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      02-08-2018, 06:39 PM   #1
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Brake Q's for autocross/track

Hey guys. I used to autocross aaaggggeeeessss ago with my E46 and I'd like to get back into it this year if I'm off on those days (so maybe 4-5 days this season). Also I'd want to hit up the track a few times this year as a beginner.

I was thinking about two setups for the brakes since they do need to replaced.


1. OEM 328i calipers with slotted stoptech rotors (front cryo-treated) and Pagid or Hawk HPS 5.0 pads up front and stoptech pads in the rear.


2. 335 four piston calipers up front and the 328 setup in the back mentioned above. Front will most likely be the stoptech slotted rotors and stoptech/hawk pads.

Would there be any issue with the brake bias with this setup? Is it better to just stick with the 328 setup in option 1?

This would be paired with 18" Apex wheels so it's around 8-9lbs loss on each axle over the stock wheels. Thanks guys.
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      02-12-2018, 12:36 PM   #2
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Focus on pads..pads...pads.

Get something like Hawk HP+ for AutoX for the cold bite.
Depending on track and level of experience, HP+ can be good on there too, or something more like Hawk DTC-something or EBC blues.

Your stock 328 brakes are big enough to stop at any track, focus on pads and tires.
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      02-12-2018, 04:13 PM   #3
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All the instructors have told me solid vented rotors as the way to go.
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      02-13-2018, 12:31 AM   #4
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Quote:
Originally Posted by Tchao View Post
Focus on pads..pads...pads.

Get something like Hawk HP+ for AutoX for the cold bite.
Depending on track and level of experience, HP+ can be good on there too, or something more like Hawk DTC-something or EBC blues.

Your stock 328 brakes are big enough to stop at any track, focus on pads and tires.
Ok good to hear. I'll stick with the stoptech slotted rotors and look into those Hawk HPS 5.0 pads. Car will be on Apex SM-10's with PSS

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Originally Posted by zinner View Post
All the instructors have told me solid vented rotors as the way to go.
Thanks zinner
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      02-13-2018, 08:44 PM   #5
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I would suggest Ceramics on the street and much more aggressive cold bite track pads when you autoX/HPDE. Swapping pads is fast and simple on the F30s.
Having a track oriented pads means you dont have to compromise.
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      02-13-2018, 09:40 PM   #6
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Don't forget about your brake fluid too. My first track day in the F30 was on the stock fluid and my pedal was getting squishy late in the day.

I've used Motul RBF600 on my last few cars with great results, only downside is you really should swap it out every year. Plus amazon has it for $16 a bottle on prime. The Porsche crowd also swears by Castrol SRF fluid. But it's a bit pricey in comparison.
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      02-27-2018, 09:05 PM   #7
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Quote:
Originally Posted by Tchao View Post
Focus on pads..pads...pads.

Get something like Hawk HP+ for AutoX for the cold bite.
Depending on track and level of experience, HP+ can be good on there too, or something more like Hawk DTC-something or EBC blues.

Your stock 328 brakes are big enough to stop at any track, focus on pads and tires.
I agree. The force of friction comes down to the coefficient of friction (u) and the normal force (N).

Ff=N*u

The coefficient of friction is based on the materials involved. Steel will always have the same coefficient so you can buy any rotor you want. The pad material will vary greatly and choosing the best one is tricky. I usually go for whatever offers me the most data on their site, the last ones I bought were Stoptech. Keep in mind that some pads do not work well without heat.

In the equation above, N is how hard your brake caliper piston pushes on the pad and rotor. The friction force is what is stopping the car.

Don't forget tires too though, they also play a huge role in friction and your stopping ability...
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      03-05-2018, 12:26 PM   #8
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Quote:
Originally Posted by Niart906 View Post
Don't forget about your brake fluid too. My first track day in the F30 was on the stock fluid and my pedal was getting squishy late in the day.

I've used Motul RBF600 on my last few cars with great results, only downside is you really should swap it out every year. Plus amazon has it for $16 a bottle on prime. The Porsche crowd also swears by Castrol SRF fluid. But it's a bit pricey in comparison.
I don't really drive to the limit, but I have been using the stock fluid effectively in the D run groups. I put in the ATE SL.6 this next track day. I am reluctant to use anything that is not labelled as low viscosity with the ABS pump in the mix.
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      03-23-2018, 04:01 PM   #9
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Late reply, but I've never had an issue with RBF600 in any of my BMWs. My previous E46 M3, E60 M5, and now my F30 335 all work well with the Motul fluid. ABS still kicks on during winter as it should, that said I do change this fluid yearly.
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      03-27-2018, 10:22 AM   #10
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Thanks, appreciate the input
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      04-22-2018, 10:56 AM   #11
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Is it okay to use low-viscosity fluid like Motul DOT 5.1 or ATE SL.6 for the occasional HDPE on a daily driver? Those of you using the normal-viscosity racing fluids like RBF600, do you change back to low-viscosity fluid in the winter?

Also, are SS lines worth the upgrade? I have a '15 F32 w/ M Sport brakes.
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      04-23-2018, 04:30 PM   #12
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Figure I would add in my experience, bought my car with the standard 328i brakes with 312mm rotors, too.

First thing I did when I got the car was swap all the fluids. I had Motul RBF600 and stainless lines installed first, I noticed a good improvement as they heated. I was a away for a month in Janurary on business and when I came back the rotors formed some bad desposits on them and caused shimmy as they heated. Not a huge loss, after looking I was close to tripping the sensor, anyway. Next I installed some EBC RedStuff and ECS Slotted rotors and man, talk about night and day difference. Way less resistance to fading, way smoother pedal modulation and way better pedal and chassis feel with application from >100MPH.

Bottom line is, I'm not worried about coming off the straight into Big Bend at Lime Rock this year, the brakes are more than up to the task for a session. A few hundred bucks on pads, rotors, and fluid makes a massive improvement.

Quote:
Originally Posted by dr.roro View Post
Is it okay to use low-viscosity fluid like Motul DOT 5.1 or ATE SL.6 for the occasional HDPE on a daily driver? Those of you using the normal-viscosity racing fluids like RBF600, do you change back to low-viscosity fluid in the winter?

Also, are SS lines worth the upgrade? I have a '15 F32 w/ M Sport brakes.
I don't see anything wrong with running 5.1 (Motul RBF660), but only you can know if you're going to be pushing hard enough where the 4 (RBF600) isn't enough for you. I run the same fluid year round and our temps range from 0-100F.

There is a lot of contraversy as to whether the SS get you any performance. I am of the mind where they are cheap enough that it is worth the gamble, especially if you're already having a flush done, anyway.
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      04-23-2018, 05:38 PM   #13
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Originally Posted by MacklinUSOB View Post
I don't see anything wrong with running 5.1 (Motul RBF660), but only you can know if you're going to be pushing hard enough where the 4 (RBF600) isn't enough for you. I run the same fluid year round and our temps range from 0-100F.
I was referring to Motul DOT 5.1 (link) not RBF660 (link).

DOT 5.1 is low-viscosity like OEM BMW brake fluid, i.e. "designed for ABS". I was wondering if that would be enough of an upgrade to be worthwhile. I would certainly feel more at ease running it year-round over dedicated racing fluild like RBF600. Again, I would only be doing 1 or 2 HDPE events a year, and some occasional autocross. Motul DOT 5.1 seems to have a bit higher DBP (522F vs 446F) and WBP (356F vs 311F) over OEM.

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      04-23-2018, 05:59 PM   #14
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Quote:
Originally Posted by MacklinUSOB View Post
Figure I would add in my experience, bought my car with the standard 328i brakes with 312mm rotors, too.

First thing I did when I got the car was swap all the fluids. I had Motul RBF600 and stainless lines installed first, I noticed a good improvement as they heated. I was a away for a month in Janurary on business and when I came back the rotors formed some bad desposits on them and caused shimmy as they heated. Not a huge loss, after looking I was close to tripping the sensor, anyway. Next I installed some EBC RedStuff and ECS Slotted rotors and man, talk about night and day difference. Way less resistance to fading, way smoother pedal modulation and way better pedal and chassis feel with application from >100MPH.

Bottom line is, I'm not worried about coming off the straight into Big Bend at Lime Rock this year, the brakes are more than up to the task for a session. A few hundred bucks on pads, rotors, and fluid makes a massive improvement.



I don't see anything wrong with running 5.1 (Motul RBF660), but only you can know if you're going to be pushing hard enough where the 4 (RBF600) isn't enough for you. I run the same fluid year round and our temps range from 0-100F.

There is a lot of contraversy as to whether the SS get you any performance. I am of the mind where they are cheap enough that it is worth the gamble, especially if you're already having a flush done, anyway.
I think there's a forum post somewhere that says OE BMW brake lines are already steel braided internally so you may not get a huge improvement with aftermarket SS lines.

Quote:
Originally Posted by dr.roro View Post
I was referring to Motul DOT 5.1 (link) not RBF660 (link).

DOT 5.1 is low-viscosity like OEM BMW brake fluid, i.e. "designed for ABS". I was wondering if that would be enough of an upgrade to be worthwhile. I would certainly feel more at ease running it year-round over dedicated racing fluild like RBF600. Again, I would only be doing 1 or 2 HDPE events a year, and some occasional autocross. Motul DOT 5.1 seems to have a bit higher DBP (522F vs 446F) and WBP (356F vs 311F) over OEM.
I've run my 2014 335i RWD with M Sport Brakes at NJ Motorsports Part and Summit Point in the intermediate groups. My modifications were M Performance Suspension Kit, M Performance Limited Slip Rear Differential, MPSS tires and M3/M4 brake pads. After coming off the track, I used an infrared temperature gun on the rotors and caliper. The highest I ever saw my rotors was lower 300F. It's possible that in more advanced run groups you're going to get higher temperatures, but my opinion is that brake pads will fade/fail before fresh brake fluid. I believe you can monitor caliper temperatures to figure out whether you need better brake fluid.

I personally run Castrol SRF brake fluid because I only flush it once per year - right before track season.
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      04-24-2018, 09:05 AM   #15
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I did SS brake lines on my E92 335i. They improve the pedal feel by making it very consistent all the way through the travel - no stretching - but won't make the car stop any faster. I don't think I'd pay for them again.

When people swap rotors and see a performance difference it was often times because their old rotors were worn down and the new ones have more mass. The new ones can therefore hold more heat and perform better. That's why drilled/slotted aren't generally as good for high performance usage, they don't have as much mass as a blank. Just get blanks.

One last thing. I'd keep the car in line with your driving abilities. It sounds counter-intuitive, but I would avoid getting a really effective brake setup. OEM rotors/pads and upgraded brake fluid are pretty much the ticket in my book. That setup should let you drive quite aggressively, but you'll be able to cook it. In other words, you have to concentrate on your braking to maintain its performance throughout your session. If you add brake ducts, high performance pads, etc, it can mask inefficient braking because the setup can take it. It will become obvious to you when you need to upgrade your brakes beyond that OEM+ setup. Your instructor should be the one to tell you that.

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      04-24-2018, 09:39 AM   #16
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Quote:
Originally Posted by dr.roro View Post
Is it okay to use low-viscosity fluid like Motul DOT 5.1 or ATE SL.6 for the occasional HDPE on a daily driver? Those of you using the normal-viscosity racing fluids like RBF600, do you change back to low-viscosity fluid in the winter?

Also, are SS lines worth the upgrade? I have a '15 F32 w/ M Sport brakes.
I attended my first HPDE last year with Motul 5.1. While it was good on the street, I boiled it on the track first day. Second event, I switched to RBF 600 at the recommendation of VAC. I was told it's fine to leave in all year. I never boiled it and drove on the same fluid since then. I drove my car in -15 F in Maine in the middle of the winter with zero issue. Stopped beautifully.
My experience is that I recommend skipping the Motul 5.1 or similar if you even visit the track once a year. Cost is dollars difference to go with RBF 600 and the performance is superior all around.
Regarding ss lines, track instructors recommend it. It's more of a safety thing than performance. My experience is the peddle is slightly more firm with them. But random debris from the track has been known to be kicked up and sever people's rubber brake lines. I think it's a cheap enough investment into safety. Kind of like upgrading the cp if it hasn't burst yet because you know it will at the wrong time.
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      04-24-2018, 09:51 AM   #17
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Quote:
Originally Posted by CJ421 View Post
One last thing. I'd keep the car in line with your driving abilities. It sounds counter-intuitive, but I would avoid getting a really effective brake setup. OEM rotors/pads and upgraded brake fluid are pretty much the ticket in my book. That setup should let you drive quite aggressively, but you'll be able to cook it. In other words, you have to concentrate on your braking to maintain its performance throughout your session. If you add brake ducts, high performance pads, etc, it can mask inefficient braking because the setup can take it. It will become obvious to you when you need to upgrade your brakes beyond that OEM+ setup. Your instructor should be the one to tell you that.

Charles
This one is really important. The OE setup isn't bad performance, it'll definitely be quicker to show you poor useage, though. Growing into the setup is key, that goes for any components.
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      04-24-2018, 07:33 PM   #18
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CJ421 MacklinUSOB What fluid do you guys use and how often do you bleed/flush? Do you run it year-round and notice any adverse differences on the street during normal driving?
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      04-24-2018, 07:36 PM   #19
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Quote:
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CJ421 MacklinUSOB What fluid do you guys use and how often do you bleed/flush? Do you run it year-round and notice any adverse differences on the street during normal driving?
I'm using RBF600 and flush once a year as recommended. Our temps here go from very hot to very cold in CT and I don't notice any adverse affects on performance on either extreme.
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      04-24-2018, 10:30 PM   #20
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Quote:
Originally Posted by dr.roro View Post
CJ421 MacklinUSOB What fluid do you guys use and how often do you bleed/flush? Do you run it year-round and notice any adverse differences on the street during normal driving?
Here's a post I made in a similar thread:
Quote:
Originally Posted by CJ421 View Post
Ask a BMW-specific shop that works on race cars what they recommend. Turner or VAC are two shops. But basic high-temperature fluid should be fine.

It's not like your car won't work on-track with the standard BMW brake fluid. It just won't have the temperature threshold; the limitations of the brakes wouldn't be as high. E.g. you might have to take a cool-down lap now and then to let the brakes cool off.

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      04-24-2018, 11:50 PM   #21
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I'm new to autocross myself I'm running sport package pads on a non sport package car (single piston caliper). I'm happy so far but the brake dust is crazy! It does have that Initial bite but not to the point where abs kicks in right away. Once I get better with my brake Technique or if pads wear out I'll upgrade to hawk pads and ss lines with new fluid.
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      04-25-2018, 10:41 AM   #22
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Regarding high temp fluid change frequency, this is my second year running RBF600 in my 335. Ran out of time and didn’t swap it for fresh fluid prior to my first track event, while I didn’t boil the fluid I did get a noticeably softer pedal. Maybe in warm year round climates you can get away with over a year on the same fluid, but not in the northeast. I’ll be sticking to my plan of yearly flushes.

As for SS lines, I was under the assumption that our stock lines had a braided metal liner. Can anyone confirm? I’ve only heard of modest pedal feel improvements with SS lines on an F30. I’ve always considered SS lines to be good insurance if your car has older brake lines.
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