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Discussion Starter #1
I was experiencing a pretty noticeable steering wheel shimmy while braking at high speeds (45+mph). So I took off my rotors and had them resurfaced at a local auto parts store. I wasn't too worried because the car has over 65,000 miles on it and I just figured it was normal wear and tear, plus it only cost $10 to do. However, it's been about 2 months and the shimmy is back! I couldn't figure out why they would be warped again so soon, so I took my Accord into the dealership and had them look at it. They observed the shimmy, but couldn't give me an explanation as to what caused it. All they recommended was to have them resurfaced again.

I'm a little hesitant to do this because I'm worried that the problem will just return again in another 2 months. Does anybody have any ideas as to what could be causing my rotors to warp like this?

I don't drive like an idiot and slam on my brakes constantly, and I always hand-tighten the lug nuts with a torque wrench, so those shouldn't be factors.

Thanks for any help you guys can provide!
 

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Discussion Starter #4
You could get a quality aftermarket rotor like EBC or Brembo. The material is better than what Honda used.
I've thought about that, but I've never used aftermarket rotors. Couldn't they warp too?
 

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Michael
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I've thought about that, but I've never used aftermarket rotors. Couldn't they warp too?
Anything metal or plastic or wood can warp. The difference in quality is what can help it resist doing so. When I compared the Honda rotors to my EBC, I could just feel the difference.
 

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One thing you should remember..... what makes your discs warped is a big temperature from lets say your surface and the center of the metal mass ( let's say emergency braking from 60mph) when you resurface.. you are actually removing more material.. so your discs will resist even less to warping because you have even less mass to absorb the heat... When your discs are warped you should just change them out. Also... in real life.. a lot of people have been thinking that their discs are warped... but in reality, the problem is brake dust deposits that form on the disc from brake pad wear.... when you apply the brakes, the surface is uneven and makes your steering shimmy... Best way to avoid this is occasionally just let your pads drag a bit on your discs to make them heat up just a little bit to clean them off... also.. a great way to keep your rear brakes clean.. is to click your ebrake 2 or 3 clicks and let them drag about 4 or 500 feet to heat them up a bit and clean them.. Actually this trick was told to me by an Audi Mechanic. you just have to do it once per 2 or 3 months...

Also like someone pointed out...aftermarket disc with better quality material could help your brake shimmy too.. Also REAL crossdrilled disc( not a normal disc just drilled thru) can help evacuate the gasses that causes heat when you brake. Brakes are a real hard thing to balance and you have to suit them to your driving style... The heavier they are.. the more they will resist warping, but the more rotational mass they will exert of the drivetrain. Also.. BBK will help warping also since they have more surface grip, but the downside is your pads will probably be cheaper... and you will have to use bigger wheels to clear the calipers. Our cars were not designed to be race cars, but with money and time and concessions... you can achieve a balance you are comfortable with!!:p
 

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Anything metal or plastic or wood can warp. The difference in quality is what can help it resist doing so. When I compared the Honda rotors to my EBC, I could just feel the difference.
I'm not disputing the difference in quality; I'm just wondering how you could "feel" it.

Have you ever calculated the stresses required to "warp" a steel rotor? They're pretty substantial and for that reason very unlikely to occur on an everyday vehicle.

In 99+% of all cases, what people experience as judder and call "warped rotors" is an localized uneven buildup of the debris layer on the rotor. It is usually caused by a variation tin the metallurgy/microstructure of the rotor at the point of buildup. Machining the rotors removes the debris layer and restores two parallel surfaces to the rotors but does not change the localized microstructure. Because the microstructure is still there, the buildup will return in a few thousand miles, and so will the judder, and so will many people's belief the rotor has "warped."

That uneven buildup can be as little as 0.0001" and still be felt by many drivers. But that variation has to be abrupt - think rumble strip. If the variation is gentle, like a smooth rolling road, there will be no judder. That's why cars have floating calipers - they float to accommodate those variations in thickness and, in unusual cases, out-of-plane or warped rotors.

I worked for a company that developed ceramic composite motorcycle rotors. Some were actually "warped." Think uniformly thick. but not in the same plane. We called the effect "potato chipping" and it resulted from uneven stress relief in the rotor as a result of the grinding operation to make smooth faces. Those rotors could have out-of-plane variations as much as 0.02" and still stop perfectly smoothly and effectively. But a perfectly planar rotor with a thickness difference between 4 o'clock and 6 o'clock of 0.0004" caused judder everyone could feel. Some riders could detect judder when the differential thickness variation was 0.0001".

So I'm pretty sure what many of us call "warped rotors" are in fact not warped.

So what causes the microstructure variation? The most common idea is that the rotors had been run hard and put away hot. The pads were hot enough to soak the rotors at that spot enough to cause a local variation in the metal structure. It's also possible, but very unlikely, that the rotor was made from crap scrap metal that was poorly mixed. Very unlikely for all but the cheapest rotors.

And what is the "debris layer" and why does it matter? It's a very thin film formed by the wear of the pad and rotor. It's what actually determines the friction/braking properties of your car. Steel rotors and autos have been around for so long that any pad will work with any metal rotor, but there will be differences in hot/cold friction, fade resistance, and wear. One of the big challenges with the ceramic cycle rotors was finding the right pad composition. Most initial efforts had almost no friction - you just kept on rolling.
 

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Michael
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How I could feel it? I guess it is the ones from Honda felt like a cheap cast. The metal is softer. If I dropped it vertically it would put a dent in it, like it just caves in slightly. The aftermarket ones I got were much harder, and had a smooth metal look and feel, rather than the "bumpy" look of OEM. Rust has been night and day different as well.
 

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As previously stated, one the rotors are resurfaced you are essentially buying yourself some time. I had a similar issue with my previous car and it is not abnormal for the shudder to return on a resurfaced rotor. If you don't feel comfortable going after market, go with oem. 65k is pretty decent on original rotors, imo.
 

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you didn't mention if you replaced the pads at 65k . If you just resurfaced the rotors at 65k pads that are worn will not dissipate heat as well as new pads, same with rotors as others have mentioned .
 

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Discussion Starter #12
you didn't mention if you replaced the pads at 65k . If you just resurfaced the rotors at 65k pads that are worn will not dissipate heat as well as new pads, same with rotors as others have mentioned .
I replaced the pads at the same time. :thmsup:
 

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Discussion Starter #13
So the consensus seems to be that I should replace the rotors. Anybody have any suggestion on what to get? I'm not looking for racing type rotors on anything over-the-top like that, but something better than OEM because I would like to not have to replace them again :)
 

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Michael
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So the consensus seems to be that I should replace the rotors. Anybody have any suggestion on what to get? I'm not looking for racing type rotors on anything over-the-top like that, but something better than OEM because I would like to not have to replace them again :)
Check out the Power Slot at $60 each, plus there is always a discount. Try the code "Welcome15", worked for me this weekend.

http://www.autoanything.com/brakes/20A50533A1.aspx
 

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I like Brembo and NAPA Ultra Premium (which are relabeled Raybestos, which are cheaper with a lesser warranty.) Many, many Centric fans on this forum. Stay way from slotted/drilled rotors. Cosmetic only and cause problems for the daily driver. If you really want to avoid this, you may want to drive your car slowly without braking for five minutes or so after a vigorous brake session. My theory is the hot soaking when you park a caar with hot brakes makes the problem more likely.
 

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Wrench Turner
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I was experiencing a pretty noticeable steering wheel shimmy while braking at high speeds (45+mph). So I took off my rotors and had them resurfaced at a local auto parts store. I wasn't too worried because the car has over 65,000 miles on it and I just figured it was normal wear and tear, plus it only cost $10 to do. However, it's been about 2 months and the shimmy is back! I couldn't figure out why they would be warped again so soon, so I took my Accord into the dealership and had them look at it. They observed the shimmy, but couldn't give me an explanation as to what caused it. All they recommended was to have them resurfaced again.

I'm a little hesitant to do this because I'm worried that the problem will just return again in another 2 months. Does anybody have any ideas as to what could be causing my rotors to warp like this?

I don't drive like an idiot and slam on my brakes constantly, and I always hand-tighten the lug nuts with a torque wrench, so those shouldn't be factors.

Thanks for any help you guys can provide!
Brake rotors warp for two reasons. Microscopic imperfections in the rotor (which grow larger over time) and the lack of the rotors ability to dissapate heat. Machining them only puts a band-aid on a gunshot wound. It's going to return, just not overnight.
Newer aftermarket (cheaper manufacturers and auto parts retailers) rotors can be bought for as cheap as $25-30. Do they work, yes. Do they last, no. So how just how do they do it? cheaper alloys of metal, combined with less cooling vanes/vents in the rotor. Torquing lugnuts does nothing in the way of contributing to warping a rotor, unless you run carbon fiber/composite rotors (Found on Ferrari's and newer ZR-1 Corvettes). Then by all means torque them.
I've done hundreds of brake jobs over the years, and the one thing I've learned from customers, if you drive aggressively, or just don't want them to constantly warp, do one of two things, drive slower/less aggressive (no chance of that happening!) or modify your cars braking system.

By no means do you have to spend a ton of money. Since the front brakes do approximately 70% of the work in stopping your vehicle, a few well placed dollars, in the form of cross-drilled, slotted, or dimpled front brake rotors (EBC makes great dimpled rotors) can make a noticeable improvement to your vehicles braking system.

Do you have to spend a lot of money on brake pads? No. A decent set of pads will run you about $50 (Ceramics for less dust). I run Centric Ceramic pads, with Stoptech front and rear cross-drilled and slotted rotors. I also run Stoptechs braided caliper hoses and upgraded the brake fluid to ATE Super Blue DOT 4 fluid. I drive aggresively at times, and I hate warped rotors. Besides, I like the option of being able to stop quick enough to just about put yourself into the windshield if you're not wearing a seatbelt... :D

Ask around, and get some opinions. If you look around, there are some great deals on aftermarket rotors, and pads. It all depends on what your budget is, and how fast you want to stop. There are great products out there to fit any budget.
 

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Wrench Turner
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Since this install I have approximately 3000 miles on them, with no pulsation whatsoever. Me personally, spend a bit more on your front rotors. You'll be happy you bought 'em, .....about a year down the road, when they still feel like the day you put them on :thmsup:
 

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Good posts by Porwal. I agree with most and it was well said. I take a few minor exceptions:

Torquing lugnuts does nothing in the way of contributing to warping a rotor, unless you run carbon fiber/composite rotors (Found on Ferrari's and newer ZR-1 Corvettes). Then by all means torque them.
I've participated in the development of carbon/silicon carbide ceramic composite rotors, although using a technology different from the Ferrari/Porsche/Vette versions. I doubt one could torque them into warping, but even if one did, it wouldn't cause judder. Judder comes from a sudden change in rotor thickness. As noted above, we made some motorcycle rotors that "potato chipped" from uneven stress relief when we machined the surfaces to be parallel and flat. You could rock the worst of them on a flat surface. If that's not warping, I don't know what is, and they stopped with absolutely no judder. It's one of the purposes of a floating caliper to handle those kinds of undulations.

We were told by the lead brake engineer of a major global automaker that the slots and holes are for cosmetics. Any gains in heat transfer and water removal are imperceptible compared to the looks thing. My view is the local microstructure changes occur when the pad heat-soaks the rotor locally after it was "rode hard and put away wet." I don't think the slots and holes do enough to make a major difference when the car is parked, frankly - a lot more surface area is created to remove heat by venting a rotor than by slotting and/or drilling
 
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