Gary Lewis Posted August 22, 2019 Share Posted August 22, 2019 Jim said it... the F250/350 uses the same calipers and wheel cylinders. Heck, I am using the big F450 master cylinder on my single piston F150 calipers. Pedal does not move down much but I have NO complaints. I just wonder if one of the other master cylinders might be even a bit nicer? I get that pedal pin position is just leverage and won’t change braking, but Jan said moving it made a world of difference. I will probably try the hydroboost pedal with the F250 master out of the ‘89 if the stud spacing matches... Yes, Jim said it. But, he also said I have the later calipers, which may be bigger. The rotors are slightly bigger, so maybe the calipers, or more correctly the pistons are. Anyway, I'm gonna give the F450 setup a try. Some day. After I win the RSK battle and get a short block 460 and install the heads and intake. And, and, and.... Link to comment Share on other sites More sharing options...
Blacktop Posted August 22, 2019 Author Share Posted August 22, 2019 Blacktop, nice job! I am always happy to see a new approach and I look forward to your report on how your set up performs. It looks great! I know this thread has taken a turn, but I did want to add a couple of notes for Gary and anyone else going for the F-450 hydroboost conversion. I don’t know where else to document this... When Jan did his conversion in his 1986 F250, he used the existing cast iron master cylinder and HD vacuum brake pedal. He was happy with the braking power, but in time the cast iron master cylinder failed. He wanted to get away from the rust that grew in the stock MC, so I ordered him a F-450 hydroboost master cylinder and reservoir (the large diameter bore). He said he had to shim the MC out about 2mm to prevent the rod from applying constant pressure to the master cylinder. He also said that the pedal feel went from nice and soft with aggressive braking to hard as a rock with a lot of force needed to stop the truck. He said it felt like manual brakes without power assist. He said it was awful. So he modified the vacuum pedal by moving the pin to the hydroboost position. He said the difference was HUGE. Night and day. It stops way better with only a fraction of the force needed. (He also said he no longer needed the 2mm or shim to prevent pressure on the MC). Great, we already knew this, *but, he says the cast iron master cylinder set up might still have had a nicer, softer, pedal feel. Our trucks don’t particularly need the large master cylinder volume because of the smaller wheel cylinders and rear drum brakes vs. discs. So is the better choice an aluminum master cylinder from a F250/350 and a smaller bore? Perhaps the higher pedal pin is to give the leverage needed for the bore size? When I set up hydroboost on my crew cab I may strongly consider using the smaller bore master cylinder. I think I might still want the hydroboost pedal to match the booster, but that might be up for debate as well. Perhaps the pedal matching the master cylinder is more appropriate? The higher pin with the F250 master might make require less force but might be too “touchy” if the resistance is too low. I don’t have answers yet, just throwing this out there since it is news to me... Interesting point regarding the best MC to use. I'm going to try using the stock size '84 cast iron mc on my hydroboost and see how it goes. I have a stock disc drum system other than the hydroboost I'm soon to fit. With the vac type brake pedal, I think the angled hydraboost mounting bracket from the mustang will make it work as the angle appears to be good. If after fitting, I am not happy, I might try moving the pedal pin. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 22, 2019 Share Posted August 22, 2019 Jim said it... the F250/350 uses the same calipers and wheel cylinders. Heck, I am using the big F450 master cylinder on my single piston F150 calipers. Pedal does not move down much but I have NO complaints. I just wonder if one of the other master cylinders might be even a bit nicer? I get that pedal pin position is just leverage and won’t change braking, but Jan said moving it made a world of difference. I will probably try the hydroboost pedal with the F250 master out of the ‘89 if the stud spacing matches... Jonathan, The master/ slave ratio will determine multiplication after the pedal, but the pedal is where you get your feedback, so I can definitely see that moving the pin will change how the brakes feel (to you. not how they perform) Heck, a mechanical linkage can be set up to be progressive -or regressive- but it is the ratio of pin to pivot and pedal to pivot that determines travel and effort for the driver. That is why I wanted to separate pedal ratio from hydraulic ratio. Link to comment Share on other sites More sharing options...
Ford F834 Posted August 22, 2019 Share Posted August 22, 2019 Jonathan, The master/ slave ratio will determine multiplication after the pedal, but the pedal is where you get your feedback, so I can definitely see that moving the pin will change how the brakes feel (to you. not how they perform) Heck, a mechanical linkage can be set up to be progressive -or regressive- but it is the ratio of pin to pivot and pedal to pivot that determines travel and effort for the driver. That is why I wanted to separate pedal ratio from hydraulic ratio. My understanding is that the higher pin gives you greater leverage and less pedal effort to apply braking. The larger F450 master cylinder requires more force, not because of volume but because the force is distributed over a larger plunger surface area. Gary, the F450 wheel cylinders are absolutely gigantic compared to any of the pickup brake components. If the later D60 cylinders are bigger it’s nothing compared to the F450, which also has huge dual piston rear disc calipers. I don’t think you *need the F450 MC volume... but I promise you won’t be unhappy with it either. I’m not unhappy with it on my F150, and if I don’t like the F250 master on my crew cab I’ll be putting the F450 one on. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 22, 2019 Share Posted August 22, 2019 My understanding is that the higher pin gives you greater leverage and less pedal effort to apply braking. The larger F450 master cylinder requires more force, not because of volume but because the force is distributed over a larger plunger surface area. Gary, the F450 wheel cylinders are absolutely gigantic compared to any of the pickup brake components. If the later D60 cylinders are bigger it’s nothing compared to the F450, which also has huge dual piston rear disc calipers. I don’t think you *need the F450 MC volume... but I promise you won’t be unhappy with it either. I’m not unhappy with it on my F150, and if I don’t like the F250 master on my crew cab I’ll be putting the F450 one on. . Did I say volume and not piston crown area? Sorry. Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 22, 2019 Share Posted August 22, 2019 . Did I say volume and not piston crown area? Sorry. Jim - Didn’t catch it, but you are right, it is the surface area. Jonathan - I know I’m going to like the later style M/C over the cast iron one, and since I have the one from the F450 I’ll use it. It’ll look SERIOUS under the hood. 😉 And, I’ll bet I like it. I’ve never liked the brakes on Big Blue as they are soft and have too much travel, and I’ve always been impressed with how hard and quick those on Blue are. So to have BB’s quick and firm will be a joy. 👍 Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 22, 2019 Share Posted August 22, 2019 Jim - Didn’t catch it, but you are right, it is the surface area. Jonathan - I know I’m going to like the later style M/C over the cast iron one, and since I have the one from the F450 I’ll use it. It’ll look SERIOUS under the hood. 😉 And, I’ll bet I like it. I’ve never liked the brakes on Big Blue as they are soft and have too much travel, and I’ve always been impressed with how hard and quick those on Blue are. So to have BB’s quick and firm will be a joy. 👍 Just remember not to put yourself through the windshield. I had a hard time letting those parts go to a better home than mine. *sniff Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 22, 2019 Share Posted August 22, 2019 Just remember not to put yourself through the windshield. I had a hard time letting those parts go to a better home than mine. *sniff I’ll try to remember to be gentle with the brakes. And I really appreciate all the work you did to remove and ship the parts, as well as to share them. 👍 Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 22, 2019 Share Posted August 22, 2019 I’ll try to remember to be gentle with the brakes. And I really appreciate all the work you did to remove and ship the parts, as well as to share them. 👍 I'm glad all those 450 parts went to good homes. The cab was probably the cleanest one I've seen around here, and Theo's '95 Flareside was so rotten it was dangerous. Bill ended up with the entire dash (in gray) and the AC system with underhood box/plenum. The Zf and parking brake are still over at Don's, afaik. Those 10 lug Superduty axles are hard to find! And they were in great shape.... right out to the tires. IDK, but I hope they didn't go through the shredder. Link to comment Share on other sites More sharing options...
Ford F834 Posted August 22, 2019 Share Posted August 22, 2019 Jim - Didn’t catch it, but you are right, it is the surface area. Jonathan - I know I’m going to like the later style M/C over the cast iron one, and since I have the one from the F450 I’ll use it. It’ll look SERIOUS under the hood. 😉 And, I’ll bet I like it. I’ve never liked the brakes on Big Blue as they are soft and have too much travel, and I’ve always been impressed with how hard and quick those on Blue are. So to have BB’s quick and firm will be a joy. 👍 Gary, you will love the results. That was the one thing I hated most about driving the crew cab in town was inadequate brakes. Perhaps my vacuum booster wasn’t up to par, but that big heavy beast didn’t stop worth beans. I could make them lock up if I really stood on the pedal, but until they locked up they felt soft and unresponsive. Made me think of the runaway 18 wheeler song where the guy thought about opening up the door and dragging his foot 🙄. The hydroboost will catch you by surprise the first couple of times you use it, but you catch on fast 😉. Link to comment Share on other sites More sharing options...
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