Will Calipers and rotors from a 92'735il work on a 93'525iT?

[gdub0717]

Hi, I have a 735il in my yard that I have for the M30 motor. Recently I acquired a 525iT. I have done some research and looks like the Fronts may work but the Rears are questionable. Would like to get feedback form anyone who has completed this swap and the benefits. Thanks.

[moroza]

Greetings and welcome!

http://www.bmwe34.net/E34main/Upgrade/Brakes.htm

E32 rear hubs are 7mm further outboard, and the rotor hats are 7mm deeper to compensate. The calipers, as well as the friction surface of the rotors, are in the same position relative to the trailing arm.

I'm (sometimes) local to you and have E32 740 whole trailing arms, including the wider-spaced hubs and brakes, on my 94 525iT. The 740 calipers and carriers are identical to 540.

735 calipers and carriers will bolt to the trailing arm (trailing arms are the same for all E32 and E34 except 525 sedans, and even there the brake mounting points are the same), but they will only properly fit 735 rotors, which require E32 hubs.

[xcastaway]

Welcome, indeed, to another local touring owner.

I use the e32 front calipers with e38 rear calipers, and combined them with e34 540i rotors on my touring. Straight across swap with your stock touring trailing arms. They certainly improve heat dissipation from the brakes, quite useful if you occasionally go blasting down back roads with her.

[moroza]

Looking into this further, I made an interesting discovery, namely that wagons and sedans had different brakes. BMWE34.net ignores this difference, as do all other sources I've found, other than the BMW parts catalog.

Rear brakes for US-market E34 and E32. All are single-piston sliding calipers.

Model	Left caliper PN*	Rebuild kit PN	Piston diameter (mm)	Rotors
525/530/535 sedan	34211160381	34211159171	38	300x10 solid
525/530 wagon	34211160927	34211158578	40	300x10 solid
540/M5/740/750 (>=1/90)	34211160399	34211158578	40	300x20 vented
750 (<1/90)	34211160385	34211157042	38	300x20 vented
735 (also E30 M3)	34211160353	34211157042	38	300x12 solid

*Add 1 to get the right caliper PN
**E32 have a deeper hat, though the friction surface is in the same location.

Conclusion: for your 525 wagon, 735 rear brakes will not only not fit without a bunch of work, and only gain you a marginal increase in heat capacity, they will actually decrease stopping power and tilt brake balance further forward. Bear in mind that E34 wagons weigh an extra ~200lb over the rear axle and end up being slightly rear-heavy (see here).

While we're at it... front brakes:
525/530/535 use 302x22mm rotors
540/735/740/750 use 302x28mm rotors
M5 use 315x28mm rotors
E31 1-piston uses 324x30mm rotors
All of these have a single 60mm piston and take rebuild kit 34111157037. Presumably, bigger rotor diameter - but not thickness - means that the corresponding piston is spaced out further from the axle centerline, which would amount to increased stopping torque. This is certainly the case for E31 1-pots, and I assume also the M5. E32/540 front brakes gain you heat capacity but don't stop any better.

E31 4-piston fixed calipers have 4x 40mm pistons, use the same 324x30mm rotors.

[gdub0717]

Thanks!
I have always loved these wagons and had some cash in hand and my compulsive nature took hold. Glad to be part of the group.
Every time I look at it the thing puts a smile on my face. This will be the daily and my E9 the weekend fun car.
Both will continue to take buckets of money, I am sure.

Looks like there is benefit to using the front calipers. Will not bother to touch the rear. The rears are needed immediately so will just replace the rotors and pads with stock.
Thanks for the feedback and research!
I am going to take the LSD(4.27) out of the 735 and put it in the wagon. Any thoughts on this plan?

Gordon
73' Matte Black e9
93' White 325iT

[m735is]

I have e32 735 front calipers and rotors with the stock wagon rear calipers and rotors on mine. I couldn't be happier. I tow a 5x8 trailer sometimes loaded with parts car scrap, works out very well. Without the trailer even better!

I wish I would have kept my 4.27 LSD for the wagon. If you swap, please post your thoughts. Mine is an auto since it matters.

[moroza]

I find most BMW gearing too short as is, but 4.27 isn't going to make much of a difference over 4.10. 3000RPM becomes 3124.

Flat black E9?! This I gotta see...

[gdub0717]

00W0W_jS4fvgItCtF_1200x900.jpg00b0b_2io1wW9gYxy_1200x900.jpg

Just starting to work on the E9. Putting on Euro bumpers and turn signals. Filling the side marker holes and installing an air dam. Maybe some suspension work in the future. The rest of the work will be on the mechanics.
I will post pictures of the e34 once I get the paint buffed.
Just installed 18" style 5's , staggered.

Yeah I figured the Diff wont make much of a difference on the highway but should handle better in poor weather. That is the main reason for making the change.

[moroza]

Chips notwithstanding, that looks very clean! E9 is the best-looking BMW IMO, maybe tied with some 90s models (like a good E34). Interiors especially are far prettier than its successor's; how's yours?

Maybe old news to you, maybe not... an LSD will get you moving where an open won't, just not necessarily in the direction you want to go. My 544iT was terrible in the snow with an S3.15: primitive rear suspension + firm swaybars + high torque at the wheels + rear weight bias = trouble. With a 2.65 open it was more docile, though still a handful. But if you're prepared for that, go for it. I might want your old 4.10; don't scrap it.

[fo3]

That e9 is awesome. Glad to have you on the e34 board with your touring too.

[gdub0717]

To the touring guys in the NW. HEY, I just picked up a black headliner, all the pieces. looks pretty nice, it came.out of a 94 touring. I have a white touring with tan interior. Was going to use it now in would just like to get out what I paid. $60. Any interest? If so, I am in nw portland. Gordon gdub0717@gmail.com

[moroza]

Mine's a hardtop, so not for me. Recommend posting in the Classifieds.

[xcastaway]

Well, I have my headliner out, waiting for me to find material to cover it. It's waited several months now, and isn't much closer to being done. Mine was grey, (Sterling Silber/Black) though, and while I could probably make black work, it wouldn't be my first choice. And I'm trying to scrape together the funds for a new clutch and hopefully a gearbox to replace the crunchy Getrag in it now, so the headliner is a few steps down on my priority list. Hoping to have her mechanically sound by the end of the summer, then attend to the things it will take to make it look nicer.