IceWater

Ok, I know that actual rotor warpage is pretty rare and that pad transfer is usually the culprit when it comes to brake judder, but my question is how much runout is acceptable in a rotor? I developed a judder driving out to the Glen for a DE, and it plagued me through the entire event and gave me a very inconsistent pedal. When I got home, I brought the rotors to work and measured them and got a total indicator runout of about .007" accross the entire rotor surface. Is that bad enough to cause a severe judder? I also suspect my bearings, so I'm going to check those too.

Thanks!
Tom

BruceWard

The factory service manual says

Lateral runout of brake disc max 0.05mm

Lateral runout of fitted brake disc max. 0.1mm

Lateral runout of wheel hub max 0.05mm

New disc thickness
front 28mm (32mm M030)
rear 24mm

Minimum disc thickness after resurfacing
front 26.6mm (30.6mm M030) - do not wear ast 26mm (30mm)
rear 22.6mm - do not wear past 22m

Surface roughness of brake disc after machining max. 0.006mm

Hope this helps, sounds like you are not too far out of spec.

IceWater

Thanks Bruce, that's a big help. Sounds like they're not great, but probably wouldn't be responsible for such a severe shake. I'll give the bearings a once over tonight and hopefully its not something in the suspension, or worse yet, another phantom that I can't figure out.

Thanks again,
Tom

BruceWard

I meant to ask if you knew how many miles were on your wheel bearings? I replaced mine at 57K and noticed a big difference afterwards. The bearings are not very expensive <$50 from Paragon. So I suggest you go ahead and change them.

Do you have any play if you push in on the top of your wheel?

IceWater

Hmmm...when I replaced them I think it was at about 100k miles and there's 150k on her now. There is a little play top to bottom, so its either the bearings or the ball joints. I'll probably grease and repack them and see how they do. Is the procedure for torquing the bearings in the manual (I have it at home)? Any grease recommendations? I see that pink mobile 1 synthetic stuff at the parts store all the time...is it any good?

Thanks again,
Tom

BruceWard

I think I used swepco, or somthing else Paragon sold me to grease them.

Every reference I have seen to torquing the wheel bearings says to take a long 6mm allen and insert it through the notch in the hub into the allen bolt in the lock nut. Then turn the nut and hub until you can "just" move the washer with the tip of a screw driver without prying against anything.

I did not have the long allen and did not understand the "through the notch in the hub" and "turn both the hub and bolt" parts so I ended up adjusting mine three times before I was happy with the outcome.

If you are going to take them apart I would go ahead and replace them. If there is anything other than a perfect mirror finish on the bearings then it is time to replace.

IceWater

So you use the ellen key to lock the hub and nut together so that when you turn the hub, you turn the nut on the spindle? That makes sense. Now since its been a while since I was last in there, what washer are we talking about and how are you supposed to "move" it with a screw driver?

Thanks Bruce,
Tom

flash968

.1mm is .004 inches - yours are out by .007 - almost twice spec - your judder is almost certainly due to rotor warpage

IceWater

I would think that being less than twice the factory spec wouldn't be too bad. I guess it depends on how the spec is interpreted. Is it the maximum value that won't give you any problems or is it a target for a new or resurfaced part? When I design parts, the tolerance I assign is much tighter than the value that starts becoming a problem. How is it worded in the manual? I can check it when I get home too.

Tom

BruceWard

Tom,

You got the turning part right. The washer is between the nut and the wheel bearing. Take the screwdriver and push the washer around. If you cannot move it then the nut is too tight. I have read elsewhere to tighten until you cannot move the washer then back off a quarter turn. I believe that is where I ended up. But it is a matter of personal preference.

Bob Blackwell and I compared wheel bearing adjustments at Parade. He likes a lot more play that I have mine set to and he has a winning record to show for it!

Here is the brake spec page from the manual.

IceWater

Outstanding. Thank you Bruce. That's a lot looser than I would have expected. I probably overtightenned them when I last did them. We preload most of the bearings I work with pretty heavily, so I guess I'm prejudiced that way.

Thanks for posting the page.

Tom