ArdWrknTrk Posted August 2, 2019 Share Posted August 2, 2019 That's sorta why I'm asking the question. It seems to me that properly functioning drum brakes would more easily be able to stop the rotation than disc brakes just given the leverage, not to mention the swept area. Given the reports I've read on hydroboost, and the braking capability of Darth, then..... Look at trucks that carry REALLY heavy loads. You don't see triaxles and semis with discs very often, do you? If I had a set of shoes and a set of pads and compared the area, using the same mu, you would really think. Then factor the reduction in lever for the disc pads and you'd wonder how a truck stops at all. Of course, in a couple of years when we have BEV's we will call it charging our battery.... Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 2, 2019 Author Share Posted August 2, 2019 You don't have hydroboost on Darth, so it is just that the brakes are working correctly? Couldn't all be the big rear brakes, right? No, I do not have Hydroboost on Darth, just the booster from the 1990 parts donor with a new (at the time) MC. I do still have the rear load compensator. Jim, on the tractor-trailers, the air brakes are a lot simpler to make and service as a drum system. The emergency system is a second spring applied, air released, actuator on the back of the service actuator. That way if the air system is damaged or in any way not working correctly, the brakes (usually rear on the tractor and all on the trailer) are engaged. Loads of fun to manually release too. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 2, 2019 Share Posted August 2, 2019 No, I do not have Hydroboost on Darth, just the booster from the 1990 parts donor with a new (at the time) MC. I do still have the rear load compensator. Jim, on the tractor-trailers, the air brakes are a lot simpler to make and service as a drum system. The emergency system is a second spring applied, air released, actuator on the back of the service actuator. That way if the air system is damaged or in any way not working correctly, the brakes (usually rear on the tractor and all on the trailer) are engaged. Loads of fun to manually release too. I've seen, and experienced what happens when an air brake system catastrophically loses pressure. I've never tried (not do I want to) unlocking the brakes. We have pneumatic releasing brakes thanks to George Westinghouse. He made his millions from rail cars. https://en.m.wikipedia.org/wiki/Westinghouse_Air_Brake_Company https://en.m.wikipedia.org/wiki/WABCO_Vehicle_Control_Systems Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 10, 2019 Author Share Posted August 10, 2019 I've seen, and experienced what happens when an air brake system catastrophically loses pressure. I've never tried (not do I want to) unlocking the brakes. We have pneumatic releasing brakes thanks to George Westinghouse. He made his millions from rail cars. https://en.m.wikipedia.org/wiki/Westinghouse_Air_Brake_Company https://en.m.wikipedia.org/wiki/WABCO_Vehicle_Control_Systems Further progress or lack thereof on the disc brakes. First item, rotors would not fit on the adapter pilots, holes were 4.9" ID, adapter pilots 5.46" OD. Had to wait till Tuesday (8/5) to drop them off. Picked them up Wednesday AM and put the right side together in the afternoon less seal so I could check runout. Runout was .007", desired .005" max. Thursday tried old trick, marked rotor and adapter and turn the rotor 180°, runout is now .002". Pressed in new Motorcraft seal (Gary, read TSB 94-19-24 before working on BBs rear hubs) and assembled the completed hub and rotor and adjusted the bearing play. I went to mount the right caliper and found this: Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 11, 2019 Share Posted August 11, 2019 Further progress or lack thereof on the disc brakes. First item, rotors would not fit on the adapter pilots, holes were 4.9" ID, adapter pilots 5.46" OD. Had to wait till Tuesday (8/5) to drop them off. Picked them up Wednesday AM and put the right side together in the afternoon less seal so I could check runout. Runout was .007", desired .005" max. Thursday tried old trick, marked rotor and adapter and turn the rotor 180°, runout is now .002". Pressed in new Motorcraft seal (Gary, read TSB 94-19-24 before working on BBs rear hubs) and assembled the completed hub and rotor and adjusted the bearing play. I went to mount the right caliper and found this: I did some other playing around with a prototype Left Eye Blind Racing and Fabrication sent me for trial. It at least lined up with the rotor fairly well, but had some interference with the rim (courtesy of Pete's Used Parts in Newport News VA). The rotor needs to be at least another 1/4" inward to guarantee clearance. Looking at the EGR instructions, the picture they have shows what appears to be a much taller "hat" on the rotor which would fit with the further in location of the caliper. Bill - You have the patience of Job. Those problems would drive me bananas! (But I may be doing some of that with Sky's Off Road on the RSK, so...) Anyway, is it fair to say you are halfway there? I hope the view is worth the climb. On TSB 94-19-24, while I don't have it on the site I probably have it in hard copy form. However, The Diesel Stop has it via that link. But I'm not sure that Big Blue qualifies for it as BB is an '85 and the TSB says 1986 - 94. And while BB's Sterling has been changed to the long pinion, I doubt anything was done to the hubs. But I'll check it out when I have to go into the hubs. Thanks! Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 11, 2019 Author Share Posted August 11, 2019 Bill - You have the patience of Job. Those problems would drive me bananas! (But I may be doing some of that with Sky's Off Road on the RSK, so...) Anyway, is it fair to say you are halfway there? I hope the view is worth the climb. On TSB 94-19-24, while I don't have it on the site I probably have it in hard copy form. However, The Diesel Stop has it via that link. But I'm not sure that Big Blue qualifies for it as BB is an '85 and the TSB says 1986 - 94. And while BB's Sterling has been changed to the long pinion, I doubt anything was done to the hubs. But I'll check it out when I have to go into the hubs. Thanks! Gary, I have it and the one that preceded it in pdf form and can email them to you. The tool kit for the Sterling says "1985 1/2 special tools. The reason you will want to check the TSB is it addresses the leak problems with the rear wheel seals on the full floating hubs. Seal design was changed from a standard style where the rubber seal runs against the axle tube (first change was to a "multi-lip" design) the final update went to a seal package where both the part in the hub and the part on the tube are fixed and the actual seal is encased in metal and pre-lubed. The actual seal is available from Amazon in the Motorcraft PN. I will get you that PN also. Keep in mind I have been dealing with these fun issues for a bit over 25 years. Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 11, 2019 Share Posted August 11, 2019 Gary, I have it and the one that preceded it in pdf form and can email them to you. The tool kit for the Sterling says "1985 1/2 special tools. The reason you will want to check the TSB is it addresses the leak problems with the rear wheel seals on the full floating hubs. Seal design was changed from a standard style where the rubber seal runs against the axle tube (first change was to a "multi-lip" design) the final update went to a seal package where both the part in the hub and the part on the tube are fixed and the actual seal is encased in metal and pre-lubed. The actual seal is available from Amazon in the Motorcraft PN. I will get you that PN also. Keep in mind I have been dealing with these fun issues for a bit over 25 years. That's good info, Bill. And thanks for the pdf's. I'll get them added to the site as soon as I can so all can use them. The second one doesn't say it replaces the first one, but it would appear to do so. Right? Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 11, 2019 Author Share Posted August 11, 2019 That's good info, Bill. And thanks for the pdf's. I'll get them added to the site as soon as I can so all can use them. The second one doesn't say it replaces the first one, but it would appear to do so. Right? Yes, it seems that way. I got real proficient at tearing down and resealing the left side on Darth's original axle. FWIW, changing the gear set to the later long pinion design does not necessitate hub disassembly, just pulling the axles far enough back to get the differential out. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 11, 2019 Share Posted August 11, 2019 Gary, I have it and the one that preceded it in pdf form and can email them to you. The tool kit for the Sterling says "1985 1/2 special tools. The reason you will want to check the TSB is it addresses the leak problems with the rear wheel seals on the full floating hubs. Seal design was changed from a standard style where the rubber seal runs against the axle tube (first change was to a "multi-lip" design) the final update went to a seal package where both the part in the hub and the part on the tube are fixed and the actual seal is encased in metal and pre-lubed. The actual seal is available from Amazon in the Motorcraft PN. I will get you that PN also. Keep in mind I have been dealing with these fun issues for a bit over 25 years. Swapping to the Scottseal saved my sanity and a lot of brake shoes. Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 14, 2019 Author Share Posted August 14, 2019 Swapping to the Scottseal saved my sanity and a lot of brake shoes. Ok, update, spoke with Glen at EGR brakes this morning, they are machining a pair of deep top hat rotors, the ones the U-Haul E350 DRW and motorhome E350 cutaways use. This should move the calipers in far enough to clear the wheel. Hopefully the caliper mounts will work without any changes. He is sending a "call tag" for the other rotors. I will post the outcome once everything is done. Link to comment Share on other sites More sharing options...
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