Changing tyre size

[DaveNP]

Glad to say I have a local trusted independant.
I worked for a while with a guy who had been a fitter for the tyre company that works kwikly (if you know what I mean ), he would regale us with stories of how he would invent work and ill advise customers so he could increase the costs and meet the company sales targets. Allegedly he was a fully qualified mechanic but we soon realised was his only qualification was in talking BS, one of his finest was when he said he fitted van tyres to his BMW saloon car, in all of the laughter afterwards I forget what his logic was.

Regarding speedo in OP's case, by my calculation the difference in tyre diameter, which will determine circumference and thus speedo reading, is about a tenth of 1%, you'll make more difference between new and old tyres of the same size.

[Jonny Cut Corners]

Originally Posted by pjwhitfield

Can someone clear something up for me?

I have a 2005 C70 with 225/50/16 tyres, these are (for want of a better phrase) rocky horse sh!t to easily pick up (and are usually twice the price of others).

Previously when attempting to pick one up I was told I could swap to a different, more common size and when I've checked the car specs (https://www.wheel-size.com/size/volvo/c70/2005/) both the 225/50/16 and 205/55/16's use exactly the same rim "7j16 ET43".

So now that I need tyres desperately I feel the need to make the move however before I ordered them I decided to give National Tyres a ring and just check to be certain.

I was virtually laughed at "no mate, you cant change tyre sizes, they wouldn't work mate"

Can someone help me out here and give me a definitive answer on this?

Just to echo what others have said, forget what the 'professionals' told you. Both sizes are basically the same rolling diameter and if they're both listed as spec sizes in the manual then I don't see an issue with insurance etc.

Obviously 205 is 20mm narrower than a 225. That less rubber on the floor so your total mechanical grip will be reduced. Not a problem for most casual drivers, but it may increase your stopping distance in an emergency.