Worn rear brake drums?

[Jimmy9190]

Do they cause shimmy/pulsation when coming to a stop? I still have the original rear brake drums, shoes, springs and adjusters on my Dakota. It has nearly 152,000 miles on it now. My truck stops very well but in the last few days I have noticed a slight pulsation/shimmying type of problem when coming to a stop at a red light or stop sign. It starts when I get to about 20 mph and persists until I am nearly stopped and stationary.

I know front rotors can cause this when they are warped or need turning. My front rotors are not very old. I believe I replaced them back in January or February 2010, about 15,000 miles ago. I used cheap Wearever rotors from AAP and I have Duralast semi-metallic pads.

I realize it could also be the front rotors causing the problem. I have not had a chance to check the rotors for runout yet. I will check them but I just wonder if worn rear drums and shoes with just a little friction material left on them can cause the same type of shimmy/vibration when braking?

I just now cooked up a combination purchase for all new drums, shoes, new wheel cylinders, a new hardware/spring kit and new left and right adjuster kits from AAP and AZ. The entire set of new rear brake parts would cost me about $107.00. I would use the FABU code for $40.00 off a $100.00 purchase at AAP and get the drums, springs kit and adjuster kits at AAP. The rest of the parts would come from AZ, and I would get AZ to honor a $10.00 off a $50.00 purchase coupon from AAP.

I am thinking it would be smart to just replace the rear brakes now as good preventative maintenance. I would appreciate your help and ideas on this.

 

[crazyoildude]

it still sounds like it is from the front

 

[Dakota1820]

not typically but yes it can happen. go somewhere secluded and safe and slow down using the e brake if it shimmy's the problem is in the rear. if its smooth look into the front. having said at 152,000 you probably are due for rear brakes.

 

[Cristobal]

Chevyboy14 is right-on in his advice. The rear ones likely need new shoes anyway though.

I will bet the shimmy though is from the front. Usually front discs or drums get hot from braking in the summer; if you then hit water they can warp a wee bit and will bear unevenly as the wheel makes its revolution. I had a 1978 Toyota that did that. It was very annoying but not unsafe in that car.

 

[eagle23]

I've found that the front rotors' being warped shows up as vibration in the steering wheel when stopping. At speed, the vibration can be quite noticeable, like a wheel out of balance.

When not applying the brakes, there would be no vibration unless the front wheels need balancing. If the steering wheel vibrated with no braking, wheel balance would be the issue.

The idea of gradually applying the emergency brake (I'll bet a large parking lot is enough space) to check the drums is a good one.

 

[Jimmy9190]

Thanks for your help. I will try the parking brake test as soon as I can. I am still going to replace the rear brakes though. At 151K on a 12 year old truck I believe it is time. If the rotors are warped, I will just replace them too. Around here it costs nearly as much to turn old rotors as it does to buy new rotors. I am driving up to Atlanta for Thanksgiving and sure do not want any surprises along the way.

 

[Mr_Incredible]

Before you go replacing parts try this:

Take off the front wheels and rotors. Clean off all rust and accumulations from the back of the wheel and both sides of the rotors. I use a wire wheel on the 4.5" grinder.

Smear anti-seize over the contact points of the wheel and rotors. Don't go real heavy with the anti-seize, but don't scrimp. Put it all back together.

Do what you can to the back in a similar way.

Test.

It could very well be that accumulated crud is causing the pulsation. It has been for me.

 

[Jimmy9190]

That is a good idea too but I had the wheels off just last week when I put new shocks on and did not see any crud or anything like that. Just a slight thin surface rust on the rotor hat.

 

[tnt31]

Originally Posted By: Jimmy9190
That is a good idea too but I had the wheels off just last week when I put new shocks on and did not see any crud or anything like that. Just a slight thin surface rust on the rotor hat.



Not tighening the lug nuts (too tight, too loose, not done in the proper sequnce, etc) could lead to that problem and could cause the rotor to warp. Since you just had the wheels off I would lean towards such a problem.

 

[Jimmy9190]

The brake shimmy problem started about 2 weeks ago, maybe a little longer. I have not had time to take a look at it until now.

 

[mechtech2]

IT could be the rears.


if you feel it in the steering wheel, it's the fronts.

 

[Jimmy9190]

I don't feel any vibrations in the steering wheel and the shimmy does not feel very much like it is originating from the front of the truck. It is more just felt in the floorboard/body of the truck as I come to a stop. I have not had a chance to do the parking brake test yet. I will be on a road trip to Tampa and back tomorrow so I hope to check it then. I am going to stop by AAP and AZ tomorrow to pick up the parts for the rear brakes and if I can get back home in time I will probably get started tomorrow afternoon. If not, I will already have the parts on hand to get an early start on Saturday morning. I will do the rear brakes first and then replace the rotors if I have to.

 

[Jimmy9190]

Well the truck passed the test when stopping using the parking brake. I tested it twice tonight in an empty parking lot and the shimmy/vibration was not there. I removed the rear wheels and drums anyway to inspect, clean and adjust the brakes. My rear brakes are in great shape for their age and miles and there is still plenty of material on the shoes. I need to take back the parts I bought and take a close look at the front brakes now.