[MSrunner]

This is the third time in 80K miles that my rotors have caused a bad vibration when applying the brakes. I do not do a lot of heavy braking or running through water. I have been lead to belive that this is something that Ford owners have to live with. Any recommendations?

 

[w_huisman]

Do some searches on here and elsewhere on the net. Lots of good info.

Here's one ... LINK

I had a vibration as well a while back. Only when I applied the brakes at over 50mph. The rotors were slightly warped. Had them turned for $12 and they've been great for the last 5,000 miles. I'm really impressed with the braking system on this truck, compared to my old 95 6.5TD Suburban.

 

[FMTRVT]

Well there not really warped. They may be hot spotted or have thickness variation.

During those three times in 80k, were they turned? On the vehicle or bench lathe?

First if it was a bench lathe, chances are better then not they are turned with too much runout in them so the issue would just some back in 5-15k miles.

Second is if they had developed a hard spot in them. Turning, if on the vehicle or bench lathe, will never remove that. And the issue will return.

The better situation is just to get new rotors, and they don't have to be cryo'd or slotted or anything else, and a set of pads that are more abrasive to the rotor. Performance Friction Z pads are my recommendation.

Keep in mind though that any rotor that is installed on the hub with a runout higher then 0.0015" (and I prefer 0.0010") is going to have a probable issue in the future. Don't matter what the pads, if the rotors have slots or whatever. The job needs to be done correctly.

 

[w_huisman]

Can you define the term "runout"?

 

[MSrunner]

Laterial movement of the rotor.Rotor runout can be measured by placing a dial indicator against the face of the rotor and turning the rotor.

 

[beckercup]

i ditched my stock rotors and pads at abut 10k miles. I haul a 32 foot race car trailer that weighs in at 7k pounds loaded with the car. I installed slotted and drilled rotors and Raybestos Fleet pads. HUGE improvement over stock

 

[w_huisman]

Laterial movement of the rotor.Rotor runout can be measured by placing a dial indicator against the face of the rotor and turning the rotor.

Apparently runout is a spec supplied by the rotor manufacturer? So it's something you can ask the parts guy to find out for you?

 

[Strokin' 6.0]

Any competent parts guy should be able to tell you what the max runout is on your specific application. Personally, I think that 0.0015" is too much; I'd stick with 0.0010", like FMTRVT said.

 

[w_huisman]

Good stuff guys! Thanks!

 

[FMTRVT]

The vehicle manufacturer gives the runout spec. The supplier of the rotors has one spec, the supplier of the hubs another. The Ford spec in the service manual for the mechanics is 0.0015" maximum. However, on the assembly line for new vehicles it was 0.0010". In my past employment we did a lot of tests on the 99 up Superdutys and it was typical to get about 0.0005 to 0.0007" when installing Ford OE rotors on the test vehicles. The hubs would not have any rust buildup on the mating surfaces though, which can be important.

The change in hubs midway during the 1999 MY was to lessen runout during operation as the bearing pack has some play in it. The current spec I believe was issued during the 2000.5 model year. I remember at the initial launch of the Excursions (which are more prone to feeling the issue) the rotors were being turned on the assembly line with Pro-Cut on-car lathes to improve the runout due to either rotor and hub supplier new specs not being in the pipeline.

In the field the issue is assembled runout (aka TIR - Total Indicated Runout). No machined part is perfect. The hub has a degree of runout and so does the hub. If both are assembled with the highest runout in the same clock orientation, you will have the highest runout possible. If they are assembled where the highest runout of the rotor is aligned to the lowest runout point of the hub, you will have the minimal runout you can achieve with that assembly. That's the goal.

Machining the rotor on the vehicle with the rotor tightened to the hub generates a low runout. If the rotor is machined on a bench lathe, the cones and adaptors will not be perfect (remember no machined part is) and will induce a certain degree of runout into the resurfaced rotor. Then your left with the assembled parts issue.