer sidewalls than other types, e.g. passenger car tires. It's the primary characteristic that gives the ST designation instead of P or LT.

Forget about bias ply and focus on the tire's actual load rating, i.e the max weight the tire is designed to carry. That number will be embossed right on the tire sidewall. And note the pressure (psi) required that capacity, also on the sidewall. Make sure you always are inflated to that pressure. The combined load capacity for the two tires must equal or exceed the actual weight carried by the trailer axle.

You ran the tires 10 psi low for some substantial portion of a 16,000 mile trip. That readily explains the uneven wear and frankly its amazing you didn't have a blow out or two or three. Count yourself lucky. Tire gurus advise that you should check your tire pressures daily before starting out. That may be a bit extreme, but you should certainly check them periodically. I would suggest weekly until you have established a safe interval that will reliably detect a loss of more than a couple psi. You don't want to run even a few percent low for very long.

Gary RV Roamer said:

Stronger in what way? How did he show that? Bias ply isn't inherently stronger than radial, but the bias construction tends to have stiffer sidewalls. However, ST (trailer) tires are always constructed with stiffer sidewalls than other types, e.g. passenger car tires. It's the primary characteristic that gives the ST designation instead of P or LT.

Forget about bias ply and focus on the tire's actual load rating, i.e the max weight the tire is designed to carry. That number will be embossed right on the tire sidewall. And note the pressure (psi) required that capacity, also on the sidewall. Make sure you always are inflated to that pressure. The combined load capacity for the two tires must equal or exceed the actual weight carried by the trailer axle.

You ran the tires 10 psi low for some substantial portion of a 16,000 mile trip. That readily explains the uneven wear and frankly its amazing you didn't have a blow out or two or three. Count yourself lucky. Tire gurus advise that you should check your tire pressures daily before starting out. That may be a bit extreme, but you should certainly check them periodically. I would suggest weekly until you have established a safe interval that will reliably detect a loss of more than a couple psi. You don't want to run even a few percent low for very long.

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Thanks Gary for the information - I checked the tires before I left California and all four were at 50 pounds. I always check them before leaving someplace and then again after running about a 100 miles or so....but somehow they all lost about 10 pounds pressure in about 2 days and 600 miles??

As for how they were stronger - the rimless tire was much more sturdy when standing up and pressing down on the top of the tire tread, very hard to try and flatten where the radial of the same size was much easier....

I will be moving up a grade to a C class tires for more weight and probably a 185. Hopefully that will help the situation.

Thanks everyone for the information...

Jim

One other point on the bias v. radial ply discussion, radial tires also have a lower "rolling resistance" which translates to "they are easier to tow", which also means better fuel mileage.  I have no idea why anybody would recommend bias ply tires these days - even the heavy truckers are discovering the advantages of radial - but their tires are a LOT more expensive!

As for how they were stronger - the rimless tire was much more sturdy when standing up and pressing down on the top of the tire tread, very hard to try and flatten where the radial of the same size was much easier....

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Well, that's probably good salesmanship but doesn't mean anything at all about tire strength. Radial tires are designed to flex more vertically, so they squash more easily in the show room and look "softer" when on the vehicle. That doesn't tell you a darn thing about the actual strength, which shows up in the tire load capacity specs.  I'll assume that salesman was well-meaning (since he doesn't make any extra money selling you bias ply), but he is also ill-informed. Or at least 25 years out of date in tire technology.

First off let me say this. Down sizing tires is hardly ever recommender and never recommended when the down size provides less load capacity than the Original Equipment tires. 

Personally I think every tire design has a market place. Bias trailer tires are kept up to date by their manufacturers and have a solid niche market. Bias trailer tires of the same size have the same load capacities as radial trailer tires. However, the bias tire may have extra durability built-in. Durability does not relate to tire strength. It just may have added protection from hazards.

Here is a reference.; ?..(http://www.carlisletransportationproducts.com/product/tires/trailers-toy-haulers-towables/sport-trail-lh).

FastEagle

My !st post
Wigpro,
            No one's lying it's just trailer tires.  You can go to any board rv, boat, truck and find opinions on all the trailer tires you want and the argument between st and lt.  I personally think you did well getting 16k out of your set because most folks have to replace them due to rot caused by under use or tread separation due to quality control or to much tire heat (under inflated n overloaded) .  I saw you were under by about 10psi so that droped your weight rating about 20% + a tire.
    I personally run Goodyear  LT AT 15" E rated tires on my 26 5th that has 7000lb cap. I have put about 7500 mi in 3 yrs towing from SoCal to CO 2 times, Oregon last summer, and about 7 runs to the Eastern Sierra's and some local trips.  The miles I put on are not easy miles either, up and over 8000' -  10,00' passes in the Rockies 7 - 9 times? , countless dirt roads, CA hwy 49 in the NoCal gold county (white knuckle day), 70 mph on 110 degree + days in AZ and NM, many a jackknife parking and turn a rounds.  One reason I went this route was the fact I was able to get a E rate 10 ply and a 110 mile speed rate and a low psi for my aluminum rims.  I have been very happy with my results but others might not be.  I included a link to Etrailer who have a lot of good info and a ST tire you may be interested in. 
Good luck to ya
Doug

http://www.etrailer.com/Tires-and-Wheels/Kenda/AM10210.html  - D rated 1600lb
Here's some good tech reading on tires: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=194

ps I got my tires at Americas Tire due to internet price match (cost + ship + road hazard + # of stores)

I always check them before leaving someplace and then again after running about a 100 miles or so....but somehow they all lost about 10 pounds pressure in about 2 days and 600 miles??

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Did you put the valve stem caps back on?  Schraeder valves aren't really great seals, and a piece of grit can keep the valve from sealing completely.

That's what the valve stem caps are for - to keep debris out of the Schrader valve and to keep the air in the tires if a valve springs a slow leak.

A B78 is a passenger tire designation  (4 ply rated) and was common on small light weight trailers. Many ST tire makers manufactured them however I haven't seen the B78 advertised in years on ST tire webs.

Bias ply is ancient tire tech. The tire dealer in question probably has lots of area lawn service trailer owners. Bias ply tires are cheap and works great  on these types of trailers that spend their life on short trips around town.

Their biggest issue  is they develop lots of internal heat at highway speeds. Much more than the radial.
I pulled flatdeck trailers to make a living when all tires were bias ply. Yeah that was many years ago. I moved all of my trailers to radial tires when they came out and saw a big increase in tire reliability and much longer tire service.

Inside/outside tire wear can be under pressure or a overloaded tire. Don't mess around with those minimum pressure tire charts for tires on a trailer. Loads on tires on a trailer change constantly ..example is a strong side wind which can cause tires on one side to run very hot and the other very cool.

Most ST tire makers recommend max pressures for good reasons. Carlisle and Goodyear both recommend max sidewall pressures. In fact its part of Carlisle new tire warranty.

The Carlisle RH is supposed to be a much improved tire the last couple of years with the addition of the nylon tread cap along with the treads steel belts. 

Good advice from Longhaul.

When you ask for a B78 13 trailer (ST) tire, most shops will give you a 175/80-13 anyway. There are bias ply ST 175/80's available, usually designated 175/80 D13 (vs R13 for radials). Greenball Towmaster is one brand that offers that size specifically for trailers.

Buy a tire made for trailers at the manufacturer's recommend size. It's not a bad idea to go up one weight rating.  Keep in mind that if you blow one tire, you can immediately overload the remaining tire, which could then blow and leave you in a real predicament.  I run my trailer tires at 45 psi.  60 is max, and lower air pressure affects handling.

You don't gain any load carrying capacity by going from a D to an E rating - unless you inflate the E tire to a pressure that exceeds the D tire's maximum pressure.

Both tires share the same weight vs. pressure ratings up to the maximum inflation pressure of the lesser tire,  the higher rated tire can only carry higher weight at higher inflation pressures.

Bridgestone shows this most clearly in their tire inflation tables.

Taking the first tire in their light truck tire chart on Page 93 as an example, an LT205/75R15 as a single tire has a maximum load rating of 1260 lbs at 35 PSI, 1655 lbs at 50 PSI and 1930 lbs at 65 PSI.  The C tire load and pressure limit is reached at 50 PSI, the D maximum is 65 PSI.

Buying a higher rated tire does no good unless you run it at inflation pressures above the rating for the lower rated tire.