C30 front brake disc smaller than rears?!

[superhifi]

2011 C30 2.0 Petrol.

Need to replace the front brake discs on my C30, and knowing I fitted 280mm to the rears last year, and just before I hit the order button I thought I'd double check the size on the calliper... I was a bit thrown when I saw they are 278mm... smaller than the rears?!

Is this right? If so, it's goes against everything I know (allbeit not that much) about brake discs and pads, where I thought you always had bigger discs/rotors on the front?

[iainmd]

That's correct. Remember that the rears are solid and the front are vented.

The lower spec cars/engines have 278mm at the front, mid-range have 300 and top-spec are 320mm. All rears are standard at 280mm.

I wouldn't worry too much for road use. I've driven P1 cars with all three front setups and, for me, there is only a noticeable difference when using the 320mm setup as the calipers are much larger. With the smaller two front setups the calipers are the same.

[T5R92011]

I personally would be chucking some of the bigger 300mm disks on given they are compatible with same caliper.

The brake setups are a bit inconsistent on these cars. For example, my S40 T5 with 230bhp from factory only got 300mm disks, but a V50 D5 with 18bhp and 18" wheels came with 320mm disks and bigger calipers, despite having 50bhp LESS than the T5.

[iainmd]

Originally Posted by T5R92011

I personally would be chucking some of the bigger 300mm disks on given they are compatible with same caliper.

The brake setups are a bit inconsistent on these cars. For example, my S40 T5 with 230bhp from factory only got 300mm disks, but a V50 D5 with 18bhp and 18" wheels came with 320mm disks and bigger calipers, despite having 50bhp LESS than the T5.

The early T5s only got 300mm discs which changed later in the production run. I retrofitted new 320mm discs, pads, calipers and backing plates to my 2004 T5.

What I would say is that, having had cars with both 278mm and 300mm front discs I noticed absolutely no difference between them TBH. I did notice a difference with 320mm but then I changed the hoses to braided at the same time which may alos have had an effect.

[iainmd]

Originally Posted by T5R92011

I personally would be chucking some of the bigger 300mm disks on given they are compatible with same caliper.

Just checked all part numbers on VIDA between the two systems. Parts that are the same: Pads, Calipers, Backplates

Different part numbers: Discs (obviously), Carriers (or retainer as Volvo calls it).

It looks like the carriers are indeed different and would need to be swapped to support a change from 278mm to 300mm so it's them plus discs.

[Simmy]

brake sizes are based on the weight aswell as bhp

[iainmd]

Just thought I'd update. Needed new front discs and pads so decided to change the front 278mm setup for 300mm. Not a difficult switch at all. New carriers required (bought used and refurbished them) but everything else was an easy swap. Not a massive change frankly but thought I may as well.