Worn brakes

[Walt]

Just came back from a track day at Spa Francorchamps and now the brakes feel a little off. I did a fluid flush using Motul RBF 600 right before I went. The brakes aren't squeaking but you can hear the pads dragging against the rotor when braking (more than usual) and I find myself needing to press the brakes harder.

Decided to do a quick fluid flush again since I figured there might be air trapped in the lines. That seemed to fix the vague brake feel.

While I was at it I checked the brake pads and the rotors too. Do you think they are too worn for another track day or are they still fine? Rotors seem a bit scored, not sure about the pads I noticed 2 'X' marks on the caliper, are those wear indicators? Is it fine until it's past the X?

What rotors and brake pads would you recommend for a car that sees a couple track days a year (<10) and is mostly used on weekends? Should I stick to OEM or something aftermarket? Perhaps something that can take more of a beating but not too much more dust or noise. I have a performance pack 2017 Mustang Ecoboost.

FRONT

REAR

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[Norm Peterson]

I suspect you overheated the pads.

As for pad condition, don't count on those front pads passing tech. Typically, inspectors want to see 50% of the original friction material thickness remaining, and all I'm seeing is barely thicker than the backing plate (around 1/3 of original pad friction material thickness). Rear pads look OK, but the rotors look like they've accumulated some uneven pad material deposits.

As for a dual-duty pad . . . I doubt there is one that meets track needs and exhibits minimal dusting and little or no noise. At the lower end of pads rated for track duty, the lower Carbotech and G-loc formulations (8's, 10's, and 12's) are pretty gentle on your rotors, while other pads are not (especially in street driving).


Norm

 

[Ewheels]

Those rear rotors are done! They look like 100% glazed pads but on the rotor...so a bit odd. I agree with Norm, weird pad deposit on the rear rotors. Either way, its a sure sign the rears got way too hot. Recommend better pads and you'll need new rear rotors or shave off the glazed portion

 

[Walt]

I suspect you overheated the pads.

As for pad condition, don't count on those front pads passing tech. Typically, inspectors want to see 50% of the original friction material thickness remaining, and all I'm seeing is barely thicker than the backing plate (around 1/3 of original pad friction material thickness). Rear pads look OK, but the rotors look like they've accumulated some uneven pad material deposits.

As for a dual-duty pad . . . I doubt there is one that meets track needs and exhibits minimal dusting and little or no noise. At the lower end of pads rated for track duty, the lower Carbotech and G-loc formulations (8's, 10's, and 12's) are pretty gentle on your rotors, while other pads are not (especially in street driving).


Norm

We don't have inspections at track days over here, as long as you have a tow hook and you are under 95db you're fine to hit the track lol. We do have road inspections though so I will replace them before that for sure. I went for a drive after flushing the fluid and the brakes seem to perform fine like before. Perhaps they are still fine for street driving but I will have to replace them before my next track day.

Would the Carbotech/G-loc pads overheat like the OEM pads did? Also what rotors would you recommend to go along with these pads? Overall I'm just looking for something more durable/long lasting.

The current brakes have about 5k street miles on them and 5 track days. The first few track days I wasn't really pushing the car since I only just started to drive on the track. Usually they consisted of about 1-3 20min sessions. It's just the last 2 trackdays where I really started pushing the car to its limits and booked full track days (4 x 25min). I didn't expect them to be trashed that quickly though. So I'm mainly looking for a set that I don't have to throw away after only a handful of track days. Performance wise the stock brakes felt okay to me, although I never really stand on the brakes I always brake early and try to be gentle which is why I was impressed with how bad they look.

 

[Walt]

Those rear rotors are done! They look like 100% glazed pads but on the rotor...so a bit odd. I agree with Norm, weird pad deposit on the rear rotors. Either way, its a sure sign the rears got way too hot. Recommend better pads and you'll need new rear rotors or shave off the glazed portion

Yeah no idea what caused the pad deposits but like you said they probably got too hot. I didn't really felt it during driving otherwise I would've backed off a bit. What pads and rotors would you recommend replacing these with? Something a bit more durable for sure, I was already braking early and being very gentle with the brakes, so if I start to push even further I definitely want something I don't have to throw away after each track day.

 

[cop on my back]

Not related to the question at all, but man, I would give my left nut to hit that course! Hands down my favorite track to watch F1.

 

[Walt]

Not related to the question at all, but man, I would give my left nut to hit that course! Hands down my favorite track to watch F1.

Believe me you'd want to have both of your nuts when hitting Raidillon/(Eau Rouge) for the first time lol. It's definitely an experience going up there, with the stock pirelli's and with an enter speed of about 200kmh (120mph) the car powerslides through that corner!

It's my favorite track to "safely" push the car. Compared to the Nordschleife where there's no room for error, you have run-off area for days. Never seen a major accident happen during a track day at Spa, other than a blown tire or something. At the Ring on the otherhand, you could find up to 4 wrecks in just 1 lap on a busy friday. Really makes you think twice pushing the pedal to the metal!

It's for sure nice to live close to both of these tracks, but on the other hand I would love to drive on tracks overseas like Laguna Seca too!

If anyone is interested I could post a little clip of me driving at Spa Francorchamps, I have some pretty fun action of following and eventually passing an Aston Martin Rapide S V12.

 

[Norm Peterson]

We don't have inspections at track days over here, as long as you have a tow hook and you are under 95db you're fine to hit the track lol.

eeeek . .

Pad friction material thickness also acts as thermal insulation for your caliper pistons, and the fluid that lives behind them.

Would the Carbotech/G-loc pads overheat like the OEM pads did? Also what rotors would you recommend to go along with these pads? Overall I'm just looking for something more durable/long lasting.

Carbotech and G-loc pads both come in a number of formulations, offering a variety of temperature ranges. I would suggest the R10 compound (XP10 in Carbotech), as 3600-ish lb Mustangs with 300 or so claimed HP are likely a bit too much for the 8's. I ran a set of XP8's some years ago, and while I didn't ever fade them I did manage to put more than a few thermal cracks in the friction material.

G-LOC Pad Compound Chart data from Vorshlag
GS-1 ~.45 ambient up to 800°F (426°C) - Street pads
R6 ~.51 ambient up to 1000°F + (to 537°C+) - Autocross pads
R8 ~.55 74°F-1250°F+ (23°C to 676°C+) - Entry level track pads
R10 ~.59 118°F - 1475°F (47°C - 801°C) - Track pads
R12 ~.62-.63 173°F to 1860°F (78°C to 1015°C) - Track pads
R14 ~.60 210°F to 1400°F (98°C to 760°C) - Endurance pad for light cars
R16 ~.65 255°F to 2000°F (123°C to 1093°C) - Aggressive track pad
R18 ~.70-.71 610°F to 2100°F+ (321°C to 1149°C+) - Aggressive track pad

Temperature ratings for the corresponding Carbotech compounds are similar - seems the same guys were responsible for developing both the CTs and the G-locs.

So I'm mainly looking for a set that I don't have to throw away after only a handful of track days. Performance wise the stock brakes felt okay to me, although I never really stand on the brakes I always brake early and try to be gentle which is why I was impressed with how bad they look.

Not sure I'd count on getting much more than half a dozen track days of 4 x 20 minute sessions or more. Being overly gentle probably isn't the way to brake on the track when you've got pads that can withstand the temperatures reached. Less time spent braking = more time for the brakes to cool when there isn't more heat being generated.

Add some brake cooling.

10's seem to last longer than 12's. I don't have experience with anything higher than 12's.


Norm

 

[Ewheels]

Yeah no idea what caused the pad deposits but like you said they probably got too hot. I didn't really felt it during driving otherwise I would've backed off a bit. What pads and rotors would you recommend replacing these with? Something a bit more durable for sure, I was already braking early and being very gentle with the brakes, so if I start to push even further I definitely want something I don't have to throw away after each track day.

Well that's not a straight forward answer. Any track pad is going to be too aggressive for the street (increased noise, dust, and wear) and any street pad will overheat on track. Gloc GS1 pads will be a decent middle ground pad, or Hawk HP+ but if you really want to dive deep at the track, I would recommend getting dedicated track pads and swap them out between track days. For dedicated track pads, I would recommend Gloc R12 front and R10 rear.
For rotors, anything with a high carbon content will be sufficient. Centric 125 Series will be one of your cheaper options. Then you can look into slotted and then two piece rotors but they get exponentially more expensive (but they last MUCH longer). All depends on your budget.

And you mentioned you would brake early to be easy on the brakes...braking early is only keeping heat on the pads/rotors for longer. This is actually more likely to overheat your brakes.

 

[Walt]

eeeek . .

Pad friction material thickness also acts as thermal insulation for your caliper pistons, and the fluid that lives behind them.

Makes sense, didn't think about that. And yeah I know it's crazy they don't have basic inspections, all they do is measure your exhaust and check if you have a tow hook. The track days I do are more oriented at street cars rather than full blown track cars though.

Not sure I'd count on getting much more than half a dozen track days of 4 x 20 minute sessions or more. Being overly gentle probably isn't the way to brake on the track when you've got pads that can withstand the temperatures reached. Less time spent braking = more time for the brakes to cool when there isn't more heat being generated.

Are you talking about the pads not lasting long or both pads and rotors? If it's just pads, maybe it will be better for me to have a dedicated track set. I flush fluid before every track day anyway so might as well swap out the pads quickly. On the other hand is it even advisable to use 2 set of pads on the same rotor?

If I would get 2 sets, would you still recommend the XP10 Carbotechs as track pad? (and maybe OEM as street pad). I still have to drive to the track though so that would be with the track pads on.

Add some brake cooling.

Do you have some pointers towards good brake cooling? I saw the vorshlag brake deflector kit but that requires a 2018 PP1 GT undertray to work which wouldn't fit on a 2017 Ecoboost PP. Other kits have hoses run through the fogs, but for the EU Mustang the fog lights are our DRL so I can't remove those. I would prefer not to cut into anything.

 

[Walt]

Well that's not a straight forward answer. Any track pad is going to be too aggressive for the street (increased noise, dust, and wear) and any street pad will overheat on track. Gloc GS1 pads will be a decent middle ground pad, or Hawk HP+ but if you really want to dive deep at the track, I would recommend getting dedicated track pads and swap them out between track days. For dedicated track pads, I would recommend Gloc R12 front and R10 rear.
For rotors, anything with a high carbon content will be sufficient. Centric 125 Series will be one of your cheaper options. Then you can look into slotted and then two piece rotors but they get exponentially more expensive (but they last MUCH longer). All depends on your budget.

And you mentioned you would brake early to be easy on the brakes...braking early is only keeping heat on the pads/rotors for longer. This is actually more likely to overheat your brakes.

Didn't think about how braking early is causing more stress than braking late, good point. Would it be advisable to run both set of pads on the same rotor? Or should I run a dedicated track rotor too? Generally speaking, how many track days would a rotor last?

 

[Norm Peterson]

Makes sense, didn't think about that. And yeah I know it's crazy they don't have basic inspections, all they do is measure your exhaust and check if you have a tow hook. The track days I do are more oriented at street cars rather than full blown track cars though.

As far as I know, every track day entity over here has a tech sheet check line for adequate pad material remaining. Certainly the ones I've run with all did.

Are you talking about the pads not lasting long or both pads and rotors? If it's just pads, maybe it will be better for me to have a dedicated track set. I flush fluid before every track day anyway so might as well swap out the pads quickly. On the other hand is it even advisable to use 2 set of pads on the same rotor?

With the CTs and G-locs, rotor wear is far less of an issue than it is with other pad formulations. I got half a dozen events out of XP10's, and this is when I was still running the car's really little OE 12.4" front brakes. Rotor wear rates in street driving with XP12s were much, much lower than with Hawk HP+ pads, closer to rotor wear rates with HPS street-only pads.

If I would get 2 sets, would you still recommend the XP10 Carbotechs as track pad? (and maybe OEM as street pad). I still have to drive to the track though so that would be with the track pads on.

I do think that 10's are enough pad . . . though there is the question of whether your car's front rotors feed air into the rotors from the outer (wheel) side or from the inner (strut) side. Strut-side, or back side air inletting is much preferred for tracking, and compatible with the usual methods of adding more brake cooling (where wheel-side air inlets obviously wouldn't be).

Do you have some pointers towards good brake cooling? I saw the vorshlag brake deflector kit but that requires a 2018 PP1 GT undertray to work which wouldn't fit on a 2017 Ecoboost PP. Other kits have hoses run through the fogs, but for the EU Mustang the fog lights are our DRL so I can't remove those. I would prefer not to cut into anything.

Not really sure what your options are. I wasn't going to sacrifice the fog lights on my '08 either, and cut my own brake cooling inlet holes in the lower radiator inlet pretty much directly under the fog lights. Threw a little spray paint at them and called it good. I'm not a car show guy.

Norm

 

[Norm Peterson]

Didn't think about how braking early is causing more stress than braking late, good point. Would it be advisable to run both set of pads on the same rotor? Or should I run a dedicated track rotor too? Generally speaking, how many track days would a rotor last?

If you choose to run a two-pad scheme, you'll want to run the street pad from the same mfr as your track pads. In CT, that'd be the Bobncat 1521 pad (though you could possibly use the AX-6 autocross pad), and in G-loc it'd be the GS-1 (possibly the R6). I'm not sure about pad compatibility among other pad mfrs, and what I do know is that mixing formulations/pad mfr products is likely to introduce problems.


Norm

 

[Ewheels]

Didn't think about how braking early is causing more stress than braking late, good point. Would it be advisable to run both set of pads on the same rotor? Or should I run a dedicated track rotor too? Generally speaking, how many track days would a rotor last?

I agree what Norm said. You can run track and street pads on the same rotors but they should be from the same manufacturer. If not, then you will get different pad compounds on your rotors and they will judder (ask me how I know )
I like having separate pads and rotors so street driving won't wear out my track parts and track driving won't wear out my street parts.

As far as rotor life, that depends on far too many variables to give you a clear answer. Your driving habits, how many street miles you drive between track days, how hot they get, which rotor specifically, bedding process, ect.

 

[kz]

Just to double check - OP - you did turn off stability control ? It uses brakes to prevent you from dying (in its own mind of course)...

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