What Is the Difference Between a 65 & 70 Series Tire?by Jim Arnold
The series number in a tire-numbering system refers to the aspect ratio of the tire's sidewall height to its width. A series 65 tire's height is 65 percent of its width, a series 70 tire's height is 70 percent of its width and so on. These differences in height affect both performance and safety issues while driving. This tire-size numbering convention is used for automobile, truck and motorcycle tires alike.
According to Walmart's advice on choosing the right size tires, several factors go into choosing the aspect ratio for your tire, as often the choice is based on consumer preference. The higher the aspect ratio number, the taller the tire will be. The lower the aspect ratio number, the higher performance the tire will generally be. Both 65 and 70 series tires can be categorized as all-season passenger tires, which generally have aspect ratios between 65 and 80, but a series 65 tire will give better response while a series 70 tire will offer a better, more comfortable ride.
According to the Generic Auto Tire FAQs in Type2's Technical Library, the shorter sidewall of the series 65 tire means a slightly wider tire that changes the car's handling considerably; specifically, "more rubber on the road provides a better grip." The series 65 provides better turn-in and stability compared to the series 70. Being a slightly taller tire, a series 70 tire would be a faster tire. Generally, series 70 tires are less expensive than series 65s.
Since series 65 tires are shorter than series 70 tires, they can make the wheel wells look empty on certain car and truck models, and this is an aesthetic concern for some owners. Generally, series 65 tires are more expensive than series 70 tires. If you're choosing a series 70 because you want a faster tire, your vehicle's performace can suffer if the series 70 tire fits but is not compatible with the tire recommendations for your vehicle.
If you're buying tires for a classic or older car that used a different tire-numbering system, series 65 tires in most instances will be too wide, according to the Tire Rack's Tire Size Conversion Chart. Additionally, enthusiasts who wish to change their vehicle's tire aspect ratio to something either higher or lower than what is suggested by the manufacturer should take note that any change from the original size can affect the clearance between the tire, fender, fender wells and suspension components, resulting in performance issues and even slightly inaccurate odometer readings. Those using series 65 tires may wish to consider series 70 tires for winter use, as taller tires are generally recommended for better performance in the snow.
Because there is greater deflection with the increased sidewall on the taller series 70 tire, it makes for a smoother ride, according to Dunlop Tires. The series 70 tire thus has better potential handling for vehicles carrying heavy loads. On the other hand, the series 65 tire has better potential for providing the crucial edge you need when driving on roads with difficult and sudden turns.
Jim Arnold has been a business and public-relations writer since 1990, working in-house at companies such as Paramount Pictures and Dolby Laboratories. His writing has appeared in "Frontiers," "Daily Variety" and "Prime Health & Fitness." Arnold has a Bachelor of Arts in journalism from Marquette University.