How much extra fuel consumption would a set of 19's make oppsed to the normal 16's ???

I know its a bit of a hard question.

 

Just changed the tyre pressure as suggested .... 34/39 .... WHAT A DIFFERENCE !!!!!!!

Economy seems to be alot better and also the car is moving faster. Was quite sluggish before.

Thanks.

 

I don't think you will see any noticable difference as long as the circumference stays the same. Keep in mind that a wide tire or a narrow tire will have the same amount (sq inches) of rubber in contact with the road as each other. Given a 3800 lb car and utilizing 35 lbs per square inch inflation, you would have an approximate 5.86 inch circle of rubber for each tire touching the ground giving you theoretically the same coefficient of friction or drag for each tire. A wider tire has a more circular contact patch (better for lateral loads; turning) and a narrower tire has a more oval (front to back) contact patch.
You should not see any difference going from 245's to 275's.

 

The origial tyres were 225 all round. Now I've put 245 on the front and 275 on the back. I've changed the pressure, So lets see whats what !!!!

Thanks for you input.

 

The extra weight alone will affect economy. The 275's on the rear will also waste some energy, albeit small...

 

A little bit of loss is ok. Previously I had NO economy !!!!!!! Gonna prob do about 500 miles this week, lets see what I can get out of the tank. Got the car booked in for a software upgrade and a starting problem to be looked at.

As soon as these bits are resolved ...... Its time to look at Modding ..... but, I need to also keep an eye on some economy.

One chapter closes, another one opens ........... CHECK THIS SPACE ......... LOL.