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Brake booster delete master size?

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Hey,

 

I'm looking to delete my brake booster for a couple reasons, 1. its kinda in the way of my turbo plenum and 2. under boost its pretty much going to be useless. These cars are pretty light so I'm thinking deleting the booster shouldn't be too big of a problem so long as I spec the right size master cylinder. 

 

currently I am running Volvo Calipers in the front and VW jetta calipers in the rear with a E12 master.  

 

From my searches Ive seen this done but can find any info on the size of the master. I pretty much want to do same thing this guy is doing. 

 

 

 

 

 

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I'm also looking to go to manual brakes so I can fit intake trumpets on my dual carb setup but I haven't really found any helpful info so I hope we can find a something here

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It is going to make a difference how you are planning on mounting the master cylinder.  Are you planning on mounting it to the stock bracket where the booster is normally located using the stock linkage from the pedal to the master cylinder?  If so 19mm will give you a reasonable pedal travel but the pedal effort will go up by close to 2x.  If you are planning on modifying the pedal box and mounting the master cylinder down by the pedals you can play with the ratio by moving the mounting point on the pedal up and down.  I did a dual master cylinder conversion on a race car years ago mounting them up where the booster usually mounts, I used a balance bar so I could adjust the bias f/r.  If I remember correctly I wound up using 5/8" master cylinders, the pedal feel was good, the effort was a bit high but easy to get used to on track.   

 

I am running a 20mm master cylinder mounted in the pedal box, on my street car,   the pedal is nice and firm with very little travel but the effort is too high.  I am going to pull it apart and move the attachment point on the pedal down and see if I can get a better balance between travel and effort.   

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Yup, the pedal ratio on a 2002 is surprisingly low- I remember 4:1, or something like that.

Normal overhanging pedals are usually 6:1 or so.

 

This means that you'll want a small master (yep, 5/8" or so)

to increase your hydraulic ratio to compensate for that.

 

Using discs in back is good- it reduces the travel you need, so something

like 5/8" will work fine, once things are all bedded in.

 

That said, the reason you don't find a definitive answer is because there is none:

very few people like unboosted discs in the first place, and those nutters who do

tend to be running very high pedal effort with something like a 19mm master.

I went so far as to try making a 13mm master out of motorcycle parts.  It might have 

worked, had I stuck with it.

But I never found a small, (less than 19mm) dual master that would come close to working.

There might be one.

 

You will have enough vacuum with a turbo, btw- just the lift from shifting

will empty the booster of air, and that gives you 2 good stops...

 

The other no- master thing is that you will want a very high friction pad. 

No MetalBastards for you- you'll want an aggressive street compound from

someone like EBC or Carbotec or Porterfield.  Raybestos is supposed to have

something that works well, but I've never used their stuff.  A personal failing.

 

Good luck!

t

 

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Yes I want to put the master where the booster currently is.  Chase bays makes a kit but it uses a single output master. I would have to some how create a 5 port manifold to interface to my system. I also don't know if i like the single point of failure.

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That is why I used a 20 mm dual master from a MB although I did couple the 2 ports on the front calipers into a single line so I have a split front to rear.  If I drive the car for a couple of hours the pedal effort does not seem that bad but when I get back into any other car my 1st time on the brakes usually triggers the ABS. 

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haha yeah i can imagine. I really like the feel of my current set up. maybe I will just have to build my plenum around the booster. 

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(edited)

I did the brake booster delete. I'm using a 2nd generation master cylinder from a Corvette with a custom made  adapter to mate the Corvette master cylinder to the factory location, modified the "bell crank" to change the pedal ratio so it doesn't feel like a brick when applying the brakes.

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Edited by Doug Riparetti

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Nice. found your thread. Do you know the bore size? 

 

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So why not start form standard and do the maths.

Single circuit Standard non assisted brakes were on 1600s
2 piston ø48mm front calipers 17.46 2 piston rear drums and 17.46 mm master cyl.
1600GT and 1800 had 19.05 mm master cylinders and servo Brakes.

I don't know the piston size of neither Volvo nor VW Calipers.

And I don't know the total linkage ratio with the brake booster.

But I do have the 1600-2 Pedal assembly w/o booster here and can take some measurements if needed.
 

 

 

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Starting with a 67 1600 with remote booster, we used a 22mm dual chamber MC on the pedal box with Volvo calipers in front and 320i drums in back. Pedal feels like about 60#s, sort of what we were shooting for: pressure halfway between a nasty V8 race car and grandma's 74 Cadillac.IMG_2251.thumb.jpg.fa3ba605f490d00872f63c98e7831fd1.jpg

IMG_2250.jpg

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1 hour ago, andyleonard said:

Starting with a 67 1600 with remote booster, we used a 22mm dual chamber MC on the pedal box with Volvo calipers in front and 320i drums in back. Pedal feels like about 60#s, sort of what we were shooting for: pressure halfway between a nasty V8 race car and grandma's 74 Cadillac.IMG_2251.thumb.jpg.fa3ba605f490d00872f63c98e7831fd1.jpg

IMG_2250.jpg

Andy Do you know what the pedal ratio is with this set up?  

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Erm...no. The original 1600 with remote booster had the single cylinder brake MC mounted to the pedal box - except with a horizontal bolt pattern, leaving no room for the clutch cylinder - and the clutch was mechanical. Using the same pedal box, I just sawed the face off, mounted a flat plate, and then bolted up the MC and hydraulic clutch master where they looked like they needed to go ... without hitting each other or the chassis rail or steering. Then I tried for a straight shot to the pedal from the center of each cylinder bore. Pedal ratio was a result ... not planned. Seems pretty good as-is though. Not sure in any case my mechanical clutch/remote booster pedals are the same as anyone's 68-up 2002 with the linkage and booster upstairs.

IMG_1908.jpg

IMG_1907.jpg

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