Gert 993

Im reading it now, nice article on how brakes work, but I disagree about rotors not warping.
All warped rotors i replaced in my life where warped!
I never changed a rotor before i measured this with a dial gauge.
I Always made 2 measurements, one on the rotors brake surface, and one on the wheelhub to make sure the rotor is warped and not the wheel hub.




I ones had a deformed wheel hub, but this ony occurs when the car was invloved in a accident. in this case the rotor have to be replaced as well, because it will not be straight anymore.
The picture is just an example, before measuring you should always fasten the wheel nuts.

The guy who wrote this article is making assumptions that the car industry is changing parts based on the symptoms without measuring.
I can hardly beleive this guy has expirience in a real service shop.

orangecurry

OK - so you and he differ in your views - that's cool.

But he is an engineer at StopTech - they make brake parts, and are very well known and used in Europe.

Gert 993

All car manufactures have specs on how far a rotor is allowed to warp.
If they did not warp, then all engineers at all the manufactures are wrong too?
Page of the Porsche 993 specs handbook below.


I know how many rotors i measured, and have seen warped with my own eyes.
These info i provide you is to help you all. I know the truth by experience.
You guys do what you believe is right.

orangecurry

like I said Gert, everyone knows lateral runout exists.

But it's caused by damage to the disc surface, and build-up of pad material.

They don't warp.

Gert 993

Good luck

pp000830

Hi Greg,
Ouch, iron rotors, international shipping, seems like incompatible terms.
Rotors tend to warp more easily as they reach their wear limit.
The rotor wear limit on the 993, I believe, is 0.05mm 0r about 20 thousandths of an inch so if the raised non-pad contact lip-edge is of any height at all measure the rotors first. As 993 rotors approach their wear limit the brakes can become quite noisy when just the pads are replaced.
Andy

techman1

1973 Olds Cutlass Supreme. Back in 1982.
The rotors were definitely warped.
Might have had something to do with a stuck caliper.

1982 Datsun 280 zx. Warped front rotor. about 1988.

Yep, rotors do warp.

As a side not, i recall asking Nissan why they warped. The service advisor said possibly not torqueing the lug nuts properly. If one is loose, when the rotor gets hot it would cause the warp.

Khloesdad

I've done a few times with drilled rotors. No issues whatsoever. Their not taking much off. Basically skimming is just truing them up. Just make sure its a reputable shop.

pp000830

Yes, it is about torquing the lug nuts on is a star sequence to the proper torque value. My understanding is so it doesn't set up stresses in the rotor hat that cause the rotor to warp during the constant heat cycling the rotor is exposed to.
Also sustained holding the car stationary with the brake peddle with hot rotors cause uneven heat conduction to the calipers and can warp the rotors. The solution is if standing after a hot run use the parking brake to hold the car and release the foot brake so the caliper is not clamped to the rotor and it can cool down evenly.

Greg Bell

Thank you all for your replies. It's good to see a debate going where both sides are presented allowing you to make an informed decision.

My take on all this, my rotors do have a lip, yes they can be skimmed and no, I'm not going to worry about it. I'll wait until they reach their wear limit then start another project to source reasonably priced rotors fro around the globe..

I'm a firm believer in point 1. made above by Gert, if it aint broke don't fix it. I was in IT for 30+ years and I lived by this mantra.

Mark in Baltimore

Rotors can and do warp; my first gen Sequoias were notorious for it. I remember going down a steep hill at a decent clip when a driver in front of me jammed on the brakes. My suddenly perfect rotors warped, right then and there. I solved the problem by buying Brembo rotors from Tire Rack.

However, that little story has absolutely nothing to do with 993 rotors, the topic at hand. I tracked/raced my former 993 for over ten years and never, ever warped a rotor. I was often at the pointy end of the grid, so I wasn't just stroking around.

I did have a pad deposit issue once when I was using Pagid Oranges. Hawk Blues, a very abrasive pad, cleared that right up. Never used Oranges again.

After hot sessions, I would leave the car in first gear and never activate the parking brake. Similarly, I avoided stepping on the brake pedal while sitting at scrutineering or the paddock in an effort to avoid heat transfer into one spot of the rotor, even though I knew the pads were likely touching the rotors anyway.

FWIW, the subject of Porsche 993 rotor warping has been discussed before and two former and very well-respected 993 technical gurus have opined on the subject: https://rennlist.com/forums/993-foru...-confused.html

Although Steve Weiner has retired and is hardly ever on the board, most everyone always took notice of his experiences and observations. Similarly, Chris Walrod, formerly of Swift Engineering and now with Singer, was another person who had a deep reserve of knowledge that could be counted on for tested veracity.

That said, Greg, your rotors may have some warping for whatever reason. The run-out can be easily checked. If they are warped, just have them turned, especially since parts are so dear over there.

Best of luck.

Gert 993

hi Mark,
Greg his rotors are not warped.
The debat was actually on warping of rotors in general, not specific for the 993.
i’m actually surprised you raced your 993 and did not warp a rotor.
It is good to hear there are no problems with the rotors of the 993’s.