Tech

I had that happen when I came in to what I felt was a bit too hard where my braking was a tad late into turn 8 at MOSPORT. This was in a Porsche 992 S or 4S during one of their track days and part of that was leaving the stability control on (personally, I have no use for nanny systems like stability control and ABS, even on my motorcycles). Certainly not a "slam on your bakes" but a much faster brake application providing a bit too much weight shift to the front. BTW, I have had that butt wiggle before in a car without nanny controls.

As long as nobody is slowing me down for it, I usually hit 152 mph prior to the turn in at turn 8. There is a long uphill straight leading up to it from the Moss Corner hairpin at turn 5B which is slower and provides a slower drive out. Turn 5C, 6 and 7 are straight in my books and allow for full open throttle to turn 8.

I am getting all pumped up for the next track day. Little wonder why I do not drive my Porsche on public roads...it is damn boring. Last year I put just over 800 miles on the GTS; I put more on my motorcycles.

Chief F1 Fan

So the progression continued throughout today and I'm really getting consistent with my lines and braking. The instructor said today "you just NAIL that Esses and you just left that GT3 in the dust 2x there." No Phil, no wiggle at all, not even the slightest and I've never heard anyone complain about that either. Strange. Maybe it's a Sebring-specific thing (pavement?) This really is an addicting activity for sure, expensive too.

SamDoe1

How fast are you blowing through tires and brake pads doing all of this? Looks like a ton of fun though!

Chief F1 Fan

I just put a more aggressive set of pads on my T by Ferodo and still had 50% left of those I took off. At that point, I'd guess those pads conservatively had ~200 laps at the Glen on the long course (3.4 miles). The tires needed replacing at 14K which is what I expected anyway.

Chief F1 Fan

addendum: I see the reason why people prefer buckets over seats for tracking. My left lower butt cheek was sore this morning when I woke up. I wondered WTH happened, first lap today I was like "Oh now I know where that ache came from!" Tracking is a violent, rollicking good time. Also going to buy one of these as well. https://www.simpsonraceproducts.com/...straints/hans/

00TL-P3.2

Any plans for harnesses? Even if just for track use.

Chief F1 Fan

^^ that's what the Simpson HANS device is meant to be a substitute for. I don't want to bolt a roll cage in to my car bc that's what's required to use harnesses in DE events.

00TL-P3.2

Gotcha.
Was thinking harness more for less fatigue on the body holding yourself in the corners. But, I'm sure the T's seats are very supportive.

Back in my autocross days, we did the poor man's harness. Push the seat back, lock the belt with a tug & pull the seat forward.
Works better with manual seats.

PhilB81

nobody willing to give you a butt massage there?

dont they make a harness that goes around your torso which then latches to a Hans to tether your head / neck?

adding the roll bar in your car would be a pain since you have the rear seat in (btw, 100% right decision to have a rear seat in my opinion).
Enjoy the rest of your time at the track!

Chief F1 Fan

No couldn't find a willing masseuse but there were a good number of hotties there. I do believe Simpson has the torso harness you speak off, a buddy has the HANS III and said it rides up so it does need to be held from below. Yeah, never will I put a roll bar in my T. I'll keep it forever and add a used P car to the fold used mostly for tracking but likely still steerable.

Tech

On the subject of brakes since you and Chief (and possibly others on here) have lots of track time, I had an issue a couple of weeks ago at MOSPORT.

This is my fourth season using the 992 S or 4S on the track and I have never had the following issue ever. The vehicle had less than 600 miles on it, basically a new car. During one of my sessions on the GP track, after about the second lap I started to get a lot of vibration and it got worse while under braking, especially heavy braking. Two more laps of that and I pulled into the pits. Doing almost 150 MPH at the end of the Mario Andretti straight, the last thing I wanted was a wheel coming off (loose wheel bolts or wheel bearing nut).

Coming to a stop in pit lane, I rotated my steering wheel CCW in order to see my tire (I felt it came from the left side) and the brakes were smoking (first time I ever saw that). The other instructor came to meet me and explained what it was (can't remember exactly what he said) and he stated "not to worry". OK, so I went back out.

Anyone know what the instructor was referring to. Some kind of "tire pick-up" and why would it get worse under braking? I work on cars - motorcycles - aircraft from A to Z and this issue is news to me.

On a similar note, as for the brake wiggle, this year I was getting it both from the front and back at the same time...very hard braking. Maybe I'll brake a bit earlier and take it easier on the brakes and tires. That wiggle could be due to the nanny controls if they are on.

Chief F1 Fan

Did you have a lot of as David Hobbes would say, "clag" on your hot tires? Tires pick up other bits of rubber when hot and make your tires a bit rougher riding. I don't know why your brakes would smoke though and when you say the brakes were smoking I assume you mean the pads?

PhilB81

LOL at the guy with “don’t worry about it”. If I’m driving a car and it develops a vibration all of a sudden, I’m would be worried about it until I know the root cause.
Did you feel any pulse on your brake pedal? Or it was purely a car shake? I mean it is possible that tire pickup on a front tire could shake the and while braking, you load the front so much more that it amplifies the vibration… Being a S or 4S, I assume steel brakes?

as far as smoking brakes, I saw that a few times with my cousins touring racing or track days, but from what I remember it was just debris from the track caught in the caliper. (Not between the pad and the disc, just one of the other nook and crannies, like a piece of “clay” sitting at the top of the pads, touching the disc a bit nestled in the caliper.

regarding the wiggle, my instructor’s fix was to roll on the brake and once you’re on, absolutely clamp hard, just don’t transition from throttle to brake in a stabbing fashion causing the nose to rapidly dive. When it was doing the wiggle, no lights were coming on the dash, and I didn’t feel the ABS kick in. That said, it’s very possible the Nannie’s intervene before displays are shown on the dash.

Tech

So I heard but I was staying off them on the correct line.

I would think it was the pads. I mean Porsche brakes are some of the best on a car, if not the best and my level of driving cannot be taxing them 100%. Although MOSPORT is known as the fastest track in North America and the brake hats were hot and I mean ultra hot, forget about laying a finger on them.

I have read stick-on weights due to high heat can let go, but then why would vibrations diminish on other runs.

Edited to add: are you disengaging your parking/emergency brakes before shutting your 992 down so that they are not in contact after a cool-down lap?

Chief F1 Fan

Yeah must be the pads burning which on my car were made by Pagid, a solid brake pad provider. Thankfully my car is a manual so the parking brakes do not ever engage automatically.

Tech

Same here, but the instructor who also races NASCAR knows more than I do when it comes to track issues. I think he called it "tire or rubber pick-up". I don't take chances coming from the aviation world where many of my friends that also instructed with me and others that I flew with with are six-feet under. Sam Fellows told me "right move" when I pulled in. His father was Ron Fellows of Corvette fame.

In any case, I am going to keep on digging for an explanation till the answer I get satisfies me.

No brake pedal shake, just a front end vibration. You got a point there and I think you got it on loading the front under very hard braking making the vibration feel worse. Yes, steel brakes on the S and 4S.

The last thing you want to do is see-saw the vehicle during braking. I saw Sam Fellows' track data and his braking was a rapid rise and a slow decay so that the front does not bounce up on rebound to upset his car.

The nanny control is a stability control where brakes are applied to maintain...control. Could be why the rear is snaking back and forth a little while under very heavy braking. This year, the front and rear were both doing that at the same time. Personally, I hate ALL nanny controls be it ABS, stability control, etc....I wish my cars and my last motorcycle did not have ABS.

PhilB81

I am no where near talented enough, so Nannie’s stay on during track days, but I do put on my big boy pants during Autocross…

you mentioning ABS brought back a good ole memory. A family member had an event on highway once. ( I mean an organized event, traffic was closed on that side of the highway) Autocross style but bigger speed, and in a transition he went a bit wide going over the “wake up”rumbles and all the gravel on the side of the highway. The back end immediately came around, he went full lock, but wasn’t enough to catch it so his next move was stomp the brakes to lock up and continue the direction of travel. Unfortunately, the car had abs so it wanted to go the way the car was pointing, which was a deep V grassy median divider, then up the other end, and crossed into the incoming highway traffic lanes (which were not blocked, only one direction was stopped) … anyways, luckily traffic was super light, but scary moment. We had a good ole camcorder in the car, he was absolutely F-bombing the ABS… this was in the late 90s, fun times…


oh regarding the weights flying off during a track day, I totally had that happen, but that was very much speed related, I don’t remember braking affecting it any. I actually skipped out my last session, I’m a bit overly risk averse, so if I’m not 100% comfortable, I don’t push myself.