ALT-4 Tips for Buying Low Profile Tires
Many people buy a low profile tire when they purchase larger wheels for their vehicle. There are a few things that people should consider when they are going to purchase a new rim/tire combination.
First and for most is fitment. You want to make sure that the tire size that your upgrading to will not rub on any of the suspension or steering components. Also, you want to make sure that they will not rub on the inside of the fender well while turning. Care should be taken to make sure that they also do not rub on the inside of the fender during long suspension travel.
Another thing to be sure of, is, tire circumference. Buying a tire is hard enough making sure it will physically fit inside the wheel well without rubbing, and using a proper offset rim. Even after making sure they fit, more than likely after purchasing a larger diameter rim/tire combination, your speedometer will be thrown off. I will explain this. Your speedometer is linked to a speed sensor which is in some way, usually via axle rotation, linked to the tire rotation. Current speed=x amount of tire rpm. raising or lowering the tire diameter affects this greatly.
There is a way to find out how close your new tire circumference is to your factory tire. on most tires you will see something like this.. 185/65/14. Broken down, this means.. tire width(in mm)/% of tire width for side wall height(will be in mm)/rim diameter. So for that size tire that is 185mm wide, the side wall of the tire will be 120mm. Then you reduce that number down to cm, by dividing by 10, giving you 12cm. Now, 2.54cm equals an inch so, we divide 120 by 2.54 which gives us about 4.7inches. Now we can find our tire diameter. We take our rim size and add the tire side wall height(in inches) to it TWICE. So, basically, 4.7 X 2 + 14= 23.4. so, if you want your speedometer to read out about the same, you have to go through a bit of math to make sure it wont be off by an inch or more. Its a lot of work picking out tires!
Lets say you want a 17" wheel and you want a tire to fit, all you have to do is the math back wards. 23.4 - 17 = 6.4. 6.4 / 2 = 3.2. 3.2 X 2.54 = 8.1(81mm). so that means you should try to find a side wall of anywhere between 80-90mm. Now here, you need to remember your ratios tire width/ side wall height(in %)/rim size(in inches). Lets say you want to put a 225 width tire on your car, what size profile will you need? Its hard to say, but most tires come in 5% increments. 35 being the lowest, so start there. 225 x .35 = 78.75, too low. lets try a 40 series, 225 X .4 = 90! Just what your looking for. So, assuming you have the proper offset, and all clearances checked, your tire will not rub, and your speedometer will still be correct.
Another thing about low profile tires is ride quality and rim danger. Most stock size tires were designed with many different performance aspects in mind. Low rolling resistance, good ride quality. When fitting low profile tires, you have to be careful when your driving. A lower profile will not absorb a shock as well as a normal size tire. This could lead to rim damage. Also, you will feel more vibrations inside the cabin of your car. A 35 to 45 side wall height wont absorb as much as a 55-65 side wall height. But, then again, 55-65 isnt really low profile! Hopefully this information helps in trying to find the proper tire for your car!
