So I don't see many posts about Brake Runout except for comments here and there that say to check it. I have my Early 99 DRW with 121K on it. I decided to do the Cryo Rotors and Hawk pads that have been so popular. I put the rotors on and used my dial indicator to check the runout. My first reading was about .007. I rotated the rotor to find the sweet spot and got it down to around .004. I bought the .003 Rotor Shim plates and put that on. With just the rotor and all 8 nuts tightened, I am down to .001. I am happy with that and put on the DRW extender and the damn thing jumps back up to .0045. I have cleaned everything and even tried rotating the extender 180* and it is still the same thing. It got dark so I need to continue on it tomorrow but it acts like the extender is bottom out on one side and not applying even pressure all the way around.

How many of you have actually checked the runout when putting on new rotors especially the Cryo rotors? I found a video on You Tube on a F250 and the Power Stop rotors and one was .006 and the other was .005 out.

I am spending all this time and money and want to get it as close to perfect as I can but man this is becoming a pain.

 

Good frickin luck!!!

Really? Reading your sig mods, I thought you would be installing a toaster or something.

Highest regards,

Denny

 

If I'm following, you're saying the runout on the disc is good until you mount the wheels - at which point the disc goes out of true by 4 thousandths? I might have to let that slide if I did the due diligence and that was the peak. I'd be more curious about the wheel runout if it the wheel impacts the disc. I've done the bent rim dance.

 

I'm sure the clamping forces are distributed different when using just the lug nuts to hold the rotor than when the wheel is bolted on.

 

You will never feel 4.5 thou. Run it.

 

Thanks for the responses guys. Just to be clear, I am not actually mounting the wheel during these checks. I have a Dully so I have the Extenders on the front hubs for the dully wheels. With just the rotor placed on the hub and all 8 nuts are torqued down, I am down to the .001 runout. But then I remove the nuts and put the Extender on and torque all 8 nuts down again, then it jumps back up to the .004 runout. The wheel would then be mounted on the extender.

It is acting like the extender is bottoming out on the hub in its center section in the area where I see the runout so the full force of the nut being torqued down is not making it to the rotor. I am going to do one final cleaning and then just go with it. The Ford specs call for .000 - .003 runout so that is why I was trying to get it down while I was there replacing everything. I am also doing the calipers and stainless steel brake lines so I was just trying to get everything as close to correct as possible.

I was curious to hear from people that have used the Stop Tech rotors to see if they even checked the runout and if so, did they have any issues. Bearings, bent hubs and so on can cause this same issue so without putting the rotors on a lathe to confirm how true they are, I am not sure if there is another issue or not.

Like mentioned, you probably won't feel .004 runout anyway but I am just trying to get some more input on the subject.

 

"Clocking" the rotors to get minimum runout is worth doing IMO, did it to the cryos on my truck now. But the dually extenders add another item to clock independently of the rotor and more time to an already time consuming process. Assuming it's clean, could be the extender is just not flat/square. Or if you have all day and lots of beer swap them left to right and start over. There will be one best combination, and if I went that far I'd promptly immortalize that orientation with a some spray paint.

 

I spent a little more time on the Drivers side tonight and started over. I didn't spend a ton of time on it but I got it down to .002 with the extender installed and everything torqued down to spec. I considered that good enough and will move on to the passenger side tomorrow.

 

I've had brand new cryo treated rotors right out of the box that needed to be turned. My buddy who owns a tire shop told me in the 30+ years he's been in the tire biz, it's not uncommon to find brand new rotors needing to be turned before he could install them because the runout is way out of spec.

He checks every rotor before they get bolted on because of that.

Stewart

 

Thank you very much Stewart! Well I got the passenger side rotor and caliper on today. It went much better than the drivers side and I am at .001 runout without needing a shim. Now on to the brake lines and shocks so I can get my tires back on and test the brakes out.

 

Some brake shops have a brake lathe that can turn Your roters while on the vehicle for minimal run out, I think the one I used was called VBG brand.

 

No worries.

It was several years ago now, but the last set of cryo rotors I bought for my old F250 had the wobble/shimmy when I bolted them on. Took them to my guy and he turned them for me and that's when I learned about how often it happens.

I don't remember the spec, but the runout on those new rotors were really bad. It's the only time it has happened, but all it takes is once and you discover it isn't too far fetched.

Stewart

 

on the rear axle of truck in signature I had to replace the part the brake rotor installs on,I call it the spindle hub,it had unexceptable run out,i'm sure the original owner put up with that for the first 210k.