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      08-25-2018, 05:51 PM   #23
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Quote:
Originally Posted by Raindoh View Post
I do need a solution that addresses the front and rear brakes. When I came in after my first session where I was driving (100% to me &#128527 the rear brakes had smoke pouring off them. So the rears definitely went past the limit as well. The rest of the day I had to coast into corners, felt like a waste.

The local track to me is notorious for being a brake killer. You have a main straight that you brake from 110-120MPH down to 25MPH which then leads onto a small straight from 80-90 down to 20-25 with more slow corners leading back onto the main straight so the brakes never get a break(no pun intended) or even a good spot to cool down on the track.

Would a st40 front and rear throw off the bias too much, could I find a st40 kit for the front that would have larger rotor for the front?
Did you have DSC on or off? If you had it “on” then that could’ve contributed to overheating the pads. DSC is working even when the light on the dash is not flashing.

You’d have much better luck with a true race/track pad vs. a hybrid street pad. However, you’d be fine with the ST40 F and R kits - others use this setup for the track (some with the stock R brakes).
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      08-25-2018, 08:19 PM   #24
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Quote:
Originally Posted by Raindoh View Post
I do need a solution that addresses the front and rear brakes. When I came in after my first session where I was driving (100% to me &#128527 the rear brakes had smoke pouring off them. So the rears definitely went past the limit as well. The rest of the day I had to coast into corners, felt like a waste.

The local track to me is notorious for being a brake killer. You have a main straight that you brake from 110-120MPH down to 25MPH which then leads onto a small straight from 80-90 down to 20-25 with more slow corners leading back onto the main straight so the brakes never get a break(no pun intended) or even a good spot to cool down on the track.

Would a st40 front and rear throw off the bias too much, could I find a st40 kit for the front that would have larger rotor for the front?
lets get this out of the way- before anyone says the rear brakes are smoking because of MDM, MDM uses the fronts almost all the time.

sometimes brakes smoke because rubber slag (those chunks you find all over the track and inside the barrels of your wheels) are still soft and fall into your brake rotor vanes. then they cook in there and make a ton of smoke.

you can get away with just a front kit for a long time. it took me a long time to kill my rear brakes, even with race pads in them. when they went, i was starting to get small cracks extending from the innermost drilled holes in the rotors. the dust boots of the calipers also started to take a dump and i was getting uneven pad coverage.

i'm not sure what you mean about finding an st40 kit with a larger rotor... they use the rotors they use. you'll be fine running an st40 front and rear, if thats what you're asking.
when i was running a front ap racing kit with my oem rear brakes (and pads), i ran a hybrid pad (ferodo ds2500) up front with the oem rear brakes. the bias wasn't bad. when i used a track pad up front (ferodo dsuno) and oem rear brakes, i noticed a bias. i'm not 100% sure what causes the bias, but i would theorize it is the bite rather than the brake torque.
under heavy braking, the rear would try to step out a bit. the car was manageable, but i had to manage it with steering input. i tried to have the car straight as i began braking, but already slightly pointed towards the corner. that way, as i began to squeeze the brakes and the rear began to step out, i used that rear stepping out to my advantage by creating more turn-in.
my point is, it doesn't get more biased than an ap racing kit with dsuno pads and oem rear brakes/pads. however, it was still manageable- so don't worry about bias in that sense.
bias you have to worry about is using a caliper that is either too small or too big- a fluid bias rather than a brake torque/bite bias. you can control and manage bite/torque bias, but you can't manage fluid bias.
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      08-26-2018, 10:03 PM   #25
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I did have MDM on (Euro Spec) I can't say if that contributed to the overheating of the brakes. I didn't feel the ABS come on.

In terms of a front kit only, I don't really want to have mismatched brakes from an aesthetics POV. I know it's silly but still want the car to look good.

I was just asking about the bigger rotors for the ST40 as the rotors are slightly smaller than stock. Just feel bigger is better in terms of absorbing and venting heat. Also seems like making the front and rear brakes same size (using ST40 F/R) may cause issues maybe the back locking up potentially if the braking force is equal F/R.

I think I'm leaning towards a ST60/ST40 setup as I want this to be the final solution and want the brakes to be overkill in the sense that I never have to worry about reaching their limit in a 20-30 minute lapping session and can push the car the entire time.
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      08-26-2018, 10:25 PM   #26
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Stoptech sizes its pistons to maintain near stock bias. An ST40 front is not the same as an ST40 rear, for example. Same goes for ST60/ST40 matched kit. BBK do not usually change bias or improve stopping significantly over stock for the first maybe ten stops from 80 mph. It’s when the stock brakes would begin to fade that BBK show their advantage. They also have better feel due to more pistons but that’s more a feel issue. Pads make the biggest difference, assuming you are not boiling fluid. If you are, try titanium shims and fluid like SRF. As for pads, listen to the racers. HPS are really Street pads.
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      08-27-2018, 03:34 PM   #27
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Quote:
Originally Posted by Raindoh View Post
I did have MDM on (Euro Spec) I can't say if that contributed to the overheating of the brakes. I didn't feel the ABS come on.

In terms of a front kit only, I don't really want to have mismatched brakes from an aesthetics POV. I know it's silly but still want the car to look good.

I was just asking about the bigger rotors for the ST40 as the rotors are slightly smaller than stock. Just feel bigger is better in terms of absorbing and venting heat. Also seems like making the front and rear brakes same size (using ST40 F/R) may cause issues maybe the back locking up potentially if the braking force is equal F/R.

I think I'm leaning towards a ST60/ST40 setup as I want this to be the final solution and want the brakes to be overkill in the sense that I never have to worry about reaching their limit in a 20-30 minute lapping session and can push the car the entire time.
I think the main point is for performance you don't necessarily need a rear BBK. You'd be better off buying a BBK for just the front, and with the money you save invest in a decent set of coil overs. You could always add the rears later if you really felt it was necessary.
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      08-31-2018, 09:07 AM   #28
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Quote:
Originally Posted by roastbeef View Post
lets get this out of the way- before anyone says the rear brakes are smoking because of MDM, MDM uses the fronts almost all the time.
Ah, ok...so if a STOCK M3 that’s setup to understeer is, let’s say understeering while trying to turn left, which brake corner will be applied to counteract the understeer? It’s definitely not a front brake.
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      08-31-2018, 09:09 AM   #29
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Quote:
Originally Posted by M3SQRD View Post
Ah, ok...so if a STOCK M3 that’s setup to understeer is, let’s say understeering while trying to turn left, which brake corner will be applied to counteract the understeer? It’s definitely not a front brake.
it would definitely be the left front brake.
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      08-31-2018, 09:18 AM   #30
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Quote:
Originally Posted by roastbeef View Post
it would definitely be the left front brake.
Wrong. The left REAR brake would be applied to get the front to rotate toward the apex.
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      08-31-2018, 09:35 AM   #31
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Quote:
Originally Posted by M3SQRD View Post
Wrong. The left REAR brake would be applied to get the front to rotate toward the apex.
are you aware of all the data dogbone has analyzed that shows MDM uses the front brakes most of the time? mdm is almost always using the front brakes to keep the car in check.
it uses the outside front wheel to counteract oversteer, and the inside front wheel to counteract understeer.
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      08-31-2018, 09:48 AM   #32
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Quote:
Originally Posted by roastbeef View Post
are you aware of all the data dogbone has analyzed that shows MDM uses the front brakes most of the time? mdm is almost always using the front brakes to keep the car in check.
it uses the outside front wheel to counteract oversteer, and the inside front wheel to counteract understeer.
It’s simple vehicle dynamics. If the front has lost grip (i.e., understeering) and is pushing wide, how does slowing a front inside corner that’s lost grip help to rotate the front back toward the corner/apex/ideal trajectory? You could lock the brake and it wouldn’t help rotate the front.

As I said, a STOCK M3 that inherently understeers, not a car that’s setup for the track that for all we know has a tendency to oversteer in every corner.
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      08-31-2018, 10:08 AM   #33
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Quote:
Originally Posted by M3SQRD View Post
It’s simple vehicle dynamics. If the front has lost grip (i.e., understeering) and is pushing wide, how does slowing a front inside corner that’s lost grip help to rotate the front back toward the corner/apex/ideal trajectory? You could lock the brake and it wouldn’t help rotate the front.

As I said, a STOCK M3 that inherently understeers, not a car that’s setup for the track that for all we know has a tendency to oversteer in every corner.
the grip isn't lost. lost grip to me would be like driving on a dry track and suddenly hitting a patch of oil.
understeering is simply operating out of the tire's slip angle. you still have traction, just not enough of it.
keep in mind, mdm may also withhold power while this is happening. so if you're turning the car and it detects understeer, it may do both. it might even use both of the front brakes depending on how much driver input there is. as you know, it doesn't take a whole lot to correct understeer.
think of how much influence the front brakes have in turning, like trail braking... mdm is almost like the car is implementing some trail braking to get some more turn-in.
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      08-31-2018, 12:29 PM   #34
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for your reading pleasure.
https://www.m3post.com/forums/showpo...&postcount=747
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      08-31-2018, 04:35 PM   #35
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Quote:
Originally Posted by roastbeef View Post
the grip isn't lost. lost grip to me would be like driving on a dry track and suddenly hitting a patch of oil.
understeering is simply operating out of the tire's slip angle. you still have traction, just not enough of it.
keep in mind, mdm may also withhold power while this is happening. so if you're turning the car and it detects understeer, it may do both. it might even use both of the front brakes depending on how much driver input there is. as you know, it doesn't take a whole lot to correct understeer.
think of how much influence the front brakes have in turning, like trail braking... mdm is almost like the car is implementing some trail braking to get some more turn-in.
Correct. Grip is not completely lost but you’re turning the wheel more and more yet the front is not heading in the intended direction. It’s definitely not like trail braking. The point is to provide a correction that puts the front back on its intended path, not take the rear of its current correct path.
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      08-31-2018, 04:57 PM   #36
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Quote:
Originally Posted by M3SQRD View Post
Correct. Grip is not completely lost but you’re turning the wheel more and more yet the front is not heading in the intended direction. It’s definitely not like trail braking. The point is to provide a correction that puts the front back on its intended path, not take the rear of its current correct path.
where are you getting this from?
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      09-04-2018, 05:38 PM   #37
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Hey OP,

I do the occasional track day but mostly street driving. I wanted something that acted just like the stock brakes for the street and would endure the brutal punishment from a 30-40 minute track session in 100 deg F private track day (I track at Thermal, the hottest place in the US).

I researched a bunch in the Track subforum and ultimately went with the StopTech 380F/365R kit with street pads and SRF fluid. Brakes were in stock at Turner for $5,600 shipped to my door in 3 days.

They just started squeaking a little on the street after 2,000 miles since tracking it so I did a "bed-in" and no more squeak.

Good luck.
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      09-24-2018, 10:40 PM   #38
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Quote:
Originally Posted by SYT_Shadow View Post
for occasional track use the PFC DD v3 rotors (a rotor-only upgrade kit) paired with typical track pads is a massive upgrade vs stock

a front only BBK is also very nice but few people are fast enough to actually 'need' that vs the Direct Drive PFC option
Quote:
Originally Posted by derbo View Post
Would this setup be suitable for a full weekend at COTA for a novice? Any concern about the oem rotors holding up for 10 sessions? Have stoptech sport pads on oem rotors in good shape. If run this kit would you use pfc11 on the rear? Also have stoptech sports out back still fairly new. BBK would eventually happen - would that money be better spent making the jump now?
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      09-25-2018, 08:54 AM   #39
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Quote:
Originally Posted by roastbeef View Post
That's a hugely interesting test he did. Thanks for linking it here.
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      09-25-2018, 09:47 AM   #40
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Yes, a very interesting read. Amazing what programs are available to analyze issues like this.
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      09-25-2018, 09:50 AM   #41
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Quote:
Originally Posted by jktx View Post
Would this setup be suitable for a full weekend at COTA for a novice? Any concern about the oem rotors holding up for 10 sessions? Have stoptech sport pads on oem rotors in good shape. If run this kit would you use pfc11 on the rear? Also have stoptech sports out back still fairly new. BBK would eventually happen - would that money be better spent making the jump now?
The kit Derbo suggested is very solid, I assure you plenty of advanced drivers would be just fine with it.
I've seen two cars do 2:11 at WGI with it on street tires, that is a pretty solid speed.

Any time you use a certain pad in the front, use the same one in the rear. The OEM balance is built specifically for this car so using the same pads front and rear gets you great results
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      09-25-2018, 12:10 PM   #42
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Quote:
Originally Posted by SYT_Shadow View Post
The kit Derbo suggested is very solid, I assure you plenty of advanced drivers would be just fine with it.
I've seen two cars do 2:11 at WGI with it on street tires, that is a pretty solid speed.

Any time you use a certain pad in the front, use the same one in the rear. The OEM balance is built specifically for this car so using the same pads front and rear gets you great results
Awesome - much appreciated!
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      09-26-2018, 05:58 AM   #43
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Quote:
Originally Posted by FuzzyPeaches View Post
That's a hugely interesting test he did. Thanks for linking it here.
yea, i thought it was pretty cool. it is makes sense when you think about it- its more simple than the marketing (or maybe our imagination) leads us to believe. the power is restricted and the brakes help control the car.

although it has the capabilities of activating the rear brakes, i'm not 100% sure when they would be used though... yaw control, maybe? sudden loss of traction where the front brakes alone aren't enough and the car is already sideways? i don't know.
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      09-26-2018, 06:23 AM   #44
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Quote:
Originally Posted by roastbeef View Post
yea, i thought it was pretty cool. it is makes sense when you think about it- its more simple than the marketing (or maybe our imagination) leads us to believe. the power is restricted and the brakes help control the car.

although it has the capabilities of activating the rear brakes, i'm not 100% sure when they would be used though... yaw control, maybe? sudden loss of traction where the front brakes alone aren't enough and the car is already sideways? i don't know.
I would be interesting to see these graphs side by side with track maps and additional data (steering input, throttle, etc.) and then maybe with values labeled at certain points to see where MDM might brake each corner. The readings are so small that we may not be able to visually see all of it on those graphs.

I hope this makes sense.
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