Just recently put on a set of Girodisc recession special rotors (all 4 corners - ran the stockers for 75,200 miles) as well as the Girodisc Magic pads (all 4 corners - ran Ferodo DS 2500 for 53,200 miles). Tangent note: Girodisc *ROCKS* on their shipping times, quality of product, and pricing!

First attempt to bed pads was interrupted by traffic; got the brakes to smell a little but there was clearly no pad transfer onto the rotors. Braking capabilities were obviously not up to par. This weekend, went out a little later and got the brakes good and hot - it was easy to tell when pad transfer occurred because the stopping distances dropped like a rock. New asphalt with new Dunlop Star Spec Z1s make the car feel like you dropped an anchor out, even without braking hard enough to invoke ABS.

Easy questions first: prior to this weekend's bedding session, the brake pedal (fluid flushed and brakes bled immediately after new rotors/pads) was extremely firm - just the way I like it. After bedding, the pedal has a bit of mush to it.

The irony: prior to bedding, stopping distances were long, pedal was very firm, and pedal effort was high. Now, stopping distances are short, pedal is a little mushy, and pedal effort is much lower.

Why is this happening and how can I get the firm pedal back?

I would really like to have short stopping distances, low pedal effort, but a very *firm* pedal.

Harder questions next: there are now 3 distinct rings on the rotors - much more pronounced on the fronts than the rears. (Yes, brake cleaner was used liberally on the rotors prior to installation.)

Ring 1 (closest to axle): bluish brown.
Ring 2 (middle ring on rotor): brownish. Appears to be pad transfer.
Ring 3 (outer ring on rotor): like new rotor. Appears to be *no* pad transfer at all.

Why?

Do I need to take any corrective action to correct Rings 1 and 3?

Thanks!

 

I'm curious since I just installed rotors/pads/fluid

 

Pads are not 100% matched to the rotor surface. That is partly what bedding helps with. So the color differences are most likely the contact points between the pad and rotor. When they wear in some more, it should event out.

The pad transfer to the rotors can't always be seen. Its a very thin layer. (And if too high, you get pulsation (aka "warping").

Could have air in the brake line. The braking would have moved it around. I would re-bleed and report back. What fluid?

 

First, hopefully you've watched my videos on this topic already. They have some helpful tips and tricks.

I have a few possible answers on this one:

1. I saw that you did a complete bleed when you installed the new discs. Have you re-bled your brakes after your bed-in? Sometimes you have old fluid and air in your system that only comes out when you are on the brakes hard. Some of this can be due to ABS. The easiest way for me to describe this is that when you cycle your ABS, it 'cleans out' your ABS system. It forces out all of the old fluid that is residing in the abs system components. That's why dealerships are supposed to cycle the abs by hand (with an electronic tool) when bleeding brakes.
2. Your caliper may have had air lodged in it. This is actually more common than you'd expect. Sometimes with fixed calipers like those on the Evo, air gets trapped in the caliper crossovers, etc. One way to solve this is to actually tap the caliper gently with a soft mallet, or remove the caliper and put it in a few different positions to make sure all of the air is out of it. We used to have this happen a lot with certain vehicles. The one that comes to mind is the 350Z Track Model. Because of how the caliper was situated, they used to get air trapped in them more often than on other cars. I know it sounds a bit odd, but it is a possibility. I'd say #1 above is more likely.
3. It could be pad related. I'm not familiar with the pad you're running, but if it has any compressibility, that could be the issue. Some pads are more compressible than others. They have a bit of give, squeeze, mush, or whatever you want to call it in them...particularly when they get hot.

IMO, you may want to try the CL Brakes pads that we sell. They do exactly what you're looking for. They are less compressible than most other pads (firmer pedal response), and they have a higher coefficient than most other pads (you don't have to push the pedal as hard).

Shorter stopping distances are a function of your tires. If you put on stickier tires, you will have the potential to stop shorter. As long as your system is optimized (which it basically is from the factory), the amount of grip you have through your tires on the road surface dictates how short your car will stop. Claims of changing out brake pads alone and getting far shorter stopping distances are overblown. On most platforms when adding a BBK, you can only shave a couple of feet at best. That is accomplished by optimizing the brake bias. Most factory setups are very conservative in that area because too much rear bias makes the rear end want to come around under braking. That's a situation OEM's want to avoid like the plague!

As SmikeEvo said above, your pads are not completely mated to the surface of your disc yet. If I understand correctly, the discs and pads are both new. I would run them cold for daily driving a few days to mate them up a bit. Then I'd go back for a bed-in, and make sure you get them good and hot.

If you watch my "swapping street and race pads' video that I linked above, you'll see a similar issue to what you describe, except in reverse. My discs start out with a full bed-in and I try cleaning them off. A stubborn ring of material remains near the center mounting hat, and I had to go back out for a second session to wear them a bit more to get that ring off of the disc. What was happening was that my race pads hadn't yet gotten completely flush with the disc face down near the hat. You're in the same situation. You haven't gotten all of the surfaces mated up yet. Just keep at it and that should occur.

As long as you don't have any splotches or uneven segments of pad transfer, I wouldn't worry about any corrective action. In other words, if the concentric rings that are on the discs now are even in their application around the whole disc, no worries.

Hopefully that helps.

 

Good stuff, gents! Thanks a million!

I'll get out and re-bed. Re-bleeding is going to have to wait a while; I've got the GMAT on Aug 6.

I knew I could count on the Evo community for knowledgeable, helpful answers!