Scottish Elises

Have the chance of a set of pre-loved (!) winter tyres for the Octavia. But it currently runs 225/45 17 just now. These are 215/45 17.

So I make that about 5mm less on rolling radius. Is this a big enough impact on gearing or other side effects to cause me to abandon?

I am sure there is a site that calculates if they will fit, normally its the other way round so you can understand if you can stretch them.

Does the width make a radial difference if they are both 45?

tut

Yes. 45 is the profile rating expressed as a % measurement of the width.

So a 225 45 tyre has a nominal profile "height" of 101.25mm

A 215 45 is 96.75 mm

Doubled up to calculate diameter, that's 9.5mm difference actually, so more than my original estimate...

I may have answered my own question!

according to that, your gps speed at an indicated 70 mph will be 68.9 and will drop the diameter by 1.01 cm so i dont think its anything to worry about.

You can get that much of a difference between the same listed size but with different manufacturers, dependant on construction type, so I doubt a potential 5mm difference will make nany noticeable difference.

Plus, the narrower the tyre the better in winter should you encounter heavy snow / ice.

I dropped down from 225 to 215 for the Honda CR-V but then never fitted them.

tut

Cool. Just need to persuade The Missus now :-/

What width are the rims? You need to check that the narrower 215 is compatible.
Most likely they are okay but the tyre will protrude less over the edge of the rim so more risk of curbing the wheel - you can use your voucher!
The car will also be riding ~10mm lower so more risk of scraping the underside of the car on a rogue speed hump, etc.....

It'll be 5mm lower.

The voucher has just been deployed

Good point re rim width. Need to check that...

This should give appropriate info:
http://www.brick-yard.co.uk/forum/tyre- ... 60146.html

That's useful. 215 is "ideal". Ok more ammo for the Missus chat !!

I use 205 65 16 during the winter and 235 45 17 in the summer