My 2006 hyundai sonata has two vibration issues. I took the car to the dealer to have it checked, however some of the things don't make sense so I'd like to know if it makes sense to anyone else.

1. when braking at high speeds, the front shakes alot. I've had this issue for 2-3 years but no one ever finds anything wrong
This time I was told by the dealer that this is due to my front rotors being rusted and all need resurfacing. I know it is normal to see some rust after the car has been sitting a while but I do not understand how rusted rotors would cause a vibration problem unless it was very excessive. I tried ask them to explain but all they said that rusting will cause vibration. I took a peak myself. The front discs look fairly shiny, I can see some light ring grooves but no rust. The rear discs seem to have some dark spots on the surface, I don't know if this is rust. The center portion seems to be rusted but I think that is normal. Also, I was told that my rear brakes are down to 3mm and my front brakes are at 5mm. My rear brakes are 1mm thinner standard. I have my brakes checked twice a year and there is no mention of rust. I brought my car into the dealer last year and there was no rust. I'm thinking there must be something else wrong with my brakes, it sounds like the rotors are defective. Has anyone else had this problem?

2. There is a high frequency vibration when I am at 70-80mph. I can feel my steering wheel moving left and right very quickly. I've had this problem for 2-3 years.

I was told that my front right rim is bent and that is the cause. I am sure that can cause a vibration, however I rotate my tires twice a year, and the vibration has always been felt after changing tires, alignment, balance, rotations. When I asked about this, the dealer said there is no way to know without changing the rim and driving again. Although my front tires are at 6/32 wear while my rear are at 8/32. Its been 6mo since my last rotation. I'm not sure what would cause this. Can a bent rim cause the same front vibration if its on the back? Can't the wheel be balanced out to account for the bend, unless it is severe. Has anyone else had this issue?

Anyways, I'm going to try another dealer and stay there the whole time so If they do find something, I can see it for myself. Hopefully they will actually look at my suspension this time. As for the brakes, if they are truely rusted or warped, it sounds like a defect.

 

Basically you could have broken it down to two problems:

1. Vibration when you brake.

2. Vibration at high speed.

Vibration when you break is due to warped rotors. How they got warped is unknown. You either have them "cut" or you replace the rotors. Try to have them cut, and see if the problem returns. If the problem returns, then you either ride with your foot on the brake, or you slide pins are sticking or pads are hung up... but something is causing the rotors pads to bind.

Vibration at high speed is usually a tire problem. What condition are your tires in? If your tires are good, or you changed the tires and it still vibrates, then yes it could be a bent rim.

The mechanic should be able to tell you if it's a bent rim in no uncertain terms when he tries to balance it.

If tires are good, and the rims are not bent, then it's time for the "load force" balancing, which means they put the whole car on a big machine and spin the wheels. They should be able to tell what's wrong then. It could be a unbalanced axle shaft or bad bearings (neither is likely.)

 

^^^ I agree 100%

1. warped rotors. Get new ones, don't cut old ones. New ones are cheap. Cutting old rotors just makes them thinner and they will probably warp again.

2. either a bad tire, an imbalanced tire or a bent rim

 

I took it to another dealer. He told me my front rotors were heat damaged, I could see a little pad transfer if I looked at it from an angle. I asked him what the runout was. At first he started explaining what runout means, but then I told him I was asking him what the measured value was. He told me he did not measure it, but said he could take it off the car and measure it. This surprised me a little because I thought lateral runout was suppose to be measured no the car to reduce tolerance stackup. I asked if it could be cut, he said no because there was rust on the rim. He told me my rear rotors were rusted, I looked at it and it did look rusted. Very rough, and pitted. I asked him why it was rusted while the front werent. he said that the only way he knows of is if the car sits for a long time. I told them that I've had this issue for the past 3 years but he had no explanation. By comparison, the first dealer said the front rotors were rusted. He also told me all my pads needed replacing. After asking him what the thickness was, he told me he hadnt measured them and went and checked and found the front ones were ok.
for the high speed vibration, he said my tires are uneven because I have high speed tires with aggressive treads. I explained that the OEM ones are Vrated and mine are lower. He told me he doesnt know about tire speed ratings. He also told me my rear wheel rim was bent but was previously repaired. I'm not sure when this happened. By comparison, the first dealer only said that the front right wheel was bent. Now I do think the tires have been wearing faster than they should. they start at 11/32 and are at around 7/32 now after 13.5K. The tread warranty is 70k.

I'm not really sure who to believe.
Anyways, I'm going to get the brakes changed and the wheels balanced. I am suspicious about the rear rotor getting rusted when my others were fine. That doesnt seem normal. Doesnt the pad usually last longer than the rotor?

 

All rotors rust. If you can see the rotors through the wheels, look at them after the car has been sitting after a rain shower. They will always have surface rust on them. The first use of the brakes makes the rust go away.

And no, pads do not last longer than rotors. The pads are the wear item, not the rotor. If maintained properly, rotors should last the life of the car. Only the pads would need replacing.

 

ah, I mis-typed, I did mean to say "shouldnt the rotors last longer than the pads". I know that all rotors rust. I check at least one of the rotors every morning. This car actually doesnt seem to rust that much overnight, I've had ones that were much worse. But my rear rotor seems to be severely rusted, even after driving and using the brakes. No actual rust, The surface feels pitted, I wish I took a photo. Basically like a bunch of dark spots and streaks all over the rotor that can be easily felt. Its like my back rotors were sitting in a snow bank for a few months. But I've never left my car undriven for more than a week. I actually thought it might be pad transfer at first but they said no. So it seems strange to me how the front rotors look fine and my rear rotors look like crap. It was also strange that when the mechanic called me out to the car, he told me not to touch the front rotors because they are hot, yet the back rotors were at room temp. I'm probably not making very good contact on the back since the surface is rough now. Anyways, I'm going to have to change the back, it would have been nice to know how the rotor became this way. It seems like a defect to me since the front rotors were not also severely rusted. Yes, it is not unusual to need a brake job at 45k, but I think it is unusual to have severely rusted rotors on half the car. maybe I'm missing something.

 

It's very possible the rear brakes are not being used much. That woudl explain why the rust isn't coming off, why they are cooler and why the fronts are warped (they are doing all of the work). Have the rear calipers and master cylinder checked.

 

I'll check it out. Although, my rear brake pads have actually worn down faster than the front ones so it sounds like they are being used. But something could have recently happened since I don't recall seeing rust before.

 

OEM rotors are cheap. The metal is inferior quality. The pads seems to be dodgy too. It's ok if you drive everyday, clean off underneath a lot, or live in Arizona, and don't brake too hard.

 

I just got done replacing the front rotors on my wifes Kia Sedona. We bought it almost a year ago and the front rotors were warped from the previous owner. The dealership we bought it from replaced the pads on all 4 wheels but it would still pulsate when braking. I purchased a pair of of CENTRIC front rotors from AutoPartsWarehouse.com and installed them last night with a set of new front pads. The problem is totally gone. The quality of the CENTRIC rotors are great. Much better than the OEM and much cheaper.