Truck brakes

[scruffy]

Mark, was there a difference in axle size/bearing size in the two 'official' classes? For example, most (but not all) 1/2 ton run a smaller diameter axle than a 3/4 ton, or if the same size the bearings are usually of a lighter capacity. I beefed a 72 Chev 1/2 ton to 3/4 load capacity, with out changing the whole rear end out. Knowing that the 1/2 ton axle was smaller and the axle bearing smaller. I got bearing chatter from them under heavy loads (cord to cord and a half of green wood), but only noticeable on corners.

 

[Corm]

I've got a 2000 Ford F250 Super Duty, V10, regular cab, long box, 5 speed, 27k miles. So far I've had two sets of brake pads, and one set of new rotors all replaced by the dealer. Last time was about 3k miles ago, and I'm starting to get some surging or pulsing in the brakes again... I really like this truck, but these brake problems are frustrating. Are there aftermarket products that would replace the stock parts and give me some reliable brakes for the long haul? I know I should probably keep hounding my dealer to make them right, but it's a real hassle finding time to get the truck down there for them to work on, and at this point I'd rather just get them fixed, and have them stay fixed. Thanks in advance for any info any of you may be able to provide.

 

[Rowski]

Who's your dealer? Paquin, Heritage, Hayes? My truck is out of warranty so no more free work. My thoughs is that it is a bad/poor design, nothing to fix it, just keep replacing parts as they break. I am still looking for aftermarket ways for correction. I am going to try to get bigger wheel cylinders for the rear drums to get the rears to do more work.

Derek

 

[Anonymous Poster]

You may not get the expected result with a larger wheel cylinder, tried the same trick on my 89 F350, things got worse, the master cylinder did not have enough output to extend the pistons farther than the smaller cylinders. What really appears to be needed is a master cylinder with greater output to the rear circuit. With today's liability issues and anti-lock designs, can't a find master cylinder with appropriate specs.

 

[Rowski]

Did alittle research at the parts store today. The wheel cylinders on the truck now are the largest bore (1 3/16"). The next one down, more comman for non dually, is 1 1/8". So if I want a larger wheel cylinder I will have to do some modifing to the baking plate and/or line routing.

I did have a thought (and it is just that) getting a rebuild kit from an 1 1/4" bore cylinder and have the 1 3/16" cylinder machined out to fit. But as you mentioned the master cylinder does not have enough output. So I'm right back to where I was!

So looks like, as mentioned, the master is the problem. Will look into that and see what I can come up with.

Thanks for saving me some time and trouble.

Derek




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[gordon]

Derek this is just my opinion but I believe your wasting your time with just the larger wheel cylinders. The larger bore might give more braking power so to speak but they will also consume more fluid in the same amount of travel and for the same amount of pedal travel less braking on the rear. The smaller bore might be the ticket less fluid use in the same amount of travel---more shoe power? Do they run the same shoes on the two different brake cylinders?

How tite have you adjusted the rear brakes? How many clicks off of lockup and can that adjustment be overcome so they will run tighter? Have you tried bleeding the brakes just to be sure that you have no blockages in lines and the master cylinder is putting out correctly. No past brakefluid boiling?
Just a few thoughts and questions. If nothing else you sure have me thinking on this one.
Gordon

 

[Rowski]

Gordon,

Halsey post made me rethink it. I have though about the smaller cylinders giving quicker respone initialy but wondered about after the point of initial braking. Basically there are 2 types for the one ton 12x3 and 12x3.5 shoes. The 3.5 being the witdth and 12 being the diameter, The dually usually runs the 12x3.5 which has the 1 3/16 bore. The single runs 12x3 with a 1 1/8 bore. I have not actually seen both sized cylinders but the specs appear to have the same mounting. As far as adjusting the brakes I have had them backed off enough so there was a slight drag, about 6 to 8 clicks of from locking. It seems to help alittle but not enough and the self adjusters don't keep them that tight. I have replaced the fluid by gravity bleeding untill fresh fluid came out then bleed them by having a person holding the pedal. I don't have the proper gauges to hook up to see the pressure in the brake system.

I'm glad your asking the questions and giving ideas, you never know if something simple is missed. My shop teacher at college always told me to remember this "keep it simple stupid!". Beleive it or not it has helped out quite a few times.

Derek

 

[Corm]

Bought it at Paquin's. They've been real good to deal with. No complaints at all about them, just those darn brakes....

 

[Von]

Derek,
Just a thought, why not change the rear drums to disc brakes? I see a lot of big trucks using them. When I had an auto restoration shop we would do race prep on alot of cars and would update the brakes by using larger front disc and changing the rear drums to disc. You might find the brakes off of a step van or something the will work.

Von

 

[gordon]

Good idea Von but he also has to deal with the antilock system as well makes a simple task much more difficult. But I believe your right it is a possible option.

Derek does your rear axle have the load sense bar going up to the bed from the rear axle? The more of a load you have in the truck the more rear brakes you get. I doubt that your truck has this but if it does this could be the root of the problem.
Gordon