How many of you check TIR & DTV on new rotors?

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I’m not ashamed to admit that I’ve been working on cars for nearly 24 years now and I have never heard of measuring a rotor’s lateral runout just until a few days ago when I came across a video on YouTube. Curious to know how many of you knew about this, or if you even check lateral runout on brake jobs? 🙂
 
I've been working on cars for more year than I'd like to remember, if I could! I've never check rotor runout. I toss the rotors when their thickness gets anywhere near the minimum number.
 
I've been working on cars for more year than I'd like to remember, if I could! I've never check rotor runout. I toss the rotors when their thickness gets anywhere near the minimum number.
It was a very interesting rabbit hole to go down. Almost made me think if the guys making the brake rotor runout shims were the ones that came up with the idea 💡
 
I have, but I don’t always do it.

Hate to say it, but even with a good hub cleaning, many rotors will not meet the OEM standards for LRO due to stacked tolerances. You sometimes have to machine the rotor using an on car lathe to get under .001”
 
How exactly would a shade tree DIY measure run out? On the bearing I guess? You would need to measure the bearing run out first but I presume its a lot less?

What is the spec for allowed run out?
For your vehicle’s particular specs I would refer to the FSM or repair manual.

Here’s a quick vid referencing how to check runout:

 
How exactly would a shade tree DIY measure run out? On the bearing I guess? You would need to measure the bearing run out first but I presume its a lot less?

What is the spec for allowed run out?

Usually .0015” or less for front rotors, a lot of cars are now under .001”

Absolutely. Are on car brake lathes becoming more popular?
Been very common for the last 20 years at the dealer level. It is usually required if rotors are machined under warranty. Even BMW has begun to allow/require on car brake lathes in lieu of rotor replacement on many models.
 
Not unless there is a problem like a pulsating pedal.
Funny you mentioned that… The more I dove into the whole thing, I learned that inadequate brake deposit transfer is the leading cause to pulsating brakes.. You learn something new everyday!
 

Usually .0015” or less for front rotors, a lot of cars are now under .001”


Been very common for the last 20 years at the dealer level. It is usually required if rotors are machined under warranty. Even BMW has begun to allow/require on car brake lathes in lieu of rotor replacement on many models.
you’ll be surprised just how “loose” the allowable runout tolerance is for 2000 Camry’s rear rotors..

IMG_6196.jpeg
 
you’ll be surprised just how “loose” the allowable runout tolerance is for 2000 Camry’s rear rotors..

View attachment 214380
Toyota has very loose tolerances for the rear rotors. For comparison, this is my Ram truck - 0.0008":
1713190786559.jpg

I'll let the test drive tell me if there's an operational problem.
At first the piston will move with the rotor. Over time it will translate to thickness variation once the rotor is worn unevenly.
 
TIR and DTV?
I guess I'm just some kind of yokel. Never even seen these acronyms before. Certainly never measured them. I always just relied on my foot on the test drive and bedding of pads. If it bumps or thumps then "ya gotta bad rotah".
 
TIR and DTV?
I guess I'm just some kind of yokel. Never even seen these acronyms before. Certainly never measured them. I always just relied on my foot on the test drive and bedding of pads. If it bumps or thumps then "ya gotta bad rotah".
Same here man, it’s just interesting learning about the finite details that go into everything. Just like how the fellas on this will into full-on mode with UOA’s!
 
Part of why a dial indicator is in my tool box. I have a Starrett at home, for the table saw and other machines, and it was about $100.

I got a Mitutoyo for about $50 for rotor/hub runout.

Better than HF, but not a Starrett.

 
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