Any Rennlisters from New Zealand?
01-09-2016, 07:15 AM
Three Wheelin'
Hi Graeme. I think we may be thinking of different degrees of pad transfer here?
I take it you are talking about it in the more common negative sense - the lumpy kind of transfer that nobody wants and usually comes from applying really hot pads to the rotors when stopped (like handbrake use in the pits at track or having to stop for an intersection just after a special stage)? Because it's uneven and thick this pad transfer causes shuddering and can even damage the rotors by interfering with their cooling so yes, quickly sanding it off as you do is about the only way to treat it.
I probably didn't choose my words well but I'm instead talking about the very thin and even transfer layer - just a very thin film - that is created on the rotors by bedding pads and rotors or at least running them hot in some cases. I figure you'll already know it anyway but it may be of use to some: that thin even film is our friend. With the pads are in their normal operating heat range there is a constant exchange of pad compound molecules between pads and the film on the rotors when we brake but it stays in equilibrium and doesn't build up. The breaking of the molecular bonds of the pad compound as it transfers back and forth from pad to rotor provides a fair bit of the braking force wihout generating as much heat as would just pure surface to surface friction. It's kind of like a thin layer of 'golden syrup' on a cold day makes it hard to slide two bits of wood against each other.
That tiny film also dampens vibrations. The reason my endurance brakes are quiet on track is that they work in their intended heat range that maintains that film. They get noisy on street because they run too cool to maintain that film and once they've scraped it off after 100km or so of road driving, the squealing starts again. Would also be eating my rotors a bit quicker.
There may be some compounds (sintered pads come to mind) that don't produce a transfer film on the rotor and instead rely on mechanical friction but they run hot and are hard on rotors.
We're all still waiting for the perfect brakes. I'm hoping they'll be one of the best aspects of electric cars once the technology is mature.
I take it you are talking about it in the more common negative sense - the lumpy kind of transfer that nobody wants and usually comes from applying really hot pads to the rotors when stopped (like handbrake use in the pits at track or having to stop for an intersection just after a special stage)? Because it's uneven and thick this pad transfer causes shuddering and can even damage the rotors by interfering with their cooling so yes, quickly sanding it off as you do is about the only way to treat it.
I probably didn't choose my words well but I'm instead talking about the very thin and even transfer layer - just a very thin film - that is created on the rotors by bedding pads and rotors or at least running them hot in some cases. I figure you'll already know it anyway but it may be of use to some: that thin even film is our friend. With the pads are in their normal operating heat range there is a constant exchange of pad compound molecules between pads and the film on the rotors when we brake but it stays in equilibrium and doesn't build up. The breaking of the molecular bonds of the pad compound as it transfers back and forth from pad to rotor provides a fair bit of the braking force wihout generating as much heat as would just pure surface to surface friction. It's kind of like a thin layer of 'golden syrup' on a cold day makes it hard to slide two bits of wood against each other.
That tiny film also dampens vibrations. The reason my endurance brakes are quiet on track is that they work in their intended heat range that maintains that film. They get noisy on street because they run too cool to maintain that film and once they've scraped it off after 100km or so of road driving, the squealing starts again. Would also be eating my rotors a bit quicker.
There may be some compounds (sintered pads come to mind) that don't produce a transfer film on the rotor and instead rely on mechanical friction but they run hot and are hard on rotors.
We're all still waiting for the perfect brakes. I'm hoping they'll be one of the best aspects of electric cars once the technology is mature.
01-09-2016, 07:19 AM
Three Wheelin'
Yes. Have asked them to look at this during big service on Tuesday. First time encountered these issues. Looks like metal has been moved into the holes. Very odd. I bedded the pads/rotors with repeated 120/30km deceleration on a back road then went for a Sunday Ron run - preset much the only time the car has been used since they were fitted. Getting big cooling "clonks" at beginning of cooling lap - audible inside car and picked up from front mounted GoPro. Never heard that before either. It would be nice if they can replace these discs/pads. Right now my 993 brakes better (doesn't bind or judder, just stops as it should). Not read about the issue on the 991 gt3 board either so it's a bit of an unusual one...
01-09-2016, 02:09 PM
Rennlist Member
Yes dust in the holes. I usually blow it out end of day. Interestingly I could break the rough edges away around the holes once cool (eg last night). However it doesn't leave perfect round holes either. I think CCS will need to clean it all up and take a good look at what is happening here...
01-09-2016, 05:03 PM
Rennlist Member
Sure. Hopefully Leong wont mind an will correct me where Im wrong.
First session in the early 18s. Getting feel for car on track and adjusting off tyre pressures. Session one was a bit slippery out on the track (still damp in places and HD have elected to paint parts of the chicanes with new white/red paint which as a warning for Monday is VERY slippery if we and they dont dry out as fast as tarmac).
Session 2 & 3 getting tyre pressures right and some more seat time helped get into the low 16s but very consistent times all scattered within 0.5s or. Adjustment of rear wing fr max attack (more downforce) and removal of front inserts along with stabilizing pressures to preferred settings. New tyres nicely scrubbed in by now and brakes deeply bedded.
Session 5 & 6 were all about improving lines and technique and with the group size shrinking some good clear laps. These two sessions edging into the mid 15s and getting consistency around them. Its all about consistency and Leong is very consistent.
Im not sure what the best lap for him was on this day but somewhere between 15 & 15.5.
The car exhibits a fair bit of understeer on stock settings as many have eluded to so I think by softening the front bar and stiffening the rear, a bit more seat time and some kinder ambients with no head wind the car is capable of breaking consistently into the 13s in Leongs hands in 2016.
Vmax on the straight was around 212, which is only 15kmph off the GT3 on the day. Without the 27kmph head wind I should say 219 is possible.
My view is same driver on a fresh set of MPSC2 and factory geo, same day and conditions the GT4 is a second slower at HD than the GT3 on the 2.7 km circuit. I have no idea but would suggest the GT3RS is one second quicker than the GT3. So Im guessing 11.8 RS, 12.8 GT3, 13.8 GT4. This all seems consistent with times from others between the cars on short tight tracks overseas. I think the longer tracks would see a larger delta as they do for more powerful cars.
Observation from driving with Leong is the car looks well balanced and planted on the track. It doesnt move around as much as the GT3 but that may have been my old tyres vs his new ones. The car sounds best in the middle rev range (2500-5000) IMO and on the track where much driving done above 4500 it didnt appear to be anywhere near as loud as the GT3 (but hard to tell when you have the GT3 engine behind your ear). I ran with the drivers window down for some of the day.
A testament to good driving is the guy with the Cherokee SRT (top of the range model 342kw but factory other than road tyres and SRF). Amaxingly n the straights that thing could haul and coming up the front straight took longer to reel in than expected. The driver a Brit called Simon who I suspect has some significant wheel time behind him could muscle it through corners very effectively...
First session in the early 18s. Getting feel for car on track and adjusting off tyre pressures. Session one was a bit slippery out on the track (still damp in places and HD have elected to paint parts of the chicanes with new white/red paint which as a warning for Monday is VERY slippery if we and they dont dry out as fast as tarmac).
Session 2 & 3 getting tyre pressures right and some more seat time helped get into the low 16s but very consistent times all scattered within 0.5s or. Adjustment of rear wing fr max attack (more downforce) and removal of front inserts along with stabilizing pressures to preferred settings. New tyres nicely scrubbed in by now and brakes deeply bedded.
Session 5 & 6 were all about improving lines and technique and with the group size shrinking some good clear laps. These two sessions edging into the mid 15s and getting consistency around them. Its all about consistency and Leong is very consistent.
Im not sure what the best lap for him was on this day but somewhere between 15 & 15.5.
The car exhibits a fair bit of understeer on stock settings as many have eluded to so I think by softening the front bar and stiffening the rear, a bit more seat time and some kinder ambients with no head wind the car is capable of breaking consistently into the 13s in Leongs hands in 2016.
Vmax on the straight was around 212, which is only 15kmph off the GT3 on the day. Without the 27kmph head wind I should say 219 is possible.
My view is same driver on a fresh set of MPSC2 and factory geo, same day and conditions the GT4 is a second slower at HD than the GT3 on the 2.7 km circuit. I have no idea but would suggest the GT3RS is one second quicker than the GT3. So Im guessing 11.8 RS, 12.8 GT3, 13.8 GT4. This all seems consistent with times from others between the cars on short tight tracks overseas. I think the longer tracks would see a larger delta as they do for more powerful cars.
Observation from driving with Leong is the car looks well balanced and planted on the track. It doesnt move around as much as the GT3 but that may have been my old tyres vs his new ones. The car sounds best in the middle rev range (2500-5000) IMO and on the track where much driving done above 4500 it didnt appear to be anywhere near as loud as the GT3 (but hard to tell when you have the GT3 engine behind your ear). I ran with the drivers window down for some of the day.
A testament to good driving is the guy with the Cherokee SRT (top of the range model 342kw but factory other than road tyres and SRF). Amaxingly n the straights that thing could haul and coming up the front straight took longer to reel in than expected. The driver a Brit called Simon who I suspect has some significant wheel time behind him could muscle it through corners very effectively...
01-09-2016, 05:23 PM
Rennlist Member
My morning's work. Finally a stereo in keeping with the older cars.
01-09-2016, 05:32 PM
Rennlist Member
^^^ Looks good on FB JMC - I still have my Becker Grandprix to install in something. The 3.2 has the (original?) tape deck - which looks the part.
Jen still owns tapes in a box somewhere?? Not sure I want to listen to 80's Madonna and Bros in the car?
Thanks for the feedback Macca - we need to put Aim's in your cars, which will be interesting to see corner speeds. As you and I have both discussed - we don't feel there is a lot with our GT3's over our well set up 993's ,so be interesting to see what a GT4 shows with the GT3 suspension package.
Jen still owns tapes in a box somewhere?? Not sure I want to listen to 80's Madonna and Bros in the car?
Thanks for the feedback Macca - we need to put Aim's in your cars, which will be interesting to see corner speeds. As you and I have both discussed - we don't feel there is a lot with our GT3's over our well set up 993's ,so be interesting to see what a GT4 shows with the GT3 suspension package.
Last edited by kiwi 911; 01-09-2016 at 05:53 PM.
01-09-2016, 07:42 PM
Rennlist Member
Go cars not show cars! Having said that, I want 50m 'respray' room tomorrow.
01-09-2016, 07:58 PM
Rennlist Member
^^^ Looks good on FB JMC - I still have my Becker Grandprix to install in something. The 3.2 has the (original?) tape deck - which looks the part. Jen still owns tapes in a box somewhere?? Not sure I want to listen to 80's Madonna and Bros in the car? Thanks for the feedback Macca - we need to put Aim's in your cars, which will be interesting to see corner speeds. As you and I have both discussed - we don't feel there is a lot with our GT3's over our well set up 993's ,so be interesting to see what a GT4 shows with the GT3 suspension package.
01-10-2016, 02:51 AM
Instructor
All good Macca! Been a little busy, happy enough to wash the car last night to get that banner on, but given what you said about time to dry out, thought I'd leave thew banner till after tomorrow.
Awesome day in the GT4 yesterday. Now I have a car with a cage my son came with me in car for all but one session. First couple of sessions a bit nervous, slightly damp track, new car, driving a manual gearbox on track after a few years with DCT, my son watching every move.... It's been a while since my last sports car so I enjoyed the precision with which you can place these cars, the lack of body roll/weight transfer especially on braking. Loved the auto rev matching on downshifts which means you can concentrate more on pedal pressure at the track.
The car felt great till I saw that my lap times were in the 1.18's, 2 sec slower than my M5.
First thing to sort was the tyre pressures and with help from Mark to understand the TPMS and race mode, it took two sessions to fine tune a setup where the pressures were at 36psi on all four corners at the end of a session. I thought this pretty cool as I could never get pressures sorted on the M5. I used to come off the track, drive out to the prison and back to allow the brakes to cool before stopping, by which time it became guesswork re the tyre pressures.
With the new car there was lots to remember at the start of each session. Turn the GoPro on before getting in otherwise I can't reach it, say yes to the race mode TPMS prompt on startup, turn on the Porsche Track Precision App, ensure its connected to the car wifi, do up the harnesses, turn on the sport mode for auto rev matching on downshifts, turn on exhaust button, then once moving, turn off the seat belt reminder so the TPMS screen can be displayed. Turn off the radio which defaults to on...
So much that I'd forgotten there was a Sport mode for the PASM in the first two sessions. Firming up the suspension took another second off the times so now in the low 1.16's
Both Mark and I were running on fumes after four sessions and went to refuel - the GTR was there to refuel for the second time.
In the fourth session I'd noticed the lack of grip in turn 10. Also noticed that even though the car was sliding it was very controllable, and with either steering or throttle I could still get it to go where I wanted, relatively easily.
I'd brought the tools to adjust the aero just in case, but didn't intend to use them unless I could do consistent lap times - something I couldn't do previously. However with the GT4 all my clear laps in the last two sessions were in the low 1.16's.
Adjusting the aero made a surprisingly significant difference. Felt more stable on turns 2 and 3, and 10 and going up the straight. Also perhaps on turn 1. Lap times in the last two sessions now in the low 1.15's. And vmax on the straight still at 212 according to GoPro footage, so corner exit speed made up for any losses due to increased drag. Unfortunately I can’t see this on the GoPro footage.
One downside with the GT4 was the difficulty in passing say the TTRS and 1M on the straights (something I'm not used to).
So a very good day at Hampton Downs. Happy that the GT4 circulates faster than my M5 on its first day. Starting to push a little harder as I get used to the car I can feel the understeer that people report, so the front sway bar adjustment will be next. A good group of guys with Greg from Wgtn in his TTRS who we'd met on SITT 2014, a new guy Mark who went very well in his 1M and has signed up for SITT 2016. And also the two guys in 911's and the Jeep that Mark mentioned. Looking forward to Monday!
A clip from the last session
Awesome day in the GT4 yesterday. Now I have a car with a cage my son came with me in car for all but one session. First couple of sessions a bit nervous, slightly damp track, new car, driving a manual gearbox on track after a few years with DCT, my son watching every move.... It's been a while since my last sports car so I enjoyed the precision with which you can place these cars, the lack of body roll/weight transfer especially on braking. Loved the auto rev matching on downshifts which means you can concentrate more on pedal pressure at the track.
The car felt great till I saw that my lap times were in the 1.18's, 2 sec slower than my M5.
First thing to sort was the tyre pressures and with help from Mark to understand the TPMS and race mode, it took two sessions to fine tune a setup where the pressures were at 36psi on all four corners at the end of a session. I thought this pretty cool as I could never get pressures sorted on the M5. I used to come off the track, drive out to the prison and back to allow the brakes to cool before stopping, by which time it became guesswork re the tyre pressures.
With the new car there was lots to remember at the start of each session. Turn the GoPro on before getting in otherwise I can't reach it, say yes to the race mode TPMS prompt on startup, turn on the Porsche Track Precision App, ensure its connected to the car wifi, do up the harnesses, turn on the sport mode for auto rev matching on downshifts, turn on exhaust button, then once moving, turn off the seat belt reminder so the TPMS screen can be displayed. Turn off the radio which defaults to on...
So much that I'd forgotten there was a Sport mode for the PASM in the first two sessions. Firming up the suspension took another second off the times so now in the low 1.16's
Both Mark and I were running on fumes after four sessions and went to refuel - the GTR was there to refuel for the second time.
In the fourth session I'd noticed the lack of grip in turn 10. Also noticed that even though the car was sliding it was very controllable, and with either steering or throttle I could still get it to go where I wanted, relatively easily.
I'd brought the tools to adjust the aero just in case, but didn't intend to use them unless I could do consistent lap times - something I couldn't do previously. However with the GT4 all my clear laps in the last two sessions were in the low 1.16's.
Adjusting the aero made a surprisingly significant difference. Felt more stable on turns 2 and 3, and 10 and going up the straight. Also perhaps on turn 1. Lap times in the last two sessions now in the low 1.15's. And vmax on the straight still at 212 according to GoPro footage, so corner exit speed made up for any losses due to increased drag. Unfortunately I can’t see this on the GoPro footage.
One downside with the GT4 was the difficulty in passing say the TTRS and 1M on the straights (something I'm not used to).
So a very good day at Hampton Downs. Happy that the GT4 circulates faster than my M5 on its first day. Starting to push a little harder as I get used to the car I can feel the understeer that people report, so the front sway bar adjustment will be next. A good group of guys with Greg from Wgtn in his TTRS who we'd met on SITT 2014, a new guy Mark who went very well in his 1M and has signed up for SITT 2016. And also the two guys in 911's and the Jeep that Mark mentioned. Looking forward to Monday!
A clip from the last session
01-10-2016, 03:15 AM
Rennlist Member
Sorry Leong, hope I didnt steal your thunder. The troupes got restless...:-)
That auto blip thing is very nifty. Kinda half way between a manual and a PDK box.
You have me curious about the wing now. Mines adjustable but no one Ive read about has every adjusted it. There is a larger wing option by Crawford which apparently makes some difference etc. I may try that.
That auto blip thing is very nifty. Kinda half way between a manual and a PDK box.
You have me curious about the wing now. Mines adjustable but no one Ive read about has every adjusted it. There is a larger wing option by Crawford which apparently makes some difference etc. I may try that.
01-10-2016, 03:26 AM
Rennlist Member
^^^ Liking 1.45 Leong!!
Lovely double apex lines too.
Interesting what you say about adjusting the aero too - I have never bothered to play with the rear wing angle either? Might try this tomorrow too?
Macca - what time do we need to arrive?
Lovely double apex lines too.
Interesting what you say about adjusting the aero too - I have never bothered to play with the rear wing angle either? Might try this tomorrow too?
Macca - what time do we need to arrive?
Last edited by kiwi 911; 01-10-2016 at 03:43 AM.
01-10-2016, 03:33 AM
Instructor
Sorry Leong, hope I didnt steal your thunder. The troupes got restless...:-)
That auto blip thing is very nifty. Kinda half way between a manual and a PDK box.
You have me curious about the wing now. Mines adjustable but no one Ive read about has every adjusted it. There is a larger wing option by Crawford which apparently makes some difference etc. I may try that.
That auto blip thing is very nifty. Kinda half way between a manual and a PDK box.
You have me curious about the wing now. Mines adjustable but no one Ive read about has every adjusted it. There is a larger wing option by Crawford which apparently makes some difference etc. I may try that.
01-10-2016, 04:00 AM
Rennlist Member
According the track manual the rear can be adjusted but the trade off as always is Vmax and possibly more understeer. The GT3 has less understeer out of the box than the GT4 and Ive softened off the front sway bar and now appear to have neutral handling.
I think adjusting the angle of an existing wing on the GT3/4 is only ging to make a small difference. You need a larger higher wing if you want to alter aero substantially.
There is always firming up the rear bar if you want further latitude for under-steer reduction.
I dont think tomorrow is a good opportunity to really try it out as Im expecting to "cord" the shoulders of my tyres after a session or two. Right on the limit of these now as you know. Im bringing the 993 as well as the GT3 tyres will become EOL pretty quickly...
I need what appears to be a torx T+35 to adjust the wing. Is that what you used?