Ford Focus front brake disks

[ganvil]

Hi all,

Can someone set my mind at ease?

I've had my ford focus 2006 (mk2) 1.8L diesel estate for about a year now. When I had the car serviced for the first time I was told it had the wrong size front brake disks installed (was 278mm).

Trusting my garage I had them replaced with 300mm disks which look right to the untrained eye. Looking in the haynes manual it specifies 278mm for the 1.8L focus. Anyone know the truth, should I have 278mm or 300mm?

Thanks for your advice.

 

[FriedFreddy]

I seriously doubt you had 278mm instead of 300mm disc's fitted as that's a 22mm difference (11mm in the radius) which would have meant 11mm of the pads were simply floating in mid air and not in contact with the disc under braking, that would also have caused a SERIOUSLY soggy brake pedal under braking !

If however the pads were all in contact with the disc's adding another 11mm on the radius would have jamed the disc's solid against the calipers locking the wheels up solid (there's never more then 2 - 3mm gap between the disc and the caliper)

 

[Mursal]

It probably needed disks due to age?

 

[Stivino]

I doubt if a three year old car would've needed new disc already. They said it was the size that was wrong, not wear and tear.
Have you checked to see what actually is on it now?

 

[ganvil]

Thanks for the replies everyone,

I didn't see the ones which came off but apparently they were relatively new, probably replaced just before I had the car (it's ex-fleet and high mileage for it's age). I've measured the new ones, they are definitely 300mm.

FriedFreddy; That was my thought- if anything the brakes used to be better than they are now (new pads / disks). The gap between these new disks and the callipers is around 2mm so that suggests 300mm is right.

Is there any other disk dimension which may have been wrong?

 

[Burnerman]

Its a most bizarre scenario, this one.....if the car had a caliper and caliper holding bracket designed for the larger disc, then a smaller one would fit - but it would give the pad wear pattern as FriedFreddy says.
It isn't possible the other way round - if the car had the smaller caliper bracket fitted, a larger disc wouldn't go on.
John

 

[stuartturbo]

I doubt if a three year old car would've needed new disc already. They said it was the size that was wrong, not wear and tear.
Have you checked to see what actually is on it now?

I have been know to replace these items a the yearly service item ( this is in 8k miles service was 4k)

but depends on driver the Meriva lasted me 18months and that 30k miles

 

[Burnerman]

If the car stands idle, especially outside, the discs will rust big time and eventually there won't be any bright metal visible.
The more you use the brakes, the better they are.
John

 

[Stivino]

Most brake discs are made from grey iron which as you will all know is a type of cast iron. It has excellent corrosion resistance. Some surface rust is normal and can even provide a protective coating, which, will quickly wear off with normal use.