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Do you have any concerns with replacing roof (tweaking the chasis)? Are they going to have the car on the straightening bench while they remove and install the new roof?
Do you have any concerns with replacing roof (tweaking the chasis)? Are they going to have the car on the straightening bench while they remove and install the new roof?
No concern at all. Doing this with car on ground. The rood panel was spot-welded on from the factory. The body shop will be using very high strength automotive body epoxy(similar if not same as on 991). They haven done this on many cars over the years with no failure.
When I was building my motor, I could NOT find the Porsche specs for the Pistons and Cylinders for the GT3 motor. I was looking for piston to cylinder clearance, ring gaps... Just could not find it. And that is with calling Mahle and speaking to a couple of engineers there and having a lot of Porsche documentation...
If you are installing aftermarket parts, the manufacturer should be able to give you that...
Now that the 2018 racing season is over, the show seasons begins for us. Same as the years before I'll be setting up and exhibiting at SEMA(Las Vegas, Oct 30-Nov 2) and PRI(Indianapolis Dec 6-8) for DSC Sport. Here's a few progress photos before I sign out. Photos from Jack @ Euro Pros. The lid work is looking good! Can't wait to get the car back.
I was getting some pad knock(aka knock-back) so here's what I did:
1) Checked wheel bearings for play.
2) Make sure floating hardware are indeed floating, not blinding.
3) For extra measure(just because I that type of guys), install 6-lb anti knock back springs behind each one of the brake caliper pistons. And I became aware that there's Titainum puck race option, so of course I want that!
The Ti puck is factory-pressed into the aluminum piston which came as an assembly. The Ti puck isn't available by itself since each piston is machined precisely to fit each puck.
The bigger OD flange of the Ti puck should promote air cooling. The 991 Cup caliper pistons have a similar large OD flange.
The back of each piston is machined to center the anti-knock back spring.
I decided to delete the dust boots on the calipers while I am in there.
Removing the standard aluminum pistons.
Installing the Ti's, one bore at a time, one caliper at a time.
I started with the rear caliper first, here's a finished one.
Four and half hours later, during that time I completely forgot to eat dinner and go #1...sorry TMI, on to the fronts.
While I'm in there, I proactively replaced the brake master cylinder as a maintenance item and cleaned out the bowl.
There are the take-off standard aluminum pistons. I can throw them at people who annoys me...LOL
Tom, I see you're running into knock-back as well. Really curious how your Ti + antiknockback works out. I like to do one thing at a time, so I started with the floating hardware. Haven't had a chance to drive it though.
Yeah, I lightly tapped the brake pedal with my left foot just before brake zone. After a day of doing that it became a habit and doesn't affect the laps.
The springs are effective. The Ti pistons don't do anything for knock-back but they do make the brake modulation pretty awesome through the run session by retarding heat transfer to the fluid.
Originally Posted by rbahr
Couple of things.
Knockback usually indicates runout on the hub - wheel bearings ok?
WRT lightweight hub - be sure to replace the $60 washer as well as Locktite
Ray
Originally Posted by Tom-TPC Racing
Yep. That was the first item I checked as per post # 861.
Sure did. Thanks.
Sorry for the lengthy multi-quotes and for being out of sequence of topic. I wanted to share a revelation on the pad knock that I experienced back in the Summer while the info is still kinda fresh in my head. So, I eventually did find play on the right front wheel bearing just before I sent the car to the body shop for frame repair. Here's the story and chain of events-
Like many of you guys, I often do the standard routine of shaking each wheel, turn and shake again every 90 degrees of rotation(every quarter-turn) to check for obvious wheel bearing play. This method is pretty much in all the pre-track tech inspection forms. While this method serves the purpose for finding a badly worn wheel bearings it doesn't always find the less obvious wear. Short of having a lateral load tester, best I can do beyond the standard wheel shake is to rotate each wheel at every 30 degrees instead of 90 degrees(that's every 1/12th of a turn instead of 1/4th of a turn), and shake vigorously until my wrists hurt like a ******... Sure enough there was 3mm of play on the right front wheel bearing at one particular spot during the rotation, and the play was repeatable at that same spot.
Thinking about it, I knew exactly when the right front wheel bearing damage occurred. It was one night in December 2017 driving home from work. I drove through a construction zone near my house, it was dark outside and I didn't see a chunk of pavement missing and felt a very harsh jar to the right front. That jar was hard enough to pop the socket off the OEM right front sway bar bar link. This happened before the engine rebuild so I replaced the right front sway bar link with another OEM link and thought that was the extent of the jar and that OEM link was 10-years old anyway. I replaced the link and completely forgot about it and went on to focusing on the engine build. I had no idea that hard jar would come back to haunt me!
Fast forward to the April 2018, the first track day with the newly build 4.0 engine, the brake pedal didn't feel as precise nor firm as it did compared to 2017, for lack of a better term, it was sloppy. That prompted me to get a $9K brake system to replace the OEM for my next track day in June. First track outing with the new brakes I experienced some pad knock at certain brake zones after the warm up laps so I spend another $2.5K on master cylinder, floating hardware, anti-knock springs, and Ti pistons for my next track in August. The tech support guy at Stoptech kept telling me it was the wheel bearing since June but I was too stubborn at the time to accept his input just because I didn't think beyond the standard wheel bearing shake routine(and you'd think of all people, I would accept the fact that the actual operating load to the bearing is Way Way more than a person can produce by shaking the wheel...Stubbornness in full effect there on my part.), and I convinced myself that if a wheel bearing is bad enough to cause pad knock then it'd cause ABS sensor issues as well. I know now that's not the case with the Stoptech brake calipers. I think the OEM GT3 calipers is more "numb" to wheel bearing play when it comes to causing pad knock, perhaps this has to do with the design pulling the pistons back enough to prevent mild-level knocks...in my experience the OEM GT3 calipers seemed to manifest advanced-level wheel bearing play to ABS issues rather than pad knock. So, I had the wheel bearing play on the right front since December of last year, I misread the symptom of the sloppy pedal from the OEM GT3 calipers and chose to replace them with the Stoptech kit which happens to react differently to wheel bearing play than the OEM GT3 calipers. And that's not a bad thing at all, now that I know what its trying to communicate to me.
BTW, despite of the wheel bearing play the anti-knock springs was the BOSS! VERY effective in mitigating the pad knock from the wheel bearing play. Like if I were in a race and developed wheel bearing play during the race, having the anti-knock springs would totally allow me to continue to race with only a slight soft pedal feel at the top 1/4 travel of the pedal to set the pads and then completely manageable and safe at the remaining travel. Whereas without the anti-knock springs the pedal was free falling until near the bottom, thus requiring a left foot tap at the pedal to set the pads.
My closing to this post is... in the way that curiosity killed the cat, my own stubbornness cost me a lot of unnecessary aggravation. I have zero regret on upgrading the brakes, the stopping power and feel is noticeably superior to OEM(once the pads are set), I only wished that I knew then what I know now- 1) pad knock after left turns = a bad right side wheel bearing, and 2) aftermarket brake calipers made from more rigid material and/or have different piston resting position reacts differently to wheel bearing play than OEM calipers.
Last edited by Tom@TPC Racing; 11-12-2018 at 11:03 PM.
Glad you found your problem. Like you, I am unable to detect a failing wheel bearing, a pretty bad one is easy! As an FYI, I have also seen a failing wheel hub look just like a wheel bearing problem!
On the bright side this thing will stop on a dime now!
Tom, did you check for rotor run out? I wonder if my wheel bearings are bad as well (but I LFB to set my pads when I'm on track). Also curious, how much additional wear you see with the springs.
10-10-2018, 02:13 PM
