The Dif­fer­ence Between Ra­dial & Bias Tires

Cana­di­ans are some­times sur­prised to learn their RVs are out­fit­ted with bias-ply tires

Snowbirds & RV Travelers - - Contents -

Ra­dial tires have been the stan­dard for North Amer­i­can pas­sen­ger ve­hi­cles since the 1970’s. How­ever, when it comes to RVs and trail­ers, many US man­u­fac­tur­ers still out­fit new mod­els with bias ply tires. What’s the dif­fer­ence, and does it re­ally mat­ter which type of tire your RV has?

You’ll be able to find out whether your RV is out­fit­ted with bias or ra­dial tires by look­ing on the side­wall. Just be­low the tire size, you’ll see the word ‘ra­dial’ or ‘bias.’ If it says ‘ra­dial,’ you’re in luck be­cause they’re built to with­stand Canada’s rugged out­doors.

How are ra­dial tires dif­fer­ent from bias? It all comes down to con­struc­tion.

Ra­dial tires, some­times re­ferred to as ‘ra­dial-ply’ tires, are con­structed us­ing a com­bi­na­tion of polyester and/or ny­lon plies that run straight across the tire, from bead to bead. With bias-ply tires, the cords run di­ag­o­nally across the tire, over­lap­ping in a criss­cross pat­tern.

Both ver­sions typ­i­cally fea­ture ad­di­tional steel belt­ing for im­proved dura­bil­ity, tire sta­bil­ity and con­form­ity to the road sur­face. Steel belt­ing also helps your tires re­sist punc­tures.

Due to a ra­dial tire’s de­sign, the side­wall and tread act in­de­pen­dently of one an­other. As a re­sult, side­wall flex isn’t trans­mit­ted to the tread, which is a good thing. It al­lows the ve­hi­cle to trans­fer more power to the ground for im­proved han­dling.

On a bias-ply tire, the over­lap­ping plies tend to be thicker and less flex­i­ble. The criss­cross ply con­fig­u­ra­tion also causes the tread and side­wall to be in­ter­de­pen­dent. So, when the side­wall flexes, so does the tread. This af­fects its abil­ity to main­tain op­ti­mal con­tact with the road sur­face. For RVers who drive on gravel roads in Canada, that’s not wel­come news.

The greater flex­i­bil­ity of the ra­dial tire—or lack thereof in bias-ply tires—also af­fects ride com­fort. Sim­ply put, ra­di­als are bet­ter equipped to ab­sorb bumps and un­even road con­di­tions, which is ex­actly what you want when you’re rid­ing along a gravel road. Mean­while, the in­her­ent stiff­ness of bias-ply tires means pas­sen­gers will feel more of the im­pact and vi­bra­tions trans­ferred from the road sur­face.

And for the Cana­dian RV com­mu­nity, it’s im­por­tant to note that bias ply tires are not read­ily avail­able in tire shops north of the bor­der. So, if you get a flat and need to re­place a bias-ply tire some­where along your jour­ney, you’ll prob­a­bly have to wait sev­eral days to have a re­place­ment shipped up from the US.

Con­versely, ra­dial tires are read­ily avail­able in tire cen­tres across Canada and the US. In the event that tire trou­ble way­lays you while you’re cruis­ing south to your win­ter home in Phoenix or Florida, you won’t be side­lined for long.

One fi­nal point, if you do de­cide to up­grade to a set of ra­di­als for your RV or trailer, be sure to switch your spare as well.

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