Swapping pads for a trackday

[Fonzey]

Hi All, I recently upgraded my brake pads to CL RC5+ for the purpose of track days. They handled a day at Cadwell brilliantly and i'm really impressed with their performance.

However, they're rather dusty and also noisy. They clunk during three-point turns in the caliper and they squeel. The road pads I had before have got loads of meat left on them and they were really silent/clean... they just faded quickly on track.

With that in mind, I considered swapping back to road pads for the winter - keeping the RC5+ boxed away until my first spring track day.

Once back in to "track season", is it unwise to swap pads around just for a track day and then back to the road pads? I guess if their compounds clash on the disc in terms of deposits - it could lead to counter productive friction, but swapping a week or so before a trackday should allow ample time to get some "matching" deposits down right?

Any reason (other than hassle) why I shouldn't do this? My Car goes on stands anyway before a track day to put my track wheels and R888's on - and pad changes in Brembo's are a piece of cake.

[dblack1]

I have heard a lot of stories of people swapping front pads for track day. I have even heard of people swapping pads at the track.
The race pads not only don't fade as quickly on the track but they also last longer on the track than a street pad.
Another thought, if you don't already, flush you break fluid before you run to the track as well, it will get any impurities out of your break lines (which can turn into gas when your brakes get hot and create a air pocket in your brake lines especially if you use a break fluid designed for higher temperatures).

[Fonzey]

Thanks mate. I've got my road pads back in now and I'll be flushing fluid before my next session.

I'll probably put the track pads back in about a week before the trackday so I can get some compound into the disc.

[ch427]

personally i cant see how pads put deposits on to discs.

[Electric Beaver]

ch427 said:

personally i cant see how pads put deposits on to discs.

That's why its so important to bed proper race pads, to build the transfer layer evenly onto the disc surface. If this is not completed properly then often the transfer layer is smeared (particularly if the pad is used hard straight out of the box) which causes judder which often is misinterpreted as warped discs. Also its important to heat cycle the pad material a few times to burn off any resins used in the manufacture.

The principle involved is adherent friction. Further reading here for the interested - http://stoptech.com/technical-support/technical-wh...

[dblack1]

ch427 said:

personally i cant see how pads put deposits on to discs.

They don't (at least not a significant amount anyway) like a piston ring they form to the shape of the surface they rub on (in other words they form to the brake rotor)

Electric Beaver said:

That's why its so important to bed proper race pads, to build the transfer layer evenly onto the disc surface. If this is not completed properly then often the transfer layer is smeared (particularly if the pad is used hard straight out of the box) which causes judder which often is misinterpreted as warped discs. Also its important to heat cycle the pad material a few times to burn off any resins used in the manufacture.

The principle involved is adherent friction. Further reading here for the interested - http://stoptech.com/technical-support/technical-wh...

Did you copy and paste that.... The article is misleading, They lead you to believe that there is this solid layer of material between the pad and the metal of the rotor, this isn't true.
Imagine a tyre on a round race track. The tyre is like a brake pad (it is a grippy surface that wears down faster than the hard surface it grips on). The race track is like a rotor. As the tyre goes around the track it leaves a little bit of rubber on the track. Over time, it fills in the small cracks with rubber, but the high spots on the track still stick up. The same happens for a brake pad and rotor, all the little gaps collect little bits of the pad material. Now imagine that somebody going down the track comes to a screeching halt. The slide down the track. They leave more rubber on the track, they might even leave enough rubber to create high spots. On a rotor, these spots where the pad material has basically crumbled off can present a high spot on the disk, which the pad skips off of. Whether the pad is new or not it is possible to do this, but it is more likely to happen with a new pad, because the surface coating on the pad is designed to wear in faster to give you more friction.

Edit:
So in other words, wear in your track pads and you will be fine.

The article also says this generates hot spots/hard spots, this is unlikely, usually those are caused by people touching their brake rotors and not cleaning them afterwords (yep thats what causes that).
Jitter as I call it, is more likely caused by rotors that were turned improperly.
Many people make a big deal out of this when it isn't (and less of a deal out of the last 2 items)-rust which is pretty common on the contact area of the rotor doesn't cause huge problems so it takes a significant amount of abuse on new brake pads to cause this.

Edited by dblack1 on Tuesday 22 October 00:25