Alignment settings to correct C4 understeer
04-09-2002, 01:02 AM
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Alignment settings to correct C4 understeer
I've heard that the following alignment settings can make a significant improvement in the 964 understeer issue:
"Reduce the front caster as much as possible and set the front wheels with about a half degree of positive camber."
Have any of you had experience with this set-up on a 964 C4? (my main concern is excessive tire wear -- although the guy I heard this from swears he hasn't had any problem there)
Supposedly, this set-up made a big difference especially in wet conditions; with the front end really sticking to the road and the overall "feeling" being much more controllable.
When I discussed this potential change with my alignment tech, he was concerned about the tire wear issue so I told him I'd try to get more input from those with experience before proceeding any further -- your thoughts?
Thanks,
Tim O'Neill
1989 964 C4
Sarasota, Florida USA
"Reduce the front caster as much as possible and set the front wheels with about a half degree of positive camber."
Have any of you had experience with this set-up on a 964 C4? (my main concern is excessive tire wear -- although the guy I heard this from swears he hasn't had any problem there)
Supposedly, this set-up made a big difference especially in wet conditions; with the front end really sticking to the road and the overall "feeling" being much more controllable.
When I discussed this potential change with my alignment tech, he was concerned about the tire wear issue so I told him I'd try to get more input from those with experience before proceeding any further -- your thoughts?
Thanks,
Tim O'Neill
1989 964 C4
Sarasota, Florida USA
04-09-2002, 11:58 AM
#2
Burning Brakes
My initial reaction would be don't do it !!!
It will give you slightly better turn in but it will also affect your tyre wear, straightline stability, tramlining, centering action of the steering, braking stability, ....I go a bit a times, don't I? <img src="graemlins/icon501.gif" border="0" alt="[icon501]" />
Could you not develop the trick that most C4 (and others) use for the slaloms where a timely touch of the brakes will get the nose down for a sharp turn in and then feed the throttle to give you just the right amount of understeer.
On long fast bends you keep pressing on and you'll be amazed how it drives throught he understeer - however if you overcook it when trying this you'll end up consulting maker for next instructions - yours not the cars !!.
This modification I would recommend for a track car not a road car.
Enjoy it,
It will give you slightly better turn in but it will also affect your tyre wear, straightline stability, tramlining, centering action of the steering, braking stability, ....I go a bit a times, don't I? <img src="graemlins/icon501.gif" border="0" alt="[icon501]" />
Could you not develop the trick that most C4 (and others) use for the slaloms where a timely touch of the brakes will get the nose down for a sharp turn in and then feed the throttle to give you just the right amount of understeer.
On long fast bends you keep pressing on and you'll be amazed how it drives throught he understeer - however if you overcook it when trying this you'll end up consulting maker for next instructions - yours not the cars !!.
This modification I would recommend for a track car not a road car.
Enjoy it,
04-09-2002, 12:31 PM
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Dear Tim,
There is one inexpensive modification that you can carry out to reduce the understeer of the C4.
Replace the 18mm rear sway bar with a 21mm version. Installation of a strut brace in the front in conjunction with the rear sway bar also makes quite a significant difference.
I highly unrecommend that you deviate from the road set up alignment settings. I can only speak from experience. You will scrub out your tyres in short order. This gets awful expensive. You will also introduce stresses in other components that you really do not want to damage. A good set of tyres and a proper factory alignment using the 1994 figures (was changed for the USA in 1994) can also make a huge difference in reducing understeer.
Ciao,
Adrian
911C4
There is one inexpensive modification that you can carry out to reduce the understeer of the C4.
Replace the 18mm rear sway bar with a 21mm version. Installation of a strut brace in the front in conjunction with the rear sway bar also makes quite a significant difference.
I highly unrecommend that you deviate from the road set up alignment settings. I can only speak from experience. You will scrub out your tyres in short order. This gets awful expensive. You will also introduce stresses in other components that you really do not want to damage. A good set of tyres and a proper factory alignment using the 1994 figures (was changed for the USA in 1994) can also make a huge difference in reducing understeer.
Ciao,
Adrian
911C4
04-10-2002, 04:29 AM
#4
I posted a similar question about getting rid of C4 understeer some time ago on the Pelican board and got the "change alignment" settings response too. I didn't like the idea. A previous car of mine got bumped out of alignment by a pothole years ago and the car literally ate up some rather expensive performance tires in about 2000 miles (in fact... the belts were showing when I realized the problem).
I like Adrians suggestions because they assist in stopping the diff from locking up. As I've become used to my C4 I've begun to push its limits more and more, and the stock results are less than satisfactory....I've literally been able to get the front wheels to "skip", allowing the front wheels to push forward in conditions where a "normal" car would either follow the intended path or the tail would begin to slide out.
This is a topic of great interest to me. I'm considering looking into figuring out a way to disable the diff locking mechanism to some degree, but it doesn't look like an easy job. C2 and older 911 owners will think you're crazy talking about 21mm swaybars, but they know not what of they speak when it comes to a 964 C4!
CHEERS,
Bill Wagner
I like Adrians suggestions because they assist in stopping the diff from locking up. As I've become used to my C4 I've begun to push its limits more and more, and the stock results are less than satisfactory....I've literally been able to get the front wheels to "skip", allowing the front wheels to push forward in conditions where a "normal" car would either follow the intended path or the tail would begin to slide out.
This is a topic of great interest to me. I'm considering looking into figuring out a way to disable the diff locking mechanism to some degree, but it doesn't look like an easy job. C2 and older 911 owners will think you're crazy talking about 21mm swaybars, but they know not what of they speak when it comes to a 964 C4!
CHEERS,
Bill Wagner
04-10-2002, 12:14 PM
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Guys, I am also going to try running 225 tyres up front this summer (using 5mm front spacers). The reason is to further try and reduce the rears tending to push the front around sharp corners at high speed. I will be using a set of Toyo T1S Proxes.
Ciao,
Adrian
911C4
Ciao,
Adrian
911C4
04-10-2002, 02:18 PM
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Guys -- thanks so much for the input. From all I've heard, this "radical" alignment set-up is not something I wish to try.
My goal, at least here initially while I'm still very much learning about this car, is to reduce the known understeer problem as much as possible without sacrificing tire wear; as this is primarily a "daily driver" type of car and the autocross or track events may or may not be a substantial use in the future (after I try a few different types of competitive driving, I may very well buy a car exclusively for the type that appeals to me most and keep this car as my street-only "fun machine").
I guess I'm looking for the best "bang for your buck" component change as a first step so I can at least improve the situation a little while I'm learning to drive the car; and then do a full coil-over kit (or similar) type of upgrade at a later date. In keeping with this goal, the 21 mm rear sway bar upgrade, addition of a strut brace, and 1994 alignment specs sound like a good plan (I assume I can get these specs from a Porsche dealer -- ?)
As I have a good deal of power (from the supercharged motor) to "assist" with my cornering technique so that will undoubtedly come into play as I learn to drive my car competitively, as well.
Adrian, please keep us posted how your 225 mm front tire trial turns out as I would like to put the widest tires possible on the front of my car when I do my (future) wheel upgrade (as I am also looking to get wider/taller wheels to maximize my tire footprint). If any of you hear of a good deal on a decent used set of 17" or 18" 5-spoke type wheels, please let me know. As an FYI, I would consider a set that needs refinishing as one look that really appeals to me is the alloy/silver rim with black spokes; and I would have a "rough" set of wheels refinished to achieve this look.
In regard to Bill's comment about the differential locking mechanism over-ride, I've heard a "rumor" about a guy in Texas that may have developed a way to vary the 2WD and 4WD operation on a C4 by controlling the center differential -- I hope to confirm this in the near future.
Thanks again...
Tim O'Neill
My goal, at least here initially while I'm still very much learning about this car, is to reduce the known understeer problem as much as possible without sacrificing tire wear; as this is primarily a "daily driver" type of car and the autocross or track events may or may not be a substantial use in the future (after I try a few different types of competitive driving, I may very well buy a car exclusively for the type that appeals to me most and keep this car as my street-only "fun machine").
I guess I'm looking for the best "bang for your buck" component change as a first step so I can at least improve the situation a little while I'm learning to drive the car; and then do a full coil-over kit (or similar) type of upgrade at a later date. In keeping with this goal, the 21 mm rear sway bar upgrade, addition of a strut brace, and 1994 alignment specs sound like a good plan (I assume I can get these specs from a Porsche dealer -- ?)
As I have a good deal of power (from the supercharged motor) to "assist" with my cornering technique so that will undoubtedly come into play as I learn to drive my car competitively, as well.
Adrian, please keep us posted how your 225 mm front tire trial turns out as I would like to put the widest tires possible on the front of my car when I do my (future) wheel upgrade (as I am also looking to get wider/taller wheels to maximize my tire footprint). If any of you hear of a good deal on a decent used set of 17" or 18" 5-spoke type wheels, please let me know. As an FYI, I would consider a set that needs refinishing as one look that really appeals to me is the alloy/silver rim with black spokes; and I would have a "rough" set of wheels refinished to achieve this look.
In regard to Bill's comment about the differential locking mechanism over-ride, I've heard a "rumor" about a guy in Texas that may have developed a way to vary the 2WD and 4WD operation on a C4 by controlling the center differential -- I hope to confirm this in the near future.
Thanks again...
Tim O'Neill
04-10-2002, 06:56 PM
#7
Three Wheelin'
[QUOTE]Originally posted by Adrian:
[QB]Dear Tim,
There is one inexpensive modification that you can carry out to reduce the understeer of the C4.
Replace the 18mm rear sway bar with a 21mm version. Installation of a strut brace in the front in conjunction with the rear sway bar also makes quite a significant difference.
Adrian
Can you give me an idea of cost for this?
Thanks in advance!
Piers
1990 C4 Coupe
[QB]Dear Tim,
There is one inexpensive modification that you can carry out to reduce the understeer of the C4.
Replace the 18mm rear sway bar with a 21mm version. Installation of a strut brace in the front in conjunction with the rear sway bar also makes quite a significant difference.
Adrian
Can you give me an idea of cost for this?
Thanks in advance!
Piers
1990 C4 Coupe
Trending Topics
04-11-2002, 03:16 AM
#8
How much will the 21mm sway bar really assist in cutting down the understeer, particularly if there are no suspension mods (like on my car).
I went around a tight u-turn like turn last weekend and the front wheels pushed forward like I was driving a snow plow...probably not going much faster than 20 MPH.
Thanks in Advance,
Bill Wagner
I went around a tight u-turn like turn last weekend and the front wheels pushed forward like I was driving a snow plow...probably not going much faster than 20 MPH.
Thanks in Advance,
Bill Wagner
04-11-2002, 06:00 AM
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Bill-
you'd be amazed how much it can make a difference. I replaced the front bar with a TRG "Carrera Cup" 23mm 5-way adjustable bar and the rear bar with a TRG 3-way adjustable "Carrera Cup" bar (18mm). Both are set to the middle position and they made a way noticable difference. So I imagine a 21mm rear will really get you setup right. I may go to last notch on my TRG to add a little bit more oversteer but I'm okay with things now at my skill level. I think Jeff C. had the 18mm rear at one point and opted to go up to the 21mm. I probably should have too.
you (I) can still definitely push in low-speed hairpins and u-turns by hitting the throttle too early. I learned quite a bit one night in the deserted parking lot of our local mall playing around with braking and throttle application at relatively low speeds to further understand the understeer characterics and transition to oversteer after adding these sways (strut brace too). Nothing like the racer guys like jeff C. but it was enlightening nonetheless.
you'd be amazed how much it can make a difference. I replaced the front bar with a TRG "Carrera Cup" 23mm 5-way adjustable bar and the rear bar with a TRG 3-way adjustable "Carrera Cup" bar (18mm). Both are set to the middle position and they made a way noticable difference. So I imagine a 21mm rear will really get you setup right. I may go to last notch on my TRG to add a little bit more oversteer but I'm okay with things now at my skill level. I think Jeff C. had the 18mm rear at one point and opted to go up to the 21mm. I probably should have too.
you (I) can still definitely push in low-speed hairpins and u-turns by hitting the throttle too early. I learned quite a bit one night in the deserted parking lot of our local mall playing around with braking and throttle application at relatively low speeds to further understand the understeer characterics and transition to oversteer after adding these sways (strut brace too). Nothing like the racer guys like jeff C. but it was enlightening nonetheless.
04-11-2002, 12:55 PM
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Dear Bill,
I highly recommend you read part 2 of Wringing out a C4 in Excellence in 1992. This was my inspiration for my modifications. The 21mm rear sway bar stiffens the rear up quite nicely. A strut brace stiffens the front which has a similar affect. 225 tyres are also supposed to help with the snow plough affect when the traction control kicks in. I will personally test this.
Piers the cost. The strut brace set me back $US225 from FVD and the rear sway bar set me back 154 Euros from Holland,
Ciao,
Adrian
911C4
I highly recommend you read part 2 of Wringing out a C4 in Excellence in 1992. This was my inspiration for my modifications. The 21mm rear sway bar stiffens the rear up quite nicely. A strut brace stiffens the front which has a similar affect. 225 tyres are also supposed to help with the snow plough affect when the traction control kicks in. I will personally test this.
Piers the cost. The strut brace set me back $US225 from FVD and the rear sway bar set me back 154 Euros from Holland,
Ciao,
Adrian
911C4
04-12-2002, 08:01 AM
#12
Three Wheelin'
Thanks Adrian
From a suspension point of view my 1990 C4 Coupe is completely standard. Can I add the strut brace and change the sway bar without doing anything else and achieve the benefits described?
To confirm, it is the rear sway bar we're talking about? I ask as on <a href="http://www.porsche964.co.uk" target="_blank">www.porsche964.co.uk</a> Bill Gregory outlines (brilliantly by the way) how to uprate the front sway bar - should I do both??
Thanks in advance!
Piers
From a suspension point of view my 1990 C4 Coupe is completely standard. Can I add the strut brace and change the sway bar without doing anything else and achieve the benefits described?
To confirm, it is the rear sway bar we're talking about? I ask as on <a href="http://www.porsche964.co.uk" target="_blank">www.porsche964.co.uk</a> Bill Gregory outlines (brilliantly by the way) how to uprate the front sway bar - should I do both??
Thanks in advance!
Piers
04-12-2002, 09:26 AM
#13
on 12 Apr 2002 "Roygarth" wrote these pearls of wisdom.... 
To confirm, it is the rear sway bar we're talking about?
If you see Adrian post, directly above yours, it says:
The 21mm rear sway bar stiffens the rear up quite nicely
That should clarify things.... <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
To confirm, it is the rear sway bar we're talking about?
If you see Adrian post, directly above yours, it says:
The 21mm rear sway bar stiffens the rear up quite nicely
That should clarify things.... <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
04-12-2002, 09:54 AM
#14
Three Wheelin'
[quote]Originally posted by Christer:
<strong>on 12 Apr 2002 "Roygarth" wrote these pearls of wisdom....
To confirm, it is the rear sway bar we're talking about?
If you see Adrian post, directly above yours, it says:
The 21mm rear sway bar stiffens the rear up quite nicely
That should clarify things.... <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> </strong><hr></blockquote>
Christer
Don't get me started! I don't want to 'queer my patch' on this site as well!
Piers
<img src="graemlins/icon501.gif" border="0" alt="[icon501]" />
<strong>on 12 Apr 2002 "Roygarth" wrote these pearls of wisdom....
To confirm, it is the rear sway bar we're talking about?
If you see Adrian post, directly above yours, it says:
The 21mm rear sway bar stiffens the rear up quite nicely
That should clarify things.... <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> </strong><hr></blockquote>
Christer
Don't get me started! I don't want to 'queer my patch' on this site as well!
Piers
<img src="graemlins/icon501.gif" border="0" alt="[icon501]" />
04-12-2002, 10:42 AM
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RoyGarth,
Don't feel bad -- I had the same question as I have also seen the (excellent) text on the UK site.
My car is also completely stock from a suspension standpoint and I, as well, would like to change as few components as necessary (initially) to help or correct the understeer (Adrian had also mentioned the 1994 factory alignment settings as part of his solution so I was going to include that with these two suspension parts).
Don't feel bad -- I had the same question as I have also seen the (excellent) text on the UK site.
My car is also completely stock from a suspension standpoint and I, as well, would like to change as few components as necessary (initially) to help or correct the understeer (Adrian had also mentioned the 1994 factory alignment settings as part of his solution so I was going to include that with these two suspension parts).