Can I use different size tyres?

Scienceless

Have IS220d Sport with 255/40/18 on the rear, need tyres now and have been offered 2 at a good price but they are 245 not 255 spec. Is it ok to fit these to the car? I've only ever bought the 255's before now. Is there flexibility in the tyre size that wheels can take in general?

Scienceless

To be exact they are 245/45/18, and I'm told by garage it's fine to do this.

mullingar

According to here

http://www.carbibles.com/tyre_size_calculators.html

The new tyres are about 50mm more in circumference. That's very little. But your speedo will under read by about 3%

Testacalda

Its not dangerous or anything but sometimes fitting different size tyres can lead to an ABS faults being logged and a light on the dash, and/or possible issues with cruise control, especially at higher speeds.

This happens because different size tyres will rotate at fractionally different RPM for a given speed, leading to the ABS system assuming there is a fault with the readings from the four wheel sensors.

Have seen this happen with lots of E class mercs, and a Camry. Other cars have no reaction

A 255/45 is 9 - 10mm taller than the 245/45

In general a 255 rim will be ok to mount 245 or a 265 on, but again its not best practice as such

Cee-Jay-Cee

Testacalda wrote: »

Its not dangerous or anything but sometimes fitting different size tyres can lead to an ABS faults being logged and a light on the dash, and/or possible issues with cruise control, especially at higher speeds.

This happens because different size tyres will rotate at fractionally different RPM for a given speed, leading to the ABS system assuming there is a fault with the readings from the four wheel sensors.

Have seen this happen with lots of E class mercs, and a Camry. Other cars have no reaction

A 255/45 is 9 - 10mm taller than the 245/45

In general a 255 rim will be ok to mount 245 or a 265 on, but again its not best practice as such

His stock tyres are 255/40/18 and the new tyres are 245/45/18 so the difference is a lot less, closer to 5mm which is less than if you have worn tyres on the rear and new tyres on the front. Its not going to make any difference and I doubt even ABS/TC sensors would pick it up.

Esel

Cee-Jay-Cee wrote: »

His stock tyres are 255/40/18 and the new tyres are 245/45/18 so the difference is a lot less, closer to 5mm which is less than if you have worn tyres on the rear and new tyres on the front. Its not going to make any difference and I doubt even ABS/TC sensors would pick it up.

I make the sidewall height 8.25mm more, so 16.5mm difference?