Is it common for new brake rotors to warp?

[Tosh]

I'm with Kaboomba: The StopTech author is inexperienced (at best) if he's never seen a true warp.

I measured the runout with a test indicator (much better precision than a dial indicator) on both sides of my 2001 Acura CL-S (on its second set of OEM rotors - which warp at ~40k regular intervals), and I get a perfect sinusoidal curve, indicating a warp and not some deposit 'phenomenon.' (PM me, and I'll send you the raw data.) On the road it's better when cold, and worse when hot (and can sometimes appear to have disappeared altogether). I have come to accept that it's not my driving habits, but that Honda undersized the rotors and/or didn't provide enough cooling airflow, and I have Brembos waiting on the shelf to go on.

 

[1 FMF]

the brake pad bedding procedure does more harm than good on a typical street vehicle.

the only reason you would want to bed in a set of pads is if you are going to track or road race the car the next day and you are short on time and looking for maximum braking performance... because it matters because you are racing the car.

to do this bed procedure on a street vehicle is only wasting brake pad material, and if you are not careful either warping your rotors because you're overheating them or impregrating brake pad material into the rotor when the rotor is hot and not moving when you come to a stop holding the brake pedal down.

any street vehicle with any new set of brakes will stop just fine enough, if it doesn't then you're driving like an idiot with no brains. The pads will bed in naturally over a few hundred miles by themselves, you don't need to force them to in a 20 minute time span.

the braking system is not complicated, ever see some of the guys doing brake jobs?
the rotor has to turn with as little runout as possible, meaning the rotation is planar. this can be upset by unevenly torqing the lugnuts on most cars, this usually happens when the guy uses is air impact wrench to tighten the lugs. the other is not cleaning the hub surface the rotor mates to, if the rotor has been on there a while it most likely needed to be hammered off becuase it was rusted on, which most likely results in a little bit of rust making the new rotor sit uneven on the dirty hub. another may be a worn wheel bearing where the whole hub has runout which will continue to happen until you fix that root cause. if you have warped rotors, it is silly to simply replace them without measuring runout on the new set, because if there is runout any rotor will warp.
another cause is the brake caliper slide pin not being lubed and moving freely, causing a pad to constantly wear on the rotor either overheating, or embedding pad material into certain spots on the rotor which technically isn't warping, and this same condition can also happen if you brake hard to a complete stop then hold the brake pedal down keeping the hot pad against a hot rotor in a single spot.

 

[compnurd]

I have heard like this also. My last couple mechanics before i started doing things myself never told me to bed in my new pads, just to take it easy for the first 2-400 miles while they "work in"

 

[Kaboomba]

On my Buick I began feeling some judder at around 72K mi on the OE, which I believe is ACDelco. It started gradually and slowly got worse, but overall braking power was fine all this time. The rotors were worn evenly, but clearly had lost material through normal use--same with pads. I replaced the rotors and pads with top-tier Wagner parts (made in USA--ThermoQuiet perhaps?). These parts have performed as well or better than the OE parts. I did notice that the brake feel improved after ~1000 miles of gentle use (no quick bedding done here).

Clearly a rotor which has seen lots of stops will be worn down and more likely to warp. The tendancy for newer cars to have rotors which are prone to warp may be due to the fact that reduction of unsprung weight is a big deal, and the mfr decided to optimize in favor of reduced unsprung weight (by sacrificing cast iron from the rotor that you now do not get to use up yourself).

 

[demarpaint]

I'm wondering if after some very hard braking, or after coming down a mountain and then having to stop in a deep puddle if the rotors could warp?

I've always had good luck doing brake jobs. I did my own little informal bedding of brakes. Taking the vehicle up to about 30 and them coming to a near complete stop maybe 3 or 4 times and then just driving. I never had a problem with squeeking, or pulsing and got good service life out of them.

 

[Throckmorton]

Originally Posted By: Kaboomba
...The tendancy for newer cars to have rotors which are prone to warp may be due to the fact that reduction of unsprung weight is a big deal, and the mfr decided to optimize in favor of reduced unsprung weight (by sacrificing cast iron from the rotor that you now do not get to use up yourself).
That sounds reasonable but hasn't the trend actually been in favor of much larger rotors, wheels,and tires?

 

[doitmyself]

Here's a different slant on the increase of brake pulsation in recent years:

"Pre-loaded wheel bearings have no end play to "absorb" hub and rotor run-out. Hence, almost 100% of any axial run-out of the hub and brake rotor are transmitted to the brake pads. This axial run-out or wobble in the rotor causes the brake pads to wear the rotor unevenly over time, producing two sections of the rotor, 180 degrees apart, where the rotor thickness becomes thinner than the other two sections. This difference in thickness is called Disk Thickness Variation or DTV."

From a site promoting the use of on car brake lathes:
http://www.rtitech.com/downloads/archive...0to%20know.doc.

They also recommend the need to turn brand new rotors on many cars due to "inherent" hub run out on cars. They obviously have an agenda here, but interesting none the less.

 

[Kaboomba]

Originally Posted By: Throckmorton
Originally Posted By: Kaboomba
...The tendancy for newer cars to have rotors which are prone to warp may be due to the fact that reduction of unsprung weight is a big deal, and the mfr decided to optimize in favor of reduced unsprung weight (by sacrificing cast iron from the rotor that you now do not get to use up yourself).
That sounds reasonable but hasn't the trend actually been in favor of much larger rotors, wheels,and tires?


The trend to larger wheels, brakes, and tires, together with reduction of unsprung weight, are aimed at improved handling. Mfrs are still concerned about unsprung weight as they upsize wheels (usually milled-out alloys) and tires (low-pro tires weigh the same or less than higher-profile tires).

the knuckle/spindle/hub+rotor assy is still a place to save weight and cost.

 

[1 FMF]

Originally Posted By: doitmyself
Here's a different slant on the increase of brake pulsation in recent years:

"Pre-loaded wheel bearings have no end play to "absorb" hub and rotor run-out. Hence, almost 100% of any axial run-out of the hub and brake rotor are transmitted to the brake pads. This axial run-out or wobble in the rotor causes the brake pads to wear the rotor unevenly over time, producing two sections of the rotor, 180 degrees apart, where the rotor thickness becomes thinner than the other two sections. This difference in thickness is called Disk Thickness Variation or DTV."

From a site promoting the use of on car brake lathes:
http://www.rtitech.com/downloads/archive...0to%20know.doc.

They also recommend the need to turn brand new rotors on many cars due to "inherent" hub run out on cars. They obviously have an agenda here, but interesting none the less.


this seems a little incorrect, or at least confusing.
most front wheel hubs are complete sealed units these days, meaning if you have a wheel bearing going bad you have to buy a whole new hub for $300+ instead of just replacing the bearing and race yourself for $20. This is a manufacturing process to save cost at the manufacturing level, along with increasing bearing life- there is an optimal preload setting to any taper roller bearing which allows for maximum bearing life. timken has some nice writeups and a tech site regarding this:
http://www.timken.com/EN-US/solutions/au...nts/Vol6No3.pdf
http://www.timken.com/EN-US/solutions/automotive/aftermarket/heavyduty/techtips/Pages/default.aspx

this preload amount is controlled when the hub and bearing is assembled and because the bearing has preload, that results in no endplay, which in turn if the hub is manufactured correctly will have zero runout. So i do not understand what is meant by absorbing runout, the hub should turn true to begin with. If it doesn't, then that's the problem. The solution to that which i think it stupid is they turn the rotor when mounted on the hub on the car to fix the runout wobble problem- the correct course of action is replacing the wheel hub with one that turns with no runout.
I say all this because a friend bought rotors from summitt for his mitsubishi eclipse a few years ago, and summit had this shim kit which said install these shim under the rotor on the stud then measure runout on vehicle, and move shim until minimal runout is achieved. It was like they new the hubs on the eclipse were f'd, needless to say my friend said that's stupid, never used the shims, and had wicked brake pulsation from day 1.

 

[cousincletus]

I see you're from the Buckeye state, so rust may be an issue, but I really doubt it. I didn't have a chance to read all the posts, but if you're having a heat problem, I would suspect the rubber flexible hoses first. Also, [censored] pads can cause overheating. GM uses the [censored] pads I've ever seen, but when replaced with good ones, the rotors will last forever. I don't think you have a rotor problem per se, but an overheating problem causing the rotor problem.

 

[cousincletus]

What's with the censored for c-rappy?

 

[labman]

It seems excessive to me, but I can live with it. I use junky a lot.

 

[FusilliJerry82]

I know, it's PG rated at worst. But more excessive than that is the censoring of initials for cusses like if you were to initialize Briggs & Stratton without the &, that's censored.

 

[grampi]

Just thought I'd check in for an update. The people who wrote that article are full of beans. According to the automotive place I took my rotors to to have them turned (yes they were warped) the guy who turned them said it's fairly common these days for new rotors to warp. He said the cheap made-in-China rotors are just poorly made and their quality control is non-existant. So it is common for new rotors to warp. He took .010" off each side and now they're smooth as silk again, but how long that'll last, who knows......

 

[Donald]

Originally Posted By: grampi
Just thought I'd check in for an update. The people who wrote that article are full of beans. According to the automotive place I took my rotors to to have them turned (yes they were warped) the guy who turned them said it's fairly common these days for new rotors to warp. He said the cheap made-in-China rotors are just poorly made and their quality control is non-existant. So it is common for new rotors to warp. He took .010" off each side and now they're smooth as silk again, but how long that'll last, who knows......


Were your rotors really warped or just not of a uniform thickness around the rotor? Others have commented on problems due to pad material being stuck on the rotor when a pad was clamped down on a hot rotor.

 

[Kaboomba]

Originally Posted By: demarpaint
I'm wondering if after some very hard braking, or after coming down a mountain and then having to stop in a deep puddle if the rotors could warp?

I've always had good luck doing brake jobs. I did my own little informal bedding of brakes. Taking the vehicle up to about 30 and them coming to a near complete stop maybe 3 or 4 times and then just driving. I never had a problem with squeeking, or pulsing and got good service life out of them.


Wow, that would be severe! I think they could warp after that, but I think the permenant effect wouldn't be a real hair-puller.

I think you are right to do a slight bedding. In my limited experience, a series of long, moderate stops followed by gentle driving for a while gives very nice pad/rotor wear and no judder. Of course, all bets are off with junk-quality pads or rotors.

 

[Kaboomba]

Originally Posted By: 1 FMF
Originally Posted By: doitmyself
Here's a different slant on the increase of brake pulsation in recent years:

"Pre-loaded wheel bearings have no end play to "absorb" hub and rotor run-out. Hence, almost 100% of any axial run-out of the hub and brake rotor are transmitted to the brake pads. This axial run-out or wobble in the rotor causes the brake pads to wear the rotor unevenly over time, producing two sections of the rotor, 180 degrees apart, where the rotor thickness becomes thinner than the other two sections. This difference in thickness is called Disk Thickness Variation or DTV."

From a site promoting the use of on car brake lathes:
http://www.rtitech.com/downloads/archive...0to%20know.doc.

They also recommend the need to turn brand new rotors on many cars due to "inherent" hub run out on cars. They obviously have an agenda here, but interesting none the less.


this seems a little incorrect, or at least confusing.
most front wheel hubs are complete sealed units these days, meaning if you have a wheel bearing going bad you have to buy a whole new hub for $300+ instead of just replacing the bearing and race yourself for $20. This is a manufacturing process to save cost at the manufacturing level, along with increasing bearing life- there is an optimal preload setting to any taper roller bearing which allows for maximum bearing life. timken has some nice writeups and a tech site regarding this:
http://www.timken.com/EN-US/solutions/au...nts/Vol6No3.pdf
http://www.timken.com/EN-US/solutions/automotive/aftermarket/heavyduty/techtips/Pages/default.aspx

this preload amount is controlled when the hub and bearing is assembled and because the bearing has preload, that results in no endplay, which in turn if the hub is manufactured correctly will have zero runout. So i do not understand what is meant by absorbing runout, the hub should turn true to begin with. If it doesn't, then that's the problem. The solution to that which i think it stupid is they turn the rotor when mounted on the hub on the car to fix the runout wobble problem- the correct course of action is replacing the wheel hub with one that turns with no runout.
I say all this because a friend bought rotors from summitt for his mitsubishi eclipse a few years ago, and summit had this shim kit which said install these shim under the rotor on the stud then measure runout on vehicle, and move shim until minimal runout is achieved. It was like they new the hubs on the eclipse were f'd, needless to say my friend said that's stupid, never used the shims, and had wicked brake pulsation from day 1.




1FMF:

Those are great articles from Timken. They make a great product (I am a discriminating, but happy, Timken customer). They have a reputation and a customer base to maintain.

I think you make some excellent points.

Someone who buys the bargain-basement hub assy and brake components is begging for trouble.

A properly adjusted hub set won't have any runout. The only geometric variation will be among suspension groups (wheel, hub, bearing, A-arm, strut, etc), found in the perpendicularity of the hub axis with respect to the plane of the brake pads (pads being oriented by the caliper, knuckle, and possible other suspension parts).

I have to surpress the gag reflex and lunge for the trash can whenever I hear somebody make a bearing or brake purchase decision based on price! Save that reasoning for something that doesn't have to keep you going in a straight line at 80mph! Or for something that doesn't have to keep you from totaling the Lexus in front of you in traffic!

DOne ranting for now. Maybe.

 

[grampi]

Originally Posted By: Donald
Originally Posted By: grampi
Just thought I'd check in for an update. The people who wrote that article are full of beans. According to the automotive place I took my rotors to to have them turned (yes they were warped) the guy who turned them said it's fairly common these days for new rotors to warp. He said the cheap made-in-China rotors are just poorly made and their quality control is non-existant. So it is common for new rotors to warp. He took .010" off each side and now they're smooth as silk again, but how long that'll last, who knows......


Were your rotors really warped or just not of a uniform thickness around the rotor? Others have commented on problems due to pad material being stuck on the rotor when a pad was clamped down on a hot rotor.



I told the guy who turned my rotors about what was said to take place in this article, and the guy said they were definitely warped. He also said he's seen the cheap made-in-China rotors warped right out of the box before they've even been used. He said the good news is since they've already warped, they shouldn't warp again. I guess in the future when looking to buy new rotors I will ask for only those made in the USA brands.

 

[Donald]

I bought the cheapest rotors at AZ for my Camry and they worked fine out of the box. I knew I was going to sell the car, but still they were better than expected. My friend who teaches auto repair at BOCES (high school) put on a cheap rotor and an expensive rotor on someone's car, after a year of use, both looked the same. His conclusion, use good pads and cheap rotors.

 

[grampi]

Originally Posted By: Donald
I bought the cheapest rotors at AZ for my Camry and they worked fine out of the box. I knew I was going to sell the car, but still they were better than expected. My friend who teaches auto repair at BOCES (high school) put on a cheap rotor and an expensive rotor on someone's car, after a year of use, both looked the same. His conclusion, use good pads and cheap rotors.


I suppose that's a good plan because if the rotors warp you can always have them turned. There isn't much you can do with bad pads other than replace them.