Minimum Front Disk Brake Rotor Thickness Specifications - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-20-2005, 07:41 PM   #1
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Default Minimum Front Disk Brake Rotor Thickness Specifications

The dealer had to resurface both front rotors at 14,000 on my 2004 GXP under the warranty. According to the repair order the rotors are now 31.2 and 31.3 (The repair order states that the rotors were 31.7 and 31.9 before they were resurfaced). Does anyone know the minimum thickness for the front rotors and if this is getting close?
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Old 08-21-2005, 12:57 AM   #2
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Source... AllDATA

Specification - Front
Brake rotor (1-36) minimum allowable thickness after refinishing: 31.08 mm (1.224 inch)
Brake rotor (LD minimum allowable thickness after refinishing: 30.7 mm (1.209 inch)
Brake rotor discard thickness: 30.7 mm (1.,209 inch)
Specification - Rear
Brake rotor minimum allowable thickness after refinishing: 10.25 mm (0.404 inch)
Brake rotor discard thickness: 9.0 mm (0.354 inch)
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Old 08-21-2005, 04:32 PM   #3
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Thanks Buzz. Based on those specs it looks like if the rotors are resurfaced again they will likely be below the minimum thickness. I'll keep an eye on the rotors and if they start to look wavy again I'll bring it back to the dealer and insist on new rotors. I still have about 22 months left on the warranty.
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Old 08-21-2005, 06:32 PM   #4
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Default Speaking of Rotors

I recently purchased new ceramic brake pads for the front and rear while I was in the states recently. I went to schedule this work at a local Opel dealer (they are a GM subsidiary) here in Berlin. I asked them to resurface the rotors and they said they don't do that. He said they don't know anyone that does that here in Berlin anymore. He told me they used to do that but not anymore. When I asked him what they do if there are grooves in the rotors he said they put on new rotors. So my question is this; if my rotors don't have many grooves or deep ones, would it be OK to just install the new new ceramic brake pads without resurfacing? I have a 2004 GXP with just a touch over 13,000 miles.
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Old 08-21-2005, 07:08 PM   #5
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If your rotors are smooth and the runout is within spec you can probably put the pads on and let er rip. Knowing these cars though if I were you with 13k miles I would buy new rotors. I think the reason why they don't turn rotors over there is because of the speeds you guys can be running at any given time. Trying to put that much heat into a turned rotor will warp them. Once they are warped you can get severe shake upon braking and even control issues at autobahn speeds. I have seen turned rotors warp from stop and go driving. (My parents mini van) The manufacturers are doing everything they can to save weight to meet our cafe standards in the U.*. That means lighter rotors are the norm. Sufficient and safe but much thinner than in the past and not much room for turning when a brake job is done.

I also have never seen a properly working and adjusted production vehicle use the brakes and rotors up like the GXP'* seem to do. I will exclude some higher performing cars from that statement as on those I don't really know. I as well as everyone I showed mine to were very surprised at the depth of the groove at 8k miles. The pads being gone at 17k or 18k miles was abit of a surprise as well. I will say this though, the GXP is one of the best stopping cars I have been in.
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Old 08-21-2005, 07:36 PM   #6
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I think if the rotors are not in need of being resurfaced (meaning the rotors are still realtively smooth and don't have any grooves in them)then it would be fine to put the new pads on without resurfacing. Each time you resurface the rotors the width is reduced. Eventually you will need to replace the rotors if they are resurfaced too many times. If you have had a professional advise you not to resurface the rotors, then I would go with that.
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Old 08-21-2005, 07:51 PM   #7
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After further thinking on this... Blacks rotors needed turning at 14k miles... Mine were turned at 17k miles... Yours are at 13k miles. Knowing this are you sure at autobahn speeds you want to slap pads on and go? My rotors had a groove the size of the pads in them. That groove had a mirror finish to it as if the pads just squeezed the metal together. I think you will benefit greatly from new rotors with the new pads. You said you were going to schedule the work to be done but it seems you backed out. I would like to know why. Reading between the lines I get the feeling they wanted to put new rotors on and you weren't sure it was necessary. What did they advise you to do?
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Old 08-22-2005, 04:31 PM   #8
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Default Scheduled for this Wednesday, 24 Aug

I actually have an appointment to have the work done this Wednesday. I will get the German mechanics advice. If he thinks I should get new rotors then I will. They haven't looked at the rotors yet. I had never even thought that they wouldn't turn the rotors here. I just thought that was common practice for all cars at least once so that'* why I asked to have it done. They are doing a few other things like adjusting the driver side headlight, oil change, and various filter changes too so I am still keeping the appointment. Thanks for the advice on this issue. I'll let you know what we decide. I do know this. If I decide to go ahead and put the new ceramic pads on w/o resurfacing and I get any vibration or pull whatsoever, I'm stopping and ordering new rotors before the ceramic pads or anything else gets damaged!
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Old 08-25-2005, 07:00 PM   #9
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Default Ceramic Pads installed

We went ahead and had the pads installed yesterday w/o turning the rotors and everything seems fine to this point. The squeaking is gone and there is less brake dust. I'll give another update when I get more miles on the brakes. Thanks for everyones advice on this issue! Regards fron Berlin!
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