I am trying to determine what the minimum rotor thickness is to be able to re-surface the rotors on a 1991 F-150 4x4. My measurements indicate the present thickness is 1.156 inches. I can't find a spec. for what the minimum is and it is not stamped on the hub like the Haynes manual suggests. Thanks!

 

Well like the Haynes manual suggest it should be cast or stamped somewhere on it try scraping the rust scale off of it in places, and see if you can find it other wise if you have a local machine shop or Ford dealer they should have a book with that spec. (expecially the machine shop because they have to know what the spec is due to it bieng supposedly illegal to turn one below that number)

 

Also any brake shop will be able to look this number up for you. Don't be surprised if the guy knows the answer off the top of his head.

 

.96" is considered throw away thickness, so it must be above that a considerable amount,

Where you have 1.156", I would say it would be safe to turn them, but price new ones, it may supprise you how cheap they are. or they may be expensive too.

you could probly take .020" to .030" but if there really bad on runout, or if you have underlying rust it may take more then that to clean them up.

 

Thanks guys. Pep Boys says it's 1.12. Hmmmm....Now I am wondering about the 0.96 vs. the 1.12. Unfortunately I think the stamp must be on the back of the rotor because I have really searched for it on the front.

 

If they're at 1.156 now, then there's now way that .96 is the throwaway limit. That's way, way too much steel.