Second hand car sold with wrong tyres on

Gloomendoom

The width does affect the circumference. A 285/55R18 tyre has a larger circumference than a 235/55R18 tyre.

Marktheshark

Bet they kept the "wrong tyres" as well !
Will be so dangerous they will have them on the part worn tyre rack for £30 each.
Did you not think, if they are such experts in Insurance law, why are they working in a tyre shop covered in muck ?

SuperAllyB

CHR15 wrote: »

The first number is the width. the circumference is the same no matter what width the tyre is.

A statement that darkmatter would be proud of.

arcon5

The second number op is a percentage. IE 55% of the 205 215 or whatever it is. So isn't the same size for each.

I suppose putting different size tyres could be seen as a modification, different speed & load rating will not! But even where the tyre size is different I think an insurer may struggle to justify cancelling an insurance policy if the policy holder didn't deliberately mislead the insurer

Joe_Horner

CHR15 wrote: »

The first number is the width. the circumference is the same no matter what width the tyre is.
[...]
second digit is the profile and third digit the diameter. these figures affect the circumference

Not quite. The profile is specified as a percentage of the width. So:

a 205/55 will be 205mm wide and (205 x 0.55) = 112.75mm high.

a 215/55 will be 215mm wide and (215x0.55) = 118.25mm high.

The diameter is the (nominal) diameter of the hole in the middle, not of the complete tyre so the complete diameter = tyre size + (2x tyre height)

Because, for the same "55" profile, a 215 will be 4.5mm higher than a 205, the total diameter for a 215 will be 9mm more than a 205.

On 16 inch (406.4mm) rims that gives total nominal diameters of:

215/55/16: 643.9mm
205/55/16: 631.9mm

So the 205 is 12mm, or 1.9%, smaller diameter

force_ten

CHR15 wrote: »

The first number is the width. the circumference is the same no matter what width the tyre is.
my car can have staggered wheels, wider at the back than the front but they all roll along at the same speed...

second digit is the profile and third digit the diameter. these figures affect the circumference

are you sure about that? I think you need to go check the maths

the aspect or profile of a tyre is a percentage of the tyre width, so in this case it is 55% of the tyre width so a 215/55/16 tyre will have a different rolling circumference than a 205/55/16 tyre

you will find on a staggered set up like you mention the aspect ratio or the profile of the rear tyres will be lower to compensate for the wider width of the rear tyres thus making the rolling circumference the same

force_ten

in my first post i did the calculation on a 225/55 and a 205/55 so i got the maths wrong as well, the correct maths should have been a 34 mm difference in rolling circumference and a 1.7% difference in the two tyres and at 70mph the 205 tyre would read 78.5mph

not as big as i first mentioned but still a difference


for insurance purposes it is always best to stick with the recommended tyre size as any variation could be seen as a modification and may have an impact on your insurance if not declared

force_ten

CHR15 wrote: »

Wowzer, the tyre shop saw you coming. went in for one and they flogged you FOUR.

put it down to experience, at least you have for new tyres now but never listen to the clowns trying anything to scare you into giving then more money

the tyres fitted to the car were not the manufacturer's recommended size, load and speed rating for the car so why were the tyre shop clowns in informing the OP that the wrong tyres were fitted to their car

the OP made a decision to purchase four new tyres based on the information given which as far as i can see was the correct information

Hoof_Hearted

Not all C4 Picassos were fitted with the same tyre size. First thing is to look in your handbook or look up the manufacturer's spec for your exact model and year.

loskie

http://www.michelin.co.uk/tyres/car-tyres#type=type_2&brand=citroen&range=c4 picasso&model=c4 picasso

or put your reg no into black circles website or similar.