Differnet sized tyres on car

Triangle

Currently i have 2 sets of tyres - one are 225x45x18 and the others are 225x40x18.

I have the 40's on the front and the 45's on the back.

What i need to know is

1) is this safe?

2) Will having 'smaller' tyres mean my odomoter does more mileage? (more tyre cycles per kilometer)

3) if it does, will it be by much?

I've ordered two new tyres same size as the 40's, but I'd just like to know for the future.

Thanks,
Trig

cormie

This is one of the million questions I've asked on this forum before;)

Click for good discussion:
http://www.boards.ie/vbulletin/showthread.php?t=2055091914&highlight=tyre

Dermo123

Triangle wrote: »

2) Will having 'smaller' tyres mean my odomoter does more mileage? (more tyre cycles per kilometer)

3) if it does, will it be by much?
Trig

It depends on which wheels your car is taking the odometer reading from.
If the smaller ones are in front, your car is front wheel drive it will probably add a tiny bit extra. There is a tyre size calculator somewhere on the web that can work out the % extra milage. I think its on page 2 of this site http://www.carbibles.com/tyre_bible.html

There is a lot of reading in this but everything you need to know should be in this.

colm_mcm

Depends on what size tyres the car came with originally. What car is it?

Plug

5mm difference wont cause nothing.

Esel

Plug wrote: »

5mm difference wont cause nothing.

Does that mean it will cause something?

And it's 5%, not 5mm. In this case, that's 11.25mm.

Biro

Would I be right in guessing that neither of those sized tyres came with the car? What car is it and what sized wheel's and tyres did it come with?
It's not unsafe to have a different sized wheel on the front axel to the rear. It would be unwise to have a different sized tyre on each side of the same axel. Also, if the car is 4wd you should keep all four wheels and tyres the same size.

Triangle

It depends on which wheels your car is taking the odometer reading from.
If the smaller ones are in front, your car is front wheel drive it will probably add a tiny bit extra. There is a tyre size calculator somewhere on the web that can work out the % extra milage. I think its on page 2 of this site http://www.carbibles.com/tyre_bible.html

There is a lot of reading in this but everything you need to know should be in this.

thanks dermo123 thats some nice info.

plug,
i thought the same, never knew it was a %

Biro,
bought it 2nd hand but i believe it came with the 45's as the previousa owner did everything through the dealer (mazda rx8)

cheers for the feedback all.

Oilrig

What was originally fitted to the car?

Anything different may have several effects.

niceirishfella

Triangle wrote: »

Currently i have 2 sets of tyres - one are 225x45x18 and the others are 225x40x18.

I have the 40's on the front and the 45's on the back.

What i need to know is

1) is this safe?

2) Will having 'smaller' tyres mean my odomoter does more mileage? (more tyre cycles per kilometer)

3) if it does, will it be by much?

I've ordered two new tyres same size as the 40's, but I'd just like to know for the future.

Thanks,
Trig

This is a profile issue. I think have the 40 profile on one axle of the car will affect your ride only i think.
A 45 profile is probably more easy on your ride (confort) than the 40, but each to their own.

Triangle

This is a profile issue. I think have the 40 profile on one axle of the car will affect your ride only i think.
A 45 profile is probably more easy on your ride (confort) than the 40, but each to their own.

niceirishfella,
Yeah I thought i was getting 45's, to be honest I like the look of the 45's better. there was a mix up in ordering them and i couldn't wait a couple of weeks before fitting replacement tyres.
Anyways, thanks all.