I've just doing some research into tyre, as I need to replace the two fronts on my Octy 2 vRS, everywhere I look it lists the tyres for it as follows: 225 40 R18, however, the current ones fitted are size 225 45 R18. The question is, will having the slighty larger profile make any difference to the drive? I understand the rolling ratio will be different, and possibly the ride comfort will be improved, but what other effects will this have, improved accelaration, mid-range or top end performance? and finally could it cause any damage to the car?

The car was fitted with the 225 45 R18 when I purchased in January, and I would estimate the rear tyres were fitted approximately 6 months prior to that date.

Any advice would be appreciated, Lee.

I expect having non standard size tyres would affect the speedo and poss your insurance.

I expect having non standard size tyres would affect the speedo and poss your insurance.

To fair they're not really 'non standard' its only 5% difference on the profile, as far as I can tell comparing the speedo to a sat nav, they're the same. Thanks for your comments though.

The official tyre size listed in the brochure is 225 40 18. THe matey that had the car before probably brought the non standard fit tyres because they were cheeper

The official tyre size listed in the brochure is 225 40 18. THe matey that had the car before probably brought the non standard fit tyres because they were cheeper

So I've found, the irony is, I can get the 40 profile cheaper!

Anymore advice?..........please!

To fair they're not really 'non standard' its only 5% difference on the profile, as far as I can tell comparing the speedo to a sat nav, they're the same. Thanks for your comments though.

VAG group speedometers are set to display a higher speed than your actual speed by something in the region of 4% while the odometer reads correct distances. I found with my car that cruising at 65 mph indicated gives me exactly 100km/h - the only problem with knowing this is that everyone else's car is calibrated similarly, so I keep catching up with motorists who follow their speedometer while I'm on cruise control following the GPS.

With the higher diameter of your tyres the speed is correct, but you'll probably find the odometer is under-reading... VAG Com should be able to change this. Bigger tyres should give slightly more grip, a smoother ride and better fuel economy but slower acceleration.