Maximum Tire Size New Defender L663

Before we get into the topic of maximum tire size, first a brief explanation of how tires are designated in the metric (European) and inch (American) systems:

In Europe, we designate tires according to the system:

Tire width in mm / height of the tire (as a percentage to the width) and lastly the diameter of the rim, this time in inches.

So a tire with the specifications 275/55 R 20 would be a tire with 275mm width, a sidewall height of 151.25mm and a rim diameter of 20 inches.

If you want to calculate the tire diameter, you add the double sidewall height of 151.25mm to the rim diameter of 20 inches (1 inch = 2.54cm), i.e. 508mm and get a diameter of 508mm+ 151.25mm + 151.25mm = 75.97cm –> rounded 810.5mm.

While we Europeans use a strange mixture of millimeters, percentages and inches, the Americans are a bit simpler:

 

Inch System

In the inch system this tire would be: 30 x 11 R 18 tire

The designation there designates: tire diameter / tire width and rim diameter – all values in inches!

So the tire is 30″ in diameter (=76,2cm) and 11″ wide (= 279,4mm) and has a rim with 18″ diameter.

 

Calculate tire diameter, why?

The reason why I explained in the above example how to calculate the diameter of the tire is that in the offroad sector it is always about achieving the largest possible tire (and by that you mean the diameter)?

Quite simply, the larger the tire, the more ground clearance (because the wheel receiver comes further up) and the larger the tire, the easier it is to roll over obstacles.

At another point, however, the diameter also plays a very decisive role, namely in the wheel housing of the vehicle. The larger the tire, the faster it rubs somewhere in the wheel housing. The wheel housing is therefore one of the factors that determines the maximum drivable tire size.

Another limitation, especially in Germany, is the TÜV. When I change the tire size, I also change the gear ratio of the vehicle and thus also the speed indicated by the speedometer. There is a certain tolerance here, which is accepted by the TÜV, but if this is left the TÜV will only be granted with an adjustment of the speedometer (talk to us, we can do this for you in many cases).

In the tire approvals you can often find different tire dimensions for vehicles. But it is interesting that the tire diameter is mostly identical for all allowed dimensions. Only the width of the tire or the diameter of the rim changes.

Example – New Defender L663 – standard tire:

255/70R18 –> diameter=81,4cm
255/65R19 –> diameter=81,4cm
255/60R20 –> diameter=81,4cm

Which also goes, without any adjustments (but is SMALLER than stock):

275/60R19 –> diameter=81,3cm
275/55R20 –> diameter=81,1cm

 

Which definitely works only with adjustments (examples):

275/60R20 –> diameter=83,8cm
275/70R18 –> diameter= 84,2cm – equals 33″ (Peter already had them on the New Defender with adjustments in the wheel well and raising)

 

series diameter: 81,4cm resp. 32″
just for comparison:
– BMW X5 M50i with 305/40ZR20 corresponds to 75.2cm or 30″.
– VW Golf with 225/45R17 corresponds to 63.4cm or 25″.

Without major adjustments, an extension up to a maximum of approx. 82.5 – 83cm or 33″ is feasible:
(sorted by diameter)

265/70R18 –> 82,2cm
285/55R20 –> 82,2cm
305/60R18 –> 82,3cm
285/60R19 –> 82,5cm
265/60R20 –> 82,6cm
285/65R18 –> 82,6cm
265/65R19 –> 82,7cm

However, one must still look here, especially with the wide wheels, that they do not grind inside or protrude too far. This depends on the rim and can be corrected with track plates if necessary.

Who would like to use still larger tires, must accept certain changes at the wheel housing and/or also speedometer or alternatively do without a German Zulasssung for the traffic. We will be happy to discuss the details with you on the phone or during a visit.

In general there are these possibilities for further customization:

Adjustment of the wheel arches, plastic processing, bumper cutting
Raising the vehicle by 1″ (~2,5cm) with rods
Raising the vehicle by 1,5″ (~5cm) with rods
Raising of the vehicle by 2″ (~7,5cm) per rods
Relocation of the radiator in the wheel well

The biggest thing currently available on the (non-German) market for the New Defender L663 are 35″ tires with a dimension in the approximate range of 285/75R18.

The tire diameter is then about 88.5cm and is thus 7.1cm larger than the series Defender. This results (only by the tire) a height increase of 3.5cm and a speedometer deviation of -8%. Approvable is such a modification in Germany currently not.

Hint:

If you want to give your vehicle special tire combinations, whether legal or not, contact us. We will help you with the selection and we will also help you (as good as possible) with the registration and acceptance. Of course we can not promise that it works and with extreme combinations there are often special features to consider, but we have accompanied such projects hundreds of times and are also available to you.

 

All information – as always – without guarantee!

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