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Rotor Problem

John C.

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My wife has been complaining from time to time about the front end of the car vibrating when stepping on the brakes going down a long hill. I heard about it a couple of years ago and didn't do anything about as I seldom drive the car and when I did it stopped straight and didn't seem to be hurting anything. I drove it today though the vibrations were more than bothersome to me. The steering wheel was actually shaking side to side. Anyway I torn down the front brakes and didn't see any problems that alarmed me but did see these spots on the rotors that could only be seen when they were removed from the spindles.

IMG_1812.jpg IMG_1813.jpg IMG_1814.jpg

Anyway I installed new factory rotors and the problem went away. These don't have any casting marks or logos stamped anywhere so I suppose they came from somewhere in China. Anyone else seen something like this?
 

John C.

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It's a Toyota 4 Runner with 178,000 plus miles on the counter. It gets parked in a garage and hasn't sat more that a week since we have owned it. We bought it used many years ago and the damage might be progressive but the vibration wasn't there when we bought the vehicle. All the rotors I've seen rusted up have cleaned off after a few long pull downs or hard stops. These kind of looks like they are harder in that one spot that the rest of the rotor. Who knows, maybe it's some chemical or heat reaction. I'll know if the new rotors fix the problem next time I go up to see my mother. Thanks for the response.
 

Welder Dave

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Oct 11, 2014
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12,257
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Canada
Brake pad material contributing to the problem or brakes not fully releasing? I recall Dodge had problems with warped rotors causing vibration and knew someone who had problems with a new truck. Dealer tried to claim it was from driving in the rain or through puddles and using heavy braking. Are you not supposed to drive if it's wet?
 

Legdoc

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Joined
Oct 6, 2007
Messages
464
Location
south texas
In my experience in another life we saw warped discs regularly typically from hard braking. Manufacturers have made the discs thinner to save weight. A re-surface "turning" may solve the issue for a while but material has been removed compounding the problem especially with a heavy foot on the brake. Down here where I live rotors can rust overnight due to the humidity. A simple dial indicator set-up and spinning the rotor will identify the amount of warp.
 

John C.

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I dial indicated them when the problem was first reported to me by my wife. The needle barely moved on the outside and never moved at all on the inside. The disks are also the same diameter as what was on my three quarter ton Ford diesel pickup. Toyota front brake systems are four piston calipers and I've never seen of them stick. I have Toyotas because of that.
 

Ct Farmer

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Dec 8, 2016
Messages
322
Location
Connecticut
Had this problem with some vehicles in a fleet once. People called it warped rotors but a really good mechanic told me that marks like that are often caused by hard braking to a stop and sitting for a long enough time to overheat a spot on the rotor where the pad is. It essentially causes localized hardening and when you brake next time that spot doesn’t grab so the pad “slips” by and them regrabs causing a pulse feeling.

In our fleet problem we were located at near a short and steep highway off ramp. You had to take a left with no light so guys had to hit the brakes hard and then wait. Different pads and rotors helped but when we moved to a new location the problem was greatly reduced.
 

Pixie

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Nov 11, 2011
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373
Location
NH
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remodeling
Vibrating rotors are a common problem on older 4runners. I have a '99. Finally changed it over to first generation Tundra rotors and calipers and no longer have the problem. Before that I was changing rotors every 1000 miles or so.
This can only be done if you have 16" wheels. My '97 4runner had 15" wheels and had the problem but not nearly as bad.

I'm told it's because the rotor thickness is inadequate on stock 4runner and Tundra ones are lots thicker.
 

BigWrench55

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Oct 11, 2018
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Somewhere
I have a 03 suburban. I don't drive it much, but same thing my wife said one day she had to shut it down. And it vibrated the steering wheel violently and wouldn't hardly stop. I checked it out and sure enough from 70mph and hard braking. The front end was shaking the wheel out of my hands and wouldn't hardly stop. It was scary to think that my wife and kids were in a death trap. This problem also presented itself after a massive down pour and she drove through a street with 8 inches of water. I replaced the brakes and rotors and the problem was solved.
 

Truck Shop

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Dec 7, 2015
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WWW.
Pulsing front brakes has been a issue since disc brakes arrived years ago. Causes -warped from heat, hard spots from heat, rotors didn't have sufficient surface area for braking the vehicle they were mounted on,
rotors were too thin or had no cooling veins/web, metallic pads, floating caliper not floating, caliper full of sludge causing pistons to stick or piston boot is leaking, frame to caliper hose is expanding.
When installing pads in a caliper that is being reused-crack the bleeder and push the old fluid behind the piston out, do not collapse pistons and push the old fluid back up the system, then bleed the brakes.
Pistons should depress easily and smoothly.

certified on Bendix hydraulic and air brake -systems.
 

Camshawn

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Jan 25, 2017
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Langley BC
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retired
Old HD mechanic I used to work with has a Ford minivan with pulsing brakes after a brake job. Took it back to the shop several times for new rotors.. Final result, over torquing the wheel nuts was the root cause. The shop was just running them tight with the impact. Cam
 

partsandservice

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Feb 14, 2011
Messages
846
Location
Georgia
Steering wheel osalation from braking comes from worn out steering components. Replacing the rotors will kick the can down the road. My experience is dealing with the death wobble in a couple of my super duty Fords.
 

Truck Shop

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WWW.
Steering wheel osalation from braking comes from worn out steering components. Replacing the rotors will kick the can down the road. My experience is dealing with the death wobble in a couple of my super duty Fords.

That may have been in your case-but the ford silly duty had or could start to have issues with severe shimmy problems with as little as 30,000 miles from new. Ag company I worked for 18 years ago
had 10 of those, out of the ten-four had the problem early on. Frod replaced all the steering components on three of them. That lasted about a 1 year and the problem returned. Those four
ended up being lemon law-ed.
 

John C.

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I did that a while back and the difference was minuscule.

I do have one thought about a possible cause. It wasn't that long ago that the self adjusters on rear drum brakes worked when backing up the vehicle and then jamming on the brakes. The adjusting lever was attached to the rear shoe and would rotate the star wheel and the shoe tried to rotate with the drum. On this car the adjuster is part of the parking brake linkage. Every time you pull up on the park brake lever, the linkage tries to move the star wheel. I did notice a while back that the brake pedal was traveling quite a ways before full engagement and real braking force. I wonder if riding the brakes on a long down hill was only pushing on the front brakes and not really moving the rear shoes? I know I had to manually adjust the rear brakes several times over the years and didn't really think about it too much.
 

HATCHEQUIP

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Oct 19, 2011
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VILLANOW GEORGIA
Back in the 70s and 80s one ton mechanics trucks ford and chev rear brakes would never wear out and were kept adjusted and trucks just didn't stop good or would lock the front in an emergency and flat spot the tires. Front brake pads were replaced every time you turned around it seemed like. Dealer would tell ya it was the proportional valves not letting full pressure to the back brakes so that they wouldn't lock up on a lightly loaded truck on a wet road . These were mechanics trucks and were always overloaded . Pulled the valves and hooked master cyl. front to front and rear to rear trucks would stop and front brakes wore less and you started seeing some wear on the rear shoes in back.
 

John C.

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I had two occurrences in one of those trucks. 1988 Ford Super Duty with the 7.3 diesel. Just changed from one freeway to another in morning rush hour in the rain. Traffic was the usual accordion, crawl then go fast then hit the brakes. I had just rowed the shifter up about 35 miles and hour when the stream hit the dam. I felt the truck start to slow for a second and then seemed to speed up. Pushing on the brakes did nothing and the truck slid into one of those mini work vans with the cage behind the driver and all kinds of long stuff in behind that. Well 16,500 pounds beats a 4,000 pound mini van every time. The long stuff in the van hit the cage which hit the driver in the back slightly and also pushed the van into another car. A couple of state troupers were in a car about 200 feet back and told us to get off at the next exit which we did. It was over except for the paperwork. It didn't leave a mark on the truck I was driving.
The second time I was stopped waiting to make a left turn on a farm road. A pickup was coming towards me pulling a big hay trailer. The trailer is what you would normally pull behind a hay truck. Apparently the guy in the pick up had caged the brakes and had a pintle hook on the pick up. He made the turn into where I was going and went in about a hundred feet and then just stopped on the road. Something drew my eyes off the back of the trailer as I made the turn and then realized that the trailer had stopped. There were of coarse no lights on the trailer. The road was dry, I wasn't going ten miles and hour and of course the front wheels locked up and I slid into the back of that trailer. The trailer out weighed me this time and got my right front fender and the hood. It didn't go deep enough to stop me from driving and the trailer didn't get a scratch. No police this time and the worst issue was telling the boss that the truck needed a touch of body work.
I have heard several versions of the same thing on all the one ton trucks. Ford, Dodge and Chevy all had the same problem. Disk brakes front and rear and they played real time experiments on the end users with the valving, the brake power ratios and pad materials.
 
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