Check the runout on new brake rotors?

Joined
Mar 30, 2020
Messages
66
Location
SF Bay Area, CA
I watched a video demonstrating how to check the runout with a dial meter. Unexpectedly, the runout was measured out of range for a brand new replacement rotor! It wasn't a problem with the hub surface the rotor mates to, but the rotor itself. They returned it as defective.

I suspect that most brake jobs don't take the time to setup a runout test for new out-of-the-box rotors. I am wondering if anyone performs this extra step to verify the quality of a new rotor?
 
No, but I do note whether it spins consistently and note the wear pattern after bedded, then check again in 100 mi when I retorque the lug nuts.

I suspect you're more likely to find that advantageous if you buy the low tier rotors. Precision machining and QC costs money.
 
Last edited:
regardless of brand most rotors are cast in CHINA!! some better than others, but another crap shoot when you go cheep!!!
 
Originally Posted by DIY4quality
I watched a video demonstrating how to check the runout with a dial meter. Unexpectedly, the runout was measured out of range for a brand new replacement rotor! It wasn't a problem with the hub surface the rotor mates to, but the rotor itself. They returned it as defective.

I suspect that most brake jobs don't take the time to setup a runout test for new out-of-the-box rotors. I am wondering if anyone performs this extra step to verify the quality of a new rotor?


I recommend being real cautious about that and not take it at face value.

Of course its possible to get anything out of tolerance and we all know things happen but with things like this its very rare.

The castings for rotors, drums, cranks and such are bored on CNC's and specifically the surfaces are turned from center mandrel jigs in most set ups I have been involved with and robot loaded.

The CNC has both tolerance sensors for dimension and accelerometers for unbalance. ( most have a QA/QC program that samples too)

Granted, we all know things will get past even the most stringent measures but to get one totally out of specification is a true rarity ( unless someone dropped it)

I would verify the equipment and set up of the guy doing the checking with the same level of scrutiny before I would pass judgment on a modern CNC manufactured part.
 
You can optimize the situation with a dial indicator, check run-out, remove rotor and remount to index to another stud location and see if the reading improves or worsens. Obviously this is trying to match the high spots on hub with low spots on mating surface of new rotor. Don't know how much the final torquing of the wheel lug nuts will affect this scenario.
 
With unit bearing hubs and throw and go rotors, I would say most shops do not check runout before the car leaves the lot.

Having owned a shop that did a lot of brakes, we typically did not. It wasn't worth the labor to throw it on the lathe and check prior to install.
If the test drive or customer feedback was positive, then it was fine. If not, we called the source of the rotors and received another set.
FYI - I supplied a set of torque sticks to my team to provide accurate torque ratings to the wheels, which I believe whole hardheartedly impacts the longevity of the brake job or tire replacement.
 
I would bet the Chinese rotors are the worst. You would be amazed how many new tires have run out issues too.
 
Last edited:
I bought in to the dial indicator hype presented by a few here that I will not mention......well, o.k., it was Hangfire, The Critic, and numerous others. As DIYers, we have license to do stuff that makes no economic sense compared to the pros that need to justify their time and value. It's fun to use and the cheap one at Harbor Freight is beyond adequate.

Here's my thread from last fall: https://www.bobistheoilguy.com/foru...t-time-rotor-dial-guage-user#Post5213185

With a name like DIY4quality, there is no excuse for you not to have this tool in your box.
 
You could chuck a rotor up in a lathe and have it measure dead nuts perfect. Once it's slapped on a hub and smashed between the wheel and hub anything can happen. I've never had an issue with a new rotor/pad job, but I certainly don't do this professionally.
 
Originally Posted by JTK
You could chuck a rotor up in a lathe and have it measure dead nuts perfect. Once it's slapped on a hub and smashed between the wheel and hub anything can happen. I've never had an issue with a new rotor/pad job, but I certainly don't do this professionally.


This is very true, rotor can be dead nuts and still show a runout issue after install. So many variables in checking runout properly.
 
Originally Posted by doitmyself
... With a name like DIY4quality, there is no excuse for you not to have this tool in your box.
Agreed. I looked at the HF gauge you used and it's sufficient. I prefer the locking vice clamp over the magnet anchor you see on some other units.

However, I also prefer a dial with more increments on the sweep. If the typical range of interest is 0.0010 to 0.0060, that's only a tiny movement on the HF dial. This Turlen gauge has a wider sweep so it's easier to read, though probably not any more accurate than the HF unit.

https://www.amazon.com/dp/B01LML96RI
 
Last edited:
Originally Posted by Lubener
I would bet the Chinese rotors are the worst. You would be amazed how many new tires have run out issues too.

The Chinese rotors are actually quite good nowadays. Drums are still a problem though.

As mentioned, I do measure the rotor runout before completing a brake job. Here is a video I made of one:

https://www.youtube.com/watch?v=g0cqf-FKOLY

Most dealers have switched to an on-car brake lathe to resolve the rotor runout issue. When rotors are machined on-car, I consistently see less than .001" of runout, often .0005" or less. If the rotor is serviceable and an on-car brake lathe is available, it is superior to installing new rotors.
 
Last edited:
Originally Posted by Zaedock
With unit bearing hubs and throw and go rotors, I would say most shops do not check runout before the car leaves the lot.

Having owned a shop that did a lot of brakes, we typically did not. It wasn't worth the labor to throw it on the lathe and check prior to install.
If the test drive or customer feedback was positive, then it was fine. If not, we called the source of the rotors and received another set.
FYI - I supplied a set of torque sticks to my team to provide accurate torque ratings to the wheels, which I believe whole hardheartedly impacts the longevity of the brake job or tire replacement.


We don't take the time to check every rotor either. Most out of the box will not give an undesirable feel. Our techs are using torque sticks and cleaning the hub face when installing which limits issues. We road test and retorque wheels with a torque wrench after every job. If any vibration is detected, we have an on vehicle brake lathe to knock those out.
 
Originally Posted by DIY4quality
Originally Posted by The Critic
Lubener said:
... As mentioned, I do measure the rotor runout before completing a brake job. Here is a video I made of one:

https://www.youtube.com/watch?v=g0cqf-FKOLY

...

Great results for that one! I see you have the lug nuts on during testing to keep the rotor tightly mated to the hub.

Yes, but you have to use some type of washer. I use these:
https://www.ebay.com/p/12008236599

That particular rotor was a Genuine Toyota (Advics) rotor.
 
Originally Posted by The Critic
Originally Posted by DIY4quality
Originally Posted by The Critic
Lubener said:
... As mentioned, I do measure the rotor runout before completing a brake job. Here is a video I made of one:

https://www.youtube.com/watch?v=g0cqf-FKOLY

...

Great results for that one! I see you have the lug nuts on during testing to keep the rotor tightly mated to the hub.

Yes, but you have to use some type of washer. I use these:
https://www.ebay.com/p/12008236599

That particular rotor was a Genuine Toyota (Advics) rotor.

Good grief, those conical washers are pricey! But I do understand that you need them to protect the lug nuts and rotor from damage if you're torquing them all down for the runout test.
 
Originally Posted by DIY4quality

Good grief, those conical washers are pricey! But I do understand that you need them to protect the lug nuts and rotor from damage if you're torquing them all down for the runout test.

Old axle nuts may work as well. Never tried though.
 
I haven't been hit with warped rotors out of box, but drums have done me wrong many a time. Last time I got advance auto to reimburse me the cost of the labor to have the new drums trued. The guy that did them for me says he takes a super light cut out of all drums and rotors because he's been burned too many times.
 
Back
Top