Recently I fitted new tyres to my vehicle. However, I 'm reliably informed the new 245x65/17 tyres shouldn't have been fitted, because the manufacturer's OE tyres are 235x65/17. What problems have I created and how detrimental are they as a whole in vehicle performance? The new tyres fitted are Davanti Terratoura 245x65/17.
Unfortunately, the original registration number you supplied only informed me that the vehicle is a John Deere and untaxed. Because of this I am presuming it is a farm vehicle and so my advice will be based on that information as I am unable to find the OE spec for the vehicle.
What is not always realised is that because the rim size and aspect ratio of the tyre are the same, this will not mean that the overall diameter is the same.
The 245x65/17 tyres will have a sidewall height 6mm above the recommended fitment and a diameter of 13mm above the recommended fitment – this will give a circumference of 41mm above the recommended fitment.
This means the circumference is 1.8% greater than the original fitment and the speedometer will be wrong. But as I am presuming this is an off-road vehicle, that is not a major obstacle.
Mechanically speaking you may notice a slight decrease in power, and provided the tyres have plenty of clearance there should be no other problems. From the recommended tyre width of 235 I would expect the wheel rims to be 8.5 and this size of rim will easily accommodate the 245-width tyre. In fact, it could safely use anything from a 225-255-width tyre.
I then received a reply that informed me the original registration letters were mistakenly transposed: the vehicle was in fact a 2009 Land Rover Freelander that was taxed and MOT’D.
As your vehicle is roadworthy, I would first mention that if the garage advised you to have the tyres fitted and sold them to you, they should replace them, but if you bought the tyres separately and then had them fitted, the garage have simply carried out your request.
The advice would be the same on any vehicle with regard to fitment of these tyres to the rims. But as your vehicle is used on the road you should be aware that the speedometer will read incorrectly. As you have fitted all four tyres I do not believe this will have an adverse effect on the four-wheel-drive system.
Land Rover do not specify the 245x65/17 as an option. Provided you take into account that your actual speed will be 1.8% higher than that indicated on the speedometer there should be no other concerns. As most speedometers do have a leeway of around 5% this should not be a major obstacle. The actual speed of the vehicle could be easily checked using a satnav or dashcam, which have GPS built-in. An app that will achieve the same result could also be downloaded on to a smartphone.