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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series > E30 (1982 - 1993)

E30 (1982 - 1993)
God's Chariot. The E30 was produced primarily from 1982 through 1991. The cabriolet was the one exception which was produced through 1993.

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  #1  
Old 12-11-2013, 12:48 PM
Stevej66 Stevej66 is offline
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1986 BMW 325 Chevy V8 engine conversion brake problem question

I am in the final steps of my 1986 BMW 325 Chevy V8 engine conversion. I have a brake problem question: My 325 has the ABS brake system but because of the booster interference with the motor I am using a Corvette master cylinder and a 7 to 1 ratio brake pedal which should give me the same pedal effort as the original BMW booster. My question/problem is when the applied pedal pressure is max I only have about half braking power at the wheels. I've been told by some BMW dealers/shops here that the ABS is not the problem. I've also been told the ABS is the problem and to just bypass the ABS and use the Corvette proportional valve which I know will work. It's a simple conversion but I sure would like to use the stock ABS system. Would sure appriciate any feedback on this issue.
Thanks,
Steve
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  #2  
Old 12-12-2013, 08:13 PM
3star 3star is offline
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id dump the ABS u dont need it and it just lengthen your braking
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  #3  
Old 12-12-2013, 11:17 PM
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cmac2012 cmac2012 is online now
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Good point, if the car will be driven primarily in Phoenix, unlikely ABS will be missed.
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  #4  
Old 12-16-2013, 03:09 AM
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I guess your adding a good bit of HP over stock and you want all the brakes you can get .With the added weight on the front you'll to retain the ABS if possible.Most of the V8 conversions I've seen have go to manual brakes or use a remote booster.The Corvette master should work ,I know when you you go to manual brakes normally you need to raise the pivot point of the brake arm by about 1" to make it work right.
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  #5  
Old 12-22-2013, 02:13 PM
Stevej66 Stevej66 is offline
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Thanks for the info,
I dumped the ABS and replaced it with the Corvette Proportional Valve and got more brake but not enough. I think the Corvette Master Cyl/Preportional Valve are loading the rear brakes to 100% but only about 75% on front because the BMW calipers are smaller than the Corvette.
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  #6  
Old 12-22-2013, 08:56 PM
3star 3star is offline
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hmm you can try installing E34 brake calipers. have you converted to braided steel lines already THat helps alot
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  #7  
Old 12-23-2013, 08:30 AM
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I think maybe you need to use an adjustable proportional valve, like for a race car then you can set it where you want it .It can't cost any more then swapping calipers.http://www.iemotorsport.com/bmw/E30-brakes/wwvalve.html Try this it should fix your problem.

Last edited by toybuilder; 12-23-2013 at 11:47 AM.
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  #8  
Old 12-23-2013, 09:19 AM
Stevej66 Stevej66 is offline
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Thanks for the info,
will the E34 calipers match mounting on my 325. Also how much bigger are the E34 calipers. Please bare with me on this because this in my first BMW conversion. Car is ready for the road except for the brakes.
Steve
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  #9  
Old 12-23-2013, 10:07 AM
3star 3star is offline
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The e34 calipers are huge lol they will definately do the trick the is a write up online about doing the conversion ur gonna need a adapter.

The rx7 Turbo 4piston calipers may work as well
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  #10  
Old 01-28-2014, 09:37 AM
Stevej66 Stevej66 is offline
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I think I've found the problem

I think this ATE Brake Proportioning Valve W0133-1617672 could be my problem. It is located on the frame rail under the MC and controls flow to the rear brakes. Mine was clogged with debree, so I'm going to clean all the lines and put it back together first without this valve because I had installed a Wilwood adjustable proprorional valve.
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  #11  
Old 02-06-2014, 09:33 AM
Stevej66 Stevej66 is offline
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Still no change

I removed the ATE Brake Proportioning Valve W0133-1617672 and even with the Wilwood adjustable valve no change.
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  #12  
Old 02-06-2014, 09:14 PM
3star 3star is offline
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OK so i got a couple ideas what's causing your problem. If the mastercylinder you bought is a smaller diameter than stock that would cause you to reach Max pedal travel before maximum clamping load is achieved.

I wasn't clear on your issue, are the brakes locking up the tires? Or is it locking uo the rears more and not the front.

Another cause of the problem that you may not be considering is your vehicles alignment and suspension setup. A small boclk Chevy is a pretty heavy engine, it is possible that the engines weight has made your camber go more negative and under hard braking when the car dives its overloading the tires causing a slide and les braking. The solution is to run more positive camber on the front or to stiffen the front shocks a few clicks if you have adjustable shocks.

Your shock dampening and camber also affects braking performance and all three are a function of weight distribution under load.
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  #13  
Old 02-06-2014, 09:19 PM
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Iin my old ae86 when I got adjustable camber poates I set them to Max and was running 2 degrees. The car steering response was incredible but it couldn't stop for ****. I changed my suspension settings by bumping up the front stiffness and that solved the issue. I got awesome steering response and great braking.
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  #14  
Old 02-10-2014, 01:05 PM
Stevej66 Stevej66 is offline
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Quote:
Originally Posted by 3star View Post
Iin my old ae86 when I got adjustable camber poates I set them to Max and was running 2 degrees. The car steering response was incredible but it couldn't stop for ****. I changed my suspension settings by bumping up the front stiffness and that solved the issue. I got awesome steering response and great braking.
The problem as I see it is I'm getting a hard pedal with 50-70% brake on front and rear. I've added a adjustable P valve with no change. It acts like the problem is the master cylinder but I've tried 2 and no change. I don't get a gradual brake application as I press the pedal. Thanks for your info.
Steve
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  #15  
Old 02-12-2014, 02:47 AM
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Did you move the pivot point ? You do realize your not the first guy to put manual brakes on an E30 sometimes you just need to go with what has been done and proven to work.I was also thinking and this is a I don't know if it'll work ,but some of the Mustangs have a system called hydroboost that acts as a booster it's hooked to the power steering and fairly small for use in limited space.I'm not sure but you might be able to rig something up that worked.
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  #16  
Old 02-12-2014, 07:30 AM
Stevej66 Stevej66 is offline
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Brake Problem

Yes I changed the pivot point and ratio to 7 to 1 which manual brakes use a 6 to 1 ratio.
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  #17  
Old 02-13-2014, 07:23 AM
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I'm not sure where your problem could be ,it soulds like your saying your brakes feel " wooden" like you push them and they're either on or off no in between. Have you tried using the BMW master cyl. ?I think at this point that would be my next try since most conversions to manual stick with the BMW parts, heck what can it hurt at this point, I'm thinking with the smaller master and the proportioning valve you'll be able to make it work.
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  #18  
Old 02-27-2014, 08:59 AM
Stevej66 Stevej66 is offline
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Brakes fixed

Finally solved the problem. I was using a GM master cylinder with a 1-1/8" bore and a modified pedal ratio of 7 to 1 and getting a hard pedal and poor brakes. The original BMW MC for my 86 325 had a 7/8" bore. I changed to a GM MC with a 1" bore which really improved my brakes. I have a Wilwood MC with a 7/8" bore and with the 7 to 1 ratio i've got super brakes. Thanks for all your help and inputs regarding my brake problem.
Steve
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