Racer opinion on GT3 handling
03-09-2012, 02:21 AM
#31
Rennlist Member
Thread Starter
FFaust thanks for that, I indeed had seen this before. What I and others are interested in is what 10GT3 has posted above regarding rotating the center track arm bushings, changing the caster curves as a result and the subsequent setup after that's done.
Is this a common practice? Searched but found no mention of it. Is a similar result possible with RSS or GMG parts?
Is this a common practice? Searched but found no mention of it. Is a similar result possible with RSS or GMG parts?
03-09-2012, 02:50 PM
#32
I was very disappointed with the handling of my GT3 when I first got it. My previous Carrera (X51 engine, ROW M030 w/GT3 control arms) had a far quicker turn-in and more neutral balance than the GT3. I went through 4 alignments to get mine setup right. Bottom line, as these cars come from the factory they are just rubbish for handing. They are setup far too conservative, basically for people who don't know how to drive a 911. There is nothing but understeer ragardless of sway bar or tire pressure settings. Just bumping up the camber doesn't fix it either. To fix it, all the center track arm mount bushings in my lower control arms are rotated to change the caster curves on all 4 corners. Turn-in is now sharp and it is dead neutral with both sway bars set in the center positions. It just sounds like he needs to get the suspension alignment setup right.
I don't think you mean 4 corners - as in rear arms as well.
For those that use the shims in the front to get added camber, you are already pushing up towards the maximum caster range where rubbing occurs with bigger tires - ie 8.9 caster range.
High caster values definitely improve the turn-in feel.
But high caster / big front rubber is a trade off. I would rather run front caster at 8.0 with a 265 front tire than 8.9 with a 235 front.
As per the Kassumul settings (spelling), my only disagreement for a 997 versus a 996 is that I think you need slightly less rear camber with the 997s. So, his -2.5/-2.4, I personally think has to be lower in the rear. I am using -2.3/-1.8 as a combo street/track setup.
03-09-2012, 03:33 PM
#33
Rennlist Member
Thread Starter
Are you talking about using the second hole in the front lower control GT3 arms for caster?
I don't think you mean 4 corners - as in rear arms as well.
For those that use the shims in the front to get added camber, you are already pushing up towards the maximum caster range where rubbing occurs with bigger tires - ie 8.9 caster range.
High caster values definitely improve the turn-in feel.
But high caster / big front rubber is a trade off. I would rather run front caster at 8.0 with a 265 front tire than 8.9 with a 235 front.
As per the Kassumul settings (spelling), my only disagreement for a 997 versus a 996 is that I think you need slightly less rear camber with the 997s. So, his -2.5/-2.4, I personally think has to be lower in the rear. I am using -2.3/-1.8 as a combo street/track setup.
I don't think you mean 4 corners - as in rear arms as well.
For those that use the shims in the front to get added camber, you are already pushing up towards the maximum caster range where rubbing occurs with bigger tires - ie 8.9 caster range.
High caster values definitely improve the turn-in feel.
But high caster / big front rubber is a trade off. I would rather run front caster at 8.0 with a 265 front tire than 8.9 with a 235 front.
As per the Kassumul settings (spelling), my only disagreement for a 997 versus a 996 is that I think you need slightly less rear camber with the 997s. So, his -2.5/-2.4, I personally think has to be lower in the rear. I am using -2.3/-1.8 as a combo street/track setup.
03-09-2012, 06:40 PM
#34
I can't post the angles at which the bushings were re-clocked as that is my techs special sauce. I use John Gladwell at Boardwalk Porsche to do my alignment. I bumped the front camber up 20 sec when he reclocked the bushings, yet caster dropped actually dropped 20 sec per side; and yes it turns in a lot better. You have to use the offset holes on all 4 corners with the reclocked bushings. They have to be pressed out, rotated and pressed back in.
Here are the basic settings setup with 150 lbs weight ballast in the driver's seat:
Front
Camber left/right -2 min 51 sec/-2 min 52 sec
Caster left/right 8 min 1 sec/7 min 51 sec
Toe left/right - 1 sec/-3 sec
Rear
Camber left/right -1 min 47 sec/-1 min 50 sec
Toe left/right 14 sec/15 sec
The general rule is the greater the power, the less the rear camber as you need the tire flatter to the surface to maintain contact patch while accelerating. A 997 should have less rear camber than a 996 as it has more power to put to the ground.
Here are the basic settings setup with 150 lbs weight ballast in the driver's seat:
Front
Camber left/right -2 min 51 sec/-2 min 52 sec
Caster left/right 8 min 1 sec/7 min 51 sec
Toe left/right - 1 sec/-3 sec
Rear
Camber left/right -1 min 47 sec/-1 min 50 sec
Toe left/right 14 sec/15 sec
As per the Kassumul settings (spelling), my only disagreement for a 997 versus a 996 is that I think you need slightly less rear camber with the 997s. So, his -2.5/-2.4, I personally think has to be lower in the rear. I am using -2.3/-1.8 as a combo street/track setup.
03-09-2012, 06:59 PM
#35
Rennlist Member
Thread Starter
I can't post the angles at which the bushings were re-clocked as that is my techs special sauce. I use John Gladwell at Boardwalk Porsche to do my alignment. I bumped the front camber up 20 sec when he reclocked the bushings, yet caster dropped actually dropped 20 sec per side; and yes it turns in a lot better. You have to use the offset holes on all 4 corners with the reclocked bushings. They have to be pressed out, rotated and pressed back in.
Here are the basic settings setup with 150 lbs weight ballast in the driver's seat:
Front
Camber left/right -2 min 51 sec/-2 min 52 sec
Caster left/right 8 min 1 sec/7 min 51 sec
Toe left/right - 1 sec/-3 sec
Rear
Camber left/right -1 min 47 sec/-1 min 50 sec
Toe left/right 14 sec/15 sec
The general rule is the greater the power, the less the rear camber as you need the tire flatter to the surface to maintain contact patch while accelerating. A 997 should have less rear camber than a 996 as it has more power to put to the ground.
Here are the basic settings setup with 150 lbs weight ballast in the driver's seat:
Front
Camber left/right -2 min 51 sec/-2 min 52 sec
Caster left/right 8 min 1 sec/7 min 51 sec
Toe left/right - 1 sec/-3 sec
Rear
Camber left/right -1 min 47 sec/-1 min 50 sec
Toe left/right 14 sec/15 sec
The general rule is the greater the power, the less the rear camber as you need the tire flatter to the surface to maintain contact patch while accelerating. A 997 should have less rear camber than a 996 as it has more power to put to the ground.
03-09-2012, 11:36 PM
#36
I can't post the angles at which the bushings were re-clocked as that is my techs special sauce. I use John Gladwell at Boardwalk Porsche to do my alignment. I bumped the front camber up 20 sec when he reclocked the bushings, yet caster dropped actually dropped 20 sec per side; and yes it turns in a lot better. You have to use the offset holes on all 4 corners with the reclocked bushings. They have to be pressed out, rotated and pressed back in.
Here are the basic settings setup with 150 lbs weight ballast in the driver's seat:
Front
Camber left/right -2 min 51 sec/-2 min 52 sec
Caster left/right 8 min 1 sec/7 min 51 sec
Toe left/right - 1 sec/-3 sec
Rear
Camber left/right -1 min 47 sec/-1 min 50 sec
Toe left/right 14 sec/15 sec
The general rule is the greater the power, the less the rear camber as you need the tire flatter to the surface to maintain contact patch while accelerating. A 997 should have less rear camber than a 996 as it has more power to put to the ground.
Here are the basic settings setup with 150 lbs weight ballast in the driver's seat:
Front
Camber left/right -2 min 51 sec/-2 min 52 sec
Caster left/right 8 min 1 sec/7 min 51 sec
Toe left/right - 1 sec/-3 sec
Rear
Camber left/right -1 min 47 sec/-1 min 50 sec
Toe left/right 14 sec/15 sec
The general rule is the greater the power, the less the rear camber as you need the tire flatter to the surface to maintain contact patch while accelerating. A 997 should have less rear camber than a 996 as it has more power to put to the ground.
From your alignment specs, if I convert quickly and round then basically you are running:
- almost -3 camber in the front with slight toe out
- 8 caster in the front (this would be spec if you rotated the struts)
- the rear camber you are not quite -2 with standard rear toe in
If your basic statement is that with an alignment of -3/-2 (f/r) with front toe out the car turns in better than as delivered by the factory - then I won't say no **** Sherlock but no **** Sherlock.
Having been up to close to those specs in the front, I cannot disagree one bit. I will say, that in my experience, you can lower the front camber down from that level and vastly improve inner front tire wear with not too much loss or that crazy good turn-in feel. That said, if you replace all 4 tires at the same time the rears will always go first so front camber is a bit of a free lunch - but you are giving up the slightest braking stability with -3 in the front.
03-10-2012, 12:12 AM
#37
Race Director
I can't post the angles at which the bushings were re-clocked as that is my techs special sauce. I use John Gladwell at Boardwalk Porsche to do my alignment. I bumped the front camber up 20 sec when he reclocked the bushings, yet caster dropped actually dropped 20 sec per side; and yes it turns in a lot better. You have to use the offset holes on all 4 corners with the reclocked bushings. They have to be pressed out, rotated and pressed back in.
Here are the basic settings setup with 150 lbs weight ballast in the driver's seat:
Front
Camber left/right -2 min 51 sec/-2 min 52 sec
Caster left/right 8 min 1 sec/7 min 51 sec
Toe left/right - 1 sec/-3 sec
Rear
Camber left/right -1 min 47 sec/-1 min 50 sec
Toe left/right 14 sec/15 sec
The general rule is the greater the power, the less the rear camber as you need the tire flatter to the surface to maintain contact patch while accelerating. A 997 should have less rear camber than a 996 as it has more power to put to the ground.
Here are the basic settings setup with 150 lbs weight ballast in the driver's seat:
Front
Camber left/right -2 min 51 sec/-2 min 52 sec
Caster left/right 8 min 1 sec/7 min 51 sec
Toe left/right - 1 sec/-3 sec
Rear
Camber left/right -1 min 47 sec/-1 min 50 sec
Toe left/right 14 sec/15 sec
The general rule is the greater the power, the less the rear camber as you need the tire flatter to the surface to maintain contact patch while accelerating. A 997 should have less rear camber than a 996 as it has more power to put to the ground.
