Outer Limits 4x4 Board

justa question on tyre size effect on fuel consumption and power. i have a 92 vitara and i was running 30"s but recently upgraded to 31"s. i noticed a huge change in fuel consumption and power with the change. but when i put the 30"s on it is back to almost stock specs. why is there a such a change.

any sugestions would be apreciated

have u measured the total height with both ur tyres. That may be how much the odo is off now with the 31's. this is also revelant to the fuel eco as well.

power is the same. increasing the rolling diameter will always sap power unless u compensate for it with more power or gearing.

cheers

[quote]have u measured the total height with both ur tyres[/quote]

what do you mean by this?

and will top speed be afected much?
the odometer has been ajusted but i max out at about 115kms[/quote]

When sitting both tires next to each other measure the height of them both. often a 31 will measure a 30 or 32.

Top speed is usually effected also.

How did u adj the odo.. what did u max out with the 30's on.

cheers

By changing the size of the tyre, you are increasing the rolling diameter, thus lowering the final drive ratio. this will effect how your speedo reads, and the odometer also. And due to the increased rolling mass, and decreased gear efficiency, you will have to put your foot down more to get up hills etc, because the engines power range has moved due to altered final drive.

You can fit lower diff gears to combat this.

hope this helps.