While automotive experts recommend using four like tires on a vehicle, and specifically the type best suited for the vehicle, exceptions are allowable within certain limits. Within these limits and especially when the limits are exceeded, problems can occur -- the effects proving as harmless as throwing off speedometer readings or as hazardous as creating steering, braking and handling issues. Damage to the vehicle can also result from tire variations.
Tire size can vary by width and height, and although a specific tire is usually recommended for a vehicle to perform optimally, there is a window of sizes that will work safely -- roughly a 3 percent change in size for cars and 15 percent change for SUVs and trucks, according to Tire Rack. Within this window, effects are felt mostly in the steering, braking, acceleration and overall driveability.
When different width tires than recommended are used, the driver may feel the car pull in a certain direction or notice differences in turning and braking, automotive engineer Jeffrey Shaffner says. The most dramatic effect of tire width comes in inclement weather, like snow, he explains. Wider tires don't perform as well in slick conditions.
When taller tires than recommended are used, Shaffner says steering will seem sloppier and the car may take bumps more abruptly. Also, it might take longer for a vehicle to get up to speed and stop. Shorter tires yield tighter, more responsive steering but also decrease ground clearance, which can cause other problems, he says.
Outside of the recommended tire size window, the negative effects magnify and can create an unpredictable and unsafe driving environment, especially in emergencies. Also, tires that are too wide can wear out the wheel bearings and cause rubbing in the wheel wells on turns, Shaffner warns.
Taller or shorter tires than recommended will throw off the vehicle's speedometer readings. According to Miata.net, shorter tires will make the speedometer read faster than the vehicle is actually going, while taller tires will do the opposite - the speedometer will read slower. In addition, Shaffner says gas mileage can change due to the rate the tires are moving -- smaller tires get poorer gas mileage.
Other Serious Effects
The most serious effects occur when mismatched tires are used on a vehicle, Shaffner says. Not only can this dramatically change the handling characteristics of a car by throwing off the weight distribution of a vehicle, it can stress and in worse cases burn out the differential or the transmission, he warns, especially if tires of a different height are mixed and the location of the oddball is on the front of a front-wheel-drive vehicle or the rear of a rear-wheel-drive vehicle. Once again, outside the "safe tire size window" effects magnify.
- Photo Credit altreifen image by Otto Durst from Fotolia.com driving 4 image by Andrzej Borowicz from Fotolia.com speedometer image by Joy Fera from Fotolia.com
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