235/35 R 19 91 Y
Ever wondered what the cryptic gobbly-gook really is that’s scrolled across the four doughnuts of rubber elevating your car above terra firma? You’re not alone!
What language is 235/35 R 19 91 Y anyway? Automotive or a one of the several dialects of automotive called Tire. For today’s discussion we’ll be deciphering the OEM tires that came with my 2016 Volkswagen Golf R. R you ready to get started?
In case you don’t have reason to memorize the stats of your tires, and let’s be honest who does these days, there are really only two pieces of data that are critical. Tire pressure you say? Nope! That information is usually found on the jamb of the driver’s door. The most important piece of information found on the tire, is actually on the inside sidewall, and it’s the D.O.T. serial number. This tells you the birthdate of that tire, and as we all know by reading the article last week written by Matt Farah for The Drive (CLICK HERE) we know that tires have a life expectancy, and it’s best not to go past the expiration date on these bad boys. Please check that date before installing them on your car or truck.
This is the first set of numbers in the series from left to right on the tire in the photo. This is a measurement of Width, specifically from sidewall to sidewall in millimeters. Specifically which points measured for width can vary from manufacturer to manufacturer, but in this example the tire is a Continental and their practice is to measure sidewall to sidewall for this measurement.
Since we are metric-averse here in the US let’s look at it in a way that’s easier to digest. 235 millimeters equates to 9.25 inches. Now think about this for a minute, using this example at any given time there are only four sections of 9.25″ wide rubber contacting the road. That’s all that’s providing grip, handling, and braking while you drive. Wider is better or performance, but everything is a balancing act and not without its drawbacks. For one consideration increased traction causes increased friction which tends to lower the fuel economy since their is more resistance by way of contact with the road surface. If you have a sports car with power enough to benefit from wider rubber, it will enhance the performance of the car. Conversely if you have a momentum type vehicle or one that may be a bit underpowered, and cannot quickly recover from scrubbing speed off, you’d actually worsen the performance by sticking wider rubber on. Another considerations include depth of the wheel wells on your vehicle, and whether you’re prepared to modify it should you choose to exceed the maximum OEM design specs. Lastly, do you want the extra weight added to your vehicle? More rubber means more weight which could in turn lead to new wheels (more weight) to accommodate the wider tires.
Ok, now that you know the first number is the series deals with width, care to take a guess at the second number? Very good! It’s the sidewall height, also known as Two figure aspect ratio. This aspect ratio of “35” means that the tire’s section height is 35% of the tire’s width. In this case that would be a little under 3.24″. This ratio is not ideal for overall ride comfort, and is indicative of “Low Profile” tires with little or no sidewall. The main advantage of smaller aspect ratios is cornering and handling. And the exact reason smaller aspect ratios are better for handling which is also its biggest disadvantage namely dealing with any imperfections in the road. Any pothole, dip or variation of a perfectly smooth surface will be transmitted through the suspension directly to the cabin. Additionally, because of the reduced height, the tire has less absorption capabilities to compress as much when it encounters imperfections which could cause the tire to pinch the wheel or fail by puncturing the sidewall. If you’re commuting logging trails or our nation’s capital, and want to avoid replacing tires as fast as your DVR records a show then look for a minimum of “50” for the aspect ratio.
R stands for Radial construction. The radial tire was invented in 1946 by Michelin, and sort of revolutionized tires. Radial construction means that the cord piles are laid perpendicular across the treads (radially from the center), and that means that any sidewall flex will not be transmitted to the tread. The footprint only lengthens. There is little to no transversal slip. The radial tire allows your car to transfer more power to the ground. Any tire with the letter “B” in this position stands for bias, and it’s the exact opposite of radial construction where the cords are overlaid over other sections. This is not ideal for comfort or performance driving characteristics. Think agricultural or special use applications. Just think of “R” for race or roads, and you’ll be fine.
19 in this example stands for Diameter. Oddly enough this is one of the only specs listed in imperial units of measurement versus metric. One for ‘Merica! Do I need to say anything more about diameter? Oh very well: di·am·e·ter
a straight line passing from side to side through the center of a body or figure, especially a circle or sphere.
This section of the tire codex deals with Load Index. You can look your tire’s capacity HERE by using Tire Rack’s helpful chart. The chart indicates that this tire can safely accommodate 1,356 pounds. Just for reference the R weighs in at 3,300 pounds.
Now the good stuff! This section deals with the Speed Rating. This system starts with the letter “L” probably for lowest speed (not really sure, but makes sense to me), and runs all the way to “Z”. “L” has a rating of 75 mph, and that then would lead you to believe a “Z” rated tire would have the highest rating, right? But it doesn’t. That award goes to “Y” at 186 mph. Any car operating above 186 mph will most likely be sporting rubber specifically designed to accommodate that car, and its higher top speed. The bad news is you won’t be able to get them from Tire Rack, and they will most likely be pricey.
So there you have it, a brief primer into deciphering that run-on sentence of alphanumeric scribbling on your tires. I hope it’s been helpful, and I wanted to you know that Continental Tire, Michelin, and Tire Rack have a ton of useful information about these products if you really want to get into the weeds with rubber!