Do you check that thickness with an ultra-sound? Some fancy plate work would get you there too, yanno what I mean? Or even some CAD files on a solid modeling program.

I can assure you all after being in the machining industry for 20 years +, there is NO extra metal laying around on a caliper ........... not for the sake of liability anyway.

Out of the MILLIONS of caliper castings poured daily, each ounce of iron saved adds up to profit. The manufacturer has eliminated all of the weight and thickness that they feel comfortable with.

I agree that most manufacturers have gone to a single casting machined left OR right which saves in machining costs .................. but modifying a part like this is Russian Roulette.

 

why doesn't everybody just stop giving him the rigamarole of that is jsut too dangerous and tell him to measure it?

most calipers are shaped like a hollow cup. just compress the caliper all the way, and measure the thickness of the cup, and the caliper wall put together. then extend the cup all the way, and measure the thickness of the cup by itself. subtract the thickness of the cup from the total, you will have your wall thickness. you could use a 1 inch micrometer, or a 2 inch micrometer with a ball attachment for measuring inside diameters. you can now grind it down to the thickness you would feel comfortable with. do this with one wheel, and put it on. go out, and make a few panic stops, and if your caliper doesn't blow up, repeat the process with the other. I would think that 3/8 (.375) inch of cast steel would be able to hold the pressure of braking, when you look at the little fittings, and hoses that are used. I am pretty sure that pressures don't go above 800 psi.

 

I am just informing someone of an option instead of buying a new set of wheels. Calipers and brackets are ground all the time in order to clearance for wheels and I have never heard of a single failure.

Does this mean that its OK to do and is "legal"? NO. But what makes it "wrong" if its done all the time and WORKS, maybe im just to practical and cant see everything from a machinists or engineers point of view.

All im saying is that people grind calipers, without failure, so you make your own desicion.

 

I'm going to agree that lots of offroad guys grind calipers, but on one of these trucks I wouldn't do it. Wheels are cheap compared to the price of these brakes.

 

When I bought my '98 Ram, aftermarket wheels with the correct offset for my big tires were slim pickins' - so I turned down the rear drums' OD enough to clear the rims' ID.

225K miles and still on the original shoes.

p.s. I'm also a machinist with a young family...

 

I'm bettin cast iron (which is brittle) and not cast steel, but I could be wrong.

I could be wrong here to, but your probably closer to 2,000psi in a panic stop.

I think we have 4-2" pistons, and a 2" piston will see 6,283 pounds of force on it's face at 2,000psi of line pressure.

If the 2,000psi line pressure is accurate, then the caliper will see a total of 12,566lbs of clamping force.

At your suggested 800psi of line pressure, you are looking at a clamping force of 5,026lbs.

You be the judge.

 

You turned down the cooling fins correct? Or the flange at the drum face?

I don't think you'd be so cavalier if your family was involved in an accident due to modified OE brakes.

 

Not sure were you are planning on doing the trimming but the FEA may help decide.



Obviously, you should start taking away material in the higher stressed areas.

 

Actually, Fronts see 800-1000 psi, and the rears see 300-600 psi.

 

OK maybe wheel spacers seem to be the most logical course of action under the circumstances, but i would need front and rear at about 350 bux and then it doesnt make the rim and tire deal such a good deal for the added wear and tear. I am going to think about it though thanks for everyone on there comments.. heres the rim on ebay. comments?
http://cgi.ebay.com/ebaymotors/17-in...spagenameZWDVW

 

Don't forget any decent steel alloy whether cast, extruded or forged, is going to have tensile strengths at least an order of magnitude higher than what the hydraulic pressure can be.

 

True enough, but I'm sure these are cast iron, and we aren;t talking tensile strength ............ this would be akin to bending strength ............ very different animal.

 

Well, if they're not cast iron, they're forged... a much stronger method of forming.

If the stress is not tensile (which part of the caliper's cross section does indeed experience), then it's a compressive load - which carries even higher psi ratings.

Thanks for helping to make my point.

p.s. the material hypothetically removed is not in a critical stress area of the casting/forging.

 

Bending is essentially tensile on the top and compression on the bottom or vice versa. in this case it will be compression on the top and tension on the bottom. While most of the force will be this bending, due to the moment being at the top (near the center) and sweeping to the midline as it moves out, the moment becomes less critcal. near the leading edge, there will be a torsional force that will be perpindicular to the moment. Blah blah blah

If indeed they are forged then you are looking at higher tensile and yield strength. Obviously after you grind it would be best to smooth and polish, further reducing any stress concentrations.

Anyways, if one does fail, you have two more right?

 

i would think that the extra iron that you would be grinding off would take away some of the heat dicipation, as in not drawing heat away from the pistons and center of the caliper as well, less metal heats up quicker which is bad for brakes, just a guess, dont hold me to it