Disk brake failure

[jwgreen]

The conversion done on this Patrol used a bracket that was only held on by those 2 bolts therefore not spreading out the load very much. The bracket I have put forward in my design has a plate that bolts to all 6 studs to spread out the load of the braking on these studs. Just food for thought.

Was it Suhail that made the brackets for you?

River, No I ended up working out a deal with the original shop in the end. He can get my brackets from me but they will not work with the Toyota calipers of the other conversion.

[RiverPatrol]

The conversion done on this Patrol used a bracket that was only held on by those 2 bolts therefore not spreading out the load very much. The bracket I have put forward in my design has a plate that bolts to all 6 studs to spread out the load of the braking on these studs. Just food for thought.

Was it Suhail that made the brackets for you?

River, No I ended up working out a deal with the original shop in the end. He can get my brackets from me but they will not work with the Toyota calipers of the other conversion.

Ok, good to know. Yes, I'm pretty sure he said they were ForeRunner calipers. What calipers did you use?

[L60Boerne]

Justin did create the missing link in terms of the bracket and then sourcing new parts. I do not think anyone but qualified mechanics should apply the pieces. These Patrols are not universally alike in some areas like the brake master cylinder and I’ve now bought four Wilwood Brake Master Cylinders and still don’t have the right one. However, the one Plateaucal sized for me is likely right, if I can find it.

So start with Justin’s brackets, disks and calipers then have a certified mechanic size the master brake cylinder and then assemble everything and make sure your rims will fit BEFORE you start or order the right rims from the start.

So far my experience is good, I went up a really aggressive trail yesterday until it vapor locked near the summit, and when I get the right MBC it should stop on a dime.

Rolling and Patrolling,
L60 BOERNE

[RiverPatrol]

Please let us know which Wilwood or other MBC is the 'right' one once it gets figured out.

[jwgreen]

The correct MC is for the use with large GM single piston brake calipers like I have in my setup need a 1 1/8" MC as per Wilwood.

David, The one I brought to you that we couldn't fit that day is the correct one. I just need to fabricate a adapter for it which is in the works and then you will be all good.

As for the difference between Patrols I agree they do have some varying characteristics but I think that the biggest difference is the manual vs hydraulic clutch setup which will likely require a slightly different adapter than the manual clutch setup will. I have collected what I believe is all the specs required to fabricate both adapters for each setup and once I have validated them I will be updating the modification thread.

[plateaucal]

This stuff always makes me nervous. Having worked as a power plant engineer for years I did my share of load calculations. However, I would never go near life safety equipment design. The liability is huge.

But just for grins I ran a quick calculation. Figure conservatively that you could get 0.5 g's from deceleration; Stopping a Patrol would require about 3000 pounds of brake force. Assuming the front brakes are 90% of that each wheel will see about 1350 pounds of force. Factor in a life safety factor of 6 (from my recollection that is correct) and design for 8100 pounds of force at the tread contact. Figure a bolt circle radius to tire diameter of about 5. Multiply 8100 time five to arrive at 40,500 pounds of sheer force in the bolts.

A agrade 8, 3/8" bolt has a tensile strength of 11600 pounds. Shear strength is 60% of that, so 7000 pounds. So you would need six 3/8" grade 8 bolts.

This is just an example, but these things should be considered and yes, fact check my calculations. My 62 year old brain isn't as crisp as it once was.

Now if the caliper bolts are taking any shear load, that is a different animal. And then there is the bracket metallurgy and God forbid if there is welding involved without a certified welding procedure.

The thing is, if you are going to modify anything on a vehicle, be prepared to assume the full liability if something happens. I can smell the lawyers already lining up (expensive cologne won't even cover that up) . So that being said, the above calculations are are for entertainment purposes only, do not use them in real life. If you modify the most important component of your vehicle, do so at your own risk and have the occupants sign a waiver of liability.

That being said, Justin's work does look really nice and I am looking forward to seeing a trail report.

[plateaucal]

Here is a good reference source for evaluating stresses. Wit this information you can look at the various stress due to torque as well as clamping pressures. Then you could send in the bracket design for FEA.

https://ijedr.org/papers/IJEDR1604140.pdf

[plateaucal]

Here is another analysis of a brake system. Really good stuff. Also shows analysis by FEA.

https://ijret.org/volumes/2018v07/i11/I ... 711004.pdf

[plateaucal]

I still have reservations regarding the dual reservoir setup for drum-drum braking. The overall stroke on the Patrol pedal is limited by the original geometry (see parts drawing on service manual). The new dual reservoir system seems like it could stand to have a longer overall stroke based on the Wilwood specs.

What about for disc-drum setups?

Any thoughts?

[Esteban]

I still have reservations regarding the dual reservoir setup for drum-drum braking. The overall stroke on the Patrol pedal is limited by the original geometry (see parts drawing on service manual). The new dual reservoir system seems like it could stand to have a longer overall stroke based on the Wilwood specs.

What about for disc-drum setups?

Any thoughts?

Patrols from 1974 and on have a dual master cylinder. Nothing changes with the pedal travel. Still 1” dia. Drums setup exactly the same.