2/16/13 3:46 p.m.

GRM experts... New to commenting, but long time lurker.

Anyhow, I'm currently working on an engine swap in my 1971 BMW Bavaria/E3. I'm installing a M62 V8 from a 1998 BMW 540i. I'll create a project post too and share pictures, but had a specific question I wanted to post here.

Has anyone converted a car to manual brakes? This will be a street only car for the most part, so I'm worried about pedal effort required. I would gladly buy a sweet wildwood pedal set with dual brake masters if I had some confidence I wouldn't need Olympian size quads to stop the car. I know older cars had manual brakes, but many had drum brakes...

My alternative is to relocate the brake booster to the space behind the headlight using the linkage from an E34. BMW did this for their V8 cars and it's been done in E30 V8 swaps, so it's definitely doable, but a lot of work.

Or, any other suggestions? I'm very limited on space at the firewall, so no booster would work there regardless of size...

Thanks, Seth

Kenny_McCormic HalfDork
2/16/13 4:36 p.m.

Some of the faster trim C2 Corvettes came fitted with 4 wheel manual discs. Its all in the leverage of the linkage and master cylinder piston diameters.

turboswede PowerDork
2/16/13 4:46 p.m.

Look up hydro-boost systems, uses hydraulic pump to provide boost to the brakes. Requires lots less space, used in a lot of engine swaps where there is less space.

GRM had an article a while back on how to properly measure and spec a brake system. I'm sure someone will post the link to the back issue, or AngryCorvair will post here (he was the author)

Good luck!

ransom SuperDork
2/16/13 4:49 p.m.

Kenny's right, but of course you don't get something for nothing, so in order to get the pedal effort where you want it, it's possible you may end up with more travel than you want.

Apologies that I don't have time to look up the other thread right now, but you may try searching for previous threads on this. I know I asked a similar question, and someone who'd done a lot of related calcs for a Formula SAE project piped up and was very helpful, and IIRC had a spreadsheet that helped figure some of this stuff out.

Bavarias aren't huge, but I'm still hemming and hawing over which way to go with my 2002, and a V8-powered Bavaria starts to sound like a lot of car to stop without some form of assistance.

Though you may not need the thermal capacity of big brakes, one place you do get increased braking torque without increased pedal travel is rotor diameter...

ransom SuperDork
2/16/13 4:52 p.m.

Ah, I forgot I could just check my watchlist; hopefully this is the thread I was thinking of, and it actually helps you...

HappyAndy Dork
2/16/13 5:37 p.m.

FWIW, I once had a '70 mustang that originally had manual drums. When the brakes were adjusted right they worked well enough. Keeping them adjusted right was a PITA! So I swapped Granada spindles and disks onto the front. The pulling and inconsistency all went away, but it was tiring to drive that way. I probably could have played with the M/C bore size to get it to a more livable effort, but life got in the way and I sold it before I resolved that problem.


Keith Tanner
Keith Tanner MegaDork
2/16/13 5:43 p.m.

By "manual brakes", do you mean mechanically activated or hydraulic brakes without power assist? I'm assuming the latter.

AngryCorvair PowerDork
2/16/13 5:56 p.m.

yep, look into hydroboost setups. they're not complicated, and they work well. if you choose to go with manual, you might need some aggressive pads to get the torque output at reasonable pedal force.

T.J. PowerDork
2/16/13 7:42 p.m.

I removed the brake booster on my Mini when it would occasionally let brake fluid get sucked into the intake under high vacuum situations and create a cool smoke screen. I actually like it better this way and there is more room under the bonnet. I have disks up front a drums in the rear. Of course the car doesn't weigh much at all, but the pedal feel is nice.

yamaha SuperDork
2/16/13 7:56 p.m.

Don't they make electric boosters there days?

02Pilot HalfDork
2/16/13 9:17 p.m.

M30-equipped E28s had a hydroboost system. If you have room on the firewall to bolt a master cylinder, plus maybe 8 inches in front of it, you have room to bolt in the E28 booster.

The_Jed Dork
2/17/13 3:50 a.m.

I've been kicking around the idea of ditching the teves system on the Mark VII and going to a manual master cylinder set up for simplicity, predictability and reliability. Not sure I'd like it though.

ddavidv PowerDork
2/17/13 5:15 a.m.

When we built the $2002 Challenge BMW, we had manual brakes cobbled together with parts from a Miata. Dumb idea. They sucked.

My vintage Ford truck has a disc conversion using manual parts engineered for the application. It works pretty well; feel is good, and pedal effort isn't terribly high, but now that I tow with it I wish I'd gone with a power setup.

If you decide to go manual, you really have to size the master cylinder correctly or it just won't work. Personally, I'd try to find a way to make it power.

GameboyRMH UltimaDork
2/17/13 8:02 a.m.
yamaha wrote: Don't they make electric boosters there days?

Turns out they do:,8335.html

bmwbav New Reader
2/18/13 12:03 p.m.

In reply to GameboyRMH:

Thanks for all the input. I'm reviewing the linked thread, great info. I'll tentatively rule out manual brakes, as I don't have a solid feeling that it would be acceptable for a daily driver. I will look into Hydroboost, but I'm not certain it will be worth the effort.

MadScientistMatt SuperDork
2/18/13 12:46 p.m.

My Dodge Dart never had power brakes. Not the original drums, and not a disc front / drum setup I pieced together out of a bunch of different OEM parts. The pedal effort and travel always seemed OK to me, even for a street car.

tuna55 UberDork
2/18/13 12:54 p.m.

I DDed my 72 GMC which has no power brakes or power steering. You had to DRIVE it. You didn't just guide it. Once you got it through your head that you wanted to turn, you needed to turn the truck, and if you wanted to stop, you needed to stop the truck, it wasn't so bad. Driving on a 60's high performance clutch was honestly harder than the manual brakes.

stuart in mn
stuart in mn PowerDork
2/18/13 2:01 p.m.
bmwbav wrote: My alternative is to relocate the brake booster to the space behind the headlight using the linkage from an E34. BMW did this for their V8 cars and it's been done in E30 V8 swaps, so it's definitely doable, but a lot of work.

I think this is the best idea, I've seen it used when swapping V8s into e28 5 series cars as well.

mr2peak Reader
2/18/13 9:15 p.m.

Definitely figure out power assisted brakes. On the street you're MUCH more likely to need to come to a full stop without warning. It would really suck to kill your project on someones back bumper...

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