Disc brake m/c conversion question

[BEEBANI]

Figured I better chime in with my .02 here. On my truck I was running stock 720 front non-vented brakes and the rear Isuzu setup that I sell. I installed a '85 720 m/c and booster on my truck. This unit is a 15/16" bore and from a disc/drum truck. All I had to do was modify the stock 620 booster bracket (extended it with a piece of pipe) and voila. I never had any problems with the brakes on that truck, stopped her from 120 mph many times without much trouble at all. The bias always seemed right on, and never had any problems with the rear locking up.

 

Sadly, I have recommended the 280zx m/c to guys buying my kit because I was told it was the way to go, but after struggling with that particular m/c on Clayton's kc with z32 brakes in the front and the Isuzu setup in the rear, I'm not so sure about that m/c anymore.

 

Fineline was running the z32 1-1/16 bore m/c on his truck if I remember right? Not sure if any of this helped, but this is what I know. ;)

[hawaii_620]

So after further examination of the early 90s Hard Body MC, it looks like it would take much more work than just "30 minutes with some simple hand tools" to make it fit, as with a Frontier MC posted earlier in this thread. Not saying it can't be done. But if cutting bolts off my 620 booster to make it "kinda" fit is what's needed, I'm not doing that just yet. I noticed that the B310 booster Charlie69 used and the 720 booster that Beebani has on his truck have horizontal mounting posts, so I'll probably try one of those boosters with my 90s Hard Body MC.

 

Could someone tell me what the diameter of the B310 booster and 720 booster is?

 

Maybe I just measured my 620 booster wrong, but I come up with a 5.25" diameter. I found somewhere that it's a 6" diameter. I'd like to know if I can fit the B310 or 720 booster in that space.

 

Thanks

[BEEBANI]

The 720 booster was quite a bit bigger, wanna say 7 or 8" in diameter. Let me do a little digging and find out for sure. I had to put a small dimple in the fenderwell to clear it.

[69FJWagon]

I personally wish someone would make an adapter plate to get rid of the booster I hate the feel or lack there of of power assist brakes.... :(

 

I finally got the proper Z32 MC for my KC now if the temp would drop below 90 I might go out and mess with it

[albyneau]

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

 

New response to an old post~ sorry guys. I stumbled upon this while "window shopping" for power brake info. Not pickin on Wayno~ just quoting his post....

 

I have to disagree with the above quote for the following~

While there may be nothing wrong with the mechanical abilities of a non-boosted system, there is the biophysical side to consider. If/when you're in a panic stop and collide with something, that leg that's pushing the whoa-pedal is very susceptible to injury~ due to the additional forces required to execute said panic stop. It's happened to me twice now; the first time in '06, which crushed (and subsequently got removed) 30% of the meniscus~ the figure 8 shaped cartilage in the knee joint, and now again with my recent rollover in my 521- which was really just a grazing blow with the side of a hill....

 

One could make the point that in a panic stop you're gonna mash the pedal anyway, but after driving your rig for some time both the conscious and subconscious brain remembers what it'll take to stop- fast, and right now. Knowing (at both conscious levels) your braking ability frees up the adrenaline-saturated brain to process other possibilities , and muscular efforts to possibly avoid an impending collision~ all in those final nanoseconds.

 

Additionally, there's math involved here involving impact forces- for those that wish to play with the numbers. Even a wimp can muster up 150-200#'s of force on a legpress machine (last time I was in the gym I was pumpin 700+), so speed times mass equals my F~@k!n knee hurts like hell AGAIN.....

 

Food for thought~ but I'm goin POWER!

 

Peace~

Scott

[burrito213]

Wayno, do you know the proportioning valve or part # that Mike bought for the disk/drum conversion to your NL320?

[burrito213]

this is what i am thinking of buying: any yay or nay to this option?

 

 

http://www.ssbrakes.com/commerce/detail/index.cfm?nPID=8862

 

 

 

SSBC A0730

 

 

will this compliment the m/c?

[wayno]

this is what i am thinking of buying: any yay or nay to this option?

 

 

http://www.ssbrakes....x.cfm?nPID=8862

 

 

 

SSBC A0730

 

 

will this compliment the m/c?

 

 

I do not know what the one is under there, and it's to wet to look.

This looks like a good one, although I know just enough about this to get myself or someone else killed.

It looks like it would simplify the brake piping, two lines going in and three lines coming out.

[mklotz70]

I'm pretty sure it's this one....

 

https://www.jegs.com/i/SSBC/884/A0707-1/10002/-1?gclid=CjwKCAjw092IBhAwEiwAxR1lRm2HP96pb_XUWdqZhCgInBeHvV4F22Xj5L84m4-PoI8Dlr8NH3NGiBoC24kQAvD_BwE&__cf_chl_jschl_tk__=pmd_2df4b2dddaa6c5834d9a6b647cf8351a9f442f34-1628927974-0-gqNtZGzNAnijcnBszQti

 

I'd get a brake light switch for the brake pedal...much more sensitive...info my my NL thread. Save the $50+ on the block with the switch.

Edited August 14, 2021 by mklotz70
fixed dead link

[burrito213]

perfect. thanks.

 

so the proportioning valve is to help the braking in the rear based on my readings?

[mklotz70]

It regulates the pressure to the rears to help keep them from locking up. In my NL, I had them dialed back so that they would not lock up in the rain....the front discs can stop that truck pretty dang quick all by themselves. :)

[Figbuck]

Hey Mike, I just did an exhaustive five day, 1600 mile test of your front disc conversion and it kicked ass. Very successful outcome. It seems like what you did would be the most basic 620 brake mod, no? I got new rear drums, shoes and cylinders and replaced the reman stock master because it was fucked after only 4K miles. So, all new front and back with the new stock MC and same booster = new truck!

 

I drove some of the nastiest roller coaster roads on the Oregon and California coasts, in some of the nastiest weather. I had waaay more fun than is allowed by law. I only broke the back tires loose twice on the brakes, and probably because I was reallly pitchin' it off into some tight corners in pouring rain. It's like driving a sports car now. The main thing I notice is that the steering has lightened up considerably. I think all that rotational mass in the weight of the drums sort of bound up the steering. I really notice how much lighter the steering is at freeway speeds too.

 

It took me a while to get used to the pedal feel after driving on useless front drums for too long. It only takes a slight toe to coast up to a stop sign or to scrub off speed when traffic slows in front of you on the freeway. If you need to stop right now, your foot goes a ways down, then lands at a nice big spongy but hard spot, that you can predictably stomp hard on. The pedal effort is really pretty easy and maybe the travel is a tad long... but I'm used to it now. It could be a tick harder with less travel, but picky picky. It's so fucking awesome to have a truck that is fun to hustle through the hills and back roads. Haven't been able to lock up any wheels yet in a straight line. I'm running 235/60s and that is a bit of meat to break loose.

 

My top secret central coast mountain testing course;

 

[burrito213]

Figbuck...

 

Can you post pics of your set up?... m/c n' stuff.

[mklotz70]

Thanks Fig! I appreciate the detailed description! :) The long travel would be shortened up a bit with a bigger bore on the m/c. If I remember right, you're running a 620 m/c?