Bias Tire Sizes & Disadvantages
Originally posted by Mingoglia
Matt,
My trailer tires are currently 225/75/15. Does anyone have an idea what size tire that would translate to if I were to go to the tow masters? Bias Ply are sized differently, aren't they? Also, what disadvantages are there to bias ply as opposed to a radial?
Approximate Tire Size Equivalence:
205/75R15 = F78/15
215/75R15 = G78/15
225/75R15 = H78/15
The equivalence is not exact, and the load range (B, C or D) must also be accounted for. But you can find either size designation in radial or bias ply. When an "R" appears in the tire size, it's a radial. Check this link for Cheng Shin--Towmaster tires in those sizes:
http://www.gbctires.com/trailer tires.html
Disadvantages that I can think of right off are:
--reduced tread life. Bad if you tow A LOT. Most travel trailer die thru ozone damage or sitting in one place too long.
--lower heat buildup resistance. Maybe yes, maybe no. Garbage radials don't seem to do any better. (I worked at an independent tire store during the Firestone 500 "troubles. ") The best radial tires have mold lines that cross the tread, not run doen the center circumference. I have NEVER seen travel trailer service tires made in the segmented matrix molds that cause the lines to cross the tread. But look at a new Michelin tire, or a new good commercial 18 wheeler truck/trailer radial.
--flat spotting. Most bias ply trailer tires seem to have nylon plies. Once a nylon tire has set in one place for a while, it will form a flat spot until it rounds out again through rolling. That's not normally a problem unless the trailer sits on the tires for months on end. And it's bad for radials also. Your trailer owners manual, if thorough, will *strongly urge* that you get the weight off the tires if the trailer is to sit in place extensively.
Advantages, possibly cynical ones, include:
++ lower initial price, and less investment lost when they eventually disintegrate.
++ no belt to come partly off and tear apart the side of your travel trailer as it flaps apart.
The tires I use on my employer's 6,000 pound gravel testing trailer are commercial Michelin XPS Rib in 9. 50R16. 5. Through a cosmic mistake, they were the low bid seven years ago. They have been excellent in terribly hard use. They have steel belts and steel cord sidewalls, and they're regoovable! Sadly, they're not available in our travel trailer sizes.