3.3TT WTF happened to my rotors? (Track Day)

[ElChanclo]

Half way into my second track day with the Z26 pads, everything was going great, having a blast on the tarmac, then a few laps into session 3 suddenly my brakes start to grind and scrape, like my pads are made of rocks. I let everything cool down, but after an hour it still grinds and scrapes. Car runs and feels fine otherwise.

Any idea what happened to my brakes? After some chatting and googling, the consensus seems to be that I glazed my rotors and/or pads.
I'll be ordering replacement pads and rotors once I figure out what I should replace them with.

What should I do for the next track day so this doesn't happen again?

 

[socalvn]

Time for pads and rotors. Something went wrong

 

[Snowwhite]

the z26 aren't heavy duty track pads. a few laps into your third session of the day is more than light track usage. From the looks of the deposits on those rotors, you cooked the pads.

For your next track weekend, swap out your street pads for dedicated track ones. on the stinger it's a really easy job, you don't have to take the calipers off to get to the pads. All you have to do is knock out the two slide pins and you can pull the pads out.

 

[GT Elite]

To me, it looks looks like the pads got completely worn out and the pad backing plates were contacting the rotors. How much pad material was there at the start of your track day? When I was tracking a Firebird, the rule was to change out pads when they were 50% worn.

While the Z26 pads are great for the street (I have them on my Stinger and Corvette) I would not consider using them on the track. For that you will need pads that are rated for higher temperatures. The trade off with these types of pads is they will most likely produce a lot of dust.

I would think that any quality solid or slotted rotor (not cross-drilled) would be fine. You may want to try and find ones that have directional vanes inside the rotor (that is what I used on the Firebird).

 

[turboAWD]

Yeah, same thing as the others said.

I accidentally (I still don't know how - rushing at the last minute, late at night, stressed at work, etc) swapped in my OEM pads instead of my race pads for my first day ever at Laguna Seca (had 5 days at Sonoma before that) last year. I meant "swapped", because I run non-OEM pads on the front, in general.

Can't find the pictures right now, but MAN, did I ever get pad deposits. And I wore through the ENTIRE pads (they were at 80%+ before because I had swapped out for other pads quite quickly) in ONE DAY. The leading edge of the pad was down to the bare metal, scraping on the rotor. And yet, I never really had brake fade / loss of braking - even down from 100+ mph in turn 2. I consider myself very lucky! But - I give credit to Kia / Brembo - those pads actually held up to some major abuse (6 sessions of "send it!!!" in one day) without overheating / glazing - even right at the end, I still had at least 80% of start-of-day stopping power. The drive home was something else - I suspect it was way worse than what you're getting.

You MIGHT be able to get your rotors turned. btw, OEM rotors are a step above R1 Concepts, etc.

So yeah - get yourself some race pads. I use this place:

KNSBrakes | Products | <!-- -->2019 Kia Stinger GT 3.3L - 350mm Front Disc

knsbrakes.com

And, MAN do they ever have a better selection than when I bought my pads - a few years ago, basically G-Loc R12 (and R16) were almost the only options. Now they have 4 or 5 different vendors. Just curious if others have opinions of best overall pads from that list? I've heard Cobalt is a good brand, better than G-Loc? (I had negative experiences with Hawk street pads on my Subaru, so I've stayed away, but I'm probably wrong about that too). Right now, I have some R12 and R16 pads that are still > 50%, so I'll use those up first (Laguna is WAY harder on brakes than Sonoma!). Plus, being laid off, it's hard to justify $$ for track days..

 

[turboAWD]

Duplicate post.

 

[ElChanclo]

Thanks for the input guys. Judging from the last pic it looks like there's plenty of pad remaining.

I've ordered replacement street pads for now (DFC 5k Adv) so we'll see how the Z26's look once they're all off.

 

[Volfy]

Brake pads are each designed with a specific heat range, in which they perform the best. A good pad mfr will publish a mu (friction coefficient) vs temp graph for each of their pads. Street pads typically have curves that plateaus early in the lower temp range and will start to fall off when temp rises. Once the pad gets much beyond the design range, the material becomes overheated, loses its design properties, and begins to break down rapidly. The end result is loss of braking effectiveness and eventually brake fade. If it is not severe enough, the driver might not feel the compromised braking and will instinctively apply more pressure to get more braking force. What this does is cause the pad material to break down rapidly. Some pad materials at the point will soften and start to deposit onto the rotor, which is what we see here onto your rotor.

If you look at some of your pics, the outer portion of the rotor get more deposits, since they see a bit higher contact velocity. The inner portions were not as bad, because they likely did not heat up as much.

At this point, that set of pads is basically trash, as their structural integrity is compromised and - more importantly - their design properties are no longer what they were before being overheated.

Contrary to popular myth, drilled and/or slotted rotors would've done nothing to help, since this is a case of brake pad's incompatibility with application. When the pad material breaks down this severely, no amount of slotting could clear the rotor of the massive amount of debris. Likewise, any drilling would add very little cross airflow - if any at all - simply because of how the typical rotor is designed, which is to flow air axially from the inside of the rotor out towards the rim of the rotor. Air, like any fluid, is "lazy" and will seek the path of least resistance. The most efficient route is straight through the inner channels built into a vented rotor, propelled by centrifugal force. There is absolutely no motive force of any kind that will cause the air flow to turn an abrupt 90deg and exit through tiny little holes instead. That is pure fantasy.

FWIW, this is why I switched to EBC Bluestuff just prior to my first track day back in last October. EBC designed and formulated that compound for exactly this sort of application. I'm sure other mfrs offer pads for similar duty.

Lastly, do not be temped to switch back and forth between track and street compounds, just for the track day. The whole reason for "seating" the brake pads is to wear the mating pair into perfect contact with each other... and pray to the Greek God of Brake Performance they stay that way. Thou shalt irk the ire of said Greek God, if thou dost switch brake pads willy-nilly.

The Bluestuff stays on my Stinger even for street. Yes the brake dust gets a bit annoying and the ultra high mu (friction coefficient) even at lower temp makes feathering braking force in slow traffic a bit delicate. However, I prefer having my car ready for the track at any moment. It is a compromise anyway you slice it. Up to you to decide your priorities and what you are willing to live - and run - with.

 

[Volfy]

FWIW, this is what my rotors look like at the end of track day last Oct:

 

[ElChanclo]

FWIW, this is what my rotors look like at the end of track day last Oct:

Sweet rims, any particular reason you run R18 on the track (instead of 19)?

And how do you find the V730's vs Sport 4S and Cup 2?

 

[Volfy]

Sweet rims, any particular reason you run R18 on the track (instead of 19)?

And how do you find the V730's vs Sport 4S and Cup 2?

Lots of reasons to run 18's.

1. To keep unsprung weight and rotational inertia to a minimum necessary, the wheel size should ideally be no larger than what is required to fit over the brakes. The OEM Brembos easily fit inside every set of 18" rims I've tried on. If I were to fit a big brake kit with larger rotors and 6-pot Brembos, but that would only fit under 19's, then I have absolutely no problem switching to 19's.

2. With 18's, I can run higher aspect ratio tires for general driving on public roads. Advantages:
a. Better tire compliance, which improves real-world grip over rough pavement and less-than-ideal road surfaces in general.
b. Taller side walls for better rim protection over pot holes and obstacles and provides a smoother ride.
c. Lower weight quickens accel/decel and improves suspension action.

3. At the track, if I so choose, I can run lower A/R tires to improve steering response and turn in sharpness. Those V730's are 245/40R18, and I plan to switch to 255/35R18 on the next set. I get all the traction benefit of, say, 255/35R19, but without the extra weight and rotation inertia with larger diameter wheel/tire. Smaller tire diameter means speedometer calibration will be off, of course, but at the track, that is a don't-care. The quicker accel/decel is of even more importance for HPDE.

4. Smaller diameter tires are general less expensive. I also find that 18's have more choices in applicable tire sizes. Between our Stinger and G70, we have 4 sets of wheel/tires for different uses.. This allows us to optimize each for its intended application. Now that we just added a '23 Stinger GT-Line, the collection will undoubtedly grow.

As for the V730... I wouldn't compare them to Michelins you mentioned. This is a treadwear 200 with barely enough tread to qualify for the DOT stamp. It's not uncommon for us to get questions from tech inspectors at track events about them being "bald". I've have the TireRack link on my phone to show them pics of a brand new V730. The outside 2/3rd is basically DOT racing slick. I would not want to run them on public roads and definitely not at the track if it was wet/raining. We've got another set of 18's with Bridgestone Potenza Sport for that. In terms of track performance, the V730 likely isn't quite a match for track favorites like RE71 and RT660. However, the Kumho lasts a lot longer, which at our level is more important than outright performance.

Hope that helps.

 

[turboAWD]

Yeah, I thought most 18s would fit as well. Sadly, the TY-5 Enkeis I bought fit, but the second set, RPF-1s (for track tires) do NOT clear the brakes. So I had to buy two more TY-5s to put the front tires on, and I can't rotate them, which was the entire point of going 245 square with my Conti ExtremeContact Force.... :-(

 

[Volfy]

Yeah, I thought most 18s would fit as well. Sadly, the TY-5 Enkeis I bought fit, but the second set, RPF-1s (for track tires) do NOT clear the brakes. So I had to buy two more TY-5s to put the front tires on, and I can't rotate them, which was the entire point of going 245 square with my Conti ExtremeContact Force.... :-(

Bummer. RPF-1 is a perennial AutoX/Track favorite. Where was it hitting the caliper? Was it at that raised flange right where the spokes meet the barrel?

As you can see in the pics above, our Enkei TFR 18x8.5 ET 38mm cleared the front caliper by a wide gap. And that's without any spacer. We typically run 5mm hubcentric spacer to correct the scrub radius within 1mm of stock 34mm, so it's even wider gap.

 

[turboAWD]

The spokes themselves hit the caliper. I am not an expert on wheels / offsets, but I already had TY-5 that fit pretty well in the front, so I ordered the same offset, assuming it would also fit. Nope.

The TY-5 I bought needed the 3mm spacer I bought (just in case) because the EC Force in 245 is THAT wide - wider than my 255 PS4S (I run 255/285 on black TY-5s on the street), got silver for the track. Looked SWEET, but then I couldn't get the fronts to fit. :-(

These days, it's been hard to get to the track, due to being laid off and trying to save $$. Just bought a new set of PS4S for the street, which was like $1.2K.

I may have erred due to the fact that I went from 18x8.5 ET 35 with the TY-5 to 18x9 ET 35 in the RPF-1s, so that I could go up to 275 if I needed in the back later. In any case: TY-5 18x8.5 ET 35 fit fine. RPF-1 18x9 ET 35 do NOT. Even with a 3mm spacer - the calipers won't clear the spokes.

I think I tried doubling up the 3mm spacer I had and that wouldn't fit either (not to mention starting to worry about enough threads on the nuts - with 3mm, they have 8 threads, I counted..).

I'm leery of 20mm spacers - I've heard very mixed things about them. Heck, my tire shop freaked out about the 3mm spacer I had (I leave it on even with the PS4S now, just to keep things simple).

 

[turboAWD]

 

[Volfy]

I've always suspected that when Enkei designed the ultra lightweight flow-formed wheels, like the RFP-1, they had to curve the spokes in more and land them farther inside the barrel, in order for the thinner spokes and lighter barrels to maintain the same load rating, as other slightly heavier wheels. That raised flange is part of that load-bearing calculation. The wider the wheel, the more they had to inset the spokes.

For me, weight saving is very important, but even then I don't consider shaving that last 1-2 lbs of wheel weight worth the possibility of not fitting the car.

As for wheel spacers, I'm not a fan of anything thicker than 5mm. If I need a lot more than, I should've looked for a wheel with offset closer to stock ET. Unless, of course, as guys is using 20mm spacer for looks. That is a whole 'nother fish all together, and not really applicable to HPDE.

Wheel stud thread engagement... ideally, you should have a minimum of ONE(1) bolt diameter engaged. So for our 12x1.5mm studs, that's 12mm / 1.5mm = 8 threads. So you are correct about 3mm spacer is getting close to the limit. I'm willing to push it a little, with up to 5mm spacer, but only if they are hubcentric with raised lip for better support.

 

[ElChanclo]

Appreciate your expertise!

Lastly, do not be temped to switch back and forth between track and street compounds, just for the track day.

Now this is a hill I might just die on (or at least strongly regret).
Considering the pads wear much faster than the rotors, you're mostly wearing the pad to match the rotor, with relatively little wear on the rotor face.
If you swap to a second pad set, those pads also mostly wear to match the rotor. It's like you're installing new pads every time you swap back and forth, except they're already bedded and ready to go! What could possibly go wrong?

Lots of reasons to run 18's...

As for the V730... I wouldn't compare them to Michelins you mentioned.

You have Stingers in 2.0 and 2.5 (not sure what your G70 has), would all those reasons still apply to the 3.3 AWD as well? At a certain point smaller wheels = less traction, but more isn't always better...

 

[Volfy]

Appreciate your expertise!



Now this is a hill I might just die on (or at least strongly regret).
Considering the pads wear much faster than the rotors, you're mostly wearing the pad to match the rotor, with relatively little wear on the rotor face.
If you swap to a second pad set, those pads also mostly wear to match the rotor. It's like you're installing new pads every time you swap back and forth, except they're already bedded and ready to go! What could possibly go wrong?

Pad wear vs. rotor depends on the pad compound. Street-oriented types like ceramics tend to wear a lot more than the rotor, especially when they get hot. That's why the OEM pads leave so much deposit on the rotors, causing the infamous shudder and vibration. These types are not necessarily all bad, as long as the type of driving and characteristics of the car (e.g., weight) are well-suited to the pad compound.

Then there are the harder more aggressive track compounds like semi-metallics, which tend to chew through rotors much faster.

At the track, there are other nuances like micro pad material transfer, which is in essence what track bedding really aims to do - leaving a very thin layer of pad material on the rotor, allowing the pad to glide on itself, producing optimum braking performance and wear. If you look on the pics I posted in post#9 above, that's the yellowish hue on the rotor. There are racing brake shops that offer services to do this for you, so your pad/rotors are already perfectly bedded prior to a racing event. For us casual HPDE enthusiasts, it's not worth it, because the micro layer won't last away from the track and will be quickly gone once returned to street driving duty.

So with all these variables, I prefer not to tempt fate and just stay with a single set of pads.

You have Stingers in 2.0 and 2.5 (not sure what your G70 has), would all those reasons still apply to the 3.3 AWD as well? At a certain point smaller wheels = less traction, but more isn't always better...

More HP does require wider tires to handle the torque. However, that's mostly for launching from a standstill and, to a lesser extent, WOT-accelerating on long straights. On most other parts of the track, traction is devoted to cornering, braking and partial-throttle accelerating, none of which matter how much max HP/TQ the car has. If I had gotten a 3.3, I would still run 18's. In fact, 18's hold a distinct advantage when you need to go wider tires for the rear wheels for power handling. With 19's, you are having to go to very low aspect ratio tires in order to go much wider, say 305/30R19, to maintain the same rolling diameters as the stock 255/35R19. Especially if you have AWD. Problem with such low profile is that there is very little compliance in the tire. If the track surface is rough and/or bumpy, those tires will end up yielding less traction, not more.

With 18's, you can run 295 or 305/35R18 and still have good amount of tire sidewall for better compliance, to handle a wide range of track conditions.

BTW, G70 only offered 6MT with the 2.0T. I think it actually suits the character of the car quite well.

 

[ElChanclo]

That's a wealth of information, I always have to read your posts 2-4 times to wrap my head around everything.

So with all these variables, I prefer not to tempt fate and just stay with a single set of pads.

How many track days have your Bluestuffs lasted? I'm also curious how even your pad wear is. I get un-even wear every which way, bottom of the pad wears faster than the top, inner pad wears faster than the outer, and rear pads wear faster than the fronts (non tracked OEM pads).

If I had gotten a 3.3, I would still run 18's.

Why didn't you opt for a 3.3 among your fleet? Especially as you go tracking.

I'm thinking of going for a square 245/45r18 setup for a smoother daily ride (and tire rotations) once the factory tires wear out, then using the OEM 19's for the track. Not thrilled about the weight, but I can't bring myself to sell em or watch them collect dust in storage.

 

[Volfy]

That's a wealth of information, I always have to read your posts 2-4 times to wrap my head around everything.

Glad you find the info useful.

How many track days have your Bluestuffs lasted? I'm also curious how even your pad wear is. I get un-even wear every which way, bottom of the pad wears faster than the top, inner pad wears faster than the outer, and rear pads wear faster than the fronts (non tracked OEM pads).

The Bluestuff has been through 3 track events and quite a few AutoXs so far. There was a visible amount of wear on the Bluestuff after the first full Track Day, so I thought they might wear out pretty fast. Since then, wear rate hasn't been as high as I originally thought. Besides, I try to stay away from venues that are fast with long straights, as they tend to be hard on the car overall, more than just brakes. I much prefer more technical tracks. Cornering is where the fun is and how a guy learns to drive fast.

The 2.0T Stinger is due for brake fluid flush, as soon as this hellishly hot weather lets up a bit. I'll get a chance to pull the pads for a closer inspection. Last I checked (with pads in situ), they appear all fairly even. We always disable ABS & TC at the track, and so there should be minimum safety nannying causing odd wear on the rears.

Why didn't you opt for a 3.3 among your fleet? Especially as you go tracking.

On this latest search, I started out looking at another G70, as my oldest son (who drives the G70 6MT) and I both find it handle better. Looking at less than 1yr old pre-owned with very low miles, I was surprised by 2 things:

1. Just how many of these there are on the secondary market.
2. Asking prices of pre-owned 2.0T were barely $1-3k less less than similar year/miles 3.3T's that originally MSRP'ed at some $10k more. While I wouldn't mind another 2.0T G70, from a price perspective, there was frankly no reason to buy one.

So, I almost pulled the trigger on a G70 3.3T Sport Prestige. Ultimately though, I came back to the Stinger. It is just a better all-around road car. Even on the Stinger, a comparable pre-owned '22 or '23 GT1 was not much higher $$ than a loaded GT-Line. But... the 2.5T just strikes a great balance between HP and efficiency. As much as we enjoy having fun on weekends. track time constitutes a very small % of miles driven. Most of the time/miles are on public roads, where I have zero interest in engaging in buffoonery (for reasons like this). Instead, I like that I can get 37mpg on my morning commute without trying very hard.

Even at the track, since my main goal is to introduce my kids to HPDE, abundant HP/TQ can actually be a distraction from learning. Ultimately, performance driving is about momentum management. Fastest guy isn't always the one with the highest HP car. It is the one that can set up optimum corner entry speed & attitude, carry the car through the turn without scrubbing off speed or upsetting the chassis, and then roll power back on at the proper time and manner to drive out of the turn. With an abundance of HP/TQ, a guy can ham-fist the corners, then just drop the hammer on the straights, and still feel pretty fast. OTOH, a modest HP car affords you no such leeway, so momentum preservation and traction management are absolutely critical. You must learn to time you inputs precisely, in order to balance the available tire traction perfectly between braking, cornering and accelerating. it's a skill that takes time/practice to acquire. Once you do, you'll be fast in any car.

Perfect example of this was at the BMW Ultimate Driving Experience I attended 2wks ago. I got to drive 2 cars. First was the 536HP/586lb-ft i4 M50. Boy was that a handful! The immense instant-ON torque was flat-out impossible to manage. I got yelled at by the instructor several times. Definitely not fun. then I got to try the 330e. The 288HP (combined) might not sound impressive, but it was very easy to modulate and the electric motor assist, though modest, practically eliminated any perceived turbo lag. It felt like a well-tuned torque-rich naturally-aspirated engine. I was able to drive it quite well around the short course I just previously messed all up in the i4 M50. Then the last run I let the instructor drive the 330e, and as expected, it was an eye-opener. Anybody who calls a 2.0T slow should go have an experience like that. In the hands of a competent pro, that 2-ton go-kart darting around the course was at once a humbling experience... and a thing of pure beauty.

The same thing holds true on 2 wheels. If you ask any seasoned track day rider what bike they'd recommend for a novice, most would say a 600cc supersport and ALL will tell yo to stay da heck away from a 1000cc race replica.

I'm thinking of going for a square 245/45r18 setup for a smoother daily ride (and tire rotations) once the factory tires wear out, then using the OEM 19's for the track. Not thrilled about the weight, but I can't bring myself to sell em or watch them collect dust in storage.

For street, my son runs 255/40R18 on his G70 6MT. I run 235/45R18. 245/45R18 square would work too, although the sidewalls are gonna be quite a bit taller than your stock 19's.

Nothing wrong with the OEM 19s for the track. Run them if that's what you have. A good set of tread wear 200 track tires will make a huge difference, despite the weight of the wheels. Unless you become seriously competitive, does a few seconds faster/slower matter that much, realistically? I would concentrate on getting the rest of the car track-prepped properly.