LOST JEEPS :: View topic - Strange shaking under braking... not the rotors

I had EXACTLY the same problem, only .004" runout at the rotor, measured one side at a time with a dial indicator, but it had horrible pedal vibration and jerking back and forth of the steering wheel when braking from high speeds. The reason is something called "pad imprinting". Certain pad compounds are very prone to this (like NAPA semi-metallic). What happens is that when the brakes are hot, you stop at a traffic light, trans remains in drive and you keep the brakes applied firmly for a minute. A layer of pad material becomes adhered to the rotor. These "high spots" are initially in sequence, causing just pedal vibration, but eventually they get out of sequence and cause the steering wheel to jerk back and forth under braking. If you have the rotors turned, the problem will be gone for a length of time that depends on your pad choice. I am using Porterfied R4S pads and ART rotors. This combo does not seem to be prone to "imprinting" so far in 12,000 miles. I would suggest trying Porterfields with the turned stock rotors as long as you do not go below the minimum thickness. If this does not work out, you can then replace the rotors with whatever you want and continue to use the same Porterfields. So, this is the cheapest way to go and I would not be surprised to hear that you have no more problems for the life of the pads with the turned stock rotors.

My suggestion on brake replacement is to remove the rubber slider pin sleeves on the two pins that have them. They tend to swell and jam the pins, over time. If you assemble with lots of slider lube, they will not rattle. Raybestos makes rotor shims (available from NAPA), so if after you get your rotors "concentric", it allows you to correct any runout.

Took me three brake jobs to figure this out. Hope this saves you time and $$$.

DOC

Author:	NJCRD [ Tue Nov 23, 2010 9:52 pm ]
Post subject:	Strange shaking under braking... not the rotors
So I've had this shaking/shuttering steering wheel feeling that feels like warped rotors when braking only they are perfect. Rotors are dead on when miced with about .0004 run off which is better then factory stock. It also has just a slight shimmy under light acceleration, but no where near as bad as under braking. Calipers are great. Pads are like new. The drive shaft was balanced in June and all U joints inspected so that eliminates that. (Oh yeah, the drive shaft took some weight causing a bad drive line vibration at 75 +) The ball joints also seem fine. Brand new hub bearings on both sides. Tires are new and were rebalanced even though they didn't need it and that didn't change anything SO, has anyone had this experience and if so what the heck was it? Possible CV joints in the front axle? Trans related? Any tips ideas and or suggestions that this board brings are very welcomed as this will become my holiday project. Thanks!

Author:	DirtyKK [ Tue Nov 23, 2010 11:33 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
is it a possibility that one of your brake calipers is sticking? i had that issue. cleaned and lubed the slide pins and all is well.

Author:	JL Rockies [ Wed Nov 24, 2010 3:23 am ]
Post subject:	Re: Strange shaking under braking... not the rotors
I vote for CRD shudder. The search function will yield 100's of posts on this topic. Sounds like torque converter issues.

Author:	steve03sport [ Wed Nov 24, 2010 9:13 am ]
Post subject:	Re: Strange shaking under braking... not the rotors
idk but my gasser is doing this too please help

Author:	tjkj2002 [ Wed Nov 24, 2010 8:56 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
Check the tie rod ends,R&P gear mounts,front driveshaft,check the runout on the unit bearings,rotate tires if not done so already,have the rear driveshaft balanced again,check rear control arm bushings,check upper tri-link bushings/ball joint,check pinion play on rear diff,and that is just to start if your 100% sure the rotors are good.

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Strange shaking under braking... not the rotors http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=57082	Page 1 of 2

Author:	NJCRD [ Wed Nov 24, 2010 11:36 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
I am 100% sure the rotors are perfect. I'll have to go through the check list you just provided.

Author:	warp2diesel [ Thu Nov 25, 2010 11:03 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
Is your 0.0004" run out figure taken on the brake lathe, or on the spindle? You can have a perfect rotor and one little piece of rust or other crap between the hub flange and the rotor inside flange, you will get a free foot massage. I would remove the rotor clean off the hub flange and the inside of the rotor flange as well with a stiff wire brush. I have aligned large equipment over 40 feet long and 8 feet in diameter to a run out of 0.0001", and 0.0005" on a bad day, clean mating flanges are essential to good alignment. As tjkj2002 points out, any slop in the suspension or steering will make the shake worse. A bad spot on your tire can also cause problems.

Author:	NJCRD [ Thu Nov 25, 2010 11:32 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
The run out was taken on the spindle. Hub Bearings to rotors mating are clean. The calipers are good. Let's assume that the braking system is not the issue. That's why myself as well as my mechanic are seeing if anyone on here has experienced something similar. We will re go through the suspension tomorrow. I'm thinking the torque converter makes the most sense. It's very slight on acceleration, but very noticeable under braking which has us thinking it may be the front cv joints as well? Anyone changed theirs?

Author:	Ripple [ Fri Nov 26, 2010 11:35 am ]
Post subject:	Re: Strange shaking under braking... not the rotors
I have a somewhat similar issue. when braking from over 50MPH i get vibration in the steering wheel, but at any speed less than ~40mph its not noticeable. but after reading here i think I'll give the front end and CV axles a going over before i invest in different rotors.

Author:	DOC4444 [ Fri Nov 26, 2010 11:13 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
I had EXACTLY the same problem, only .004" runout at the rotor, measured one side at a time with a dial indicator, but it had horrible pedal vibration and jerking back and forth of the steering wheel when braking from high speeds. The reason is something called "pad imprinting". Certain pad compounds are very prone to this (like NAPA semi-metallic). What happens is that when the brakes are hot, you stop at a traffic light, trans remains in drive and you keep the brakes applied firmly for a minute. A layer of pad material becomes adhered to the rotor. These "high spots" are initially in sequence, causing just pedal vibration, but eventually they get out of sequence and cause the steering wheel to jerk back and forth under braking. If you have the rotors turned, the problem will be gone for a length of time that depends on your pad choice. I am using Porterfied R4S pads and ART rotors. This combo does not seem to be prone to "imprinting" so far in 12,000 miles. I would suggest trying Porterfields with the turned stock rotors as long as you do not go below the minimum thickness. If this does not work out, you can then replace the rotors with whatever you want and continue to use the same Porterfields. So, this is the cheapest way to go and I would not be surprised to hear that you have no more problems for the life of the pads with the turned stock rotors. My suggestion on brake replacement is to remove the rubber slider pin sleeves on the two pins that have them. They tend to swell and jam the pins, over time. If you assemble with lots of slider lube, they will not rattle. Raybestos makes rotor shims (available from NAPA), so if after you get your rotors "concentric", it allows you to correct any runout. Took me three brake jobs to figure this out. Hope this saves you time and $$$. DOC

Author:	tjkj2002 [ Sat Nov 27, 2010 1:55 am ]
Post subject:	Re: Strange shaking under braking... not the rotors
DOC4444 wrote: I had EXACTLY the same problem, only .004" runout at the rotor, measured one side at a time with a dial indicator, but it had horrible pedal vibration and jerking back and forth of the steering wheel when braking from high speeds. The reason is something called "pad imprinting". Certain pad compounds are very prone to this (like NAPA semi-metallic). What happens is that when the brakes are hot, you stop at a traffic light, trans remains in drive and you keep the brakes applied firmly for a minute. A layer of pad material becomes adhered to the rotor. These "high spots" are initially in sequence, causing just pedal vibration, but eventually they get out of sequence and cause the steering wheel to jerk back and forth under braking. If you have the rotors turned, the problem will be gone for a length of time that depends on your pad choice. I am using Porterfied R4S pads and ART rotors. This combo does not seem to be prone to "imprinting" so far in 12,000 miles. I would suggest trying Porterfields with the turned stock rotors as long as you do not go below the minimum thickness. If this does not work out, you can then replace the rotors with whatever you want and continue to use the same Porterfields. So, this is the cheapest way to go and I would not be surprised to hear that you have no more problems for the life of the pads with the turned stock rotors. My suggestion on brake replacement is to remove the rubber slider pin sleeves on the two pins that have them. They tend to swell and jam the pins, over time. If you assemble with lots of slider lube, they will not rattle. Raybestos makes rotor shims (available from NAPA), so if after you get your rotors "concentric", it allows you to correct any runout. Took me three brake jobs to figure this out. Hope this saves you time and $$$. DOC 0.004" is 0.002" to much lateral runout for the KJ's front rotors.Plus adding "shims" will never correct rotor runout,you will be laughed out of room full of engineers with that one.Also that "imprinting" happens to all rotors and pad combo's and why I never sit a a stop light in "D",always shift into "N" with just enough peddle force to keep the brake lights on. If your having runout issues with "straight" rotors and new hub bearings the best thing to do is to clean the surfaces and use a on-the-car brake lathe to turn the rotors so they are true with the hub.Required for most newer Fords and highly recommended for any vehicle with serviceable bearings unless putting on new rotors but may have to turn them with the on-the-car lathe anyways.

Author:	DOC4444 [ Sat Nov 27, 2010 10:12 am ]
Post subject:	Re: Strange shaking under braking... not the rotors
To clarify, if the rotors have been trued on a brake lathe, they should be both straight and concentric. However, what many people don't know is that with a lot of brake lathes, the rotor is attached on the outside face, so it is trued to that surface, NOT the surface that attaches to the hub on the vehicle. Most of the time these surfaces are parallel, but are not always perfect. You can also have a little distortion of the hub face on the vehicle. So, the indexable Raybestos shims allow correction of runout created by the above issue and the "fit" of the rotor to the hub. I have used them many times over the years with both machined and new rotors on numerous vehicles to good effect. I did not mean imply that shims could correct for a warped rotor or one that has "varying" thickness around its circumferance as occurs with "imprinting". I stated that the shims can be of use AFTER the rotors have been made concentric and if the "mating" of the rotor to the hub is not perfectly in the same plane. BTW, you are using some sort of spacers under the lug nuts and torquing all the lug nuts to full torque in the correct pattern before checking runout on the vehicle with a dial indicator, right? DOC

Author:	NJCRD [ Sun Nov 28, 2010 11:59 am ]
Post subject:	Re: Strange shaking under braking... not the rotors
Doc, is there any other way to measure them? That's how the measurement was taken. And the calipers are fine, no sticking, binding, etc. Pads show no sign of wear either.

Author:	DOC4444 [ Sun Nov 28, 2010 4:15 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
NJCRD, The problem is that the "thickness" of the rotor is varying around the circumferance, probably at least .0010", or more. You have "peaks and valleys" all the way around that are out of phase with each other. I have never tried this, but I suppose if you are really careful, you could use a micrometer across the total width of the rotor, measuring every 1/4" all the way around to convince yourself. However, if you put them on a brake lathe, you will have take at least .005" off each side of the rotor to true them up. Most brake lathe operators can only check one side at a time with a single dial indicator, essentially as you did on the car, so this won't add anything. If both inner and outer surfaces of your rotors were both flat and parallel, .004" of runout would only cause mild brake pedal pulsation and the steering wheel would not jerk back and forth. You need to machine or replace the rotors to correct this problem and I would toss the relatively new pads you have if the brakes displayed no symptoms when you first installed these pads. They are apparently "prone" to this problem. Porterfield R4S pads seem to be much less prone to "imprinting" than most. Also, try to avoid holding the brakes on in drive, particularly when hot, at stoplights. DOC I

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Author:	Metal Man [ Sun Nov 28, 2010 4:27 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
I would put a new set of front rotors on it and save your "good" ones for spares. I would also set the spares not too far from the scrap pile so I wouldn't have to move them too far later.

Author:	usa591 [ Thu Dec 02, 2010 2:42 am ]
Post subject:	Re: Strange shaking under braking... not the rotors
Crazy--I have the exact problem as well! I only get the shudder when I'm braking from freeway speeds to exit on an offramp, not at, say, 35mph. I had my rotors turned about 6k miles ago and can't believe that I'd have to do it again so soon. Another weird sensation: about 15% of the time when I'm braking and going through the final 5mph to 1mph deceleration zone, I feel a grinding sensation. Weird.

Author:	onthehunt [ Thu Dec 02, 2010 12:09 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
I would never have a rotor turned unless it was a high dollar cryo-frozen one. They are made so thin and the steel is crap these days. You turn the rotor because it has warped. It warped because it was overheated. After turning, you have even less metal to dissipate the heat which caused your problems in the first place. Turning rotors is nothing but a money maker for shops. They know you will be back.

Author:	tjkj2002 [ Thu Dec 02, 2010 12:11 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
onthehunt wrote: I would never have a rotor turned unless it was a high dollar cryo-frozen one. They are made so thin and the steel is crap these days. You turn the rotor because it has warped. It warped because it was overheated. After turning, you have even less metal to dissipate the heat which caused your problems in the first place. Turning rotors is nothing but a money maker for shops. They know you will be back. Very correct,but you can not trun cyro frozen rotors as theyt are to hard to turn on a regular brake lathe.

Author:	JL Rockies [ Thu Dec 02, 2010 12:37 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
could be the torque converter... just sayin'

Author:	AJN [ Thu Dec 02, 2010 1:35 pm ]
Post subject:	Re: Strange shaking under braking... not the rotors
I had this same problem, not on with the CRD, but a BMW. Turned out to be the tires. Go figure... Went through the full exercise of inspecting and replacing brake components, then the same with suspension including various bushings, spacers and anything that was removable. Balanced the driveshaft (which on BMW are already balanced but figured I'd cover all the bases), even went so far as to balance the wheels seperately then remount the tires and balance again, etc, etc, but the vibrations continued to persist. Finally decided to put new tires and whamo!! all instances of vibrations disappeared. Who'd have thought the tires, right?