Need a little brake help. Give you some backgound info. This is in a little hot rod 1941 pickup weighing about 3000 lbs. Has a 48 ford straight axle with speedways disc kit up front, a ford explorer 8.8 with drums in the rear. New master cyl, new rubber hoses, 3/16 brake line all around and an adjustable proportioning valve. It is set up with drag link steering (side steer). Here is our dilemma: in a real easy stop the brakes work fine, in a medium or quick stop the truck pulls hard to the right and wants to lock the right front wheel. In a hard stop it wants to start to lock the right front first but quickly equalizes and will brake fairly straight and hard. It is like the fronts are not equalizing. I have bled this system many many times thinking I had an air bubble trapped in the left side. We just recently changed over to the discs up front over the drums. The drums would do the same thing. Master cylinder is on the firewall. I have tried it with and without residual pressure valves no change. If you brake very lightly and let the brakes equalize first brakes seem to act like they should. The only thing I have not tried rerouting is the front hard lines. They are not equal lengths. The line comes from the master cyl down to a tee at the front crossmember. from the center of the crossmember it sits about 2" to the left. From the tee a line goes to the left and right rubber hoses. The right hand steel line is about 2" longer than the left. I don't see any problems with this but it is the only thing that I haven't done. Wheel bearing are tight new king pins ( there is a slight amount of wiggle between the kingpin and the axle, nice and tight in between the king pin and bushings. 3/8" toe in. 4- 5 degrees caster. Truck drives straight with no pull, problem only shows up in a quick medium brake. Any suggestion I am about to pull my hair out.
I am now running disk brakes up front. But the drum brakes acted the same way. Both caliper seem to move equal distances when brakes are applied. I have adjusted proportioning valve to the point the rear brakes are not applied. Did this to see if the front was the problem or if the rear was the problem, it is definitely in the front brake system, but I cant seem to identify the problem.
I would make sure the calipers are moving at the same time. it could be the left caliper is sticking at the start of braking. though since you said it did it with the drums to I would look for corrosion or a blockage in the steel lines?
If it happened with the drums and the discs' I would suspect something like bad suspension alignment etc. Check loose kingpins, bent frame, steering linkage,tie rods etc etc. Nick
Everything on the suspension is new except the springs and the axle itself. There is a slight amount of play in the king pin where it slides through the axle. King pins are tight but like I said there is a little slop where the kingpin is secured in the axle. bore looks good but here is a little play that I cant get shimmed out.
I know the speedway disc brake kit I installed was not a PERFECT fit. I had to grind on the caliper brachet where it seated to get a good fit. Then had to do a bit of filing, or grinding, to get one caliper freed up so it wouldnt stick inside the brachet. It was real tight on the slide pins, so I opened up where the caliper sets. This may not be your problem, but thought it might help. Was on a 46 ford car.
I will double check that tomorrow. Right side will lock up almost a second faster than the left. We are going to pull the left hand line and tee tomorrow and check for an obstruction. If you put slight pressure on the pedal before you stomp on it it will brake straight. If you just do a medium panic stop the truck tries to swap lanes. So frustrating.
You could have a bad brake hose that is restricted internally. Buy 2 new ones just to rule it out, they're cheap enough. I don't think that you have an air or line problem. The next thing I'd check is for a sticky caliper, also make sure they're on tight. Make sure your front wheel bearings are not loose, especially on the side it is pulling to. Double check anything in the front end for looseness. Bob
do you have a residual valve on each front disk or just one before the tee?? if you have one for each it sounds like the one on the left is not holding pressure, pushing the pedal slow would let it build pressure equally(both sides) and when you hit the pedal fast it does'nt have time to equalize and the right side locks up until pressure equilizes then the left one comes on
I had a residual valve plumbed in before the tee, it is now removed no difference before or after. Master cyl is above the brakes (mounted on the firewall) therefore I shouldnt need one. Re tightened everything new brake hoses just put on yesterday no difference. I will be rechecking calipers tomorrow to see if they are binding. Thanks for the replies.
Long story, short answer... Back in 82 I was fleet manager for a farming operation. The main office was 300 miles away and when we ordered our 1 ton flatbed trucks (8 of them ) the main office had them delivered to us on the company semi trucks. Included in the order was another 3/4 pickup and a bronco. All 10 trucks had a very similar, curious habit of locking the right rear wheel on anything slightly more than gentle braking ! I did the usual things, even sent them one by one to the local ford dealer..No answers! After 6 months of tearing my hair out I lucked onto the problem. Our flatbed driver was using big binder chains to tie the rear axle down. Every one of them had the right rear steel line crushed almost flat by the chain/binder...He tied them all down the same way, and the flat spot was not 2" apart on any one truck ! Fast forward 12 years or so..I bought a cheap s10 pickup from my buddies wrecking yard..The left rear locked up with medium/hard pedal.. You know it did not take any time at all to find the trouble ! Pulled the drum and checked it out,all ok.. Quick scan of the hard line, BINGO ! Crushed by the j-hook from the tow truck.. Short answer....Look closley at the hard line for any super tight bends or flat spots ( maybe floorjack in the wrong place, or axle hitting in bump ?? ) Let us know what you find. Good luck. Dave
Since the problem existed when you had the drums on the truck and has not changed after swapping to disk that should eliminate everything you changed in the brake swap from the issue. I'd be taking a serious look at the hardline on the left side to make sure that there wasn't a kink in the tubing or a smashed spot. If there is a brass fitting on that side that doesn't have a matching fitting on the right side check that fitting. I ran into one situation on one of my rigs where someone had installed a brass fitting that had an extremely small orifice in it. (it was a natural gas fitting stuck in a fuel line but you get the idea). Look for something that is different from one side to the other. Have you tried swapping front tires side to side? When I used to do front end work every day I saw a lot of problems caused by the tires that got blamed on suspension,steering and brakes. Something as simple as the tire pressure not matching might cause issues.
Check to see if the Rotors are the same thickness.Any more than .010 from side to side can cause problems, The same is true with the drums, but the fact that you can adjust the shoes on the drum brakes compensates for the differance. If you are experiencing a soft to low pedal make sure the rear brakes are adjusted correctly.
Well I rechecked calipers for movement and both calipers slide freely. The only thing I have left that I havent pulled apart apart is the front hard lines. There are several brass fittings on the tee . I am going to check the tee and the left hard line. I have swapped tires from side to side. I have adjusted rear brakes. I have checked front end alignment. I have completely tightened up the front suspension. I hope it is the hard line. I have to remove radiator and misc to get to it. Will let you know of the outcome.
I removed the line replaced the tee with fewer fittings, line looked ok but went ahead and made a new one. I will get it all back together and test drive this afternoon.
Still pulls to the right in a med quick braking action. So we swapped front rubber lines side to side re-bled and tried again. Same thing pulls to the right. Hard lock up style braking the truck locks up straight down the middle of the road, light and slow braking action straight and true. Truck drives right down the middle of the road no hands. No unusual tire wear patterns.I am at a loss.
You didn't elaborate on the front axle setup so this is general info. We have seen serious steering input problems with radically dropped axles and parallel leaf spring arrangements in that under hard braking the large moment arm due to the axle drop will generate enough force to "wrap up" the springs pushing the top of the axle rearward causing unwanted steering linkage input, just like you are experiencing, especially if your drag link attaches at the top holes on the spindle. Can also happen with transverse springs with bad spring bushings. Since the same problem disc or drum I would have to say it's not in the brakes.
It is a parallel front and rear spring setup. Axle is out of a 48 ford pu. Factory spring and axle with no modifications. 6.5 inch bolt on steering arm Top side of the drivers side spindle. S-10 manual steering box mounted under the frame with pitman arm pointed up. All linkage was new last summer. This included tie rod, tie rod ends, drag link, shocks ect. Problem was minor with the drum brakes. With disc brakes the pull seems to be amplified.
This sounds like it might be my problem. after looking at the suspension again. You say the axle wants to move rearward but as I look at it I think It would move the top of the axle forward which would make the rear of springs wrap up. This in turn moves the steering arm on the axle which would make it steer to the right. Correct me if I am wrong. Next question is how do I fix it?
The more I look at this I believe that axle wrap that eciguy suggested is the most likely cause. My question is what can be done to fix it without totally re-engineering the suspension. Would new leaf springs help? Change to cross steering? any suggestions?
That there is simple yet brilliant and valuable information you can only get here from experienced people like ECIGUY. I may never need that information but I might one day know someone who does. Thank you ECIGUY and others like you for being there to help.
Have you checked to mae sure that the calipers are not binding on the pins/slides. If they are not moving in and out smoothly on the alignment pins they will stick on hard applications. Are you running a combination valve in line with the brake setup? That would be a valve which combines the pressure differential switch, proportioning valve and stop light switch.
Calipers do slide freely. I am not running a combo valve just a proportioning valve. Looking at the springs today there is a considerable amount of flex in the springs which could allow the top of the axle to move enough for some steering movement. I wish eciguy would elaborate what they did to remedy some of the situations he discussed.
Just thought I would post an update. We decided our problem was spring wrap. We put on new stiffer springs which improved the problem but did not correct it. So we decided to make a link and bracket assembly to try and eliminate the unwanted axle movement. Got everything together and went for a test drive Truck drives and stops like a dream now. Thanks ECIGUY for the heads up on spring wrap.
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