Drum brakes to disc brakes?

[KenC]

I've got an '84 318 and I want to convert the rear to disc brakes. What all would this entail? Parts list?

[AdamF 88iS]

Its a bolt on conversion from any 325.

Dont forget to change the master cylender too beacuse the front/rear proportion is different for the drums. If you don't do this you'll lock the rears too soon.

[e30evolution]

you prolly want to change the front ones as well..... i think if you have drums in the rear ytou have solid rotors in the front... so you woul wat to get new front strut casing assembly, and rear hub..... i would get SS brake lines, because the rear lines will be different... one thing i am not sure of would be a proportioning valve to divide up the pressure because the drum brakes do not require as much pressure to operate as disc brakes they usually have a valve to reduce pressure so most of your braking ends up on the front

what i would do is look to see if there are any valves between the master cyl, and the rear axel on your car and a car with AWDB, you might need to remove,, or add one

[e30evolution]

ok... i guess the valve is in the master cyl.... i have my stock one if you want it.... $50 shipped to the lower 48, and if you want i could ship you all 6 of my ruber lines

[Stu]

Technically speaking, it is a "bolt-on," but it is rather extensive. I planned to perform this swap on my sisters old 318 (which had a stroker M20, and needed brakes), but she decided to sell the car.

It requires swapping the trailing arms from a 325/318is. This is not such an easy task. If you plan to keep the car mostly stock, with the M10 engine, you should just do a 325 front brake conversion. This only requires a set of calipers and rotors.

Considering how much more braking is done by the fronts, you'll be fine with leaving the drums out back and 325 parts up front, with good pads....unless you plan to get serious with your motor.

If you DO want to do it though, let me know, becuase I have a spare set of disk-brake rear trailing arms.

[Fraser]

If you DO want to do it though, let me know, becuase I have a spare set of disk-brake rear trailing arms.

Same here.

Stu, why do you say swapping the trailing arms is not an easy task? I've done it countless times- is there something I'm missing?

[george graves]

What about the parking brake cable? - Make sure that's the same - has to hook up differently on rear disk cars then drum cars....


George Graves

[Bill 84 318i]

Just keep the parking brake cables with their respective trailing arms. Just slide them in and out of the car.

[Stu]

Oh, are they easy? :?

Well, that noteworthy, but for my money, it's still not worth it do to a rear disk swap onto an early 318. Again, unless it's built (M20, M50, racecar..)

[mcgrath]

Dont forget to change the master cylender too beacuse the front/rear proportion is different for the drums. If you don't do this you'll lock the rears too soon.

Not true. I have converted my 85 318i from an 87 325i all the way around and still use the 318i master cylinder. all four wheels lock at the same time.

[demlotcrew]

Mcgraph is correct the master cylinder is the same regardless of model of car the only difference is the ABS the master has a blocked output. (2 not 3)

I would not touch the master cylinder as the ETK shows them to be the same and ive done the conversion before and would recommend it to anyone! its well worth the effort as the brakes are 100% better and dont need constant adjustments to keep them working on top form. The handbeake cable needs to be changed too as thats different and also make sure you have an empty fuel tank as you need to take the inlet pipe off to get a bolt out.

HTH

Andrew

[a3ternus]

A BMW mechanic told me that the drum-to-disc change is not SO simple...
Also,someone at a junkyard wanted 350euro for a pair of 3.20i discs (front).
That means over 600e for the convertion...or more ?!?
A3TeRnuS

[demlotcrew]

well i have done it and ill tell the its dead easy it took me Two days but thats because i was taking my time and doing one side at a time with all the arms bare and putting brand new components on, like disks cable calippers shoes and so on, i also changed the bushes whiile i was there oh and the hoses also got replaced.

But its all very simple plug and play stuff nothing to it, one problme i did have was with a seased brake like but with some heat it came off a treat.

[rs4pro3]

My friend did it to his 84 318i shell that we swapped an 86 325e engine into. He just took the whole rear subframe, diff, arms, halfshafts and all and bolted them in and changed the parking brakes. No master cylinder changes or anything. He mentioned about replacing the T in the back but that may off been to rust as there was a gapping hole in the floor pan on the 318i shell.

[a3ternus]

Hmmm,something tells me I asked the wrong person... :roll:
A3TerNuS