Adjusting front / rear track how will it effect GEO & Handling?
09-24-2012, 07:38 PM
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Adjusting front / rear track how will it effect GEO & Handling?
Hi there
Am asking here as a lot more knowledgable guys here than the 997 section in general, recently fitted Gen2 GT3 front and rear sway bars along with GT3 front arms, with 9mm shims either side. Car also has 7mm spacers front and 5mm spacers rear.
So current setup is:-
7mm spacers up front (widens front track by 14mm)
GT3 lower front arms with 9mm shims either side (increasing front track a further 18mm)
Front camber is -1.80degrees
Front toe is neutral
Front caster is 8.30
Front Arb is one setting from softest (if hole 1 was hardest and 4 softest I'm currently on 3)
5mm spacers in the rear (rear track widened by 10mm)
Rear camber is -1.75 degrees
Rear toe is total +0.25 minutes (toe in)
Rear Arb (GT2 Arb) is on softest setting
Needless to say above settings and the car is better without a doubt, understeer greatly dialled out, more grip overall and feels better.
BUT!
On dry track there is still a little understeer, far far less than there was so all ok. However on the road in the dry car has very minor understeer and is easily provoked into oversteer, maybe a hint more understeer would be nice. However in the wet, car feels very neutral and oversteer coming out of a tight corners when applying power can be quick.
As such I'd like to dial just a very small amount of push (understeer) back into the car.
Here are my thoughts on some ideas:-
1. Swap spacers around, so 5mm front and 7mm rear, will doing this effect the camber/toes at all? I also feel the front track has maybe being widened too much, so swapping spacers around be a good idea?
2. Tyre pressures? To dial in a tad understeer which way do I adjust front/rear?
3. Would setting front sway bar 1 stiffer help, how would it effect the car, too bouncy on front on bumpy roads?
I feel the car is more or less spot on, and just want to put a miniscule amount of understeer back into the setup, just need to know best way to achieve this.
Am asking here as a lot more knowledgable guys here than the 997 section in general, recently fitted Gen2 GT3 front and rear sway bars along with GT3 front arms, with 9mm shims either side. Car also has 7mm spacers front and 5mm spacers rear.
So current setup is:-
7mm spacers up front (widens front track by 14mm)
GT3 lower front arms with 9mm shims either side (increasing front track a further 18mm)
Front camber is -1.80degrees
Front toe is neutral
Front caster is 8.30
Front Arb is one setting from softest (if hole 1 was hardest and 4 softest I'm currently on 3)
5mm spacers in the rear (rear track widened by 10mm)
Rear camber is -1.75 degrees
Rear toe is total +0.25 minutes (toe in)
Rear Arb (GT2 Arb) is on softest setting
Needless to say above settings and the car is better without a doubt, understeer greatly dialled out, more grip overall and feels better.
BUT!
On dry track there is still a little understeer, far far less than there was so all ok. However on the road in the dry car has very minor understeer and is easily provoked into oversteer, maybe a hint more understeer would be nice. However in the wet, car feels very neutral and oversteer coming out of a tight corners when applying power can be quick.
As such I'd like to dial just a very small amount of push (understeer) back into the car.
Here are my thoughts on some ideas:-
1. Swap spacers around, so 5mm front and 7mm rear, will doing this effect the camber/toes at all? I also feel the front track has maybe being widened too much, so swapping spacers around be a good idea?
2. Tyre pressures? To dial in a tad understeer which way do I adjust front/rear?
3. Would setting front sway bar 1 stiffer help, how would it effect the car, too bouncy on front on bumpy roads?
I feel the car is more or less spot on, and just want to put a miniscule amount of understeer back into the setup, just need to know best way to achieve this.
09-24-2012, 07:49 PM
#2
Hi there
Am asking here as a lot more knowledgable guys here than the 997 section in general, recently fitted Gen2 GT3 front and rear sway bars along with GT3 front arms, with 9mm shims either side. Car also has 7mm spacers front and 5mm spacers rear.
So current setup is:-
7mm spacers up front (widens front track by 14mm)
GT3 lower front arms with 9mm shims either side (increasing front track a further 18mm)
Front camber is -1.80degrees
Front toe is neutral
Front caster is 8.30
Front Arb is one setting from softest (if hole 1 was hardest and 4 softest I'm currently on 3)
5mm spacers in the rear (rear track widened by 10mm)
Rear camber is -1.75 degrees
Rear toe is total +0.25 minutes (toe in)
Rear Arb (GT2 Arb) is on softest setting
Needless to say above settings and the car is better without a doubt, understeer greatly dialled out, more grip overall and feels better.
BUT!
On dry track there is still a little understeer, far far less than there was so all ok. However on the road in the dry car has very minor understeer and is easily provoked into oversteer, maybe a hint more understeer would be nice. However in the wet, car feels very neutral and oversteer coming out of a tight corners when applying power can be quick.
As such I'd like to dial just a very small amount of push (understeer) back into the car.
Here are my thoughts on some ideas:-
1. Swap spacers around, so 5mm front and 7mm rear, will doing this effect the camber/toes at all? I also feel the front track has maybe being widened too much, so swapping spacers around be a good idea?
2. Tyre pressures? To dial in a tad understeer which way do I adjust front/rear?
3. Would setting front sway bar 1 stiffer help, how would it effect the car, too bouncy on front on bumpy roads?
I feel the car is more or less spot on, and just want to put a miniscule amount of understeer back into the setup, just need to know best way to achieve this.
Am asking here as a lot more knowledgable guys here than the 997 section in general, recently fitted Gen2 GT3 front and rear sway bars along with GT3 front arms, with 9mm shims either side. Car also has 7mm spacers front and 5mm spacers rear.
So current setup is:-
7mm spacers up front (widens front track by 14mm)
GT3 lower front arms with 9mm shims either side (increasing front track a further 18mm)
Front camber is -1.80degrees
Front toe is neutral
Front caster is 8.30
Front Arb is one setting from softest (if hole 1 was hardest and 4 softest I'm currently on 3)
5mm spacers in the rear (rear track widened by 10mm)
Rear camber is -1.75 degrees
Rear toe is total +0.25 minutes (toe in)
Rear Arb (GT2 Arb) is on softest setting
Needless to say above settings and the car is better without a doubt, understeer greatly dialled out, more grip overall and feels better.
BUT!
On dry track there is still a little understeer, far far less than there was so all ok. However on the road in the dry car has very minor understeer and is easily provoked into oversteer, maybe a hint more understeer would be nice. However in the wet, car feels very neutral and oversteer coming out of a tight corners when applying power can be quick.
As such I'd like to dial just a very small amount of push (understeer) back into the car.
Here are my thoughts on some ideas:-
1. Swap spacers around, so 5mm front and 7mm rear, will doing this effect the camber/toes at all? I also feel the front track has maybe being widened too much, so swapping spacers around be a good idea?
2. Tyre pressures? To dial in a tad understeer which way do I adjust front/rear?
3. Would setting front sway bar 1 stiffer help, how would it effect the car, too bouncy on front on bumpy roads?
I feel the car is more or less spot on, and just want to put a miniscule amount of understeer back into the setup, just need to know best way to achieve this.
09-25-2012, 07:24 AM
#5
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That's what sway bars are for as mentioned already, but few people know how to tune the sway bars.
09-25-2012, 12:15 PM
#6
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Can you explain how changing the spacers effects downforce please, genuinely curious.
09-25-2012, 01:21 PM
#7
Before you do anything:
- make sure you have reasonably new tires so that you aren't chasing your tail
- old / heat cycled out rear tires can produce produce a happy tail as you described as your sways settings seem reasonable
The obvious choices are:
- stiffen the front bar 1 to 2 holes
- increase front tire pressures slightly
- lower rear tire pressures slightly
- lower rear ride height slightly
In very tight 2nd gear corners, 911s have snap oversteer potential - you don't need / want to get rid of this - otherwise the car won't work everywhere else. At the same time, you have to decide if you setting the car up for a rotating autocross track or a high speed circuit - autocross you need oversteer sometimes a lot - a fast circuit this doesn't work as well.
It sounds like from your description that you actually want 2 things:
1) slightly more overall push (add more front bar / slightly increase front tire psi)
2) slightly more rear grip on throttle (more weight over rear axle (lower rear), soften rear tires, less rear bar (you can't), you could try swapping front and rear spacers but don't think your butt dyno will be sensitive enough, wider rear tires)
I repeat - make sure you have new rubber before you start doing anything or you will only make the car worse.
- make sure you have reasonably new tires so that you aren't chasing your tail
- old / heat cycled out rear tires can produce produce a happy tail as you described as your sways settings seem reasonable
The obvious choices are:
- stiffen the front bar 1 to 2 holes
- increase front tire pressures slightly
- lower rear tire pressures slightly
- lower rear ride height slightly
In very tight 2nd gear corners, 911s have snap oversteer potential - you don't need / want to get rid of this - otherwise the car won't work everywhere else. At the same time, you have to decide if you setting the car up for a rotating autocross track or a high speed circuit - autocross you need oversteer sometimes a lot - a fast circuit this doesn't work as well.
It sounds like from your description that you actually want 2 things:
1) slightly more overall push (add more front bar / slightly increase front tire psi)
2) slightly more rear grip on throttle (more weight over rear axle (lower rear), soften rear tires, less rear bar (you can't), you could try swapping front and rear spacers but don't think your butt dyno will be sensitive enough, wider rear tires)
I repeat - make sure you have new rubber before you start doing anything or you will only make the car worse.
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09-25-2012, 01:51 PM
#8
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Before you do anything:
- make sure you have reasonably new tires so that you aren't chasing your tail
- old / heat cycled out rear tires can produce produce a happy tail as you described as your sways settings seem reasonable
The obvious choices are:
- stiffen the front bar 1 to 2 holes
- increase front tire pressures slightly
- lower rear tire pressures slightly
- lower rear ride height slightly
In very tight 2nd gear corners, 911s have snap oversteer potential - you don't need / want to get rid of this - otherwise the car won't work everywhere else. At the same time, you have to decide if you setting the car up for a rotating autocross track or a high speed circuit - autocross you need oversteer sometimes a lot - a fast circuit this doesn't work as well.
It sounds like from your description that you actually want 2 things:
1) slightly more overall push (add more front bar / slightly increase front tire psi)
2) slightly more rear grip on throttle (more weight over rear axle (lower rear), soften rear tires, less rear bar (you can't), you could try swapping front and rear spacers but don't think your butt dyno will be sensitive enough, wider rear tires)
I repeat - make sure you have new rubber before you start doing anything or you will only make the car worse.
- make sure you have reasonably new tires so that you aren't chasing your tail
- old / heat cycled out rear tires can produce produce a happy tail as you described as your sways settings seem reasonable
The obvious choices are:
- stiffen the front bar 1 to 2 holes
- increase front tire pressures slightly
- lower rear tire pressures slightly
- lower rear ride height slightly
In very tight 2nd gear corners, 911s have snap oversteer potential - you don't need / want to get rid of this - otherwise the car won't work everywhere else. At the same time, you have to decide if you setting the car up for a rotating autocross track or a high speed circuit - autocross you need oversteer sometimes a lot - a fast circuit this doesn't work as well.
It sounds like from your description that you actually want 2 things:
1) slightly more overall push (add more front bar / slightly increase front tire psi)
2) slightly more rear grip on throttle (more weight over rear axle (lower rear), soften rear tires, less rear bar (you can't), you could try swapping front and rear spacers but don't think your butt dyno will be sensitive enough, wider rear tires)
I repeat - make sure you have new rubber before you start doing anything or you will only make the car worse.
Thanks for the input!
Car is on relatively new rubber, MPSS all round, with 5-6mm left all round.
Think I am gonna swap the spacers around, if anything just to improve the look a little and try stiffening the front bar by 1 setting.
Any downsides to stiffening to the front bar other than changing the balance of the car?
09-25-2012, 02:47 PM
#9
- be making the car slower (only stop watch will know)
- most likely be making your car slower in the wet (softer cars work in the wet)
- need more front camber to improve grip in the corners (I think you should do this anyways)
09-25-2012, 03:35 PM
#10
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One of the reasons I want a little more push though is I am more confident to push harder, I am a little in fear I might go a bit to fast into corner entry or get on the power to much in the wet and have little to no warning and be straight into a big oversteer moment. I am not the worse driver, done over 30 track events, but at the same time I am also no race driver.
As such I thought maybe one setting stiffer, could give me confidence to push a bit harder as if I go a bit to quick, its gonna have a bit of intial push, before just trying to rotate round on me.
Think for now I shall change spacers around and add like another 2psi to the front tyres to see how it effects things. Then if I want more push stiffen the bar a setting.
Whats a good/ideal front camber for a road car which is driven daily in both dry and wet conditions along with doing track events 4-5 times a year? At the moment I am -1.80degrees.
Also when I change tyres I intend on going from 235 front and 295 rear upto 245 front and 305 rear, good or bad idea?
09-25-2012, 04:37 PM
#11
You could argue that while learning you should have narrow tires - but lets just let that go for now and get you tires that would make sense.
You added a gt2 rear bar and you are 'only' running a 295 tire - not that this really matters but everything matters in small ways - the 305 rear is a better match for that gt2 bar (remember the gt2 comes with 325 rear tires) - if you have a widebody order the 325 PSS rear it now exists. Since your fronts will likely out last your rears - I don't see why you wouldn't order 2 rear tires now - but that's me.
Since you are doing all of this, I would highly recommend doing it 1x - ie get the new tires now and get it set up for the rubber you are going to run - since you have softer spring rates (I think), I would recommend the 235/35/19 PSS as the 245/35/19 is almost 1/2 an inch taller and you may get rubbing on big bumps if you run too low - the tire does fit with no problem however - ride height and spring rate dependent.
These wider rear tires are also slightly taller (the 325 especially) so you may want to drop the rear to keep your desired rake.
