First Time Rotor Dial Guage User

[doitmyself]

I'm hooked! Blame The Critic and Hangfire. I installed new front brake pads and rotors yesterday and have to admit that I like using a dial gauge to check runout. My first rotor was good at 0.002 and the second one started at about 0.003. By changing the rotor position I was able to get both rotors below 0.001. Cool playtoy. The job probably would have been o.k. as is, but it's always fun to take it to the next level.

FYI: 2014 (April '13) Jeep Patriot 85K miles on OEM brakes. First time trying EBC rotors and Ultimax2 pads. First time OCD painting of rusty calipers and bracket, LOL = day long brake job. There IS a jack stand behind the jack.
Based on o.k. YouTube review - Harbor Freight dial gauge that will see very infrequent use:
https://www.harborfreight.com/Clamping-Dial-Indicator-63656.html
https://www.youtube.com/watch?v=ykM5xjUU3LQ


Edit: Maybe should be moved to tool section?

 

[demarpaint]

^^ Trav hooked me on it several years back.^^ Boy does it make a different vs. slapping on rotors and hoping for the best. You got lucky with your rotors, I had two sets I had to move a few times to get them dialed in.

 

[Hall]

My concern with checking is what if you get 0.004 or 0.005 runout and can't correct it ? Your only choice is to return the rotors, right ? It would really suck if it's your only car and you've already done one side !

 

[demarpaint]

Originally Posted by hallstevenson
My concern with checking is what if you get 0.004 or 0.005 runout and can't correct it ? Your only choice is to return the rotors, right ? It would really suck if it's your only car and you've already done one side !

You can often correct that down to about 0.002 by moving them on the hub. I have. 0.002 is perfectly acceptable. And if I couldn't correct it I would send the rotor back, slapping it together on the one side with the old parts until I got a replacement. To me that beats driving until I need brakes again with a sub-par brake job.

Typically I check the rotors for run-out on both sides before putting the pads and calipers back on. So I might opt to wait and do it all at once, once the replacement rotor is in hand.

 

[Rolla07]

Very nice, I want one now! Thanks alot lol!

 

[demarpaint]

Originally Posted by Rolla07
Very nice, I want one now! Thanks alot lol!

Well worth the $$, and the HF tool is actually pretty nice.

 

[Trav]

Originally Posted by hallstevenson
My concern with checking is what if you get 0.004 or 0.005 runout and can't correct it ? Your only choice is to return the rotors, right ? It would really suck if it's your only car and you've already done one side !

Usually unless you are using cheap crap rotors the runout is being caused by the hub face, first you clean the face spotless if that doesn't bring it in spec you can use a rotor shim.
On some cars that use wheel bolts instead of studs and use a screw to hold the rotor to the hub the shims are the easiest way to correct runout. You could leave the screw out but when you rotate the tires but the rotor can then move on the hub unless you install a wheel mounting stud when you remove one of the wheel bolts (that's the easiest way).

 

[SZR48207]

Those of you who are going to buy this dial gauge - Make sure you grab the 20% off coupon that is always on HF's website (main page) so you'll save around $6 on it.

 

[Hall]

Originally Posted by Trav
Usually unless you are using cheap crap rotors the runout is being caused by the hub face, first you clean the face spotless....
That's good to hear then. I do clean the hub face well - it should only be dirt, rust, etc that you're removing. I mean, cleaning it isn't equal to remachining the face. I do have what are generally considered quality rotors but if I name them, someone will critique them !

Originally Posted by Trav
if that doesn't bring it in spec you can use a rotor shim.
I was thinking excessive runout was caused by non-parallel faces, i.e. angled faces. In that case, a shim would have to be tapered wouldn't it ? Otherwise, it's just a spacer, I'd think.

 

[demarpaint]

Originally Posted by Trav
Originally Posted by hallstevenson
My concern with checking is what if you get 0.004 or 0.005 runout and can't correct it ? Your only choice is to return the rotors, right ? It would really suck if it's your only car and you've already done one side !

Usually unless you are using cheap crap rotors the runout is being caused by the hub face, first you clean the face spotless if that doesn't bring it in spec you can use a rotor shim.
On some cars that use wheel bolts instead of studs and use a screw to hold the rotor to the hub the shims are the easiest way to correct runout. You could leave the screw out but when you rotate the tires but the rotor can then move on the hub unless you install a wheel mounting stud when you remove one of the wheel bolts (that's the easiest way).

A great thing to have. It might pay to have those on hand for my next brake job. I haven't run into a rotor in recent memory that couldn't be dialed in after cleaning things up and/or by simply rotating it one or two studs forward or backwards. But I know those lousy rotors are out there.

 

[maxdustington]

Beyond pro-grade lies the final frontier: The Critic/Trav/Hangfire/clinebarger-grade!

 

[MONKEYMAN]

Originally Posted by maxdustington
Beyond pro-grade lies the final frontier: The Critic/Trav/Hangfire/clinebarger-grade!

Yep!

Years back I was helped with vibration on low mile rotors. Members here walked me through dealing with run out. I ended up installing a shim on front passenger side. It addressed the hub issue. Never had a problem after that. Still have my Harbor Freight dial gauge. It is an essential tool when I do rotors.

 

[Trav]

Originally Posted by hallstevenson
Originally Posted by Trav
Usually unless you are using cheap crap rotors the runout is being caused by the hub face, first you clean the face spotless....
That's good to hear then. I do clean the hub face well - it should only be dirt, rust, etc that you're removing. I mean, cleaning it isn't equal to remachining the face. I do have what are generally considered quality rotors but if I name them, someone will critique them !

Originally Posted by Trav
if that doesn't bring it in spec you can use a rotor shim.
I was thinking excessive runout was caused by non-parallel faces, i.e. angled faces. In that case, a shim would have to be tapered wouldn't it ? Otherwise, it's just a spacer, I'd think.


The shims are tapered for that reason and the reason for the cut out arrow in the shim. A non tapered shim would be pointless.

 

[Trav]

Originally Posted by demarpaint

A great thing to have. It might pay to have those on hand for my next brake job. I haven't run into a rotor in recent memory that couldn't be dialed in after cleaning things up and/or by simply rotating it one or two studs forward or backwards. But I know those lousy rotors are out there.


They are not cheap and a last resort, I have a few common sizes otherwise I get them at Napa once I know the thickness needed.

 

[bionictony]

i just wire brush the surface and hope for the best with new rotors. with old rotors i wire brush and note orientation with marker.

 

[Trav]

To do a perfect brake job you should also check caliper parallelism and use IPA pressure gauges on the pistons, that is getting a deep into it but well worth doing.
Guys have fun researching these things. If you do more a couple of brake jobs a year I suggest getting the IPA gauges.

 

[bdcardinal]

Originally Posted by Trav
To do a perfect brake job you should also check caliper parallelism and use IPA pressure gauges on the pistons, that is getting a deep into it but well worth doing.
Guys have fun researching these things. If you do more a couple of brake jobs a year I suggest getting the IPA gauges.


IPA TOOLS Is this the one?

 

[Trav]

Yes that's the one.

 

[bdcardinal]

Originally Posted by Trav
Yes that's the one.


Ugh, more tools to buy.

 

[Trav]

In Europe brake system dyno's are very common almost every garage has one but in the US for some reason they are almost unheard of,
This tool will provide similar information when you compare brake pressures between left and right, you will find bad hoses or calipers that are not working 100% right away before buttoning it up and finding out the brakes are not what they should be or has unusual brake pad wear patterns when everything else is nice and free,

Brake parallelism is usually not an issue but easy to check with feeler gauges and can be corrected with shim washers or shim stock. Reman calipers with brackets should be checked, sometimes they surface grind the bracket mountings and don't get it right.