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My apologies for the delayed response. I was to have two days at Thunderhill this past weekend with some better ducts on the car. Unfortunately, I messed up and put the wrong pads on the car and cooked them in about four laps. I was so disgusted with myself that I drive back home and dismantled everything including the ducts. now that I have the correct pads, I will put everything back together and head back to the track shortly. I promise to take photos of the ducts this time and share here. More to follow in a week or two.
Kurt.
Kurt I just have to say I love the updates and videos you posted in this thread. Very cool!
...1. Tires. I am using Michelin Pilot Cup 2 tires and at the last event, I could not control the pressures and they would soar into the 50psi range. I even started them exceedingly low at around 25psi. This would keep them in the mid 40psi range but from my research, these tires should be kept a bit below 40. Let me know if anyone has heard differently. For this event, I had them filled with nitrogen (with several purges) but the results were the same. The tire company that filled them told me that I should only see a 1 to 2 psi increase. Assuming they were correct, I had all tires filled to 40psi with nitrogen. So much for 1 or 2; try 10 to 15psi! I started the with 38psi in the fronts and after the first session, they were at 55psi! I dropped them down by 10psi and then had significant roll over per this photo:...
As I did not have any nitrogen with me, I had to add some air. I finally was able to get them to stabilize at 43psi which seemed to be a reasonable compromise between roll over and pressure. I know it is a heavy car so maybe low 40s is the best compromise given all issues....
3. Brakes. I had been working with racebrakes.com and they still cannot come up with a rear track pad. To their credit, they have been trying but apparently do not show the correct part number for the red caliper set up. I will send them a set of my worn pads so that they can make a set. The fronts they provided, worked great. What did not work so great is the Mercedes brake fluid. I have another post on the Forum where I incorrectly indicated that I wanted to use DOT 6 fluid. Sorry about that. I wanted to use the Motul 600 which, technically, is a DOT 4 fluid but seems to perform well my car. I will try it again for the next one because in this event, the fluid let me down. In just a couple of laps, the pedal started to get soft. I essentially nursed it the rest of the day and never achieved VMax in any straight and lifted/coasted in most just to be sure I didn't overwork the fluid. Once in the pits, I checked the rotor, caliper, and wheel temps. My laser thermometer maxes at 600F and I would get an "ERR" message on the rotors indicating a temp above 600F. Clearly, I need to address this issue. Better fluid and I will be engineering some cooling ducts before the next event as well...
Kurt
Hi Kurt, thanks for the track updates. I have a couple of questions if you don't mind as I am considering putting my Edition 1 on the track.
1) You mentioned changing the brake fluid to Motul RBF 600. Did you? What was your verdict compared to the original? I personally run Castrol SRF in my other cars. But with Motul RBF 600 being 1/3 the cost of the SRF, I may be willing to try it. You tell me...
2) You used the stock brake pads in your original track event. The track I will likely be going on will likely not have as "heavy braking" as Thunderhill; maybe 2 medium braking zones by my definition. I don't even think I would get into ABS as the track is arguably more of a "rhythm" track: Club Motorsports in NH. At Thunderhill, are there a lot of heavy braking zones which could have contributed to your pads/brake heat issues? I don't intend to track the car regularly. I'm just wanting to try it. So, I'm hesitant to purchase track-spec pads to be used once.
3) Looks like you kind of corded the front tires. Did you eventually change front camber settings or go with camber plates?
4) On the stock Michelin PSS, what pressures should I run at? Back in the good old days when I used to track a lot, we would set our tire pressures typically 3 psi HIGHER than what was shown on the door jambs as a starting point. Today, it seems that I am coming across people who are setting their tires 10-15 psi LOWER than what's showing on the door jambs. They say that by the time that they are warmed up at the track, the pressures would have risen to what it says on the door jambs. They say that if they start at 40 psi, the pressure could rise to 55 psi or more. Thus, they start off at 25 psi. I suppose this makes sense. But leading up to that point, they are seriously rolling over the sidewalls that looks very unsafe.
1) Given what you described for your upcoming track day, you will be fine with Castrol; I think it is comparable to Motul.
2) You might be fine on the stock pads but I would say there is still a strong chance that you may experience some fade. If you do experience fade and with the setup you describe, it will likely take some time (perhaps hours) for them to cool enough before you can go back out. I would suggest that you at least change the front pads to something more track dedicated. I would suggest Raybestos ST47R; https://www.porterfield-brakes.com/Product/29592.html. They are $400 but they will last you several track days and given your track day description, I doubt you will have any fade issues. Plus, the front pads are so easy to change that I would strongly suggest you do it. If you end up roasting the brakes then your track day is probably shot. When you consider the cost of the track day lost, you pretty much would have paid for the track pads.
3) I did change the camber. I found a company on the forum here that makes a kit for the front and rear. I went with the front only and was able to get around -2.78. It made a world of difference. It still under-steers on the tighter corners but much, much less. The company I used was K-Mac. They are a sponsor here so check them out. I believe their kit was around $500 if I remember correctly.
4) Start low! You want your track hot pressure to be around 34-38psi hot. Most street tires should not go above 38-40 while slicks should be even lower. Hoosiers should not get above 34. You will likely have to start out around 26 or so. Given your track description, you may not be generating as much heat as on the tracks I run so start around 30 in the first session and adjust accordingly as the day goes on. I typically see about a 10-12 psi increase during my sessions at Thunderhill, Laguna, and Sonoma. Each of these tracks can really generate tire heat. You will get TPMS low pressure warnings but just ignore them. I would have your dash set to display the tire temps so you can see them go up. Increase your speed as the temps go up.
As a follow up, I did have the wrong pads and now have the correct ones and plan to be on track day within the next month. I will have the brake ducts back on so I will post some pictures as well as a few videos.
1) Given what you described for your upcoming track day, you will be fine with Castrol; I think it is comparable to Motul.
2) You might be fine on the stock pads but I would say there is still a strong chance that you may experience some fade. If you do experience fade and with the setup you describe, it will likely take some time (perhaps hours) for them to cool enough before you can go back out. I would suggest that you at least change the front pads to something more track dedicated. I would suggest Raybestos ST47R; https://www.porterfield-brakes.com/Product/29592.html. They are $400 but they will last you several track days and given your track day description, I doubt you will have any fade issues. Plus, the front pads are so easy to change that I would strongly suggest you do it. If you end up roasting the brakes then your track day is probably shot. When you consider the cost of the track day lost, you pretty much would have paid for the track pads.
3) I did change the camber. I found a company on the forum here that makes a kit for the front and rear. I went with the front only and was able to get around -2.78. It made a world of difference. It still under-steers on the tighter corners but much, much less. The company I used was K-Mac. They are a sponsor here so check them out. I believe their kit was around $500 if I remember correctly.
4) Start low! You want your track hot pressure to be around 34-38psi hot. Most street tires should not go above 38-40 while slicks should be even lower. Hoosiers should not get above 34. You will likely have to start out around 26 or so. Given your track description, you may not be generating as much heat as on the tracks I run so start around 30 in the first session and adjust accordingly as the day goes on. I typically see about a 10-12 psi increase during my sessions at Thunderhill, Laguna, and Sonoma. Each of these tracks can really generate tire heat. You will get TPMS low pressure warnings but just ignore them. I would have your dash set to display the tire temps so you can see them go up. Increase your speed as the temps go up.
As a follow up, I did have the wrong pads and now have the correct ones and plan to be on track day within the next month. I will have the brake ducts back on so I will post some pictures as well as a few videos.
Thanks.
Kurt
Thanks for the input!! Just another follow up since I just confused myself...
The door jamb shows tire pressures 48 front and 45 rear.
The gas fillup cover shows 38 front 33 rear for the same tire size, lower weight load and up to 155 mph...
What gives? It's conflicting information! I only have roughly 15k miles and my OEM Michelin PSS tires are wearing evenly. I've been running 48 front and 45 rear. They go up to roughly 51/49 with highway driving.
What are your thoughts on this conflicting info?
NEVERMIND: It seems that the door pillar rating is for up to 180 mph and fully loaded. I'm not going anywhere near that. I'll drop down to 38/33 for street and follow your recommendations for track. Thanks!
Thanks for the input!! Just another follow up since I just confused myself...
The door jamb shows tire pressures 48 front and 45 rear.
The gas fillup cover shows 38 front 33 rear for the same tire size, lower weight load and up to 155 mph...
What gives? It's conflicting information! I only have roughly 15k miles and my OEM Michelin PSS tires are wearing evenly. I've been running 48 front and 45 rear. They go up to roughly 51/49 with highway driving.
What are your thoughts on this conflicting info?
NEVERMIND: It seems that the door pillar rating is for up to 180 mph and fully loaded. I'm not going anywhere near that. I'll drop down to 38/33 for street and follow your recommendations for track. Thanks!
Kurt,
How is that single, floating piston rear brake caliper holding out during track days?
Never did understand why AMG drop the 4 piston unit for the single, assuming cost no issue, however I can see the point being made for weight savings. Personally it looks cheap on any AMG and the one BMW is using on the 5, 6 & 8 series M cars is even worse.
How is that single, floating piston rear brake caliper holding out during track days?
The rear brakes on my C63 S sedan are perfectly fine for track days. I run in Race mode and leave traction control in Sport mode, since it virtually never interferes. I also seldom see traction control being engaged. I mention this because that (and using cruise control) is what will wear the rear brakes.
I also carry an infra-red temp gun and often check the after-session rotor temps. The rear rotors never seem to get very hot and are typically <200 deg C after a cooldown lap. The fronts are often >300 deg C after a cooldown lap (my home track is a short track that's brual on brakes and tires).
I go through at least 7x the number of front pads, compared to rear pads, and the rear pads are stock pads whereas the fronts are track pads. Normally, the front brakes take around 80% of the braking load.
I'm sure AMG conducted a reasonable amount of R&D before using the single floating caliper but I'd still like to know if the 4 piston unit is better and if it feels different to the driver.
Kurt,
How is that single, floating piston rear brake caliper holding out during track days?
Never did understand why AMG drop the 4 piston unit for the single, assuming cost no issue, however I can see the point being made for weight savings. Personally it looks cheap on any AMG and the one BMW is using on the 5, 6 & 8 series M cars is even worse.
Without a doubt, it is and looks cheap. The rears are fine which is rather amazing considering the brake bias is more towards the back on these cars (at least according to my local dealer). I tried only a front track pad and stock on the rear and it was a disaster; brake fade was pretty quick. So now, I use track quality pads front a rear. I would advise the same for any aggressive track day/driver.
The rear brakes on my C63 S sedan are perfectly fine for track days. I run in Race mode and leave traction control in Sport mode, since it virtually never interferes. I also seldom see traction control being engaged. I mention this because that (and using cruise control) is what will wear the rear brakes.
I also carry an infra-red temp gun and often check the after-session rotor temps. The rear rotors never seem to get very hot and are typically <200 deg C after a cooldown lap. The fronts are often >300 deg C after a cooldown lap (my home track is a short track that's brual on brakes and tires).
I go through at least 7x the number of front pads, compared to rear pads, and the rear pads are stock pads whereas the fronts are track pads. Normally, the front brakes take around 80% of the braking load.
I am glad to hear that they hold up for you and they will on some tracks that don't present heavy braking areas for many drivers. Tracks like Thunderhill, Willows, COTA put a massive premium on brakes. Tracks like Laguna and Sonoma, not so much. Also, it depends on how aggressive you are. If you really get on it and push the car, you will likely encounter it on most tracks. Most magazines and pros will attest that the stock steel set up will fade on most tracks after 8 or so hard laps. The carbon ceramics are a much better setup for thermal management. I have often considered this but the cost just does not seem worth it when I only track this car about once or twice a year. I have another more dedicated track car (McLaren 600LT) that I throw my money away with. Thanks for sharing your experience though as I don't want folks to think the brakes are total crap.
Thanks Kurt, however I'm a little surprised about the rear brake bias you mentioned. If that was the case (base comparison; 51% braking from rears) then that speaks positively about the rear floater but I was under the impression that the majority of the braking power/load was carried by the fronts.
Regarding the CCB value, your point is well made I just can't get past my desire for that color and contrast you get with them.
I tried only a front track pad and stock on the rear and it was a disaster; brake fade was pretty quick. So now, I use track quality pads front a rear. I would advise the same for any aggressive track day/driver.
Interesting. I've also been using track pads on front and stock on rear. My "home" track is a short track with 2 heavy and 1 significant brake zones and is reputed to be one of the worst for brake/tire wear. Normal pads will get pad-to-rotor gassing fade in 3-4 aggressive laps and even track pads get burned away pretty quickly after 6-8 aggressive laps. I'm guessing that my front rotors are hitting 800+ deg. C. Needless to say, if the brake fluid isn't clean/high-temp, brake-boiling would kill a track day in short order.
Since the car has never felt "squirrly" during the heaviest brake zone (braking from 190+ kph/120 mph down to 80 kph/50 mph for turn-in on a 50+ kph/30 mph corner), I never really thought about the rear brakes maybe not "carrying their load" of the braking. Since I'm in the process of ordering some pads, I'm going to try some track pads for the rear.
Question: Aside from what I assume was better braking, did you realize any improvement in front-pad life by moving to the track pads for the rear brakes?
Thanks Kurt, however I'm a little surprised about the rear brake bias you mentioned. If that was the case (base comparison; 51% braking from rears) then that speaks positively about the rear floater but I was under the impression that the majority of the braking power/load was carried by the fronts.
Regarding the CCB value, your point is well made I just can't get past my desire for that color and contrast you get with them.
AMG RB,
I am venturing into speculation here and perhaps some brake engineer will chime in but my guess would be that the bias differential is based upon pressure applied between front to rear. Given pure physics, we can be sure that means that the fronts still provide a majority of the effective braking force just because of the weight transfer. So even though the "bias" may be to the rear on a pressure percentage, that would be to give the fronts a bit more assistance. Again, I am just speculating here but we can be assured that the front brakes do most of the work regardless. This is evidenced by the size of the front brakes vs. the rears.
Interesting. I've also been using track pads on front and stock on rear. My "home" track is a short track with 2 heavy and 1 significant brake zones and is reputed to be one of the worst for brake/tire wear. Normal pads will get pad-to-rotor gassing fade in 3-4 aggressive laps and even track pads get burned away pretty quickly after 6-8 aggressive laps. I'm guessing that my front rotors are hitting 800+ deg. C. Needless to say, if the brake fluid isn't clean/high-temp, brake-boiling would kill a track day in short order.
Since the car has never felt "squirrly" during the heaviest brake zone (braking from 190+ kph/120 mph down to 80 kph/50 mph for turn-in on a 50+ kph/30 mph corner), I never really thought about the rear brakes maybe not "carrying their load" of the braking. Since I'm in the process of ordering some pads, I'm going to try some track pads for the rear.
Question: Aside from what I assume was better braking, did you realize any improvement in front-pad life by moving to the track pads for the rear brakes?
User 33,
Yes, track pads last longer than stocks on track. Any your assessment of fade and off-gassing on track is spot on.
Very impressive and innovative way to "improvise, adapt and overcome". Great contribution here. I can see this modification turning into a specially designed carbon fiber piece with near OEM fitment.
Very impressive and innovative way to "improvise, adapt and overcome". Great contribution here. I can see this modification turning into a specially designed carbon fiber piece with near OEM fitment.
Well done Kurt.
Thanks. I noticed that the first few edits do not appear as smooth as when I reviewed the draft version. I will look into this and do better next time. Rookie mistakes.
User 33,
Yes, track pads last longer than stocks on track. Any your assessment of fade and off-gassing on track is spot on.
Kurt
Sorry, wasn't quite clear ... (always running track pads on front) when I add track pads to the rear (instead of stock pads), should I expect the front track pads to last longer due to increased braking at the rear? If you're **** like me and keep stats on pad wear after each track day, you'd know this ... but I realize I'm not always what would be considered "normal."
#;-))
Thanks. I noticed that the first few edits do not appear as smooth as when I reviewed the draft version. I will look into this and do better next time. Rookie mistakes.
Kurt
Thanks for that video - interesting, simple idea, I probably would need to come up with some flattened "duct intakes" or I would scrape them off on the next speed bump but it looks someone could make a nice brake duct for us to buy one day.
... here is my video on brake duct installation. I hope it helps.
Appreciated the video. I've done something similar. No video, but here are some pictures ...
I wasn't ready to change rotors (yet), so I cut the backing plate without removing it:
... using a combination of die-grinder/cut-off tool and a hand-held/ground-down hacksaw blade (that part was difficult):
The backing-plate duct-flange was made from aluminum flashing material purchased at a local hardware store (joint is pop-riveted):
This is actually after multiple track days.
I used some U-pieces I made from the aluminum flashing to help hold things in place ... there's about a 3-to-1 compression/expansion of the ducting from lock-to-lock. It's also only 2.5-inch ducting as that's all that'll fit.
First version, without extension scoop.
Making a paper pattern to add a scoop to get more airflow:
Putting a rolled edge onto the flashing used for the extension scoop:
Scoop from close-up front view ... ducting secured on inside using hot-glue gun and the 2 vertical screws are just to keep the opening from collapsing (and they're nylon screws, so they'll bend, for the time when I inevitably bottom-out the scoops coming off a driveway, etc.):
Current version of scoop-extenders, which are working quite well:
If you think the plastic-base part of the scoop looks familiar, it is ...
The scoop-extenders are easily mounted using 2 screws and a zip-tie ... takes less than 10 minutes:
Thanks for that video - interesting, simple idea, I probably would need to come up with some flattened "duct intakes" or I would scrape them off on the next speed bump but it looks someone could make a nice brake duct for us to buy one day.
I think there is something between each of ours that just might be perfect!
Yeah, I'll soon be replacing my rotors so, while they're off, I'm going to see if I can't figure out a better routing for the ducting. I see that others often route "up then drop down" ... which could avoid the high degree of expansion/compression required of the duct from wheel lock-to-lock (which, for mine, is about 5:1 and stresses on the ducting, at the stretch limit). However, there's also a tradeoff with lost airflow due to longer ducting with an additional bend. Hopefully the front scoops are forcing enough air into the ducts that the 2.5" diameter is the primary limiting factor, not bends or length.
If I was _real_ energetic, I'd remove all the front cowling and see whether there isn't some way of routing the ducting higher up ... but from what I've seen in WIS and from looking around with a boroscope, that'd be a wasted effort (sooooo many radiators!).
I have some EBC RP-X front pads coming, as well as some EBC Blue Stuff for the rears. I'm hoping that, along with upgrading to (braided steel brake lines and) the Brembo 2-piece rotors, will allow me to get at least 2 track days from 1 set of front pads. EBC Blue Stuff is the most extreme front pads (with OEM rear pads) I've used, thus far. The Blue Stuff fronts evaporated in 1 track day. Part of the price when running a 4,000 lb/>500 HP car on the track, I guess.
user33, wow, very and equally as impressive as kfehling's efforts and ingenuity. I'll reiterate that before too long the solution to this challenge you guys face will be improved yet again and once again we will all benefit. One question comes to mind regarding brake line upgrading; I've been told Kevlar lines are higher performance than braided steel lines, is this true?
Sorry, wasn't quite clear ... (always running track pads on front) when I add track pads to the rear (instead of stock pads), should I expect the front track pads to last longer due to increased braking at the rear? If you're **** like me and keep stats on pad wear after each track day, you'd know this ... but I realize I'm not always what would be considered "normal."
#;-))
Sorry for the misunderstanding. Just guessing again but I would have to think similar pad compounds front to rear would result in better and more even wear characteristics.
07-20-2020, 02:04 AM
