wrong tyre size, does it matter??

davemorton

Ordered a pair of tyres from the internet to fit onto my car.
Just realised I had ordered the wrong size.
Tyres already fitted are 185/55/15's
Ones ordered are 185/65/15's
If I keep one size for the front, and one for the rear, will it make much difference?

mcjordi

it will fail its mot if you have different size tyres on each "axle" ie the front two must be the same and the back two must be the same
if you put them both on the same axle then its fine..

molerat

If you fit them to the driving wheels your speedo will read 6% slower than you are going, at indicated 60mph you will be doing 64 mph although as your speedo normally over reads it will probably be about accurate with those tyres.

notbritishgas

Niot an expert but I think the new tyres will make a difference, how important I am not sure.
The new tyres will have a larger diameter, the 55 and 65 is the height of the tyre wall measured as a % of the width,185.

In the old tyre the height is 101mm and the new is 120mm, so that is nearly an inch different so the diameter is nearly 2 inches larger.

This could be a problem with clearance to the wheel arch or gearing if put on the driving wheels.

RDG

As the 55 and 65 are the tyre profile then it will make a difference as the rolling radius will be increased. According to an online calc here (http://www.etyres.co.uk/tyre-size-calculator.htm) it will be 36mm.

This will increase the ride height of the axle they are fitted to slightly so the car may look a bit odd, also you will need to check you have enough clearance within your arches, most cars this shouldnt be a problem.
If fitted to the drive wheels you will also get a false reding from your speedo as the number of revolutions will not match its calibration. from the calculator a 6.15% difference.

The bigger side wall will also soften the suspension

cyclonebri1

Assuming its front wheel drive, bang 'em on the back, they just drag around and do nothing but keep the boot off the deck, :D:D.,
I'm actually serious and that way gearing/speedo/wheel arch issues should be avoided.

Lum

So long as they will physically fit and not scrape on the wheelarches as you go over speedbumps, and assuming this is a front wheel drive car then I agree with everyone else, just shove them on the back.

You may gain a little more grip at the back which will change the handling characteristics of the car, so don't immediately get into your car and start hooning it through the B roads at illegal speeds.

If you drive in a normal, sensible, manner you probably won't even notice any difference.

flashg67

Bigger tyres have to go on the back...

Danny11

Stick em on the back just like everyone else says.

arcon5

Send them back and order the correct ones

Joe_Horner

The only problem you may have is if you have to use your spare (assuming you have one these days!) at any time on the axle with the bigger tyres on. Won't make it fall off the road but will be illegal at that point.

Other than that (which is pretty unlikely to happen) stick 'em on the back and enjoy your car's new stance