Rear Rotor Thickness

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DPDISXR4Ti

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Does anyone know what the rear rotor thickness is? Does it vary at all depending on the model? Like, maybe the Sport models use a thicker rotor?

Just curious, as I was trying to adapt the rear LS calipers to a project car, and the relatively narrow rotor channel in the caliper is giving me grief. I should be able to open them up a bit on the mill, but I was hoping to avoid that.
 
minumum thickness is 12.75mm so max I'm guessing is around 14-15. The backs are solid (non-vented) to my knowledge so I believe that's where your issues are coming from. Alldata shows no special specs on 03 for sport/base etc. so I can assume they're all the same. I'd consider grinding the pads down instead of the calipers, especially if it's on a hot rod.
 
beaups said:
minumum thickness is 12.75mm so max I'm guessing is around 14-15. The backs are solid (non-vented) to my knowledge so I believe that's where your issues are coming from. Alldata shows no special specs on 03 for sport/base etc. so I can assume they're all the same. I'd consider grinding the pads down instead of the calipers, especially if it's on a hot rod.
Click to expand...

Thanks, but they actually ARE vented, not solid. I will say however, they are the thinnest vented rotors I've ever seen. The issue for me is that I'm using a different rotor which is about 20mm thick, so I'll need to both clearance the caliper AND surface the pads if I want to use this caliper.
 
seems like you could take 2-3 mm off each the inside and outside pad and fit?
 
Yea, the pads will be easy. I have some used ones here that came with the calipers that will probably work fine. To machine the calipers however, I'll have to fabricate some sort of fixture to hold the caliper for machining. Not a big deal, but I could have done without that step.
 
last time i did this I had a table grinder. I jimmied a way to suspend the caliper and just applied fluid pressure to make it "compress" around the grinder disc. worked like a charm.
 
Interesting. I hadn't even considered using the caliper's capabilities as an asset in this operation. I have a Clausing knee mill, so my focus is just on how to get the caliper held in a fixed position and let the table do the movement. If I disassemble the bracket from the caliper body, I'll make it a much easier process.
 
DPDISXR4Ti said:
Does anyone know what the rear rotor thickness is? Does it vary at all depending on the model? Like, maybe the Sport models use a thicker rotor?

Just curious, as I was trying to adapt the rear LS calipers to a project car, and the relatively narrow rotor channel in the caliper is giving me grief. I should be able to open them up a bit on the mill, but I was hoping to avoid that.
Click to expand...


First off, minumum thickness is stamped on the rotor, usually the back side, around the edge. All LSes use the same riotor. And as DPDISXR4Ti said, all 4 rotors are vented. You can tell by looking at the area between the inner and outer surface. The vanes mean it's vented rotor. Not to be confused with slotted and drilled. If the rear calipers seem "narrow", it could be because the piston needs to be turned in. You can't push the piston in like on the front calipers because the caliber is also the emergency brake. You will need a piston turn in tool to twist the piston back into the bore. If you need an emergency brake on your project car, you might want to find a different caliper. Like one that uses a small drum brake inside the rotor. I believe GM products use that arrangement.
 
The narrow section I'm referring to is the rotor channel where the outermost portion of the rotor passes through the caliper bracket. No amount of piston turning is going to change the dimensions of machined iron. ;)

Curious, why are you thinking I would not want to use a cable-actuated e-brake? The inner drum setup is nice (Porsche uses it as well), but it adds a layer of complication I have no interest in adapting.

BTW, the caliper piston tool is nice to have, but needle-nose pliers will do the job most of the time.
 
DPDISXR4Ti said:
The narrow section I'm referring to is the rotor channel where the outermost portion of the rotor passes through the caliper bracket. No amount of piston turning is going to change the dimensions of machined iron. ;)

Curious, why are you thinking I would not want to use a cable-actuated e-brake? The inner drum setup is nice (Porsche uses it as well), but it adds a layer of complication I have no interest in adapting.

BTW, the caliper piston tool is nice to have, but needle-nose pliers will do the job most of the time.
Click to expand...


For some reason I was thinking the Ford set-up was the complicated one.

I really don't think you'll want to machine the caliper any thinner. IMHO, you'd be adding a weak area to the caliper. Remember, on the LS, the rear rotors are just a fraction smaller than the front. The reason (if you didn't already know) the rear rotors are vented is because of the high amount of rear brake dialed in. It's part of the anti-dive geometry. The rotors may look thin, but they sure are stout!

So, what's the project??
 
What I've noticed on the factory LS rotor is it's darn near a one-use item. By the time you need brakes on the car, the rotor is worn enough that you are at or under the minimum thickness by the time you clean them up using the factory guidelines to cut them. I believe Ford calls for you to cut them until they are clean then make a final cut of .008. There's just not enough material there to do that on a used rotor. I've looked at 4 different rotors...all were this way.
 
I'm trying to remember how I did this. I had to do 14 years ago on my Fiero because the pads were so thick causing the rims to contact the calipers during hard cornering. IIRC I think I just HELD the caliper (caliper mounted to the frame thing still) with my hand with both pads on it and the grinder (or was it a sanding disc) acting like a rotor. Appiled pressure via a hand vacuum/pressure tool (the kind you pump) with some brake fluid in it. It worked like a charm. I just can't remember if I somehow mounted the caliper or if I held it by hand. I'm pretty sure I held it by hand. Also the pad material came of very quickly IIRC so you'll want to be careful
 
LS4me said:
For some reason I was thinking the Ford set-up was the complicated one.
Click to expand...
I don't think it could be more simple. A cable pulls a lever which acts on the piston to pull the pads against the rotor.

LS4me said:
I really don't think you'll want to machine the caliper any thinner. IMHO, you'd be adding a weak area to the caliper.
Click to expand...
We're talking about an area where there is plenty of metal. It would not surprise me at all to find that these same calipers are used on cars with thicker rotors, and the passageway is machined larger FROM THE FACTORY. Anyone know if the Jag S-type uses a thicker rear rotor? I'm pretty sure the same caliper is used on that car.

LS4me said:
So, what's the project??
Click to expand...
It's a Merkur XR4Ti (note my ID). I currently have T-Bird calipers on there, which are similar to the LS calipers (in fact, both are made by Varga). But the e-brake cable setup is much improved on the LS caliper, and that is precisely what is giving me grief with the T-Bird variant.
 
beaups said:
minumum thickness is 12.75mm so max I'm guessing is around 14-15. The backs are solid (non-vented) to my knowledge so I believe that's where your issues are coming from.
Click to expand...

Digging this old thread of mine up, as I was looking for this info again today. I'm pretty sure the info above is entirely wrong. Everything I'm otherwise finding indicates that the rear LS rotors are 20mm thick and vented. I know the poster quoted above was guessing at the new thickness, but there's no way a rotor with a min spec of 12.75mm is going to be 20mm when new.

This topic came up again with my custom use of the LS calipers, since I recently changed from using Contour front rotors to Focus rear rotors. They're both about 10" but the Focus rotors are solid - about 11mm. Using min thickness comparisons of 18mm (LS) to 10mm (Focus), that gives me 4mm more potential piston travel (18 - 10 = 8/2 = 4). Wondering if that puts me into the danger zone?
 
# of Bolt Holes : 5
Bolt Circle Diameter : 4.25"
Brake Rotor Diameter : 11.33"
Brake Rotor Discard Thickness : .73"
Brake Rotor Thickness New : .79"
Brake Rotor Type : Disc Brake Rotor Only
Center Hole Diameter : 2.54"
Height : 1.28"
Maximum Lateral Runout : .004"
Mounting Type : Type K - Rotor Only. Wheel Studs Are Pressed Into The Hub Only. The Rotor Is A Loose Fit On The Hub & Is Retained By Either Machine Screws Or The Wheel Nuts. See Diagram For More Information.
Vented / Solid : Vented
 
here's what I have -

opps - sorry - I have the StopTech technical drafting copy of the rotors - but it's too big to upload....

ok - converted to jpg...

Capture.JPG
 
I just measured a new '02 rear I have setting here. Digital caliper says it's actually .797 inch thick, or 20.2 and a fraction MM.

KS
 
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