Any Rennlisters from New Zealand?
10-22-2014, 01:54 AM
Addict
Rennlist Member
Rennlist Member
Join Date: Dec 2003
Location: Auckland, NZ
Posts: 2,085
Likes: 0
Received 0 Likes
on
0 Posts
10-22-2014, 01:58 AM
Rennlist Member
Yeah its interesting. The GT3 series has had the same rear tyre widths from 2003 997.1 GT3 to 2013 991 GT3 (305). The only thing that has changed is the wheel diameter and thus the size of the contact patch. Power has increased by almost 60 bhp over those three generations.
Going below factory recommended rear widths like you did (especially in a 4WD car) I would not recommend.
The issue with overtiring the rear of the car is understeer a trait already inherent in the platform. I found that going from 265 to 285 at the rear was creating a very noticeable amount of under-steer but the LSD was freshly rebuilt with a more aggressive GT set of ramp/plates so that was a significant contributing factor.
The PS2 is an excellent tyre IMO but it is now outdated. They were top of the pile 12 years ago when they were standard fitment. The MPSS is the most logical choice today in the Michelin range (assuming the sizes you need are available). The technology has definitely improved.
Going below factory recommended rear widths like you did (especially in a 4WD car) I would not recommend.
The issue with overtiring the rear of the car is understeer a trait already inherent in the platform. I found that going from 265 to 285 at the rear was creating a very noticeable amount of under-steer but the LSD was freshly rebuilt with a more aggressive GT set of ramp/plates so that was a significant contributing factor.
The PS2 is an excellent tyre IMO but it is now outdated. They were top of the pile 12 years ago when they were standard fitment. The MPSS is the most logical choice today in the Michelin range (assuming the sizes you need are available). The technology has definitely improved.
10-22-2014, 02:58 AM
Rennlist Member
I have 0 track experience and very little road compared to others, but am really happy with the MPSS performance on road. My only complaint is that they make me somewhat over confident due to the fact they just don't seem to come unstuck...
Based on the hours I poured over online reviews and discussions, I was looking at those and the Hankook RS3's (Z222). Because I don't actively track the car and live in Auckland (rain...) I went with the MPSS. I'll probably put RS3's on my second wheels once I chew through the aging Proxes1 they currently have.
Shhh. Don't jinx it! This is the busiest the forum has been in weeks.
Based on the hours I poured over online reviews and discussions, I was looking at those and the Hankook RS3's (Z222). Because I don't actively track the car and live in Auckland (rain...) I went with the MPSS. I'll probably put RS3's on my second wheels once I chew through the aging Proxes1 they currently have.
Shhh. Don't jinx it! This is the busiest the forum has been in weeks.
10-22-2014, 03:29 AM
Rennlist Member
Hankook RS3's rate well. The new compound version even more so and is the I believe the one you could want - however it is not available via teh NZ distributor at this time only via USA.
Ive become an AiM man. Solo DL (OBDII) with the new (released next week) SmartyCam HD rev 2.0 with separate microphone (now supported). Simple one cable to each device powered by OBDII power supply and permanently mounted using KW Machine Works custom roll bar bracket etc. Auto power on/off, auto record start stop, full sized SD card capture with immediate overlay of up to 16 data channels onto the video. Im sick of missing footage and lap times due to flat batteries or forgetting to turn on gear. Now I can also compare lap traces with other AiM owners. It will be fantastic to have full telemetric data overlays immediately available in the video too! This set up is for GT3, the VBox and Sony will be relocated to 993 and the GoPro and various mounts relegated to car exterior camera work...
Ive become an AiM man. Solo DL (OBDII) with the new (released next week) SmartyCam HD rev 2.0 with separate microphone (now supported). Simple one cable to each device powered by OBDII power supply and permanently mounted using KW Machine Works custom roll bar bracket etc. Auto power on/off, auto record start stop, full sized SD card capture with immediate overlay of up to 16 data channels onto the video. Im sick of missing footage and lap times due to flat batteries or forgetting to turn on gear. Now I can also compare lap traces with other AiM owners. It will be fantastic to have full telemetric data overlays immediately available in the video too! This set up is for GT3, the VBox and Sony will be relocated to 993 and the GoPro and various mounts relegated to car exterior camera work...
10-22-2014, 03:45 AM
Drifting
Join Date: May 2013
Location: Auckland, New Zealand
Posts: 2,373
Likes: 0
Received 0 Likes
on
0 Posts
Need to find a way to have a bit of final fun with the Boxster tyres before changing them out :-P
CCS are getting right in behind the 20th Anniversary Targa Tour this year. Looks like we will have some RSG contingent waving our flag (Ron/Patsy, Steve/Barbara and Richard/Doug). Gonna be an absolute blast and probably the only event this year Im sore to have missed. Lets hope they can keep those Caymans on the black stuff this time.... http://www.nzherald.co.nz/cars/news/...ectid=11345228 Not sure who on here is planning on participating in the May Targa NI event? Im a definite this time around (planned my travels around it!) and Im hoping Doug will be a starter in the Boxster. It would be great to have a small group of us out there again....
Really looking forward to the SI tour next week. 750 km of closed South Island roads in a 991 GT3 - wahoo!!
10-22-2014, 03:58 AM
Drifting
Join Date: May 2013
Location: Auckland, New Zealand
Posts: 2,373
Likes: 0
Received 0 Likes
on
0 Posts
The Lightspeed #4 backdate is looking brilliant.
https://rennlist.com/forums/964-foru...-ideas-34.html
https://rennlist.com/forums/964-foru...-ideas-34.html
10-22-2014, 05:40 AM
Drifting
Ignore the big fella's, but look at that 964 longhood conversion to the left. The sloping 964 rear lights have been used. Not seen that before. Could be quite effective.
10-22-2014, 05:47 AM
Rennlist Member
It is definitely that Dave. Infact if you can pull your eyes away from the two bikies and the trannie with lippy and eye shadow in that photograph you would have to say they may well have opened up something new there that I think could work very well. Nice PMOs on the 3.6 donk too. Heat exchanger looks interesting too - custom design. Squeal like a Pig boy...LOL
10-22-2014, 06:16 AM
Rennlist Member
That Lightspeed car does look great Doug. Are you still considering aesthetic changes for yours?
Dave, under seal looks better. Looking forward to seeing the end result.
Unsure about the motley crew in that photo. Would almost rather see another post about VTEC engines...
Dave, under seal looks better. Looking forward to seeing the end result.
Unsure about the motley crew in that photo. Would almost rather see another post about VTEC engines...
10-22-2014, 07:00 AM
Burning Brakes
Join Date: Oct 2003
Location: Kapiti - New Zealand
Posts: 1,239
Received 0 Likes
on
0 Posts
Interesting comments below from Petevb on the 991 GT3 forum about tyre contact patch.
"Increased footprint length for increased grip. Quoting myself from earlier in the thread:
The change to 21s is going to be driven primarily by grip. It's not an accident that as cars get more powerful the tire diameter tends to go up. Think drag racers, funny car, top fuel, even F1 for some extreme examples. Part of the reason is to extend the length of the contact patch, which does improve grip, particularly at speed, where friction usually drops off.
The best "tire models" include speed, because rubber's friction is also a function of how long it's in contact with the road. This is because it's a viscoelastic material, meaning "flows" into the roughness of the road to grip, and as speed increases it has less time in contact with the road to flow. By increasing the OD of the tire you increase the length of the contact patch, thereby increasing the time the rubber has to flow. A long contact patch also reduces the slip angle a tire operates at, increasing the tires responsiveness in the process.
Porsche themselves have used progressively larger diameter rear tires- the RSRs, for example, for half a decade used a tire over an inch taller in the rear than the Cups to increase grip. Unfortunately in motorsports wheel diameter has been frozen by rules at 18" for nearly two decades to limit costs, so an increase in sidewall height was required to get this larger OD, slowing the rear tire's response. This leads to a number of undesirable traits that must be countered, including slower turn-in and both transient and steady state oversteer. It would be far better to run a short sidewall and get quicker response.
Porsche seemed to prove this by winning Le Mans with 20" wheels before they were banned, but they aren't banned on the street, so as power and grip climb to ex-Le Mans levels it's no surprise we're seeing larger wheels. It is heavier and more expensive, the large, low profile tires requiring more segments in the multi-piece tire molds, costing more to make. However on a high power car that both needs the grip and has the horsepower to spin big wheels you should see better overall performance for those penalties.
https://rennlist.com/forums/991-gt3/7...l#post11539342 "
"Increased footprint length for increased grip. Quoting myself from earlier in the thread:
The change to 21s is going to be driven primarily by grip. It's not an accident that as cars get more powerful the tire diameter tends to go up. Think drag racers, funny car, top fuel, even F1 for some extreme examples. Part of the reason is to extend the length of the contact patch, which does improve grip, particularly at speed, where friction usually drops off.
The best "tire models" include speed, because rubber's friction is also a function of how long it's in contact with the road. This is because it's a viscoelastic material, meaning "flows" into the roughness of the road to grip, and as speed increases it has less time in contact with the road to flow. By increasing the OD of the tire you increase the length of the contact patch, thereby increasing the time the rubber has to flow. A long contact patch also reduces the slip angle a tire operates at, increasing the tires responsiveness in the process.
Porsche themselves have used progressively larger diameter rear tires- the RSRs, for example, for half a decade used a tire over an inch taller in the rear than the Cups to increase grip. Unfortunately in motorsports wheel diameter has been frozen by rules at 18" for nearly two decades to limit costs, so an increase in sidewall height was required to get this larger OD, slowing the rear tire's response. This leads to a number of undesirable traits that must be countered, including slower turn-in and both transient and steady state oversteer. It would be far better to run a short sidewall and get quicker response.
Porsche seemed to prove this by winning Le Mans with 20" wheels before they were banned, but they aren't banned on the street, so as power and grip climb to ex-Le Mans levels it's no surprise we're seeing larger wheels. It is heavier and more expensive, the large, low profile tires requiring more segments in the multi-piece tire molds, costing more to make. However on a high power car that both needs the grip and has the horsepower to spin big wheels you should see better overall performance for those penalties.
https://rennlist.com/forums/991-gt3/7...l#post11539342 "
10-22-2014, 07:09 AM
Burning Brakes
Join Date: Oct 2003
Location: Kapiti - New Zealand
Posts: 1,239
Received 0 Likes
on
0 Posts