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Discussion Starter #1
08 Hemi--front brake rotors and brakes done at 32,000 mi, now have 36,000 and the brakes pulsate when lightly using. Seems to be intermittent. Any ideas why?

Thanks,

BCB
 

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If something was broke it wouldn't be intermittent it would happen all the time. Maybe the caliper bolts or something worked it's way loose with only 6k miles it's possible. Pulsing brakes are usually wrapped rotors but like I said it would always do it. Do you hear any other noises when it happens the abs kicking on would feel like that sometimes to.
 

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Discussion Starter #3
If something was broke it wouldn't be intermittent it would happen all the time. Maybe the caliper bolts or something worked it's way loose with only 6k miles it's possible. Pulsing brakes are usually wrapped rotors but like I said it would always do it. Do you hear any other noises when it happens the abs kicking on would feel like that sometimes to.
Thanks--everything is tight--it almost feels like the ABS is being actuated. I am hoping to get a few ideas before I run to the dealer.

BCB
 

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I would bet your rotors are warped. You either have to get the rotors resurfaced or buy new rotors. Even though the pulsating feeling is intermediate, you can still have bad rotors.

All vehicles that I had driven with "warped" rotors always pulsated more at certain speeds and sometimes never pulsated at other speeds.

Read Robby's post regarding the term warped rotors.
http://www.jeepcommander.com/forums/showpost.php?p=131528&postcount=27

His post can be found in this thread.
http://www.jeepcommander.com/forums/showthread.php?t=9868
 

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Discussion Starter #5
I would bet your rotors are warped. You either have to get the rotors resurfaced or buy new rotors. Even though the pulsating feeling is intermediate, you can still have bad rotors.

All vehicles that I had driven with "warped" rotors always pulsated more at certain speeds and sometimes never pulsated at other speeds.

Read Robby's post regarding the term warped rotors.
http://www.jeepcommander.com/forums/showpost.php?p=131528&postcount=27

His post can be found in this thread.
http://www.jeepcommander.com/forums/showthread.php?t=9868
Thanks Bob123--I did not know that my brake system had a rear bias--all my previous GC's were definately front biased--It feels like the rear brake rotors might be the problem--will pull them today and see. Thanks for Rob's link.

BCB
 

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After I resurfaced my front rotors the pulsating feeling went away, however, the vibration in the steering wheel is back at certain speeds.

I should have replaced the front rotors instead of resurfacing them.

I always focus more on the front rotors since most of the braking occurs in the front. Just my two cents.
 

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Discussion Starter #7
After I resurfaced my front rotors the pulsating feeling went away, however, the vibration in the steering wheel is back at certain speeds.

I should have replaced the front rotors instead of resurfacing them.

I always focus more on the front rotors since most of the braking occurs in the front. Just my two cents.
Rear discs were warped--first time this has happened to any vehicle I've owned and I average 180,000 miles 'till trade:SM130:

BCB
 

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How did you determine that your rear rotors were warped? I believe shops use some type of measurement system to see how "wavy" a rotor is.

Let us know how your brake experience goes.
 

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Number one reason brake rotors get warped - people do not torque the lug nuts! If ALL lug nuts are not torqued to the same setting the rotor will warp over time - it takes a while for the damage to show up.
 

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Number one reason brake rotors get warped - people do not torque the lug nuts! If ALL lug nuts are not torqued to the same setting the rotor will warp over time - it takes a while for the damage to show up.
That is not how the rotors get warped.
 

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Even though Robby mentioned "...cause of warpage is unevenly torqued lug nuts." For me this cannot be the cause since I always properly torque down the wheels whenever I take the wheels off. Most importantly the shop that regularly rotates my tires also uses a torque wrench.

After thinking about the shops procedure, it's possible the force each bolt is exerting onto the rotor is non uniform since my shop (I believe) uses a impact wrench, then a torque wrench when tightening. They do not tighten the bolts in several increments, like I do, which may be another cause of warped rotors according to Robby.
 

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Number one reason brake rotors get warped - people do not torque the lug nuts! If ALL lug nuts are not torqued to the same setting the rotor will warp over time - it takes a while for the damage to show up.
http://www.tirerack.com/FAQ/results.jsp?category=Brakes
What causes brake rotors to overheat and warp?

Overheating brake pads beyond their designed temperature range releases large amounts of gas and uneven, sticky deposits of melted binders/fillers that coat the rotor surface. Every time the brake system heats up, those uneven deposits will grip the pad more aggressively than the areas without the deposits. The brake pad will slip over the non-coated areas because it can’t grip as well on those bare areas. These heavy concentrations of compound material are called hot spots because they cause uneven overheating on the rotor surface. This can actually alter the molecular structure of the cast iron rotors forming hard spots. Severe overheating forms a compound within the cast iron structure called cementite which is harder and more abrasive than the surrounding iron. It’s also not as effective as a heat sink as the surrounding cast iron. The compound cannot wear down these hard spots and the result is more heat building up in those areas and a thumping you can feel whenever you apply the brakes. Continued use of the rotors will expand these areas of cementite and uneven heat distribution. Eventually this will distort and warp the rotor. Once cementite forms in the rotor, it cannot be removed. The rotor needs to be replaced.
There's no such thing as 'warped' brake rotors
http://www.examiner.com/article/there-s-no-such-thing-as-warped-brake-rotors

Eliminating warped rotors forever!
http://www.epinions.com/content_4738556036

.
 

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Discussion Starter #13 (Edited)
How did you determine that your rear rotors were warped? I believe shops use some type of measurement system to see how "wavy" a rotor is.

Let us know how your brake experience goes.
With the wheel off the shop used a dial indicator attached to the frame and determined the rotors to be distorted. There was still life in the pads but we chose to install ceramics per Jeeps specs. We turned the rotors. I think the rears could have gone to 50,000 with good rotors.

Thanks jeep5253--great stuff!

BCB
 

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How Over-Torquing Warps Rotors

  • Wheel lugs flex under duress. Wheels nuts that are over-tightened or not tightened in the proper sequence can cause uneven tightening against the hub surface of the rotor. This is most often caused by mechanics who tighten lug nuts improperly using a pneumatic gun without the use of a torque stick or a do-it-yourself mechanic tightening them out of sequence with a lug wrench. Because one or more of the wheel nuts is not as tight as the other(s), the particular tightening balance off-centers the rotor. Once a rotor warps, it is difficult to undo.

Read more: How Does an Over-Torque Warp a Brake Rotor? | eHow.com http://www.ehow.com/about_5672302_over_torque-warp-brake-rotor_.html#ixzz1vbqPAnZX
 
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