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5/19/2011 9:08 am  #1


something is to thick

it is either my pads, rotors, caliper pistons, or a combination there of.  when I rebuilt my rear Jag calipers I purchased new pistons, new pads and new rotors.  when I got it all together I found that the distance between the pistons and the rotor was about .02" thinner than the thickness of the pads, so now I am faced with a decision, I can make 4 thin mettle spacers out of some thin sheet steel to space the halve of the calipers apart or take a flat piece of steel, place some sand paper on it rough side up and shave .02 " off of each pad.  If I make the spacer I will have to use more shims behind the rotors to center the rotors in the calipers and will have the extra time it will takes to make the spacers, but will have full pad life.  if I shave the pads shimming out the rotor will be easier but the pads will have a little less life.  All opinions REQUIRED what would you do and why


If it isn't broken..... modify it anyway!!!!
 

5/19/2011 9:44 am  #2


Re: something is to thick

Rear brakes wear at a much slower rate then fronts. Also they equal maybe 15% of your stopping . Can the pads be surface ground flat? Are you also sure they are the matching parts so something else doesn't occur?

Or can the caliper and pads assembled slide over the rotor unbolted? Meaning maybe something is not machined to the correct location. I would rather fix it right once I could.

Last edited by Ralphy (5/19/2011 9:49 am)

 

5/19/2011 12:10 pm  #3


Re: something is to thick

Ralphy wrote:

Can the pads be surface ground flat?

that is why the sand paper in placed on a pice of steel.  as the pad is worked over the paper it will slowly remove material across the entire surface.

Ralphy wrote:

Are you also sure they are the matching parts so something else doesn't occur?

good news for me is that the same parts were used for almost 30 years and the ones that were different were WAY different so I know I have the right parts.  my guess is that all three replacement items (5 in total) have a + or - tolerance and all 3 happened to be on the + side.  we are only talking .02" total, and with 2 pads, 2 pistons, and 1 rotor each one would only have to be off by .004" to create the issue I am having.

Ralphy wrote:

Or can the caliper and pads assembled slide over the rotor unbolted? Meaning maybe something is not machined to the correct location.

Thats part of the equation.  these Jag calipers are hard mount (no floating parts except the pads) and a piston pushes from each side. because of that shims need to be used between the rotor and drive axle to center the rotor in the caliper.

Ralphy wrote:

I would rather fix it right once I could.

I couldn't agree more thats why I was thinking spacers between the caliper halves but then I thought next time I do the brakes the rotors will probably be turned down so it will not be an issue and I probably will only have to do the rear brakes once maybe twice in the next 30 years.  it's not like this car will be seeing tons of miles.  thats why I am wanting other opinions.  thanks for the input!!!


If it isn't broken..... modify it anyway!!!!
     Thread Starter
 

5/19/2011 12:43 pm  #4


Re: something is to thick

Let me ask again, with the calipers loose/free and pads installed, can you slid the caliper assembly onto the rotor? If so do you have enough clearance plus .020, pads to rotor?

I edited this in!
Just looked at what I think you have. Opposed piston fed by a crossover line so no fluid runs from one side to the other. Personally I would not fool with the caliper. I would either cut the pistons shorter or remove pad material. If you do sand the pads as you say, measure the pad thickness before you start. Then as you go measure the thickness at all four corners of the pad making sure of even removal.

Last edited by Ralphy (5/19/2011 1:01 pm)

 

5/19/2011 1:01 pm  #5


Re: something is to thick

Sorry I didn't answer that directly before. with the caliper loose the gap between the pads is .02" to narrow to slide the rotor in between them.


If it isn't broken..... modify it anyway!!!!
     Thread Starter
 

5/19/2011 1:08 pm  #6


Re: something is to thick

Added above,

Just read again, all opinions required, I guess I met your requirements! LOL

Last edited by Ralphy (5/19/2011 1:15 pm)

 

5/19/2011 3:40 pm  #7


Re: something is to thick

Ralphy I appreciate your input.  being a Corvette guy I will give you one more piece of info just to make sure your opinion has all the facts   Jag calipers are as you said two piece they are held together with 4 bolts.  Kits that convert the solid rotors to vented rotors use a 1/4" spacer between the two halves of the caliper to get the extra clearance.  I was thinking of doing the same thing only using really thin steel to accomplish the same thing.


If it isn't broken..... modify it anyway!!!!
     Thread Starter
 

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