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Recently purchased a wonderful 991.1 GTS Cab. from a great rennlister. Loving this car. I had noticed, however, a slight pulsation in the brake pedal that I felt was probably from some worn rotors, which had visible signs of grooving. The rotors I knew had been turned once and the brake pads where the Centric Posi-Quiets. I had taken the GTS on a spirited mountain drive and I had to back down due to brake fade and severe pulsation. Time for new rotors and semi metallic Textar pads (OEM). Decided on the Sebro slotted rotors which seemed like a cost effective decent rotor. Finished installing my new rotors and pads today. To confirm the cause of the pulsation, I had purchased a Magnetic Dial Indicator to get a reading on lateral run out, both on the worn rotors, and the new set up. The old rotors had a 12/1000s runout, which is way out of spec. Upon installing the new rotors, I cleaned the the surface rust of the hub with scrotch brite hub cleaning kit. Worked great with my drill as it comes with a drill bit attachment. The new Sebro rotors all had a lateral run out of 2/1000 which is normal. This confirms there is no issue with the bearings or hub that could contribute to the lateral runout. Took the GTS for a test drive to bed the pads, and happy to report zero pulsation, and no noise from the brakes. Can't wait to hit the Smokies again for another drive. Here are a couple pics related to the job today.
Coincidentally I just bought that exact same gauge and used it to check the runout on my pickup truck's rotors just last weekend... it was well-priced and highly rated on Amazon. It proved a little tricky getting those arms articulated into a good place for measurement, I wished they were just a tad longer, but after some experimentation it worked out nicely.
Purchased the SEBRO SLOTTED rotors from Europaparts (https://www.europaparts.com), found out they are a bit cheaper at some other sites. Rotors came within 3 days however, so I was happy. Here are some screenshots of the sale page with part numbers.
David - nice write up. I'll have to read up on this runout tool and exactly what it tells the user. I'm in Charlotte too, are you part of the PCA? If so maybe we can meet at an event. My buddies and I try to do a mountain run once a month at least. Some of the PCA drives are just too slow (funeral like).
David - nice write up. I'll have to read up on this runout tool and exactly what it tells the user. I'm in Charlotte too, are you part of the PCA? If so maybe we can meet at an event. My buddies and I try to do a mountain run once a month at least. Some of the PCA drives are just too slow (funeral like).
Yes, long time PCA member. Don't go to the meetings though. DE's, autocrosses over the years. I have a friends with a GT3 RS, Cayman, M4, and a Noble that we go for drives with a couple times a year. Would be nice to get out a bit more frequently to those amazing mountain roads. Definitely reach out to me when you plan another drive. I need an excuse to test out the brakes. Do you have a 991.1 GTS? Trying to tell from your avatar.
The lateral runout measures any warping or lack of squareness of your measured item. You can test the rotor, hub, wheel ect. The gauge sits on one spot, and you turn the wheel to see if the gauge moves in or out. Would hate to install a brand new rotor, only to have it wear unevenly due to some rust build up on the hub, for instance. I have done many brake changes for years, but only now learned about this simple yet vital measurement.
I always paint the hub to rotor contact surface and the rotor to wheel contact surface with a very light coat of antiseize compound an never have corrosion issues.
10-03-2018, 11:22 PM
Pulsating Brakes
