[skx24]

Had front brakes replaced and rotors turned on my '13 LTD 21,000mi.
Was told the rotors were warped. Upon completion I asked the service advisor whether the lug nuts were torqued because I did not see any torque wrench being used anywhere in the shop. The service advisor stated that the air impact wrench was set to the torque setting.
Question to the forum: is this true or just dealer bs? I'm thinking if not torqued correctly over-tightening the lug nuts may have caused the warping of the rotors. Thanks in advance.

 

[D.Spec]

1. It is dealer BS
BUT
2. Over-tightening lug nuts wont warp your rotors

Yes, every rattle gun will have a maximum amount of torque that it can apply.
The issue is that torque is a rotational measurement. So when using a torque wrench, you need to apply constant pressure until you hear the click. If you just yank on the wrench over and over, you wont get an accurate torque figure.
This is essentially what the rattle gun does. It applies it's maximum torque for an instant, and then releases, and then reapplies. hence the rattling sound. it's the head beating on the nut over and over again. There's no way rattle guns can torque to the same accuracy that a proper torque wrench can. It'll over-torque them 9 times out of 10.

In saying that though, over-torqueing your lug nuts will cause your wheel studs to snap, or strip them before doing anything else. I've never seen or heard of a rotor warping due to over tightening of lug nuts.

The main killer of rotors is heat. Driving and working the brakes a lot and not letting them cool down before putting you handbrake on is the quickest way to warp them, and something people don't often realise.

If you want to see how tight the nuts are, just get a torque wrench and set it to 5nm above the recommended torque. Put in on a nut and lean on it. if they move before you hear a click then you're all good. if not, they're tighter than they should be. Back them off, grease them up and reinstall them. It'll save your studs some grief...
...but not your rotors

 

[pico]

Back them off, grease them up and reinstall them.

There are strong arguments concerning the torque specs for lubricated fasteners. If one should go on dry, then the torque spec changes when lubed.
.

 

[ronbo1313]

Over torquing CAN warp your rotors. Google it.
I always loosen my lug nuts then re torque with a torque wrench if my vehicle is worked on.
In a shop time is money.

"Brake rotors do not warp from heat, even when driven by the most aggressive traf*fic officer. Instead, they wear unevenly. This uneven wear is caused by the brake pads themselves as they intermittently touch an out-of-true rotor. The root cause of the uneven wear is one of two things: either the rotor was installed out-of-true with the hub, or the tire was improperly torqued to the hub during the last tire change. "
link: http://www.hendonpub.com/resources/article_archive/results/details?id=1787

 

[Rickl]

The service advisor stated that the air impact wrench was set to the torque setting. .

He may have meant that they were using a "torque limiting bar" which was chosen to have the correct torque setting. Such as this one from Harbor Freight.

 

[katekebo]

As Mechanical Engineer, here are my $0.02

D.Spec is right about torque wrench vs. impact wrench. Impact wrench is nowhere near as accurate as torque wrench, especially when old and worn-out. Wheel lugs / nuts should be tightened with a torque wrench.

pico is right about lubricating lugs before tightening. Torque specs for wheels nuts are DRY torque. Actually, you should never put grease on wheel lugs / nuts.

 

[D.Spec]

Over torquing CAN warp your rotors. Google it.
I always loosen my lug nuts then re torque with a torque wrench if my vehicle is worked on.
In a shop time is money.

"Brake rotors do not warp from heat, even when driven by the most aggressive traf*fic officer. Instead, they wear unevenly. This uneven wear is caused by the brake pads themselves as they intermittently touch an out-of-true rotor. The root cause of the uneven wear is one of two things: either the rotor was installed out-of-true with the hub, or the tire was improperly torqued to the hub during the last tire change. "
link: Raybestos Brake Tech School, Part One: Rotors Don't Warp | Hendon Publishing

Firstly, I apologise for not not explaining my statement about heat warping rotors further. The application of heat does not warp rotors. It's the cooling process after the application of heat where things can go wrong. As stated, if you heat up your rotors and apply the handbrake when you park the car before giving them a chance to cool, then the part of the rotor touching the brake pads will cool at a slower rate than the part exposed to air. It's the difference in the rate of cooling that causes the warping. The rotor needs to cool evenly. If the difference is too great, your rotors will warp or crack. See 'Thermal expansion' and 'metallurgy'.

Also: Improperly torqued and over-torqued are not the same thing. Your article is talking about having some nuts torqued more than others. That will cause the rotor to not be correctly aligned, and yes. When that happens, the the pads will just chew it to ****. In saying that though, if your wheel calls for 100nm of torque and you torque all 5 of your nuts up to 400nm, the rotor will still sit in proper alignment and no harm will come to it. I stand by my statement. Over-torquing wont warp rotors

There are strong arguments concerning the torque specs for lubricated fasteners. If one should go on dry, then the torque spec changes when lubed.
.

So many arguments for and against lubing nuts. I think it's about 30% of the internet actually I will concede that torque specs are always quoted dry and will change when wet.

Torque specs for wheels nuts are DRY torque. Actually, you should never put grease on wheel lugs / nuts.

Dry torque confirmed :thumbs_up: I'm interested as to why you say that lug nuts should never be lubed. Is it simply because of the hydroponic barrier created? or something else?

 

[JuneBug]

As stated, if you heat up your rotors and apply the handbrake when you park the car before giving them a chance to cool, then the part of the rotor touching the brake pads will cool at a slower rate than the part exposed to air. It's the difference in the rate of cooling that causes the warping. The rotor needs to cool evenly.

It's statements like this that make me doubt your knowledge of the RAV4. As far as I know, the RAV4 has NEVER used rotors and brake pads for the handbrake. It uses a DRUM built into the rotor with brake SHOES for the handbrake. At least from the 2006-2016 model years.

Oh, and I once owned a Mustang, and after having new tires installed, I noticed the pulsing in the front brakes. I took it back to the shop and the manager personally hand torqued the lug nuts in front of me. No more pulsing.

 

[D.Spec]

It's statements like this that make me doubt your knowledge of the RAV4. As far as I know, the RAV4 has NEVER used rotors and brake pads for the handbrake. It uses a DRUM built into the rotor with brake SHOES for the handbrake. At least from the 2006-2016 model years.

Oh, and I once owned a Mustang, and after having new tires installed, I noticed the pulsing in the front brakes. I took it back to the shop and the manager personally hand torqued the lug nuts in front of me. No more pulsing.

Hahaha. After owning a Rav for all of 3 weeks now, I'll happily admit that I know nothing about it. I was just making a generalisation regarding the sorts of things that actually do warp rotors in cars.

Thanks for the Rav-specific info though. :cheers:

Like you said with your Mustang: after getting re-torqued, the pulsing went away. Had the rotors been warped, then re-torquing the nuts would have had no effect on the pulsing since the rotors would have still been warped.

 

[JuneBug]

Like you said with your Mustang: after getting re-torqued, the pulsing went away. Had the rotors been warped, then re-torquing the nuts would have had no effect on the pulsing since the rotors would have still been warped.

OK, you're right, the rotors weren't warped, but the rims must have been in a bind causing a similar effect.

 

[FixIt]

The main cause of brake rotor warping is sticky caliper slides and pad mounts. If the pads don't retract from the rotor when the brake pedal is released, the pads will lightly touch the rotor, causing it to overheat and that is what causes the rotor to warp.

 

[mwn]

"The main killer of rotors is heat. Driving and working the brakes a lot and not letting them cool down before putting you handbrake on is the quickest way to warp them, and something people don't often realise."

You do understand that no vehicles have their parking/hand brake handle attached to the front brakes and front rotors are the ones that most often end up "warped"?

 

[Mikey D.]

The main cause of brake rotor warping is sticky caliper slides and pad mounts. If the pads don't retract from the rotor when the brake pedal is released, the pads will lightly touch the rotor, causing it to overheat and that is what causes the rotor to warp.

In the early 2000's Daimler Chrysler was being sued in a class action suit over brake warpage. The OEM pad manufacturer and the OEM rotor manufacturer were pointing fingers at each other.

I had 3 Jeep Grand Cherokees and 2 needed the rotors replaced prematurely. First time was a warranty issue, after that they said we were responsible and it happened once more.

My '90 GC was fine until Chrysler did a recall on the front brakes in 2000 due to a rust issue - replaced the originals with those inferior parts and all heck broke out not long after that. One of my '03 GC's needed a replacement (still using the inferior parts) while the other '03 had different rotors from Chrysler and never had a problem.

Never had any warpage problems on any other vehicle that I ever drove before.

Guess you can add inferior parts to that cause list too.


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[FixIt]

You do understand that no vehicles have their parking/hand brake handle attached to the front brakes

Certain year Subaru vehicles did have the packing brake on the front wheels.

The 1983 Subaru Brat used this design.

 

[ronbo1313]

Another problem that people think is wrapping of the rotor with pulsating is that the brakes weren't probably "bedded".:surprise Bedding is a transfer of brake material to rotor. I was told years ago by a Wagner Brake tech to drive my car at 20 mph and brake about 20 times to transfer material.:smile

 

[D.Spec]

"The main killer of rotors is heat. Driving and working the brakes a lot and not letting them cool down before putting you handbrake on is the quickest way to warp them, and something people don't often realise."

You do understand that no vehicles have their parking/hand brake handle attached to the front brakes and front rotors are the ones that most often end up "warped"?

Subaru, Alpha Romeo, Peugeot, and Renault (to name but a few) are manufacturers that have created vehicles with handbrakes that attach to the front wheels ;-)

 

[.233562]

Torquing tire lug nuts.

Recently had a pinhole leak in the sidewall of my right front tire. Took to dealer and for new tire replacement. Took tire home and mounted on my 2015 Limited. I used a Beam type torque wrench to tighten the lug nut to 76 Ft/lbs. One thing to add; a torque wrench needs to be calibrated periodically to check it's Precision and accuracy. I have worked in calibration laboratories on electronic and physical/dimensional test equipment, including various types of torque wrenches. The beam type torque wrench is what I would recommend. Also, proper usage of a torque wrench is key. On my torque wrench, the flexible handle must be kept straight when torquing. Of course no added extension is to be used with the torque wrench except the short socket that goes into the lug nut. Otherwise the torque will be off.

 

[mavrick1903]

If I'm not mistaken, grease should not be applied to studies or plugs. Rather: use anti seize.


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