Wheels and tyres

Fitting different or larger wheels and tyres 

Tyre chart

There are many different options when changing your wheels or tyres. In fact the combinations are almost endless. That is one of the reasons why a lot of people who modify their vehicles turn their attention to the wheels. It is a highly individualistic affair, so therefore I will not tell you what brands to go for.

The information I am putting up here is solely designed to help you with measurements and fitting of various sizes. This will help you to understand the sizing and measuring techniques used in the wheel industry.

First of all, your stock EJ-EH has 13 inch rims that are 4.5 inches wide. The original tyres were like pizza cutters and of a crossply bias. That means no steel belts folks. This gave very roly poly handling, but if you are going for a concourse rebuild you will have to retain them for originality. There are companies that can supply whitewall versions, or put them on using a latex insertion technique. Most EJ-EH’s now have 185/ 75 / R13 radial tyres fitted. This is the most common sized steel belt radials used.

What does this mean? 185/ 75/ R13? 185 is the width in mm of the tyre. 75 is the series, and is a percentage of the width. Therefore the height of the tyre is 75% of 185 or 139mm. The R means Radial (other letters give higher speed ratings up to Z which is 240kmh plus). 13 of course is the rim diameter.

Here is a chart which you can use to work out which tyres are the same or similar height, so you don’t end up with huge ballons, or tiny donuts. find the size of tyre you currently have, and work your way left to right to find larger rim sized tyres that would be suitable for your vehicle. The tyre code is in the top of each cell, and below the code is the tyre height in mm, the minimum rim width required in inches and the actual fitted tyre width in mm. Using the chart we can see that our standard 185/ 75/ R13 has a very similar tyre height to a 195/ 50/ R16. The only factor you would have to take into consideration is the difference in width and if your vehicle is lower.

This brings another factor into it all. Your rim offset. Rim width is measured internally where the bead of the tyre seats. Therefore measuring a rim completely across its outside width is wrong. You will find a 7 inch mag will measure almost 8 inches across the outside width. The offset is measured from the central point of the rim, and is positive in mm if the wheel sits further in to the car centre, and is negative in mm if the wheel sticks further out of the car. The other way to measure is backspace, and it is measured by laying the rim flat on a bench and sticking a ruler through the central hub hole and getting the measurement in inches to the face of the rim that touches your hub or disc on your car.

Most reputable tyre and wheel stockists have all of the original offset measurements, and can work out your wheel and tyre combo for you. You must remember that a HR front end will change the offset required, and different discs will change your offset also. See the info on disc front ends. You will also have to check with your insurance and State road authority to see if the rims you would like are legal.