2002 Sonata Brake Pulsating Update

A long time ago I posted questions about causes of brake pulsations. This is an update on the problem.
History: Under warranty dealer turned rotors twice and replaced the
rotors once, then refused to do any more warranty work. I was determined to get to the root cause of the problem.
I purchased a runout gauge and started measuring the runout at various stages of pulsations and wear. It turned out after new rotors and a couple of rotor turnings that runout was not the problem. There was not a correlation between pulsations and runout.
I purchased very expensive racing rotors and pads to try but they were worse than Hyundai parts. I suspected brake pad material was the cause of the problem. So I started buying differ pads to try since I read that all manufacturers use different formulas for their pad's material.
What worked? The cheapest pads sold by AutoZone. They have been on for 6 months now and are still smooth. With the racing rotors that have been turned once. It has been an interesting endeavor but the problem seems to be solved for now.
Feedback is welcome and I hope this may help someone else with this issue.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
southluke wrote:

Ha!! I love a good experiment.
Thanks for sharing your efforts.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
southluke wrote:

Unfortunately, I can't find the site now, but there is a site that discusses this and makes a pretty compelling argument that most brake pulsing is due to an uneven distribution of pad material on the rotor and NOT due to a physical warping of the rotor. The site discusses how to properly break in pads to prevent this and also how you MAY be able to correct it via several successive and hard stops. I've done this and it worked and I'm not a believer in this theory. Your experience thus far seems to support this as well.
Matt
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I think this is the site you are referring to. http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml #
Voyager wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hank wrote:

That isn't the original site I read years ago, but it has much the same information.
Matt
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'll ditto Matt's post, less the website which I haven't seen, and add a little.
I believe the root cause to be a variation in coefficient of friction around the circumference the rotor. Pads leaving material in various places on the rotor is one way to cause this variation in friction.
Another way for this to occur is simply via corrosion. If you leave your car sit for a few days outside (or just overnight in some areas), you'll see some light rust on the rotors (if you can see through the wheels). Roll the vehicle so that each wheel makes about half a turn, and you'll see that there's an absence of rust on the portion of the rotor which was behind the pad. Over time, the rotor accrues varying levels of corrosion around its circumference.
In most cases, I'm unable to make the problem go away by hard braking. When resurfaced, rotors display little runout, but after resurfacing, the problem is gone. This leans me toward the latter issue rather than the former, since the corrosion does eat away unevenly at the surface, even if it isn't noticeable with the eye.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I've experienced the same problem. It came on after I had a brake job done: new pads, all new rotors: 2000 Sonata. All aftermarket parts. The pulsation came on a while after the work was done. My mechanic is good.
Let's assume that it's a case of melting pad binder material. It's hilly around here with a few "San Francisco"-type grades. A long time ago when disk brakes weren't common, I learned to "jab brake" from a racing driver; the idea was to prevent brake fade by slowing with hard jabs, allowing the drums to cool between the jabs. A hard habit to break ("brake," get it?).
If so, is there a decent DIY solution such as manually sanding the disks?
Richard
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
> southluke wrote: > A long time ago I posted questions about causes of brake pulsations. This is an update on the problem. > > History: Under warranty dealer turned rotors twice and replaced the rotors once, then refused to do any more warranty work. I was determined to get to the root cause of the problem.
> > I purchased a runout gauge and started measuring the runout at various stages of pulsations and wear. It turned out after new rotors and a couple of rotor turnings that runout was not the problem. There was not a correlation between pulsations and runout. > > I purchased very expensive racing rotors and pads to try but they were worse than Hyundai parts. I suspected brake pad material was the cause of the problem. So I started buying differ pads to try since I read that all manufacturers use different formulas for their pad's material. > > What worked? The cheapest pads sold by AutoZone. They have been on for 6 months now and are still smooth. With the racing rotors that have been turned once. It has been an interesting endeavor but the problem seems to be solved for now. > > Feedback is welcome and I hope this may help someone else with this issue.
Matt,
Yes, you sent me that link a year or so ago and I tried it 2-3 times. It seemed to help but not enough to make the brakes tolorable. But the article was very good info that had even more relavent concepts.
Thanks...Luke
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
> southluke wrote: > A long time ago I posted questions about causes of brake pulsations. This is an update on the problem. > > History: Under warranty dealer turned rotors twice and replaced the rotors once, then refused to do any more warranty work. I was determined to get to the root cause of the problem.
> > I purchased a runout gauge and started measuring the runout at various stages of pulsations and wear. It turned out after new rotors and a couple of rotor turnings that runout was not the problem. There was not a correlation between pulsations and runout. > > I purchased very expensive racing rotors and pads to try but they were worse than Hyundai parts. I suspected brake pad material was the cause of the problem. So I started buying differ pads to try since I read that all manufacturers use different formulas for their pad's material. > > What worked? The cheapest pads sold by AutoZone. They have been on for 6 months now and are still smooth. With the racing rotors that have been turned once. It has been an interesting endeavor but the problem seems to be solved for now. > > Feedback is welcome and I hope this may help someone else with this issue.
I tried sanding the rotors, thinking it would clean them up. Even with heavy industrial sandpaper and electric sander, it did not help.
Update: It has now been approximately 25,000 miles and all is still good. I looked at the pads the other day and they were not hardly worn at all. Never before did the car go this long without the pulsating. I recommend turning the rotors and get the cheap pads.
The car has 100,000 miles on it now and I finally changed the spark plugs. The ones in the rear were burned away worse than any I have ever seen, but the car still ran fine. Interesting.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.