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Project E46 M3: Part 5 - Bigger Brakes all Around

Too much of anything can sometimes be bad…except with brakes!

by Pablo Mazlumian

In Part 4 we witnessed the beginning of the car’s aesthetic transformation and also saw a dramatic increase in all performance categories thanks to the addition of a new wheel and tire package from D-Force and BF Goodrich.  One of the aforementioned categories that really benefitted was braking.  Going from a 60-0mph in 10 less feet, or experiencing a 0.14G improvement in deceleration, after all, is hardly going to go unnoticed.
 
 
Last time, we saw dramatic, numerically proven improvements from our D-Force and BF Goodrich combo.

The stock E46 M3 brakes are very good in their own right.  All M3s, while top-notch contenders in handling and acceleration for their class, usually come with more braking power than needed.  It's a good thing, too, because the more braking power the merrier.

Our E46 M3 seemed to work well with the stock-sized, 225mm front tires.  ABS interruptions were only apparent during hard pedal applications.  For a track weekend, simply swapping in more aggressive pads, while performing a DOT4 brake fluid flush, seems to do the trick for many enthusiasts wanting multi-lap good times without brake fade.  With the move to the 245mm, softer BFG Rival rubber up front, however, it started to take a lot more pedal effort to trigger the ABS system.

The increase in tire size, along with the softer compound, can only mean one thing for the stock brakes during high performance driving—and that's more heat.  With the factory one-piece rotors and single-piston setup, this would mean possibly moving up to a more aggressive pad setup—perhaps even one that’s not very street friendly—to make up the difference.  But this will mean more dust, maybe even more noise, and quite possibly chewing up rotors in a shorter period of time.  Plus, if the pad is really meant for racing, it won't bite well on the first stab, especially on a cold day (and I've already hit the neighbor's dog once before).

An alternative to this is to change out the entire brake system for something larger, and that’s what we did with the help of our friends at UUC Motorwerks and Wilwood brake systems.

 

This month we’ll be featuring a Wilwood four-wheel big brake kit that has been adapted by UUC Motowerks to fit the E46 M3.

 

While a brake job like this can be done using a jack and a couple of jack stands, it was nice to have access to a lift nearby.  Thankfully, all you need are some basic tools like Allen keys, socket and box-head wrenches ranging from 1/4in SAE to 17mm, and perhaps a screwdriver to push the old brake cylinders back in their bores during removal.

 

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Comments
Protodad
Protodadlink
Wednesday, November 20, 2013 11:11 AM
Awesome kit from UUC. It also seems to be far far cheaper than the BBK's from other companies.
Rockwood
Rockwoodlink
Wednesday, November 20, 2013 11:27 AM
The difference in multi-piston and single-piston setups in brake feel is amazing, and I'm truly becoming a "believer" in these setups...

Does the master cylinder flex much on the firewall when you mash the pedal? Good brake feel gains to be had there as well.

BTW, what does a 600whp and 1000whp Supra have in common?

12 second timeslips... ;-p
Pablo Mazlumian
Pablo Mazlumianlink
Wednesday, November 20, 2013 11:48 AM
@ Protodad: Indeed they are huge bang for this kind of buck!
@ Rockwood: Initially I was only feeling a little smushy resistance or vibration through the pedal after a hard brake, but I did a re-bleed and it seemed to take care of it.
And yes, I'm aware of that joke, lol. But it should actually read more like, "what does a 600whp and 1000whp Supra 'with street tires' have in common" ;).
GrantC
GrantClink
Wednesday, November 20, 2013 11:56 AM
Wilwood's FAQ says the larger piston should be at the _trailing_ edge of the pad, not the leading edge. Did you make a typo? or did the double-bleeders lead you to install them backwards?

"Q: What's the purpose of having a big piston and a small piston in a Caliper (staggered pistons)?
A:

Multi-piston calipers, normally with six or more pistons, have bore sizes that increase in size from front to rear.

This allows a pressure differential between the leading and trailing edge of the caliper, thus providing an even wear pattern along the entire length of the brake pad, hence it controls brake taper. This is necessary because incandescent material and debris from the leading edge of the pad is trapped between the pad and rotor; it tends to float the trailing edge of the pad off the rotor. A larger piston at the trailing edge of the pad provides more pressure to compensate for this debris buildup and keep the pad flat against the rotor."

http://www.wilwood.com/TechTip/TechFaqs.aspx#CP
Nick B
Nick Blink
Wednesday, November 20, 2013 12:00 PM
@Rockwood and @Pablo - I thought the answer is "they only see the dyno..." :) lol
Pablo Mazlumian
Pablo Mazlumianlink
Wednesday, November 20, 2013 12:59 PM
Grant, you are correct. It was a typo. I mistakingly called it the leading piston since it was the one furthest forward, but it technically is the trailing piston. Thanks for pointing that out. I will change it shortly. The rotors and calipers have directional arrows on them for correct installation so it's hard to mess that up.
Nick, there is some truth there too, especially if they are built, then dyno'd, and then they break and never leave the shop, lol. With Project Supra I promise to at least hit 11.9.. ;-P
Vince
Vincelink
Wednesday, November 20, 2013 7:17 PM
The replacement rotors and calipers pictured do not appear to be floating. Doesn't either the caliper or rotor need some float?

The front rotors are bolted to the rotor hat with fully threaded fasteners. Wouldn't it be a good idea to have a shank on the bolts to transmit the cyclical load between the rotor and hat vs the threads on the bolts?
bigBcraig
bigBcraiglink
Wednesday, November 20, 2013 10:40 PM
Vince - While it's not ideal to put threads in shear, there are a lot of them so it shouldn't be much of an issue. The cost of custom fasteners to have a shoulder that short then go threaded doesn't make much sense on an otherwise budget-friendly brake setup like this.

Pablo - You stated the pistons are stanless for better heat transfer. Perhaps it's worth clarifying here that "better" is less in this case, not more. Stanless has about 1/4 the conductivity of mild steer iirc which is indeed nice to keep the fluid cool. I'm really liking the way this car is shaping up by the way, I've enjoyed seeing these posts!
Pablo Mazlumian
Pablo Mazlumianlink
Thursday, November 21, 2013 6:02 PM
Vince, it is my understanding that full-floating rotors (like you see in the Euro spec M3's) have the advantage of "less" heat transfer to the hat, but the downside is potentially some added vibration over non-floating types. Most rotors are non-floating.

As far as floating calipers go, usually it's the single or dual piston setups that need this, which are cheaper designs. Stock BMWs brakes are like this, as are many other OE brands. With an opposing, multi-piston setup like the 6- and 4-piston Wilwoods feature here, they are fixed and not only offer more braking power but usually more even pad wear as well, thanks to the multi-piston setup.

Craig, those quotation marks were for you, ;). You are correct--better to clarify, which I'll do here in the body of the text in a sec.

Thanks for the comments, y'all!
Hexer
Hexerlink
Saturday, November 23, 2013 1:25 PM
We run some m3's here in europe, its hard to fined better brake disks than the CSL ones, or stock M3, floating, aluminum centers and steel stick which hold the rotor, so heat transfer is lot less to the bearings.
But not just the heat transfer is the case here, the thermal expansion makes thees floating disks way better. Try ones after a hard braking leaving the feet on the disks, 90% it will get oval and start to hit, not the case with the floating ones, chanses ar a lot smaller.
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