Turning Front Brake Discs - Min. Spec.?

Well, after installing the new disc (+ pads + wheel bearings) on the front driver’s side, it seems Superblue still has a bit of steering wheel “wiggle” (and pedal pulsation) sometimes when stopping. :angry: The suspect was the disc on that side was warped, and a visual inspection of same seemed to confirm that suspicion. However, it appears now that something else is also amiss, and I’m thinking it may be the passenger side disc is warped as well. :frowning_face: The plan is to take the old disc from the driver’s side and, assuming it can be “trued up” by turning, have that done, vs. buying another new disc. So, I will be taking it to one of the usual big auto parts chain suspects to have that done (if possible). :+1: Question is, what is the minimal acceptable thickness for the front discs? I know the new thickness is about .95" … I have searched all through the Jag factory repair literature and not found this spec. :confused:

Always replace rotors/pads on the both sides. Never just one side alone.

That’s why I’m doing it … Any idea on the min. spec.?

Often the minimum spec is stamped on the rotor. If you can’t find a spec then I’d probably go with new thickness -.050"


The discs should have no more than .002" runout measured about 1/2 from the outer edge of the rotor when mounted on the car. This is done wuth a dual indicator. If the mounting surface on the hub was not properly cleaned when new rotors were mounted to them, that much runout can be easily induced. If cleaning that surface doesn’t help, the hub itself may need truing, or the new disc may be warped.

I wouldn’t be shocked if they don’t recommend turning them, hence the no published spec. Seems like they aren’t overly expensive new, check rockauto maybe.
Cheap dial indicator and a magnetic mount from harbor freight are a good investment for stuff like that, and for wheel bearing play.

For the cost of having someone turn the rotor, you could probably buy another new one. And both sides will match.

Good quality rotors are $100 each. Cheapies only $50. If you buy another new one, make sure to get exact same brand you bought for right side.


I guess that’s what I’ll do, Gregmatic … The first one cost around $45.00 (Centric brand). :thinking:

Well, a local friend of mine convinced me to take the disc to an O’Reilly’s (btw, apparently AutoZone no longer turns brake discs) near him anyway and see what they show for the runout and disc thickness on it (that way we know for sure whether the old one was warped and, if not, then likely the passenger side front disc is :wink: ) … First of all, the charge to turn a disc is no longer just $8 but is now more like $22. :open_mouth: Secondly, and this is what is shocking - as soon as the tech found out the disc was off a Jaguar he said, BION, “Sorry, but Jaguar does not allow us to turn their brake discs.” WTH ??? Have you ever heard of such a thing? I just shook my head and walked out. My plan is to take it to another O’Reilly that I usually use for my parts and where I know the techs, and see if they try to make the same claim. :thinking:

Jaguar may well not recommend cutting disks. Or if there isn’t a published spec that’d be a good reason not to do it for a company like that. Liability and all.
Hardly anyone turns disks anymore, with rare exception they are cheap to just replace.


$22 to turn the rotor. $45 for a new one. I’d think your time and effort is worth more than $23? Just buy a new one.

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No, never heard that. Not for the older models. Might well be true on later models.


Lift the affected wheel, take the wheel off. Put axle stand under the car. Get the angle grinder with sanding disc. Put the wheel chucks under the rest of your wheels. Turn your engine on and switch into drive. With the rotor spinning use angle grinder to equally sand the working surface of the disc rotor from both sides. You just need to “kiss” it slightly. Try to keep as steady as possible. This way you will make the entire assembly true / with minimal runout left. After that just put the wheel back and do some miles - to brake in the discs and pads perfectly.

WTF! Sorry Paul but that is the last thing you want to do. I’m a toolmaker by trade and there is NO WAY I would try to correct a warped rotor this way. As has been suggested either find a shop that will, providing there is sufficient meat left, machine the rotors or purchase a PAIR of rotors, always do like for like with brakes, if you refurb a caliper do both likewise replace pairs of rotors.


Buy another disc. On the rare occasions that I have had a disc resurfaced I have been disappointed. Either the problem was not fixed or returned shortly afterwards. As Greg has mentioned prior, the cost of an off brand disc is minimal. My advice?
Buy another disc from the same source you got the first. Good lock


I have read .60 as to other specie. That would be my criteria.


  1. use a caliper and measre the one on the car. Enough metal to remove and stay thick enough.

  2. use a dial guage with the disc muted. measure run out. I meant rotor. run out translates to your issue.


It seems I remember when I was getting rotors turned on my Datsun at one of the chain stores they told me ( that in addition to the minimum thickness requirement)they wouldn’t turn rotors that had been turned before.

5 yrs. ago, I’d advise just as above- splurge on new rotors, enjoy. But lately I have had very bad luck with the China Rotors that are MOST difficult to avoid. They glaze over- then flake badly! In US- label, brand, and vender guarantee seam to mean little. At least keep your old ones. Bad iron is just bad iron.

I have found you can still find decent rotors if you pay for them. $75-100 each seems to be the cost. The cheaper ones like you mention can be had for under $40 each.

Good rotors i continue to buy are EBC and Brembo. You can feel the quality in the weight of the rotor. Giant dumbell!

Most but possibly not all of Brembo aftermarket rotors have been made in China for a long time. That said, I’ve used them and they have been fine for street use. I came across some crappy chinese rotors a few times doing work for other people but it’s been a long while. Don’t doubt they still exist though. Bosch and ATE haven’t disappointed me yet but I wouldn’t swear where any of them are made.