My 1971 521

[d.p]

Here’s another pic of the caliper. I assume that brake spring should move freely but it doesn’t at all. Super tight

 

 

 

[d.p]

 

 

 

how free should these levers move? Cause right now they don’t move hardly at all and require a fair amount of force to move them.  

Edited May 17, 2022 by d.p

[bilzbobaggins]

I would assume they take some arse to move.  Are there two holes for adjustment on the L bracket piece that the cable hooks on?  Where the clevis pin goes through? 

[d.p]

Just now, bilzbobaggins said:

I would assume they take some arse to move.  Are there two holes for adjustment on the L bracket piece that the cable hooks on?  Where the clevis pin goes through? 

Yeah they do and there are two holes but almost impossible for me to get the pin in the closer holes (ones closer to the L).   
 

 

 

 

[bilzbobaggins]

I almost wonder now if the parking brake holder brackets are making slack over a factory mounted position.  Trying to help but I am well in the bag.

[thisismatt]

I would bet the disc parking brake needs more force over a shorter distance, whereas the stock drum ebrake has a longer lever for more mechanical advantage at the drum.  Might be able to change the leverage at one of the intermediate pivots.  These style disc parking brakes are kind of crappy...probably why a lot of manufacturers use the disc hat as a mini drum brake for the parking brake.

 

If you need more slack, there's at least one more turnbuckle in the cable towards the front, but I think you need to get rid of all the slack once it's hooked up, and possibly even preload the caliper springs a little.

[Crashtd420]

Hey dp this may or may not be relevant but did you happen to try to push the piston in manually at anytime while messing with them?

The reason I say is because these pistons need to screw back in to reset vs  being able to use a clamp to push them back....

[d.p]

2 hours ago, Crashtd420 said:

Hey dp this may or may not be relevant but did you happen to try to push the piston in manually at anytime while messing with them?

The reason I say is because these pistons need to screw back in to reset vs  being able to use a clamp to push them back....

 

Nah I never did that.  Maybe pushed the spring one time and realized how tight it was and just moved on.   I agree there does seem to be too much slack in the cable itself but having a hard time getting it all out. Here is a rudimentary drawing of it:

 

 

 

The turnbuckle that goes through the frame is bent (in red) so whether that has something to do with it I don't know but I doubt it cause it worked prior.  Also there is another lever mechanism up by the trans before the cable goes through the firewall but I left that out. 

 

 It seems like with drums it was easy to pull the cable and push the shoes out without much resistance.  Now with the discs they seem to need a lot more leverage/pull to push the piston in and clamp down on the rotor.  Something I am just not getting with the way it sits today.  I adjusted the back turnbuckle out because with the calipers having the park brake on the back the cable needed to be longer to reach them.  I then tightened (shortened) the turnbuckle in front of the cross member and that tightened up the parking brake but didn't do much of anything in terms of applying the p.brake any better than it did before.  Also the springs at the back of the cable where they meet the calipers is shorter then the distance between the front mount and the back clevis that attaches to the p.brake spring arm.  So other than protecting the cable from rubbing on the block/ujoints not sure they are accomplishing anything.  

 

It just seems to be too much slack and not enough leverage/force to apply them.  Fuck I may take it my buddys shop and put it on a lift and have a different set of eyes.  

[Stoffregen Motorsports]

Hate to say it, but your parking brake with the disc brake calipers will never be as good as it was with the drum brakes.

 

You could try to re-engineer the cable pull system to gain more leverage, but that would take some actual fabrication knowledge and a welder. And some patience.

[d.p]

23 minutes ago, Stoffregen Motorsports said:

Hate to say it, but your parking brake with the disc brake calipers will never be as good as it was with the drum brakes.

 

You could try to re-engineer the cable pull system to gain more leverage, but that would take some actual fabrication knowledge and a welder. And some patience.

 

I never said I wanted it to be as good, I just want it to work.  And I don't believe I need to re-engineer anything as others have done this before me.  There is a solution to this without actual fabrication knowledge and a welder but its yet to present itself. 

[thisismatt]

I bet one or both pivots could be redrilled in a way to increase the pull from the handle, but shorten the pull & increase the force at the calipers.

[Stoffregen Motorsports]

1 hour ago, d.p said:

 

I never said I wanted it to be as good, I just want it to work.  And I don't believe I need to re-engineer anything as others have done this before me.  There is a solution to this without actual fabrication knowledge and a welder but its yet to present itself. 

Everything and anything can be improved upon, always.

15 minutes ago, thisismatt said:

I bet one or both pivots could be redrilled in a way to increase the pull from the handle, but shorten the pull & increase the force at the calipers.

Yep, this amounts to re-engineering. It's not a bad thing, and I'm not saying the kit sucks and you should re-do it, but more pull and more leverage are the two factors for a cable-pull parking brake. One will give more travel (pull), one will give more strength (leverage).

 

I am saying that it will never be good, possibly not even adequate. I've installed many rear disc conversions over the years and I have yet to see one that works well on all counts.

[mrbigtanker]

On 5/16/2022 at 11:21 AM, d.p said:

 

redial the bolts? What the difference really between my 720 leafs and new bell techs other than their age?  Remember I am doing all this shit in my garage so whatever I do has to be done with regular old hand tools and occasional outside assistance.  

Re-drill 

[banzai510(hainz)]

5 hours ago, Stoffregen Motorsports said:

Hate to say it, but your parking brake with the disc brake calipers will never be as good as it was with the drum brakes.

I think somebody made fun of me and my block of wood as a wheel chock

[datzenmike]

3 hours ago, Stoffregen Motorsports said:

I am saying that it will never be good, possibly not even adequate. I've installed many rear disc conversions over the years and I have yet to see one that works well on all counts.

 

There's a lever (long and short arm) low down on the firewall that connects the cable from the hand brake to a cable that goes under the cab. Drill a second hole on the shorter lever to make even shorter, increasing the mechanical advantage.

[gene knight]

On 5/15/2022 at 5:11 PM, d.p said:

 
I’m ready for an easy project.  Not sure swapping leafs would be easy.  Don’t see many people that have done it and the one dude who did was asking me questions about it.  I’m probably the wrong guy to ask about it lol. 

i am running 1985 nissan 720 4x4 leaf springs on my 521/ grimace

[gene knight]

On 5/15/2022 at 8:18 PM, mrbigtanker said:

https://www.belltech.com/products/belltech/lowering/belltech-3-quot-drop-rear-leaf-spring-each-5974.html

what do i order them for cuz i dont see my year of datsun? i only saw pinion shims and rubber bump stops and only  leaf springs for 1988 d21/ hardbody trucks

Edited May 18, 2022 by gene knight

[Stoffregen Motorsports]

17 hours ago, datzenmike said:

 

There's a lever (long and short arm) low down on the firewall that connects the cable from the hand brake to a cable that goes under the cab. Drill a second hole on the shorter lever to make even shorter, increasing the mechanical advantage.

Great place to start.

[d.p]

19 hours ago, datzenmike said:

 

There's a lever (long and short arm) low down on the firewall that connects the cable from the hand brake to a cable that goes under the cab. Drill a second hole on the shorter lever to make even shorter, increasing the mechanical advantage.

 

I had actually reversed that lever because it was hitting the 5 speed when I dropped it in.  I can try to revert it to see if that helps and go from there.  

[d.p]

6 hours ago, gene knight said:

i am running 1985 nissan 720 4x4 leaf springs on my 521/ grimace

 

What did you do about shacking bushings? 

[Stoffregen Motorsports]

Here's a link to Energy suspension leaf spring bushing by size guide - https://www.energysuspensionparts.com/energy-suspension-universal-polyurethane-bushings.asp

 

If you have basic measurements, you can find it there.

[d.p]

I already have some of those but they were too long so I needed a way to cut them.   I am wondering exactly what Gene did not what I can do as I already know that. 

 

[mainer311]

I cut urethane bushings with a hack saw. A sharp box knife works too. 

[gene knight]

14 hours ago, d.p said:

 

What did you do about shacking bushings? 

i went to local shop where i do my leaf spring/coil spring work and had them use the stock bushings and compare what they have and if you need some let me know i get good prices 

[d.p]

7 hours ago, gene knight said:

i went to local shop where i do my leaf spring/coil spring work and had them use the stock bushings and compare what they have and if you need some let me know i get good prices 

can they get all of them for switching to 720 leafs? If so I’m interested.