Disc brake m/c conversion question

[mklotz70]

Cool....that's an interesting piece of info! Thanks :)

[burrito213]

ok. so to be safe, i will be running the 620 m/c but the safe part is do i need to buy residual valves? - being such a small system i doubt i would need any but then you are asking the newb when it comes to bare bones construction of a brake system which will eventually be on the 320

 

i am going to probably buy the ssbc or wilwood proportioner. - i'm sure there is others but i will stick to these two options for now

[mklotz70]

You do not need the residual valves.

 

Either proportioning valve is fine. On my wife's truck....the first disc brake conversion about 10 years ago.....I ran a combination valve from an S10 pickup with no ABS. It's worked great. Without it, the back end would lock up real early, even in moderately hard braking. You can google the combo valve. On the NL, I used the adjustable prop valve....a lot easier to plumb. :)

[yello620]

ok. so to be safe, i will be running the 620 m/c but the safe part is do i need to buy residual valves? - being such a small system i doubt i would need any but then you are asking the newb when it comes to bare bones construction of a brake system which will eventually be on the 320

 

i am going to probably buy the ssbc or wilwood proportioner. - i'm sure there is others but i will stick to these two options for now

 

I was looking at www.speedwaymotors.com this evening and saw the adjustable valve for $41.99, I dont remember them being that cheap a few years ago. Might be a good source forthis item.

[Aaron]

OK got my master cylinder in the mail this week, and worked with getting it in place today. Thought I'd let everyone know how it went and the problems i came across.

 

I ordered the master cylinder off of the '78-'79 620.

So to start things off you need to open the hole in the firewall about 1/4" in diameter and I had to oval the mounting holes in the cylinder its self to get it to sit flush on the firewall.

 

First problem was the return for the fuel tank breather is angled just under where the new brake lines will be. So I just bent it slightly to run parallel to the brake master and will loop the soft line in front of the new master cylinder.

 

 

Second problem. It might not be a problem on all brands, but on the Raybestos master cylinder I ordered, the bleeder screws exit towards the drivers side. When both the brake master and the clutch master are in place the bleed screw won't let the clutch master to sit flush on the firewall. I'll probably solve this by finding shorter bleeder screws. It would have been nice if the screws exited the other side. Maybe another brand?

 

 

Just to show how tight things are.

 

 

Still need to have a push rod made up for it (sometime this week I hope).

[yello620]

Nice progress, keep us updated.

 

Shorter bleed screws should not be a problem to find, maybe even the old bleeders from your now unused front wheel cylinder. Not sure ifthey are the same size, but worth checking.

[mklotz70]

I probably should have mentioned that, but that's the other difference, besides bore, and one of the reasons I go with the other m/c.

 

The vent tube was under the clutch m/c, which didn't change, so I don't see why it was a prob....maybe it just looks okay because of camera angle?

 

The pushrod is coming in the disc kit. You'll need to source the clevis from the clutch m/c in the s/y, unless you have one laying around. The stock brake m/c was not adjustable, but the clutch m/c's were. :) I should be shipping today. :)

[Hyphy]

I hate to resurect, but.....

 

I cant recall ever driving a non boosted disk/disk brake setup, but given the proximity of the brake and clutch m/c's in the 521 it'd be much simpler to avoid adding a booster at all. Any opinions and experience on that setup would be appreciated. Also, did the 79-81 280zx disc/disc 15/16" m/c come boosted? That m/c appears to be an ideal option.

thnx

[yello620]

I hate to resurect, but.....

 

I cant recall ever driving a non boosted disk/disk brake setup, but given the proximity of the brake and clutch m/c's in the 521 it'd be much simpler to avoid adding a booster at all. Any opinions and experience on that setup would be appreciated. Also, did the 79-81 280zx disc/disc 15/16" m/c come boosted? That m/c appears to be an ideal option.

thnx

 

The 510 guys do the disc/disc without a booster all the time.

 

And Yes the 79-81 15/16 master is from a boosted car.

[mklotz70]

I've used that m/c in several rigs and it's been fine....but I've got short, stocky legs. For someone with long legs, there's a lot more angle at the knee....it will seem like a lot of leg effort.

[Hyphy]

Would that m/c work just fine without a booster? or is there a better disk/disk m/c option? I would imagine a lil bit of pushrod lengthening may be involved, but that seems fairly straightforward.

[mklotz70]

They work fine without the booster....just take a lot of leg. The rule of thumb is anything 1" and bigger on an m/c requires a booster.

 

I put info up somewhere about the pushrod lengthening.......but danged if I can find it! :( If someone does....post a link here or pm me with it...please!! :)

 

I used a M8x1.25x120mm allen head bolt to make the pushrods. I think I have a line on the clevis'.....if that pans out, I'll do the rod with an M10.

[Hoosier77]

All this talk about master cylinders and you guys still use the old ones? I pulled 2 off of some 98-01 frontiers in the yard and in about 30 minutes had it modified to fit a 620 booster, its a super large bore and it for drum/disc so we will see how it works when i get my conversion done. Oh and it is also alot shorter and nicer looking, has a single reservoir with a nice cap too!

[ppeters914]

All this talk about master cylinders and you guys still use the old ones? I pulled 2 off of some 98-01 frontiers in the yard and in about 30 minutes had it modified to fit a 620 booster, its a super large bore and it for drum/disc so we will see how it works when i get my conversion done. Oh and it is also alot shorter and nicer looking, has a single reservoir with a nice cap too!

The Frontier brake m/c has a 1-inch bore, so a booster is a must unless you have Hulk-like legs. There may not be room for a booster for some folks....like my 411.

 

You're also going to have to make an adapter as the mounting ears are at 3 and 6 o'clock instead of 12 and 6. Depending on the vehicle, may not be enough space, i.e. too close to the clutch m/c. I ran into that problem trying to use a 300ZX brake m/c on my 411. Returned it and went with the 280ZX 15/16-inch brake m/c.

 

And I'll repeat the warning about where the bleed screws and/or brake lines mount. There's a VW 7/8-inch brake m/c that would've been perfect.....except the brake lines connected on the side next to the clutch m/c. No way on the 411.

 

Pete "did I mention I have a 411?"

[yello620]

All this talk about master cylinders and you guys still use the old ones? I pulled 2 off of some 98-01 frontiers in the yard and in about 30 minutes had it modified to fit a 620 booster, its a super large bore and it for drum/disc so we will see how it works when i get my conversion done. Oh and it is also alot shorter and nicer looking, has a single reservoir with a nice cap too!

 

So, in other words, you found something different that still needs modified to fit, have no idea what bore it is, no idea if it might have been designed for ABS brake systems, and you have absolutely no idea if it will even work when the rest of your mystery system is completed. :D

 

I guess that i dont see the useful content here..

[Hoosier77]

excuse me? Why so rude? The frontier master cylinder is 1/16 of an inch bigger, a lot shorter, available new or like new not re-manufactured like the old masters, It took 30 minutes to make it fit perfectly on the STOCK BOOSTER with a few simple hand tools. Its close to the size of the 15/16 bore, only a bit larger and looks a hell of a lot better. Hydraulic pressure is Hydraulic pressure, One could assume its close to the same pedal as using the 15/16 bore cylinder and the frontier I took it off of had drums and disc. No I'm not a hydraulic brake specialist but when I have the opportunity I sometimes use trial and error to find things that work better than 30 year old rebuilt bull shit. :fu:

 

 

 

 

 

 

 

[ppeters914]

Definitely not arguing against nice, clean, shiny and new. It's exactly what I had hoped to achieve on my 411, but could not as I stated in my earlier post.

 

That you got it to work is resourceful and commendable, however, your original post infers this is a relatively simple unbolt old POS brake m/c and bolt in newer Frontier brake m/c....and it isn't/won't be for many folks.

 

You also don't mention what vehicle this is on and there's no vehicle in your profile.

 

Pete

[Hyphy]

Well he did say for his 620 in his first post. Sadly that setup won't always work so this talk about m/c's is still valid. It's much cheaper to test and what not with stuff at the junkyard and then buy a new one once you know it'll work. Then you have a tested setup and a new part. Not many new frontiers floatin around the yards.

 

On a side note: I might relocate the clutch m/c anyway to allow a booster. Shift it over and rebend/make clutch pedal Maybe a s13 or 300z one. Still gotta research more.

[mklotz70]

hyphy......the clutch doesn't take a ton of pressure.....you can just weld an extension onto it to move it over 2-3".

[wayno]

This is what I did for my power brakes on my 521.

[Charlie69]

Mike Klotz’s front disk brake conversion on my 1966 520

 

1981-1982 Datsun B310 brake power booster

1984-1986 Nissan 300zx master cylinder 15/16”

1978 Datsun 620 booster spacer

 

The only mod I had to do was add about 3” to the rod because of using the 620 spacer

Remember I am running an automatic transmission so I did not have to worry about mounting a clutch master but if you use Wayno’s example the clutch master will still fit.

 

 

 

 

 

 

 

 

 

 

[burrito213]

ok....now i am worried. do i have to worry about this?.....power boosster, spacer....etc....?

 

i have the 620 version for my nl320 and i dont want to have to worry about much.

 

any help?

 

 

[Hoosier77]

you guys are right the pedal on the frontier is stiff!!!!!!!!! hard as a horse dick!!!, we will see how it feels with beebanis d21 conversion on it!!!

[wayno]

ok....now i am worried. do i have to worry about this?.....power boosster, spacer....etc....?

 

i have the 620 version for my nl320 and i dont want to have to worry about much.

 

any help?

 

 

Get it going before you start to worry about power brake boosters, I don't have a booster on mine and it stops fine, nothing dangerous about it. My work truck also has disc brakes with no booster and it stops just fine also, unless I overload it, which I often do, then I just drive sanely. wayno

[Charlie69]

ok....now i am worried. do i have to worry about this?.....power boosster, spacer....etc....?

 

i have the 620 version for my nl320 and i dont want to have to worry about much.

 

any help?

Burrito do not worry what you have will be fine. This thread (in my opinion) is to show options when selecting a combination that will work.

 

For those people that are confused let me try to simplify the power booster master cylinder confusion.

 

The bigger the bore diameter of the master cylinder the bigger the power booster needs to be.

 

As Mike Klotz noted that his combination of no booster & larger master cylinder bore made for a harder or stiffer pedal.

 

This is why I went with a 15/16" master cylinder on my B310 booster, The stock 310 master cylinder is 13/16" so I incresed by 1/8" in master cylinder bore whis will result in a little harder/stiffer pedal. Also should equal shorter stopping distance because of the disk brakes on the front & the larger diameter master cylinder. People that are increasing the master cylinder bore by a large amount are the ones that are complaining about it being hard to push the brake pedal. If I do not like this combination when I get the truck on the road I have a new 310 13/16" master cylinder that I will install.

 

Without being a mechanical engineer in hydraulics it is strictly trial & error. But by reading about other combinations that people have tried a person can make a more educated choice when choosing a combination for their vehicle.

 

Remember that drum brakes have to travel longer distances to brake than do the disk btakes.