Sourcing the parts (August ’18)
Just picked up some big brakes for the old girl! i know that buying brakes for a non-running car is an odd choice…but you don’t find a lot of 90s BMWs around any more. I drove out to pull them myself, met a few really nice scrappers, had an all-around good day in fact. It’s a shame this car was scrapped. Engine seemed healthy so I’d presume a dead transmission or an abandoned car. Check out how well preserved those tools are!
Installing the parts
After a little cleaning & lubing, I installed the components today. As advertised, the larger calipers on the 540i 740i are a direct fit. Be sure to grab the carriers as well when you find a set, and you might as well take the front rotors if they look OK. The 740i rear rotor won’t fit, so I left them at the salvage yard and ordered a new set of rear rotors from the ’94-95 E34 540i. I also opted to install a spare set of E24 M6 front rotors, since they’re a bit worn and not really worth selling. The M6 rotors are internally vented and slightly lighter. IMHO a good choice.
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- Front set ready to go
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- Here’s the stock E28 brake.
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- E32 740i rotor weighs 15.5#.
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- E24 M6 rotor weighs almost 17#.
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- Here’s the 740i front caliper, 13# with hose.
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- Stock E24 front rotor, just over 12#.
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- Stock vs. M6 sizes.
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- You can see how much larger the M6 part is here.
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- Stock E24 front caliper is 11#.
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- I know it’s rusty, but it’s installed!
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- Stock rear E24 setup. Solid rotor.
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- 740i rear caliper on the left, E24 on the right
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- Massive upgrade!
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- E34 540i rear rotor is nearly 13#.
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- E24 rear rotor is only 9#.
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- 740i rear caliper, carrier & pads come in at 7.5#.
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- 635CSi rear caliper, carrier & pads are only 6#.
Was it worthwhile? I’m told it is, although my lower back grumpily disagrees. I’ll update this page once I get the system purged & bled.
I was curious about how much the E23 540i setup increases sprung weight so I also carefully weighed everything as I did this job. Per each side, the E34 540i front caliper is 13#, E24 M6 rotor is 17#; total weight is 30#. Stock E24 is 23#, so the upgraded front setup is about 30% heavier than the stock E24 setup. The E34 540i rear caliper is 7.5#, rotor is 13#; total weight is 20.5#. Stock is 15#, so the upgraded rear setup is about 33% heavier than the stock E24 setup. We’re also required to run 16″ wheels to clear these larger front brake, so we gain a good bit of sprung weight there as well.