X-drilled & Slotted Rotors CAN be cut!

[Lil bastard]

@Randall - You sure can, very easy to do. This is why you should never use an impact wrench to replace the wheel bolts (and insist that your shop doesn't either, despite what they may say).

These are too prone to over-torque the bolts due to variances in the air pressure and gauges. They will produce significant differences in torque between all 5 wheel bolts.

Impact wrench is OK for removal, but always replace manually, using a torque wrench for final tightening in a cross pattern.

[tholyoak]

Believe what you wish, but there is no way over torquing your wheel lugs is going to warp a rotor.

The wheel stud attaches to the hub, not the rotor, the rotor sits flat against the hub, sandwiched between the wheel and the hub. If you were able to exert enough torque by over torquing, you would distort the hub not the rotor. Secondly if you did warp the rotor in this fashion, you would warp the mounting surface, and turning the disc would not cure the runout problem.

There many reasons to use a proper torque wrench to attach the wheels but warping the rotors in not one of them. Now if you under torque the wheels, the rotor could distort under braking forces if not clamped with the correct force between the wheel and hub, which will lead to damage.

Todd

[CJ_Boxster]

Oh i forgot to post my rotor thickness after the cutting. Both rotors i cut measure at 23.53mm and 23.54mm thickness.

About the warping cause by over torqing the lugs... Zimmerman told me that can happen as well as people at Brembo.

Personally i think it was a combonation of over torqed wheels and too much zinc plating... My shipment of Zimmermans were delayed cause of a defect in the plating so they replated them once more before sending them to me and i noticed that the plating was also on the surface area of the discs where the brake pads touch so i think when my brake pads were trying to rub that zinc off... that it generated more heat & slippage and causes them to warp... But thats just a theory

[CJ_Boxster]

Originally Posted by tholyoak

Believe what you wish, but there is no way over torquing your wheel lugs is going to warp a rotor.

The wheel stud attaches to the hub, not the rotor, the rotor sits flat against the hub, sandwiched between the wheel and the hub. If you were able to exert enough torque by over torquing, you would distort the hub not the rotor. Secondly if you did warp the rotor in this fashion, you would warp the mounting surface, and turning the disc would not cure the runout problem.

There many reasons to use a proper torque wrench to attach the wheels but warping the rotors in not one of them. Now if you under torque the wheels, the rotor could distort under braking forces if not clamped with the correct force between the wheel and hub, which will lead to damage.

Todd

Todd your missing one factor in your theory there... What does the Rotor do when its gets Hot..... It expands and not just the disc, the Hat of the rotor also expands when hot, and if the torq on the lugs is too tight, it will not allow the hat to expand with the heated surface area of the disc and will cause warping.

Ever seen a 2 peice racing Rotor... The Disc/Surface area is separate from the hat and only held together by little nuts and bolts, This is because the heat that will be generated will be so high that a solid 1 peice rotor design's hat will not beable to expand enough to prevent warping. If the Hat cannot expand, it'll warp

[tholyoak]

You are entitled to your opinion and maybe I am wrong but I don't believe the rotor hat is going to expand appreciably when sandwiched between the hub surface and the wheel. Which are also going to expand. And even if it did, the difference in the expansion between being sandwiched with the correct 96ftlbs of torque vs say a mis-torqued wheel at where some lugs are at 120ftlbs of torque is not going to lead to appreciable distortion of the rotor hat.

Secondly on a street car you are never going to experience the types of temperatures you refer to in race cars. I would be pretty concerned if I saw someones rotors glowing red hot at night on the exit ramp as you see at night during Le Mans. The most common way people warp rotors on the street is when they run them too thin or they do some heavy braking and while the rotor is hot they still have their foot on the brake, thus the pads make contact with the rotor both melting some pad material to the disc and/or resulting in differential cooling of the disc leading to warping.

Todd

[Lil bastard]

Sorry to say you are misinformed.

I had a shop mount some tires for me and within 50 mi. all 4 rotors were warped. They readily admitted they accidentally over-torqued the bolts due to a malfunctioning air regulator in the shop and paid $850 out-of-pocket to replace them.

There are a number of articles out there on this subject. Even AutoZone warns of this in their DIY Tire Change guide - page down to the WARNING box - http://www.autozone.com/az/cds/en_us/0900823d/80/1b/d6/9f/0900823d801bd69f/repairInfoPages.htm

[tholyoak]

This is the last I will say about this, and go ahead and believe what you want.

When your tech, tells you that over tightening of wheels can warp rotors you are either not understanding him or he doesn't understand what he was originally told.

Over tightening of the wheel will not causes warping the rotor, what it can do is distort the hub flange on which the rotor sits. This distortion causes rotor runout problems, that when you measure with a dial gauge on the rotor surface will appear to be warped rotors. If left alone this problem will result in further braking issues.

There is no physical way that over torquing of the wheel to the hub will cause physical warping of the rotor. That is my opinion from working on Porsches for almost 20 years, not on what I read on the Autozone website or my local garage mechanic told me.

Todd

[Lil bastard]

@tholyoak - I'm sorry, normally I wouldn't pursue an arguement. And I don't mean to belittle or diminish your mechanical abilities in the least. I've read many of your posts and they contain valuable information, I don't think there's any question about your skill level. But in this case, you're simply wrong.

It's not a matter of what one believes, this is fact. I too have been repairing and maintaining cars of all sorts for 20 years and then some, incl. porsches, so I can assure you there was no misunderstanding of what my Tire shop told me.

The reason I'm persisting is that this is one problem which is easy to avoid, but has expensive consequences if the procedure's not done correctly ($800+ for a set of rotors). I don't want readers to get the impression that this is a matter of belief because it isn't.

Over torqueing of lug nuts and wheel bolts is a major cause of rotor warping. Full stop.

If you won't accept an article from AutoZone as proof, here are a dozen more that you can look over, and I hope, learn something new from.

• http://www.articleblast.com/Auto_and_Trucks/General/Warping_Automobile_Disk_Brake_Rotors_are_Preventab le/
  
  http://www.automedia.com/Replacement_Rotors/ccr20050201rr/2
  
  http://www.alldata.com/techtips/2001/20010430b.html
  
  http://www.thecarconnection.com/Enthusiasts/Ask_a_Mechanic/On_Site_Mechanic_for_Dec_27_1999.S209.A1474.html?p g=2
  
  http://www.mpt.org/motorweek/goss/21008.shtml
  
  http://en.wikipedia.org/wiki/Rotor_(brake)
  
  http://autorepair.about.com/library/faqs/bl815.htm
  
  http://www.ctbrakes.com/faqs.html#16
  
  http://www.thevolvosite.com/volvo-brake-rotors-and-warping.htm
  
  http://www.brakewarehouse.com/brkewrhsefaqs.asp#top61
  
  http://www.bestbrakes.com/how_to_install_brakes.shtml
  
  http://www.mpt.org/motorweek/goss/2436.shtml