Is there a Brake Master Cylinder Upgrade for Big Brake Kit?

[youngblood750]

hello!

I have Manual E46 M3, it's main purpose is track experience. it's not dedicated track car yet. but I use it for track driving most of time.

Previous owner had installed 4pistons brake caliper in front. it's So called Brembo F50 caliper. And I also installed 4 pistons brake caliper on rear wheel. It's relatively smaller caliper than front. it's so called brembo f40 caliper.

As I heard from somewhere, more pistons in calipers requires more hydraulic force at the brake master cyliner. So our e46 m3 had equiped with single piston caliper when it came to market. then Now I can feel that the capacity of stock brake master cylinder is not enough for current set-up for my car.

it's really problematic when I have to do heel-and-toe. brake pedal feels spongy in the early stage of braking. even right after air bleeding. after air bleeding, it feel slightly better feel, but it won't last as I needed.

I want more firmer feeling of brake pedal. now it's really hard to do heel-and-toe when I fully apply the brake pedal. It goes too deep and gas pedal is way above the brake pedal when I fully apply the brake pedal.

Is there any solution for this? Anyone with Big Brake kit with same experience?

and is there After Market brake master cylinder for stronger hydraulic force? racing master cylinder? I don't want to delete the brake booster like real racing car. that's maybe too extreme. hope Stronger Master Cylinder will help.

When I had a Sports Bike, I changed Master Cylinder to brembo RCS19. then feeling of brake lever was amazing. It was firm and easy to feel, and easy to control of friction on front tire. hope that same thing can happen to my car with master cylinder upgrade.

what I really want is brake pedal would be above gas pedal's level when I fully apply the brake. So I can easily do heel and toe.

[eacmen]

To go down this path you will need alot of measurements about your chassis to really dial in the correct bias. See attached pdf for example.

Also if you change the master cylinder you will likely need to delete the booster and factory ABS.

Lee from Massive Brakes is the best resource i’ve seen for aftermarket brake masters on this chassis.http://cloud.tapatalk.com/s/637b01b3...Data_Sheet.pdf


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[youngblood750]

To go down this path you will need alot of measurements about your chassis to really dial in the correct bias. See attached pdf for example.

Also if you change the master cylinder you will likely need to delete the booster and factory ABS.

well, deleting the booster and Factory ABS is way further than I thought.

I am hoping replacing some parts solve the issue. Is there any possibility that brake booster deteroiating by the time? then I can change new one.

[ZiMMie]

Technically an e65 MC should help as it has a bigger bore. 27MM vs 25.4.
Its a great upgrade in the e39 M5(also 25.4 bore size)


It will take a bit of work to retrofit it tho since you have to relocate the pressure sensors.
But there are OEM solution for that (using eg.34336760914 to relocate the pressure sensor)

[youngblood750]

Technically an e65 MC should help as it has a bigger bore. 27MM vs 25.4.
Its a great upgrade in the e39 M5(also 25.4 bore size)


It will take a bit of work to retrofit it tho since you have to relocate the pressure sensors.
But there are OEM solution for that (using eg.34336760914 to relocate the pressure sensor)

that's interesting solution.

[eacmen]

I would try a brand new factory MC before trying to retrofit something else. It helped my pedal travel and feel immensely.

The pedal travel is also sensitive to pad thickness, as you wear the pads down the pedal travel will increase. This can be mitigated by tapping the brake pedal with your left foot moments before heel toe.

You can also take the brake pedal out, braze it and bend it slightly to ensure it does not sink below throttle.


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[Fresh1179]

I think you would go down a rabbit hole of chasing issues if you replaced the MC with some type of aftermarket solution. I’m not sure I would want to delete ABS, especially if the car is a hybrid street/track car. There is a relatively simple solution that won’t fix the long pedal travel, but may help you dial in the relative height of the brake pedal to the accelerator pedal. That would be after market pedals. You will need to drill holes into your brake pedal (and the others pedals if your choose a kit), but you can “shim” the brake pedal with washers at the 4 drill attachment points for the aftermarket brake pedal. Just make sure that you have a low profile nut and check the placement of your bolts on the back so you are not losing any brake travel with interference from the bolts. Add small washer, check feel, rinse and repeat. When you arrive at a better feel for you, make sure the pedal is totally stable and put some red loctite on the nut. Check every once in a while to ensure stability. It’s not an elegant solution, but it works. Check the post above for a solution as well. In conjunction, you may be able to achieve your desired feel. It is absolutely correct that your pad thickness and wear has an effect on the travel, so take that into account. I’d burn off half my fronts, then do the procedure in order to meet in the middle. It’s a much simpler procedure than modifying the entire brake system.

Edit: I would also check out the various pedal providers, and choose and accelerator pedal accordingly. Ultimate Pedals (and I’m sure other manufacturers) allows you to modify the accelerator pedal to meet your preferences/technique. I have a wide foot, and chose a small extension on the top of the accelerator which works with my ankle pivot technique and does not interfere with two foot driving.


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[maw1124]

Technically an e65 MC should help as it has a bigger bore. 27MM vs 25.4.
Its a great upgrade in the e39 M5(also 25.4 bore size)... It will take a bit of work to retrofit it tho since you have to relocate the pressure sensors.
But there are OEM solution for that (using eg.34336760914 to relocate the pressure sensor)

This is the approach I've seen used most often when going to bigger brakes within a manufacturer, which is to get the MC from the larger brake set. I'm surprised not to see, for example, M5 or E9XM brakes on these cars, in which case you'd use the MC from those systems. I more often see it in older MB circles (e.g., 500E brakes upgraded to SL600 brakes).

GL

BTW, have you installed SS brake lines yet?

maw

[Wernd]

Have you tried a different fluid? Pedal feel can be greatly affected by your choice of brake fluid. I generally run ate type 200 or project u and love both. I once tried motul (can't recall which type) and my pedal feel was straight trash so I've never tried it or any other type fluid since.

[mrgizmo04]

Pad selection and material also matters. Some pads have more compressibility vs others (like PFC vs Hawk), resulting in mushier feeling and longer pedal travel.

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[bigjae46]

I have Stoptechs front and rear and the brake pedal is a little less firm early on which I'm fine with. Better than the on/off feel of the OE brakes but most people prefer the immediately stiff pedal.

I'd check any non-hard lines near the ABS module and calipers. Then activate the ABS, thoroughly bleed the brakes, activate the ABS again, bleed again. Should get zero air bubbles and clear fluid on the second bleed. Finally I'd inspect the calipers - dust boots and pressure seals.

If the brakes are still spongy then get the specs of the calipers - piston sizing by position. Then do all of the math to figure out if the calipers will work with the stock system.

Chase Bays makes a booster delete for manual brakes. If you're going to delete ABS then you need to change the master cylinder to get less front bias. Again, more calculations and more math.

For THIS reason is why I just went with an off-the-shelf system.

[youngblood750]

Have you tried a different fluid? Pedal feel can be greatly affected by your choice of brake fluid. I generally run ate type 200 or project u and love both. I once tried motul (can't recall which type) and my pedal feel was straight trash so I've never tried it or any other type fluid since.

Pad selection and material also matters. Some pads have more compressibility vs others (like PFC vs Hawk), resulting in mushier feeling and longer pedal travel.

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I am currently using ferodo product. pads are DS uno on frotn and DS2500 on the rear. and brake fluid is Ferodo DOT4 spec.

well, It was a bit better when right after bleeding the brake system, but last weekend I went to track day without having done bleeding. then it was horrible. plus Tyres has been almost gone too. but brake pedal feel was horrible and very inconsistent without bleeding. it was combination of bad tyres and brake system without bleeding. I should have bled brake system. current brake fluid is only 4 months old and had 2 track days. I thought it was relatively new but I was wrong maybe.

[tlow98]

This is the approach I've seen used most often when going to bigger brakes within a manufacturer, which is to get the MC from the larger brake set. I'm surprised not to see, for example, M5 or E9XM brakes on these cars, in which case you'd use the MC from those systems. I more often see it in older MB circles (e.g., 500E brakes upgraded to SL600 brakes).

GL

BTW, have you installed SS brake lines yet?

maw

I too am surprised to see no e90 upgrades for the e46 mentioned. Maybe being single piston calipers isn’t enticing enough for people? Would like to know if it’s 1) possible, and 2) “worth” it. Of course, the second is far too subjective to really consider.

[ZiMMie]

This is the approach I've seen used most often when going to bigger brakes within a manufacturer, which is to get the MC from the larger brake set. I'm surprised not to see, for example, M5 or E9XM brakes on these cars, in which case you'd use the MC from those systems. I more often see it in older MB circles (e.g., 500E brakes upgraded to SL600 brakes).

GL

BTW, have you installed SS brake lines yet?

maw

Its because all M cars shares the exact same bore size. E36 m3/e46 m3/e92 m3/e60 m5 etc all are 25.4MM.
also some of these chassis have different type design MC which will not fit the e46 booster.


If i was in his situation and tired everything else, ill explore the e65 MC retrofit option.

[Wernd]

Try ate type 200 and report back. I bet it solves your problem