Disc brake conversion

Issues with shocks/springs, tires, stopping, etc.
StuartL
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Disc brake conversion

Post by StuartL » Mon Oct 24, 2016 12:57 pm

Been a few years since I sold my 710M, was just talking to a friend about the drum brake limitations in the 710/712 Pinzgauers and he said that the design and manufacture of a disc brake conversion kit (for self installation) wouldn't be that complex.

What level of interest would people have in a conversion kit? It's likely to include all the hub/disc parts, brake lines, mounting hardware, master cylinder/servo assembly, etc.
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Buzz
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Re: Disc brake conversion

Post by Buzz » Mon Oct 24, 2016 7:10 pm

I would be interested. For me, the drums are the weakest part of the original design.
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TechMOGogy
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Re: Disc brake conversion

Post by TechMOGogy » Mon Oct 24, 2016 7:24 pm

Perhaps disks on the frontRear drums are better offroad
72 Pathfinder | 75 710M 2.7i | 96 350GDT Worker

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Haf-e
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Re: Disc brake conversion

Post by Haf-e » Mon Oct 24, 2016 10:20 pm

What is the thinking on keeping rear drums? Why are they better off road? Curious to know.
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1971 Pinzgauer 710M

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Disc Brake Conversion Kits for 710 and 712 Pinzgauers
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StuartL
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Re: Disc brake conversion

Post by StuartL » Tue Oct 25, 2016 5:39 am

One of my frustrations with my 710M was the need to clean out the drums every time you forded through water with less than 99% purity. I found that dirty water (or wet mud, if you want to call it that) wrote off brake pads faster than a Peugeot could break down. It was a driving force in my decision to sell the truck.

I too am curious why you'd specifically choose to keep the rear drums if replacing the fronts.
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TechMOGogy
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Re: Disc brake conversion

Post by TechMOGogy » Tue Oct 25, 2016 8:29 am

I have always been told that rear drums hold better on up hill climbs when offroading, you don't get any squeal when spinning in sand, and they are more protected than disks from rocks and other larger items - could all just be an old wives tails?
I do know that the 2016 Toyota Tacoma has rear drums still - perhaps just Toyota trying to save $
Also, for upgrade and cost benefit, I would rather have the disc's on the front and keep rears as they are - 1/2 the price!
72 Pathfinder | 75 710M 2.7i | 96 350GDT Worker

pinzinator
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Re: Disc brake conversion

Post by pinzinator » Tue Oct 25, 2016 12:03 pm

I did a disc brake conversion on a 1965 Olds Cutlass, it was easy to do since all the parts that were included were designed to bolt right in. The spindles had to be replaced, then just install the calipers and disc. Someone has to fabricate the correct parts for the Pinz, I doubt it would be inexpensive due to the low demand. GM made millions of A-body cars, so converting the Cutlass was relatively cheap.

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Haf-e
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Re: Disc brake conversion

Post by Haf-e » Tue Oct 25, 2016 4:34 pm

Part of the challenge of a disc brake conversion with the 710/712 Pinzgauer is that the stock 16 inch wheels have very little space inside of them - so any conversion would also require the wheels to be changed out to something with more room inside of them to fit the caliper on the rotor. The trail ready beadlock wheels certainly have enough room inside of them - but they are 17 inch rims so new tires would also be required.

I am pretty sure that all of the previous disc brake conversions (such as Classic Sue's) have required the wheels to be moved outward to fit the rotor onto the portal box. Also, nearly all other wheels do not have as much backspacing as the stock wheels - so the new wheels will stick out even more - potentially affecting the handling and stressing the wheel bearings and portal housings.

I am not saying it is impossible - just very challenging... and perhaps it would be to much of a compromise.
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Disc Brake Conversion Kits for 710 and 712 Pinzgauers
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David Dunn
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Re: Disc brake conversion

Post by David Dunn » Tue Oct 25, 2016 7:20 pm

Disc brakes on a gas Pinz is not new, and by no way will ever be cheap, or “self installed” by the layman.
First, the backing plate is a casted part of the outer half of the reduction box. This means to mill off the plate or supply an outer half of the reduction box.... boy, that already sounds cheap. :roll:

SDP had done a disc brake conversions on some 712 (based on 716/18 disc brakes). SDP had determined that the Pinz required dual front calipers to have the proper braking, and single calipers on each of the rears.

The use of disc/drums on vehicles was purely economic, the rear disc assembly required adaptation of the emergency brakes ( usually in the form of another mechanical caliper or drum brake). Around 2005ish, I had a “entry” level GMC ½ ton truck with 4 wheel disc brakes, the following year GMC went back to disc/drums to cut cost for these trucks.

The reasons for not having drum brakes keep mounting. Drum brakes loose basically all stopping power when wet (aka puddle or river crossing, requiring riding the brakes to dry them). Disc brakes retain contact with the rotors all the time and the occasional sand particle will squeal, drum brakes have return springs to reduce the contact to a minimum and the squeal usually ends up a grinding. Drum brakes have a leading and trailing shoes that the momentum of the drum and force on the pedal exerts more stopping force when going forward than in reverse.

Also on a disc/drum system, it also requires a proportioning valve between the different systems to keep the drums from locking due to the additional pressure needed for disc brakes….

And if you still think any form of drum brakes are superior, just think of Mercedes and the Unimogs. During the run of the 406/416 series Mercedes changes over from 4 wheel drum brakes to 4 wheel disc brakes. And this is between the agricultural , municipal and military Unimogs. Customers might have been able the brake system they wanted for a while, but drums went the way of the dinosaur. :wink:

Do a search on this site, maybe some of the old disc brake threads might be here 'post' hacks, and from what I remember, other than the factory type dual caliper type retrofit, they were all single front caliper and of questionable improvement over the drums.
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Jimm391730
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Re: Disc brake conversion

Post by Jimm391730 » Tue Oct 25, 2016 11:28 pm

I drove one of the only disc conversions that SoCal had done, I was NOT impressed -- in fact, it was a reduction in braking confidence (in dry conditions). I'll chalk the lack of performance to SoCal, not to discs.

Since there is a weight shift to the front axle during heavy braking the force is usually about a 70% front/ 30% rear proportion; this can be had with a larger diameter disc, larger or dual pistons (and sometimes dual calipers) on the front, or some combination thereof.

My opinion:
Number one, I'd have to have confidence in a disc conversion performance before taking the plunge.
Number two, the smplest option would be a disc that could fit over the existing hub (replacing the drum) and an adapter plate thatwould bolt to the backing plate to hold the calipers; all would need to fit into the stock 16" wheels.
Number three, changing the hub, going to larger rims, machining or replacing the backing plate, etc. for me would generally negate the benefit that discs would provide. Other than wet performance (and I've lost over 90% of braking after a deep water crossing) I am pleasantly surprised how well the stock drum brakes work, especially after I replaced the failed vacuum booster!
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712W and 710M

one2many
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Re: Disc brake conversion

Post by one2many » Wed Oct 26, 2016 12:41 am

I would be interested in a disc conversion in the same way that I'm interested in any upgrades that improve our Pinzgauers.
That being said I would need to have confidence in the kit in question before I would commit to purchase, the cost of said kit is a huge factor as well. Any kit that's in keeping with the current engineering standard of our Pinzgauers is likely to be pretty expensive but I would be happy to be proven wrong on that last point.

As David pointed out the drums backing plate is part of the portal making a simple/cheap design difficult to come up with without modifying them. For me it would be a big plus if the design of the disc conversion wasn't permanent meaning one could return to drums if needed. The engineering certification and compliance of a big change to the braking system is a prohibitively difficult and expensive process in many countries meaning most of us would likely just fit it and enjoy it and the local registration authorities would be none the wiser. That is until you need to show the legitimacy of your vehicle for any given reason like deciding to sell.

Short answer is YES I would be interested but there are too many factors to discuss in one post, perhaps your friend or you could elaborate a bit on the kit he has in mind and cost etc. Just going on how much its already been discussed over the years I believe the Pinz community would welcome a disc brake option if it ticked all the boxes.
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StuartL
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Re: Disc brake conversion

Post by StuartL » Wed Oct 26, 2016 6:55 am

Thank you all for your thoughts and comments. We'll investigate a little more and post back here if we decide to go further.

On that note: Is there anyone with a 710/712 around Berkshire/UK would would be interested in helping us develop a kit?
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David Dunn
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Re: Disc brake conversion

Post by David Dunn » Wed Oct 26, 2016 3:26 pm

Gut Automotive used to sell a "proper" disc brake conversion.
There are pics of it at the bottom of this page on one of their 712 projects.
http://www.gut-automobile.ch/en/pinzgau ... pinzgauers
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The Trojan Horse... the 1st Pinz used to covertly carry troops into battle .




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Haf-e
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Re: Disc brake conversion

Post by Haf-e » Wed Oct 26, 2016 6:25 pm

Yes - GUT does offer a nice conversion kit - they replace the drum brake backing plate / casting on the portal boxes with a new machined part and a new hub also. This then requires different rims. It is very pricey - if I remember correctly its about $2,000 per axle + the new wheels.
Haf-e

1971 Pinzgauer 710M

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Disc Brake Conversion Kits for 710 and 712 Pinzgauers
www.klugewerks.com

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David Dunn
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Re: Disc brake conversion

Post by David Dunn » Wed Oct 26, 2016 7:16 pm

For some reason 5k sticks in my mind , not sure if $ or Euros, or how much or what it included... I've slept a few times since then. :roll:

The conversion "could" have been new complete outer axles/portals assembly and brakes setup from a TD. Then use TD rims.

IIRCC, Vinces' old race 712 had the original rear 2 axles backing plates machined off and adapters were fitted to hold the calipers, and the fronts were TD's outer axles housings with steering knuckles (all original TD parts). The rear hubs would have been re-drilled to fit the TD rims and rotors. I do remember they were TD rims, as I had bought the spares for the Pink Cow. :P Now that truck did show people the improvement of the TD's brakes on test stops, as it did make bug splat out of a few passengers on the inside of the windshield. :mrgreen: ... In my defense, I did tell them to hold on :twisted:
Though I have never tried hard, GG doesn't stop as quickly or abruptly. But that has to do with the ABS,ETC and EBD... and auto trans. :lol: :mrgreen:
.
The Trojan Horse... the 1st Pinz used to covertly carry troops into battle .




ATL Pinzgauer XM 718K TUM(HD) 6x6 FFR (aka The Green Grail)

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