Quick question regarding tyre sizes

[Doxster]

Sorry if I've posted in the wrong section.

Just a quick question for those in the know.

I need a new set of tyres for one of our cars. OE size is 235/50 r18. It appears to be an 'unusual' and therefore 'expensive' size.

I have been advised that I can put 245/45 r18 without any issues. This size seems to be far less expensive.

It appears to me that the rolling circumference for these sizes is close but not equal.

Assuming the tyres have the same load and speed ratings etc am I likely to encounter any issues (eg odometer/ABS etc etc) by changing to the 245/45 r18?

Many thanks in advance

[JagXJR]

It will change but not by much. More of concern is how your insurance company will view the change as you are modifying the car from the manufacturers specs. I would ask them personally before doing this. Otherwise they have a "get out of gaol free card" should you want to make a claim.

[CYMR0]

As both cars listed in the garage are German, there is a very strong chance that they will have a range of pre-approved tyre sizes (i.e., manufacturer's spec is not limited to the tyres that they were delivered with).

If that is the case, refer to that list.

[cootuk]

http://www.etyres.co.uk/tyre-size-calculator

about 2% difference, but depends on your insurance company allowing it/charging

[Doxster]

Thanks for the input everyone.

I couldn't find any recommended lists online. All of the information I did find however stated 235/50 only.

Think I'll play it safe and stick with OE sizes.

Cheers

[LukeKerr]

Sticking to the OEM sizes is the best option unless you are looking to customise the car.

[mrmr96]

cootuk said:

http://www.etyres.co.uk/tyre-size-calculator

about 2% difference, but depends on your insurance company allowing it/charging

Says 14mm in diameter. So 7mm per "side", which I guess isn't too far different from brand new tyres vs. legal limit tyres.

[BritishRacinGrin]

If warranty and insurance aren't a problem I wouldn't hesitate to make that change, assuming the extra 10mm width doesn't put the tyre outside of recommended widths for that rim (unlikely).

I have done this myself on my own car, I went from 225/60r15 to 205/65r15 in order to open up much greater tyre choice.