General Front and Rear Tyres Different Sizes

[Blackwell92]

Just been to the garage to replace my rear tyres, on inspection I noticed my front and rear tyres are different sizes:

Front: 185/65R15 88H
Rear: 175/65R15 84H

Both the exact same tyre brand and tread pattern, is this a problem? Appreciate any feedback, thank you!

 

[varesecrazy]

Just been to the garage to replace my rear tyres, on inspection I noticed my front and rear tyres are different sizes:

Front: 185/65R15 88H
Rear: 175/65R15 84H

Both the exact same tyre brand and tread pattern, is this a problem? Appreciate any feedback, thank you!

Hi.
They Should all be the same.

185 is the width

85 (is the 'aspect ratio') height of sidewall.. as a percentage of the width.

So having differing widths.. BOTH X 0.85
WILL GIVE DIFFERENT HEIGHTS..

Not a vast difference in your case..

In essence the ABS COULD think the wheels are skidding as the hubs are rotating at different speeds.

However in my experience the ABS does NOT generally flag up any warning over minor differences..

If you think about it.. the fronts wear a LOT quicker than the rears.

So could have a 12mm Diameter difference.. just through the wear in tread depth

 

[chris3234]

Hi.
They Should all be the same.

185 is the width

85 (is the 'aspect ratio') height of sidewall.. as a percentage of the width.

So having differing widths.. BOTH X 0.85
WILL GIVE DIFFERENT HEIGHTS..

Not a vast difference in your case..

In essence the ABS COULD think the wheels are skidding as the hubs are rotating at different speeds.

However in my experience the ABS does NOT generally flag up any warning over minor differences..

If you think about it.. the fronts wear a LOT quicker than the rears.

So could have a 12mm Diameter difference.. just through the wear in tread depth

Should be within the margin of error for the sensor's
Some cars have different sizes from the factory
Don't think any Fiat's do but I know several mercs that have wider front tyres as standard

 

[varesecrazy]

Should be within the margin of error for the sensor's
Some cars have different sizes from the factory
Don't think any Fiat's do but I know several mercs that have wider front tyres as standard

Different circumference..? or adjusted aspect ratio to compensate??

Pretty sure the old Smart car had different rim diameters front and rear.

 

[chris3234]

Different circumference..? or adjusted aspect ratio to compensate??

Pretty sure the old Smart car had different rim diameters front and rear.

Was a family member a few year back so can't remember but the back definitely had narrower ones not sure height wise

 

[portland_bill]

It used to be legislated that large ones go to the rear, not the front. Can't think of any reason why that should change. More grip on the front can lead to the rear stepping out, and oversteer is more difficult to control than understeer. Determine which is the correct size. Until the wrong ones need replacing, put the larger ones on the rear.

Many supercars have larger rear tyres. The original Smart does have larger ones on the rear, but this is unusual for normal cars.