Can I turn my rotors?
#1
#3
To answer your question on turning, yes it's possible.
The trick is finding out what yourrun-out is (how warped the rotor(s) are),
and then seeing if you can still have useful spec when you are done turning them.
You'll need a dial-mic and a base for it. I attach mine to the fork,
add a slight compression to the tip past touching the rotor,
then rotate the rotor, observing the maximum and minimum readings.
Subtract the minimum from the maximum and you will have your run-out.
Then take a micrometer and measure the thickness of the rotor. Subtract the run-out
from the current thickness. This is what your rotors will be when finished turning.
If that still meets the spec for minimum thickness on your rotors,
it can be turned to true.
Personally, you should add (imo) .2mm to .3mm to that to allow for future wear,
when making the call.
As an example, my F3 manual shows 4.8 to 5.2 as stock thickness.
The minimum is 4.0mm.
The maximum tolerance for run-out is .30mm.
If the current run-out is .70mm, I have to shave .40 (usually .20 per side)
to get back to the maximum tolerance.
I would shoot for .15 to .20 (again for future wear) meaning, I actually need to take
off .55 to .60mm (or .275 to .30 per side).
If the disc is currently 5.0mm thick, that means I'll end with 4.35 to 4.4mm of meat.
That works and I still have a decent margin.
If the disc was less than 4.75mm? Then, NO I would not pay to turn, I would replace.
At that point, you will be less than my (admittedly, arbitrary) minimum for extended/useful life.
Hope this helps you in your decision process, Ern
The trick is finding out what yourrun-out is (how warped the rotor(s) are),
and then seeing if you can still have useful spec when you are done turning them.
You'll need a dial-mic and a base for it. I attach mine to the fork,
add a slight compression to the tip past touching the rotor,
then rotate the rotor, observing the maximum and minimum readings.
Subtract the minimum from the maximum and you will have your run-out.
Then take a micrometer and measure the thickness of the rotor. Subtract the run-out
from the current thickness. This is what your rotors will be when finished turning.
If that still meets the spec for minimum thickness on your rotors,
it can be turned to true.
Personally, you should add (imo) .2mm to .3mm to that to allow for future wear,
when making the call.
As an example, my F3 manual shows 4.8 to 5.2 as stock thickness.
The minimum is 4.0mm.
The maximum tolerance for run-out is .30mm.
If the current run-out is .70mm, I have to shave .40 (usually .20 per side)
to get back to the maximum tolerance.
I would shoot for .15 to .20 (again for future wear) meaning, I actually need to take
off .55 to .60mm (or .275 to .30 per side).
If the disc is currently 5.0mm thick, that means I'll end with 4.35 to 4.4mm of meat.
That works and I still have a decent margin.
If the disc was less than 4.75mm? Then, NO I would not pay to turn, I would replace.
At that point, you will be less than my (admittedly, arbitrary) minimum for extended/useful life.
Hope this helps you in your decision process, Ern
#4
To answer your question on turning, yes it's possible.
The trick is finding out what yourrun-out is (how warped the rotor(s) are),
and then seeing if you can still have useful spec when you are done turning them.
You'll need a dial-mic and a base for it. I attach mine to the fork,
add a slight compression to the tip past touching the rotor,
then rotate the rotor, observing the maximum and minimum readings.
Subtract the minimum from the maximum and you will have your run-out.
Then take a micrometer and measure the thickness of the rotor. Subtract the run-out
from the current thickness. This is what your rotors will be when finished turning.
If that still meets the spec for minimum thickness on your rotors,
it can be turned to true.
Personally, you should add (imo) .2mm to .3mm to that to allow for future wear,
when making the call.
As an example, my F3 manual shows 4.8 to 5.2 as stock thickness.
The minimum is 4.0mm.
The maximum tolerance for run-out is .30mm.
If the current run-out is .70mm, I have to shave .40 (usually .20 per side)
to get back to the maximum tolerance.
I would shoot for .15 to .20 (again for future wear) meaning, I actually need to take
off .55 to .60mm (or .275 to .30 per side).
If the disc is currently 5.0mm thick, that means I'll end with 4.35 to 4.4mm of meat.
That works and I still have a decent margin.
If the disc was less than 4.75mm? Then, NO I would not pay to turn, I would replace.
At that point, you will be less than my (admittedly, arbitrary) minimum for extended/useful life.
Hope this helps you in your decision process, Ern
The trick is finding out what yourrun-out is (how warped the rotor(s) are),
and then seeing if you can still have useful spec when you are done turning them.
You'll need a dial-mic and a base for it. I attach mine to the fork,
add a slight compression to the tip past touching the rotor,
then rotate the rotor, observing the maximum and minimum readings.
Subtract the minimum from the maximum and you will have your run-out.
Then take a micrometer and measure the thickness of the rotor. Subtract the run-out
from the current thickness. This is what your rotors will be when finished turning.
If that still meets the spec for minimum thickness on your rotors,
it can be turned to true.
Personally, you should add (imo) .2mm to .3mm to that to allow for future wear,
when making the call.
As an example, my F3 manual shows 4.8 to 5.2 as stock thickness.
The minimum is 4.0mm.
The maximum tolerance for run-out is .30mm.
If the current run-out is .70mm, I have to shave .40 (usually .20 per side)
to get back to the maximum tolerance.
I would shoot for .15 to .20 (again for future wear) meaning, I actually need to take
off .55 to .60mm (or .275 to .30 per side).
If the disc is currently 5.0mm thick, that means I'll end with 4.35 to 4.4mm of meat.
That works and I still have a decent margin.
If the disc was less than 4.75mm? Then, NO I would not pay to turn, I would replace.
At that point, you will be less than my (admittedly, arbitrary) minimum for extended/useful life.
Hope this helps you in your decision process, Ern
#5
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Nick
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