New Discs/Rotors incoming - do I need new pads?

[enzed4]

I have a set (front and rear) of slotted/dimpled discs on their way to me. Just wondering if I need to replace the brake pads at the same time. I have near new front OEM pads, and I think the rears are ok, but I could replace them as general maintenance if required.
The new discs are like for like as far as size goes (300mm front, 294mm rear), so the existing calipers/pads should be fine as far as I can see.
Thanks.

 

[Grumpyowl]

I would yes, the pads will have worn to the old discs.

 

[AlfaScozzesi]

You should always use new pads when fitting new discs.

 

[Lance]

As above, yes new pads.

I changed my discs fairly recently and am pretty sure they were 286mm front and 280mm rear. Mines a 2.5 but older than yours and not an SI though, so the size may differ. Might be worth a check before pulling the old discs off the car.

Couple of tips if you've not done these before........make sure you have a good quality and good fitting allen key for removing the disc retaining bolt, as chewing the head off this is a real pain. Also, a decent 16mm ring spanner or socket for removing the caliper carrier, plus a breaker bar as these are very very tight.

Cheers

 

[bmwaddict]

You should always use new pads when fitting new discs.

 

[Ducklakeview]

As said, you should always fit new pads when replacing rotors. The reason being is that in order to properly bed in, the mating faces need to be as flat as possible. Old pads will be as flat as the discs you are replacing, and will wear the new discs into the same pattern. This may also cause localised heating and warping of the new discs.

Mike

 

[buzyg]

Been said changing the Discs then change the pads. False economy & poor engineering practice not too. Old pads will wear your new rotors prematurely. :wink:

 

[enzed4]

Great advice from all - thanks very much . I have been using OEM pads but find they're a bit 'dusty' - does anyone have any recommendations on ceramic brakes? Or a particular compound that isn't so prone to brake dust? Brand names may not help much as a lot of stuff can't be bought here (unless ordered from overseas), but any suggestions welcome, and I'll do the research to see if I can get them here.
I used this as a reference for disc size http://www.z4-forum.com/forum/viewtopic.php?t=8399 which states 2) Both 3.0i (and the Euro 2.5si) have 300mm vented in the front and 294mm vented in the rear
Also used the Mtec brake site's search which listed the 2.5Si fronts as 300mm and the rears as 294mm, so that's what I ordered. I measured one of the fronts when I had the wheel off a while back and pretty sure it was 300. Fingers crossed it's a proper fit.
Lance - interesting about the breaker bar for the caliper carriers. I've had the front calipers off before and only needed a large screwdriver to lever them off (large as in about 30cm). Haven't done the rears so hopefully they won't be any worse.

 

[hughmungus]

You'll need the breaker bar to undo the bolts holding the calliper to the hub as they are very tight, also get a decent drill 7mm to drill the holding studs out as mine where stuck solid on the front, rears where fine with an Allen key however. Don't forget to copper grease any metal on metal bits including the retaining bolts as well.

 

[Lance]

The caliper bolts to the caliper carrier via two long allen bolts (easy to undo). This carrier bolts to the hub via two 16mm bolts, it's these that can be hard to shift and it needs to come off to remove the discs.

 

[enzed4]

Seems like a bit more to this job than I thought, but armed with the above advice I should be ok. Discs should be here late next week I hope, so I might be able to source some replacement pads before then. If it comes to it, I can always get OEM pads from the dealer...
I'll be sure to post some before/after pics when I do the job.