View Full Version : trailer tires bias vs radial

09-20-2005, 09:45 AM
I have always run bias ply tires on my trailer. Since bias ply tires are getting harder to come by I'm thinking about switching over to radial tires.

Can anyone tell me what the difference is between bias tires and radial tires?

Will I get better or worse gas mileage?

Will the trailer track better or worse behind the tow vehicle?

09-20-2005, 10:48 AM
You can use either type of tire on a trailer as long as they have "ST" ratings. Trailer tires need stiffer sidewalls than automobile and even light truck tires in order for them to track straight. The only advantage to bias ply tires is that the sidewalls are generally stiffer than on radials. So many people think that they track better and can handle heavier loads. Radials run cooler than bias ply tires, so they generally last longer when used at higher speeds. So the choice as to which is better depends on how close to your tire's maximum load rating you will be operating. For heavy loads, bias might be better. For lighter loads and higher speeds, radials are generally better. In any case, radials will always give you better fuel economy because of the lower rolling resistance afforded by the design.

09-20-2005, 12:08 PM
Thanks drstressor for the info and answering my questions. Also, the additional info that you provided will come in handy.

I didn't know about the "ST" rating at all. Will using radial tires without the ST rating be any reason for concern or is it just the strength of the sidewall?

09-20-2005, 12:13 PM
I have the Goodyear Marathon radials on my trailer for about 2,500 miles without any incident. Has anyone had any bad experiences with them?

09-20-2005, 12:16 PM
Don't use radials unless they are ST rated. The sidewalls flex too much and the trailer will tend to wobble rather than track in a straight line. This is not a good thing with a heavy load and will damage the tires.

BTW, ST stands for *"Special Trailer".

I have had Marathons on my trailer and they worked well for about 10,000 miles. That's about what you can expect from a good set of tires on a trailer.

09-20-2005, 12:26 PM
OK, thanks for the reply.

09-20-2005, 01:34 PM
Thanks Doc, in that case hopefully I can get another season out of them ;D

09-20-2005, 02:26 PM
The rule of thumb is 5 years on a set of tires regardless of the miles.

09-20-2005, 05:55 PM
On radials, ST stands for the speed rating of the tire. Generally between 90 and 100 MPH. Radials are not rated for trailers and generaly are not recommended. The reason is the difference of side wall plys between Bias and radial tires as well as the adheasive quality of the tire. The heavier plyed sidewall on bias tires prevents the trailer from fishtailing back and forth. Radials have less sidewall plys so they will give a more soft cushioned ride making it easier on the passenger. Radials will balloon out. Bias plys are normally nylon and nylon when it sits for some time, will develop a flat spot until the tire heats up. Radials have steel belts which have the advantage of less rolling resistence. Thus giving you much better milage. Take note that the rubber content verses the carbon content in the tire will deal with road adheasion and wear. Bias tires use less carbon so the tread is a softer content and will have better adheasion. (less slide) Radials are a harder/denser mix and will give you much better milage but adheasion will suffer.
I have a 15' Klamath on a EZ loader trailer and the bias tires lasted only one season. My decision was to put radials on it for much better milage. They work fine being within the weight rating. The only thing I would be extremely causious of is rough road use. The sidewalls will take very little abuse at all. Sharp rocks ...... If you do install radials have inner tubes installed in them. This is good preventative messure against poping the bead loose on the wheel rim.

09-20-2005, 07:09 PM
The rule of thumb is 5 years on a set of tires regardless of the miles.

unless you are heading to Lake Powell across the Extra-Terrestrial Hwy. at a really nice clip and come up on some cows in the road, and your surge brakes lock up the front trailer tires and put flat spots in them ;D ;D ;D

09-20-2005, 08:14 PM
Dale, a lot of what you posted is just flat out wrong. >:(

ST (Special Trailer) radials are fine for trailers and have in fact have significantly replaced bias ply tire on OTR truck trailers. I've researched quit a bit about trailer tires over the years. If you don't believe me, read some of the links below.



http://www.subaru.com/owners/carcaretips/index.jsp?pageid=091903trailer_safety&navid=TRAILE R-TIRE_SAFETY


Remember, I never lie and I'm always right. ;) ;D ;D ;D

09-20-2005, 08:30 PM
I think what Dale is referring to is the speed rating which is usually a single character an "S" speed rating is a tire rated to 112 MPH. Doc is referring to the ST incorporated in the tire size like ST/205 75 15 which would refer to a trailer tire. Should be two different things.

09-20-2005, 08:32 PM
Yeah. Dale had that confused. Along with a few other things. ;)

09-21-2005, 05:04 AM
Ask FISHSTALKER about rebuilding a kitchen and I bet he'll kick your butt with his knowledge. Remember Dale, even when Doc is wrong he's right ;) ;D ;D

09-21-2005, 05:31 AM
So my 6 year old trailer tires need replaced even though the boat lives in the garage?

09-21-2005, 07:04 AM
It's UV light from the sun and the stress of bearing a static load when the trailer isn't moving that does most of the damage. I would recommend getting 6 year old tires inspected by someone who isn't just going to try and sell you new tires. Look for superficial cracks in the sides. They usually indicate that the tires are getting brittle.

Mickey, I'm not really always right. ;) But I don't post anything if I don't know what I'm talking about.

09-21-2005, 07:11 AM
Me either ;)

09-21-2005, 07:14 AM
OK. We're both full of it then. ;) ;D

09-21-2005, 07:16 AM
Dale, a lot of what you posted is just flat out wrong. >:(

ST (Special Trailer) radials are fine for trailers and have in fact have significantly replaced bias ply tire on OTR truck trailers. I've researched quit a bit about trailer tires over the years. If you don't believe me, read some of the links below.

Well..........excuse me, comments stating "I am flat out wrong" and that "I am confused about a lot of things" surprises me and does make me grit my teeth. Having worked for four years as a commercial tire Rep up until 1996. Of coarse I have no doubt there have been many advances in the industry and that I may not have present day knowledge of.
I will state that most of what I had posted echos the tire characteristics and differences that Doc had posted.

Unfortunately Doc states that the ST tire is a RADIAL.
In fact it is a BIAS PLY tire. I use the following quotes from the information sites Doc supplied.

"THE METRIC SYSTEM - (ST205 75D 15) currently being phased in by trailer tire manufacturers, indicated the tire application type (ST-special trailer), the section width (205mm), the 'Aspect Ratio' (75), the construction type (D= bias ply), and rim dia.(15") "

Modern ST tires feature materials and construction to meet the higher load requirements and unique demands of trailering.
"The major difference is reflected in the polyester cords used in ST tires," said Tim Fry, senior development engineer with Goodyear Tire & Rubber Co. in Akron, Ohio."

"Incidentally, all ST tires have a maximum speed rating of 65 mph."

"Eastern Trailer carries a full line of nylon bias ply trailer tires. These 'Special Trailer' (ST) tires have been constructed for better high speed durability and bruise resistance under heavy loads. Trailer tire construction varies substantially from automotive tires, therefore it is essential to choose the correct tire for your towing application. In general, trailer tires have the same load range (or ply) from bead to bead and are bias ply construction. This allows for a stiffer side wall which provides safer towing by helping to reduce trailer sway problems. The use of 'Passenger Car' (P) or 'Light Truck (LT) tires a on a trailer is not recommended because their construction, usually radial or bias belted, allows for more flexible side walls. This could lead to increased trailer sway and loss of control."

I stand with my original post and the information contained in it. Take it for what it's worth. In any event it is good to be challenged so that any "confusion" can be corrected and the truth be told.

09-21-2005, 07:35 AM
Dale, ST tires come in both radial and bias.



Things change over time. ;D

09-21-2005, 08:13 AM
I stand corrected. :-X This is new since I left the business. I am not familiar with Maxxis brand name but that means nothing. It says it's a high speed tire but does not list a speed rating? Other States allow trailering speeds higher than 55MPH. 65mph in Nevada and if memory serves me right, it's 70mph in Oregon.
Thanks for the update Doc.

09-21-2005, 08:56 AM
Hey Sellhomes2fish do your radial tires have the "ST" rating?