Question about DOWNGRADING M3 brakes (yes, you read that right)

[phenryiv1]

So this may seem like a completely odd request for info but a friend and I are looking at what it will take to downgrade 1998 M3 brakes to something smaller.

Here we go...

Reason: My friend (95maxrider) just bought a 1998 M3/4/5...to rallyX. Rally wheels (in particular rally tires) are typically 15" so we need to downgrade his brakes to allow them to clear 15" wheels.

For the sake of argument, we'll use e46 Style 46 wheels ( http://www.bmwstylewheels.com/bmw/46 ) as his goal wheel, as he already has them (from his dearly-departed e28) and they already have rally tires:



Clearly the front is simply the reverse of the "regular" e36 M3 brake upgrade that is popular on here. We pulled info from the Turner page and here.

http://www.turnermotorsport.com/p-12...i323i328i.aspx
http://jj100d.blogspot.com/2011/03/e...ike-legos.html

I read a few threads for info:
http://www.bimmerforums.com/forum/sh...ear+brake+swap
http://www.bimmerforums.com/forum/sh...kes-on-97-328i
http://www.bimmerforums.com/forum/sh...to-328i-Brakes

It seems that he needs to identify a way to make 325/328 rear brakes work with his M3 rear end.

I happen to have a 1997 328i and would be willing to do the swap but before we go wrenches-crazy and just start swapping stuff from one car to the other, what all is needed to DOWNGRADE his rear brakes to 325/328 brakes? Since most "regular" e36 rear brake upgrade threads recommend using e46 components there is not much in the way of info about the M/non-M rear brake interchangeability.

And since I will be (at least for now) still running a non-M rear differential, what all will we need to get off of a parts car since I will still need it?

And will be have bias issues with either swap?

How about the parking / e-brake issues? How would those be handled?

I may edit this post as I get more info.

[pbonsalb]

Yes, put 328i front spindles and brakes on. For the rear, you should be able to grind down the caliper to clear. I have run 15 inch drag wheels on my M3 after doing this. You can also change to 328i rear trailing arms and axles, but the axles are a little weaker so this is not the first choice.

[95maxrider]

Checking in, thanks for posting up Patrick!

[phenryiv1]

Yes, put 328i front spindles and brakes on. For the rear, you should be able to grind down the caliper to clear. I have run 15 inch drag wheels on my M3 after doing this. You can also change to 328i rear trailing arms and axles, but the axles are a little weaker so this is not the first choice.

Did you experience any odd front/rear bias by downgrading to the 328i brakes?

[pbonsalb]

I did not do this but would not expect anything to worry about. I have M3 front with ground M3 rear. A drag racing friend had 328 front and ground M3 rear and no issues but he switched this year to 330i front brakes that are bigger than M3.

[spyderg0d]

Buy 328.. Swap engine to 328.. Problem solved. Sell m3 with no engine. Just won $4000.

[flyfishvt]

No need to down grade the brakes. I have an m3 and I use these 15" rims with my drag radials.

http://www.bmwstylewheels.com/bmw/27

You will have to grind down the brake calipers a tiny bit. These rims should look very familiar. They were used on lots of 97-98 e36s

[pbonsalb]

I think the OP wants to run 15s in the front of his M3 as well as the rear.

[phenryiv1]

Buy 328.. Swap engine to 328.. Problem solved. Sell m3 with no engine. Just won $4000.

He already owns the M3 but we considered that route. In the end the other benefits of the M3 won out, plus he got it for a "328-like" price.

- - - Updated - - -

I think the OP wants to run 15s in the front of his M3 as well as the rear.

Correct.

[95maxrider]

Yes, put 328i front spindles and brakes on. For the rear, you should be able to grind down the caliper to clear. I have run 15 inch drag wheels on my M3 after doing this. You can also change to 328i rear trailing arms and axles, but the axles are a little weaker so this is not the first choice.

What wheels did you use? Neither of my sets of 15s were anywhere close to clearing, even with 12mm spacers.

- - - Updated - - -

No need to down grade the brakes. I have an m3 and I use these 15" rims with my drag radials.

http://www.bmwstylewheels.com/bmw/27

You will have to grind down the brake calipers a tiny bit. These rims should look very familiar. They were used on lots of 97-98 e36s

Those look promising. So you ran those in the rear of your M3? Thanks!!

[somebody5788]

I'll trade my 328's brakes and stuff for your M stuff. Make us both happy hahahah. I have new Akebono pads too.

[flyfishvt]

Yes I run them on the rear of my m3. As I said you have to grind a little off the top of the calliper. I also use 10mm spacers on the rear. Pbonsalb and others do the same thing.

[95maxrider]

I'll trade my 328's brakes and stuff for your M stuff. Make us both happy hahahah. I have new Akebono pads too.

Thanks, but I already sourced all the parts for the front.

- - - Updated - - -

Yes I run them on the rear of my m3. As I said you have to grind a little off the top of the calliper. I also use 10mm spacers on the rear. Pbonsalb and others do the same thing.

Hmm, well let me know if you want to sell them. A quick search online didn't find much!

So it looks like they have a pretty similar offset (+47) to my style 46 wheels (+42). What size tires are you running, and how close are they to the fenders? Got any pics? If you have any around, I would love to get some measurements off them!

[flyfishvt]

I use 10mm spacers. No pics. They are my drag radials. I swap them onto the car when I get to the track

[95maxrider]

I use 10mm spacers. No pics. They are my drag radials. I swap them onto the car when I get to the track

How did you find out that they fit, are they known as a wheel that fits over a lot of brakes?

[flyfishvt]

Yes they are known for that among the e36 turbo crowd.

[95maxrider]

Well after about 2 hours of grinding on the rear calipers, some 12mm spacers, and a set of style 27 15x7 wheels.....I still couldn't get them to fit.



This is what we thought people meant by "light" grinding:



Well, that wasn't even close. Much later, the calipers looked like this:









This is what I ground off from one side:



And yet they were still not even close to fitting. Can anyone help me out here? How much more grinding am I supposed to do?

[flyfishvt]

I use the same rims for my drag radials on my m3. I use 10mm spacers. When I got to the point you're at in that second pic I dusted the calliper with primer. Then I put the wheel on and torqued it down till I could just barely spin it. Now look at the calliper and see where it's rubbing. I found most of the rubbing was not on the front where the M is. I found it was on the rear. All the material I took off came off those 2 arches that go from the M to the rear of the calliper.

[95maxrider]

I use the same rims for my drag radials on my m3. I use 10mm spacers. When I got to the point you're at in that second pic I dusted the calliper with primer. Then I put the wheel on and torqued it down till I could just barely spin it. Now look at the calliper and see where it's rubbing. I found most of the rubbing was not on the front where the M is. I found it was on the rear. All the material I took off came off those 2 arches that go from the M to the rear of the calliper.

Yeah, I was using a marker to see where it was hitting and it was more towards the outer part of the caliper where the M was. I'm concerned that I'm going to take away too much material if I keep grinding. Do you have any pics of what you did? How long have you been driving around with the calipers like that? Thanks!