Number54

Its time for my first brake disc change. I have a pair of Demans sitting ready to be installed, but I have a question....

My pads (Pagid RS19) have about 50% left. Should I get new pads at the same time? Is there a risk the used pads cause bad/uneven wear on the new rotors? I was advised to get new pads even though I've done plenty of pad swapping on the same rotors in the past (but different pads, different rotors, different car).

Thanks.

Mikelly

I prefer breaking new rotors in with old pads, personally... Also, the rule of thumb we use is if there is 9mm of pad or less, don't head to the track with them. You'll cook the fluid before the end of a weekend. Remember, the pad material is a big part of heat disipation. The less pad material, the more heat transfer thru the backing plate and into the caliper and boiling the fluid.

996FLT6

Run with older pads. With new pads u can glaze your rotors if not broken in properly. Less chance of doing that with old pads plus at 50% plenty of usage left. Mike

acadian_dad

Use old pads. Along with the ^ comments ... new pads (esp. Pagid track pads) and new rotors can be a very tight fit ...

SH || NC

Old pads. Will you be swapping between street and track pads?

Derek@TRG

With 50% life remaining on your pads i would leave them in with the new rotors. On our Rolex/ALMS cars we have done every combination: new pads/used rotors, used pads/ new rotors and new/new.

If you do the bedding procedure proprely , bring up to temp very gradualy, you wont have an issue with any new/old combo of parts.

I am currently running a special for Rennlist members, buy a set of Pagid pads , get 15% off a bottle of Castrol SRF brake fluid.

Number54

Nope, track pads only.

Number54

Thanks all, sounds like I'll keep the old pads and bed the rotors properly.

dan212

Aside from running Pagids at less than 50% thickness

I am curious why it makes sense to bed in brakes with used pads. I've heard this before. But the old pads will have some grooving and camber (right term?) from the old rotors - so wouldn't they make a less than solid / complete contact than virgin pads?

Just Curious

philooo

same question as dan212, I am curious why new pads would not be better fit as they are both virgin ?

Mikelly

I forget who told me this, but it was basically said that a properly bedded used pad will break in a new rotor more consistantly, transfering a more uniform media to the rotors surface. I want to say Craig at Rennstore, or maybe Robert at Lufteknic... Somebody told me a long time ago that's why it was good practice.

HiWind

Bob Roleau made similar comments to ^ related to the brake poll thread.

"New old is the best way by far. The Stoptech website has this in their technical session and racers adhere to it as much as possible. New New makes it hard to properly bed the pads and it is too easy to overheat new rotors causing premature cracks. Pas bed in faster and easier on used rotors. It's a win-win."

i was also puzzled as new flat on new flat seems to make intuitive sense.

996FLT6

The old pad has that transfer layer from the old rotor so bedding in with an old pad decreases the chance of glazing the new rotors vs new on new. Is there a metallurgy expert out there- I don't know wtf transfer layer makes the braking better. Mike

Doublej

Depending on how ridged your old pads are it can take a bit of work to get them I bed evenly across the new rotor.

If you do go this route you want to be sure you get the entire section of the rotor up to temp for proper bedding.

What you don't want are concentric rings of transfer. You'll have much less braking power, uneven wear, along with more heat.

mrd_spy

you always fit new pads when fitting new disks

ALso I see a trend in the USA where you guys swap out raod pads for track pads for track days

which is a massive no no here in the UK

Pads like Pagid are very fussy about the surface and what been on before.