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How Do You Calculate For Spacers?

Spacing the wheels out increases cornering grip and makes the car look better. But you don’t want to space your wheels out too far or the tyres may rub on the arches and the car could fail the MOT inspection.

You could get out your pen, pad and calculator and attempt to work it out but that’s too much hassle.

You need to make a device called a plumb bob. This is a piece of string or fishing line with a weight at the end. I normally tie some washers or a large nut to the end. This keeps the string straight and hanging straight down.

Tape it to the arch directly over the centre of the wheel. Make sure the plumb bob weight is off the ground.

Take a tape measure and measure from the widest part of the tyre to the inside of the string.

This wheel would be perfectly flush with the arch if you fitted a 17mm spacer. However, you are unlikely to get something that precise. It’s up to you if you want to round the number down to 15mm or up to 20mm. Personally, I’d round up. Don’t get too much bigger than required though.

I wouldn’t suggest having the tyres stick out more than 5mm from the arch line.

What About 5 Stud Wheels?

Again, the same method could possibily be used if you have the same centre bore and PCD. You may be able to fit the wheel using 1 bolt and lower the car onto the wheel for the measurement.

Why Do I Have To Lower The Car Down?

The weight of the car has to be on the wheels to make the correct measurement for spacers as the geometry of the suspension and the position of the wheel changes as the body lifts up.

What If I Can’t Fit The Wheels For Some Reason?

Yes, some 5 stud wheels don’t have an offset that will allow test fitting without the spacer as they’ll foul the suspension components. Also, if you haven’t actually bought the wheels yet, you have nothing to measure. In these types of instances, you’ll need a visual calculator and a few readings. Thankfully, it’s something I had made for the site and is available to site subscribers.

Wheel & Spacer Calculator