Provided the tire and the rims have the same internal diameter, you can change tire size on the same rim.
Since tires are flexible, you can change the width and the height.
Most drivers do not give much thought to their tires and wheels size except their outlook or beauty.
However, you should be considerate about the size of the wheel and the tires you put on your vehicles.
They are both essential, and using inappropriate tires is costly and can be very dangerous.
Does Tire Size Really Matter?
Yes, the size of the tire matters.
Let me put it this way your car gets more grasp on the road when the tire is large. Thus, with the increase in the tire’s width, a larger surface area of the road is covered too.
Therefore, the increased contact with the road means that your vehicle has more grip, thus, the increased ability to move and handle.
So, you should consider looking at the size of the tire because it matters!
About the size of the wheel, well, it depends.
First, you need to understand that wheels and tires are independent thus not interchangeable words.
Tires are part of the set-up of the wheel. Look at it this way, your car has a specific set size of the rim, but it is possible to buy different sizes for those rims provided the middle of the tire is the right size.
Thus, vehicles whose rims are oversized fit larger tires compared to other cars.
Reading Tire Sizes Numbers
It is possible to learn and understand all numbers and letters on your sidewall with a bit of explanation.
Such numbers are an indication of the tire’s size, type as well as performance.
Type of the Tire
A P-metric tire has the letter “P” at the start of the tire’s size.
P-Metric tires are tires designed with a particular standard in the US for passenger vehicles.
On the other hand, Euro metric tires lack letters at the beginning of the tire size.
Thus, P-metric and Euro metric tires do not have the same load capacities.
Also, the letter “LT” at the beginning or end of tire size indicates that the tire is useful in light trucks.
Some automobile manufacturers design light trucks with “LT” tires. Hence, the need for higher inflation pressure for the tires compared to passenger-type tires.
However, to be sure about your car’s specific type of tire and inflation pressure, you should consult your placard or owner’s manual.
One would wonder whether the tire’s breath is measurable from the sidewall to the other side of the wall in millimeters.
Well, simply, the starting three numbers in the tire’s size represent the width.
If the tire’s size is P215/65 R15, then the tire’s width is 215 mm.
The wheel diameter is equivalent to the size of the tire it is supposed to occupy.
Thus, to get the diameter of the wheel, you need to measure from one end to the other end of the wheel.
For instance, a tire of P215/65 R15 fits a wheel with a diameter of 15”.
Aspect ratio is the first two digits that come after the slash mark on the tire’s size.
For example, if the tire’s size is P215/65 R15, 65 indicates that the tire’s breadth is equivalent to 65%.
Thus, when the aspect ratio is high, the sidewall of the tire is also high.
Speed rating gives the tire maximum speech capability.
Usually, you will find the speed ratings at the top side of the vehicle’s speed capability.
For instance, tires with the highest speed rating have the highest speed capability as 130 mph or 210 Km/h.
Therefore, it is illegal to speed past the recommended limit.
Load index shows the highest amount of load supported by a tire when there has been proper inflation.
Also, you can find the maximum load of the tire on its sidewall, in either pounds or kilograms.
Two Different Size Tires on Front and Rear
The vehicle will operate fine provided both front wheels and rear wheels are the same, and the geometry’s suspension is designed to accommodate it.
If the vehicle is four-wheel-drive and the wheels are different in the front and rear, it can be dangerous with centre differential not unless the design was for that purpose.
Therefore, if you fit a space saver wheel with a smaller diameter than the actual one, ensure to keep your speed at 80KM/h and below. Also, you should only drive to the distance where you are getting a wheel replacement if you don’t want to damage your differential.
If you speed up the vehicle, it is likely to pull towards the direction of the small wheel.
Cars should use a space saver wheel just like trucks spare tires of different sizes.
Does Changing Tire Size Affect Transmission
Changing the tire size affects your final drive ratio but not your transmission. The difference you get depends on the difference in the tires compared to stock tires.
Larger tires lower your final drive ratio; therefore, the car will go further with every tire revolution. Hence, the speedometer will also read low.
Smaller tires are likely to raise your final drive ratio. Thus, your vehicle cannot go as far with every change of the tire.
However, the effect is not much, and tires with a huge difference are even more challenging to fit.
You may fail to notice as much unless you raise the vehicle or do something that significantly allows the tires to differ.
Can you put 235 tires on 225 rims?
Yes, you can put 235 tires on 225 rims. However, it is only possible if the car rims can accept large millimetres.
225 tires are 225mm vast tires used for light vehicles.
The diameter, weight and overall form factors are less in 225 tires than in 235 tires.
225 tires are perfect for small cars, which can carry a smaller load, while 235 tires are 235millimetres wide tires and are useful for heavier cars.
Their diameter, factor, form, weight, among other measurements, are more than 225 tires.
Thus it is recommended to use 235 tires for heavy cars because they provide more stability than 225 tires.
Final Thoughts on Changing Tire Size on the Same Rim
Wheels and tires are essential components of your car. It is important to note that you cannot use wheels and tires interchangeably. Tires are part of the wheel’s design.
Thus, the rim of your car has a specific size, but you can purchase tires for fitting the rims provided the tire’s middle is of the correct size.
Hence, you can change the size of the tire on the same wheel.
Also, give it a second thought when choosing tires for your vehicle, not just for their beauty but for their service.
Therefore, to avoid making mistakes, know your vehicle and ensure your wheels are safe.
Hi I’m Marshall based in 1478 Doctors Drive Santa Monica, CA. I’m your DIY Car Repairman with more than 5 years experience in automobile repair, a skill I learned from my old man.
I started this blog to share my experience on both simple and technical aspects of your car.