[Beefye30]

Hey

I’ve just got some new discs and I’m measuring 0.05mm difference in thickness on each disc, high to low. Straight from the box, not fitted yet as doesn’t seem right?

Not a good start 0.05mm when shooting for 0.15mm max run out when fitting,?

car is e65 745i

 

[Doug Huffman]

Whence 0.15 mm TIR and how measured?

 

[Beefye30]

Measured the disc thickness with a micrometer, got 0.05mm difference from position 12 to 6.

confirmed with granite surface plate and DTI

 

[Beefye30]

0.15 max total runout when installed is what the disc manufacturer recommends.

 

[Doug Huffman]

0.15 max total runout when installed is what the disc manufacturer recommends.

That's what I figured, but that's not what you reported measuring in post #1, "0.05mm difference in thickness ..."

 

[u.nanimous]

Not understanding the issue. 0.05mm is less than 0.15mm so why not put them on and do the runout check? Are they OEM?

So you have a granite surface plate? Do you also keep the room at 20°C? Do you have up to date traceability to NIST?

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[Beefye30]

Haven’t fitted the discs yet,
What I am saying is i have 0.05mm error before I even start, fitting and measuring runout.

 

[Beefye30]

/u-nanimous

that’s what I am trying to figure are the discs not ok before i fit them, but yes I will be fitting a testing runout. And no they are aftermarket and I’m dubious of there quality,

yes got a few surface plates not calibrated but checked with a calibrated dti 😝

 

[u.nanimous]

I guess it depends on the thickness variation tolerance but there is still 0.1mm to go for the TIR.
You could just get them turned and hopefully that lessens the thickness deviation.

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