Can I put new brake pads on worn discs?

[RR76]

I've ordered discs but will take few days to arrive, I can pick up pads locally though. Currently the discs are very worn(few mm track ripped into them) and the pads must be virtually to the metal as making some nasty noises.

Ideally I want the car today, if I put new pads in with the worn discs would it see me through till about next Thursday or would they just rip to pieces?

[steveo3002]

not ideal , but yeah if its an emergency do it ....any defects on the discs will mark the new pads

[dontlookdown]

You can in extremis do this. I have done it myself when young, skint and foolish. But the brakes may not actually work any better with the new pads in than they do now, and you may also damage the new pads. So if you can possibly wait for the discs to arrive, do.

[warch]

What they said.

I vaguely remember reading some advice once that new discs should be run in, to get them up to temperature but with no harsh braking but I doubt anyone does that these days*

• Expects deluges of posts from PH posters who do do that these days.

[Tony1963]

If the pads you’re buying are cheap, buy two sets so you can fit new pads and discs next week. It’ll work out cheaper in the long run, and safer.

Good luck.

[InitialDave]

warch said:

What they said.

I vaguely remember reading some advice once that new discs should be run in, to get them up to temperature but with no harsh braking but I doubt anyone does that these days*

• Expects deluges of posts from PH posters who do do that these days.

My bed in is several hard braking runs from 60 or so down to a walking pace without actually stopping, repeated consecutively maybe half a dozen times, then cruise along to let things cool down.

[E-bmw]

You theoretically don't need to bed in road pads & discs these days but I tend to do similar when fitting new.

[tapkaJohnD]

Excuse if egg-sucking advice, but clean the new discs before you fit them. They may have a greasy anti-rust prep on them!

[Chris32345]

warch said:

What they said.

I vaguely remember reading some advice once that new discs should be run in, to get them up to temperature but with no harsh braking but I doubt anyone does that these days*

• Expects deluges of posts from PH posters who do do that these days.

Not needed on OEM spec disc's and pads just on track style ones usually

[Pericoloso]

Last time I fitted new discs , couple of years ago , came with running in instructions .

Can't remember what they were but basically , drive a bit , brake , not too hard and repeat a few times .

[GreenV8S]

It depends how flat the old discs are. If they have wear ridges, the new pads won't work at all well until they have worn to match the ridges. And after they've done that, they won't work well on new discs until they have worn flat again, and in the meantime risk causing local hotspots on the new discs which can cause uneven wear and brake judder problems in future.

[HustleRussell]

I wouldn't do this. The new pads will conform to the old discs which will not have a flat braking surface, will be scored and ridged if you've run the old pads right down, Then you'll put these unevenly worn pads on nice flat new discs which will immediately introduce an unevenness into the heat and wear pattern on the new discs.

Just wait until you have the discs.

[gazza285]

Just keep using the old pads until the new discs arrive.

[RR76]

gazza285 said:

Just keep using the old pads until the new discs arrive.

The old pads were right to the metal literally boring a hole out of the disc.

[GreenV8S]

The new pads on the old discs will be OK for a couple of days although unlikely to give great braking since the pad won't match the shape of the disc.

When you fit the new discs, fit new pads with them and keep the slightly-used pads as emergency spares for next time.

Make sure you clean the calipers and regrease as required, and don't just stuff the new parts in.