When to replace front brake discs? Min disc thickness for unknown brake discs?

[spinnaker]

I have had my car for a couple of years and was considering what bits I might do before the next MOT in March. The previous owner replaced the rear discs and pads with fresh Brembo disc but not the front. I'll have to look back through the car's receipt history to see when the front brakes were last done. I don't know which manufacturer was used (I may find out from the history later) but I can see no markings on the disc bell or the rim of the disc telling me the min thickness. How do I go about finding out the min thickness to see if they need replacing or not?

 

[Alex]

Thread edited to stop folk having a thrombo.

 

[PeterHoward]

What! Complete tosh! If you take your discs down to that level you're in big trouble!

Thats machining where the disc has been balanced

 

[Alex]

Yeah, probably.....got it off PH

How can you tell if brake pads & discs are worn out? - Page 1 - General Gassing - PistonHeads UK

 

[remarklima]

There's a min width spec for each car and disc, so a pair of calipers and you're set! From memory, the 997 is 34mm thick when new and 32mm is min thickness... But that's from memory so could be very wrong on the numbers!

 

[911UK]

There's a min width spec for each car and disc, so a pair of calipers and you're set! From memory, the 997 is 34mm thick when new and 32mm is min thickness... But that's from memory so could be very wrong on the numbers!

that is correct
34mm new, 32mm minimum thickness

 

[PeterHoward]

2mm is normal, not the 6mm Alex has advised

 

[911UK]

2mm is normal, not the 6mm Alex has advised

i've added a note to the post just in case

 

[PeterHoward]

It doesn't help this forums rating in technical information helpfulness

 

[Alex]

Alright keep your hair on.

 

[PeterHoward]

easy...............

 

[Alex]

 

[911UK]

It doesn't help this forums rating in technical information helpfulness

i believe it has cleared up an internet rumor with fact
2 birds with one stone

 

[Alex]

For reference I just took my brake disc off and took a photo. Land either side of the slot is between 1mm - 2mm, hence why I believed that was referencing the wear limit, as well as being told by a local mechanic and reading it on line. Back marker is slightly less as I just took a flick off it on my lathe cost the face looked a mess..

Photo to prove it happened.

 

[spinnaker]

that is correct
34mm new, 32mm minimum thickness

Perfect, thanks everyone. I measured the disc thickness with a micrometer earlier and one side is 38.3mm and the other was a fraction more. There looks to be plenty on the pads so I'll check back through the history but it sounds like they're fine for now.

I didn't mean to start a ruckus! I appreciate the help.