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Hello all,
I have been scouring the internet for big brake kits for my 325Xi. My issue here is that most pre-built kits are in the $2k range and the lowest from ECS (which doesn't seem to be a big brake kit) at $800 mark. Being the car loving enthusiast that I am I had the grand idea of doing some custom work to make bigger calipers and rotors fit. Now before I get too ahead of myself I should note that I have 19" 335i wheels that I purchased with the car and stoptech SS brake line on all four, so there is room for the upgrade. Also before I start to talk more about money I would like to say that yes, money is a concern, which is why I am using this as an excuse to become more in-tune with my car and really get involved. So onto the juicy stuff. While searching I decided to see if there were more options for the e46 330i, which there where. My only thought is that there might be differences in the braking systems that I am not aware of, which in that case I would find a trashed 330i for parts and grab a cheap master and booster (same thing?). My other concern is that I can't seem to find rear BBKs for the e46 at all! My OCD would prefer to have all four the same size. Another thought that was planted by my friend was to find a BBK for another car and find an adapter bracket like he did for his 2003 M3 (he took brembos off a Porsche) and I have seen some cheap 6 piston brembos off the old Cadillac CTS-V that may work. Now one may ask, "Why do you need a BBK on a 325XI?" and the answer is, because when you want to look like you have more "SPEED AND POWA" than you haveyou do things like this, and also race car. So please bring forth any ideas or suggestions (other than by a M3 or 330i, jesus I see alot of those) and lets change the face of 325Xi braking.:thanks:
 

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Now one may ask, "Why do you need a BBK on a 325XI?" and the answer is, because when you want to look like you have more "SPEED AND POWA" than you haveyou do things like this, and also race car.
Not a great answer to that question.

The proper big brake kit to purchase is no big brake kit. Sell the car and buy a 330, preferably a ZHP, add a supercharger, and then start thinking about a big brake kit.
 

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Before everyone comes in here to take a big dump on your post, I'll just post my experience so far.

RallyRoad sells brackets and lines to adapt the front and rear Porsche 996 calipers. You use M3 rotors all around, or if you don't get the front calipers machined you can run CSL rotors up front. With the standard M3 rotors I BELIEVE you can clear 17" wheels with an aggressive offset. I'm currently running +42 18" wheels that require a 10mm spacer to clear the calipers because of the spoke design. Not sure about what size wheels you need with the CSL rotors, but I think 18's will clear. This setup will cost you around $1000 for all 4 corners, and it's a nice upgrade.

Most people will recommend buying a 330 or just upgrading to the 330 brakes. This is a viable option because the stock brakes work pretty alright for what they are. It sounds like you just want something big and cheap, so the RallyRoad setup is the way to go. There is also another company (I forget the name, something like CTS-V brake something something) who adapt the CTS/ATS calipers to Nissans and such. They are currently developing BMW brackets but I don't know when they'll be ready or what models they'll fit.
 

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As far as I know, RallyRoad are the only ones I know of who have anything for non-M rears. You could swap in an M3 rear end and be open to a bunch more options, but then you're stuck with the diff being an odd ratio. The only solution for that would be to swap in a different gearset to match the fronts. This is probably more time, money, and effort than you're willing to spend.

People have also tried to fit the BMW 4/6 piston calipers up front (can't remember what cars they came from) as well as the BMW 2(?) piston rears. While the calipers bolted up just fine they were stuck with non ideal rotor solutions. Again, you wanted cheap, so RallyRoad brackets with Porsche calipers is the way to go. Don't forget that XI cars have the larger (330) parking brake, so the rear rotors are unique if you have a 325xi.

A good place to start if you want to try and cram something bigger under there would be to see if anybody who owns a 996 has upgraded their calipers to something even bigger without needing to change the caliper bracket. Within the next couple of weeks I was going to try and collect as much information together as possible to create a definitive brake upgrade guide.
 
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