Question about 325i brakes

[Jean]

I'll be installing 325i trailing arms once I get new bearings and bushings on them, and at the same time upgrading front brakes to 325i calipers and vented rotors and 325i non abs bmc.

Will I need a proportioning valve ? Does the 325i come with such valve ?
I can't figure out why I would need one if I am running a 325i brakes front/rear

Thank you.

[Mike325]

All cars come with one. It makes it so less pressure goes to the rear brakes. Here is a good read.

http://www.stoptech.com/tech_info/wp_proportioning_valves.shtml

[Jean]

Alright, where is one located on a stock e30 ?

Who makes one with a remote "dial" to adjust this from inside the car ??

[FredK]

I believe the stock one is located towards the rear of the engine compartment, on the driver's side, where the hardline from the ABS unit that goes towards the rear brakes meets up with the hardline that runs underneath the car. It is part 5 in the attached diagram.

[Jean]

Thanks, I take it all i'll need to do is replace it with a 325i pn # ?

[Mike325]

Yes, #5 is for the car you have I believe. The #8 one is for eairlier cars. Double check though.

[Jean]

I looked at realoem.com and the brake pressure regulator is listed as the same PN for both an early 318i and newer 325i. It is not listing, however, PN for the item # 8 at all ?

[Mike325]

Just look up the year 325i that you have. You want to get the corrcet one for your year.

[Jean]

I don't have a 325i, I have a 318i that I am upgrading the brakes on .

[FredK]

I checked almost every permutation of E30. Part 8 does not exist for any of them.

However, what I did find is that the 318i (M10) uses the same proportioning valve as the 325e, 325i, 325ix, M3, 318is (M42). So, you should be safe in using the same proportioning valve.

But, the 318i DID come with a stepped bore master cylinder to further control brake bias (PN 34311156273). The ETK lists the bores as 19.05 and 20.64mm.

So, if you're going to switch over to the 325i braking system, what you need is to get the 325i master cylinder. However what I am not sure about is the ABS. It seems like there are a lot of different combos of MCs that depend upon production date.

If I were to try this, I would just swap over to a disc system from a non-ABS vehicle, like a <5/87 325i.

[Jean]

Thanks for confirming that the proportioning valve is the same. I am getting a new 325 MC, and my car does not have ABS, so I'll order a non ABS part from BMA.

[Jean]

Going to be doing this swap next weekend. Got a pair of 325i calipers, new brembo blanks, oem front/rear lines and mc on order.