Hi all,

I am very confused i have bought genuine ford st mk2 alloy wheels for my focus mk2 1.6 tdci. The tyres were originally from a transit st because the tyre pressure was above normal 45psi so i reduced them to 36 rear and 34 front.

But my mpg has gone down and now it shows for every 1 mile 3 miles gets knocked of the distance left to refuel.

what to i do thanks

How does the tyre circumference compare?

Have you re-programmed the car for the new alloy size?

How does the tyre circumference compare?

Have you re-programmed the car for the new alloy size?

i havent got the ecu reprogrammed didnt know you had to.

and with tyre circumference difference is 20mm

The difference in tyre circumference will be throwing the on board computer out, including speedo, mileage, mpg, etc.

The bigger wheels are also likely to be heavier, which is going to contribute to a drop in mpg...

The difference in tyre circumference will be throwing the on board computer out, including speedo, mileage, mpg, etc.

The bigger wheels are also likely to be heavier, which is going to contribute to a drop in mpg...

what should i do now. The person i bought it off said it was a straight swap with nothing else to do.

give the mileage and mpg time to settle, the speedo will be a little bit off until you re-programme the car with the new tyre dimensions, but depends how bad it is, you might be ok.

also you will need to tell your insurance if you havent already

Presumably the tyres are wider as well? Causes more friction = uses more fuel.

I would buy correct sized tyres personally, but you will lose some MPG swapping from the light and skinny 16s to the 18s.

I wouldnt worry about it and just buy the correct size tyres when the ones you have are worn out. Regarding the distance to empty i would just go off the fuel gauge until you get your new tyres.

I have done some digging. The old wheels were 205/55/16 and the new ones are 225/40/18.

The over all difference in circumference is 5mm which is 0.79% increase, not 20mm dont know where i got that from lol

What if i disconnected the battery would that reset everything?

225/40/18 are the right size specified by ford. That increase is nothing mate. Are you sure youre not speeding a bit cruising round with your new wheels? We all do it lol!

My distance to empty doesnt go down in 1 mile increments, its calculating on how youre driving so cant give an exact figure as you might speed up and use more fuel or do a long slow motorway run which would be different again. Just switch to a different info display and enjoy your wheels knowing you do already have the right size tyres fitted on them.

Have you fitted a steering rack limiter kit?

No i havent what does that do?

I fitted 18s to mine without the steering limiter kit. No running at all. Even on full lock. I must be lucky lol

Sent from my iPhone 5s.

you are supposed to fit a steering rack limiter as the larger wheels tend to rub on the wheel wells. been a few discussions about it on here before

only costs 20quid so you may as well really

i still have one for sale actually from when i was gonna fir bigger alloys to my focus but ended up buying a new car

you are supposed to fit a steering rack limiter as the larger wheels tend to rub on the wheel wells. been a few discussions about it on here before

only costs 20quid so you may as well really

i still have one for sale actually from when i was gonna fir bigger alloys to my focus but ended up buying a new car

I actually have the kit but as I said, nothing rubs or catches anything. If I do coilovers I'll get it fitted.

Sent from my iPhone 5s.

you are supposed to fit a steering rack limiter as the larger wheels tend to rub on the wheel wells. been a few discussions about it on here before

only costs 20quid so you may as well really

i still have one for sale actually from when i was gonna fir bigger alloys to my focus but ended up buying a new car

when im driving i dont hear any strange noises of rubbing or anything like that. The car hasnt been lowered and i dont intend to get it done its not in my budget. But i will check again just to make sure thanks for the heads up