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Old 09-26-2017, 10:14 AM   #1
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Need some help on suspension modifications please.

I have a basically stock 2004 986 S with 31,000 miles and have been bitten by the autocross bug this year. One of the items I did change was I went to 17" wheels and summer performance tires, replacing the all season tires.

Some of the photos I've seen of my car on the track looks like I am experiencing body roll. Tell me if I'm wrong.

I would like to stiffen the car more but I also want to keep the car for street use as well. What would be some suggestions for improvement. I was thinking of a rear stabilizer or maybe a front stabilizer that mounts in the frunk.

Please let me know your thoughts.





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Old 09-26-2017, 11:11 AM   #2
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Great question. For street use I like the S setup. There will be sacrifices in quality ride in street use when beefing up the suspension for track use. Other variables are how much money are you willing to spend and what street sacrifice are you willing to give up?
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Old 09-26-2017, 11:37 AM   #3
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stiffer front sway bar. will reduce body roll and improve turn-in. will not detract from ride quality. m030 (there used to be a great chart that showed the relative thicknesses of the various bars) is good option that doesn't require special drop links. or a 996 gt3 front sway bar - will require aftermarket drop links, but is adjustable. don't use H&R - too stiff, too heavy.

don't mess with the rear (yet); the boxster tends to get tail happy quick when you start messing with it.

also look at alignment - as much front camber as possible, keep rear about half degree less. the amount of adjustability (or lack thereof) will ensure that you won't get so much camber that your car gets darty or your tires start wearing funny.

i think when you say 'stabilisers' you mean strut braces which are different - they are there to keep the top of your struts from pulling apart under hard cornering - don't think you are there yet.
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Old 09-26-2017, 12:40 PM   #4
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This page has chart for early cars through 2002.

CB-Racing, 986 Suspension Info

Using this info, on my 2000s, i went with the m030 S front bar and the m030 non-S rear, (since it was stiffer than m030S bar)

After that I installed ROW m030 springs and shorter sport shocks to lower the car a little.

Felt just right for track days and still street-able.
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Old 09-26-2017, 12:42 PM   #5
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Here's a chart with the sway bar stiffness, that also includes the stiffness for the Eibach bars:

http://986forum.com/forums/511625-post9.html
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Old 09-26-2017, 03:53 PM   #6
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Sorta depends on how far you want to go with it. My 986 was in development for 10 years and I have spent a lot of time riding right seat in other peoples cars, both novice and top national drivers.

Some stuff I like:

>The M030 kit including struts and sways, corner balance and alignment. It is a pretty great setup for a dual purpose car. It firms things up just enough for AX/DE but is still very street friendly.

> Springs and GT3 A-arms, corner balance and alignment. This is what I have on my 987.2 now and it feels very much like the M030 kit with better camber settings and better tire wear.

> PSS9 struts, comp sways, GT3 arms, corner balance and alignment. This is the Spec racing setup and works pretty well on track but is marginally street friendly.

All of these work well if set up by a pro shop that knows these cars well. It will transform the cornering response of your car and make the most of your contact patch.

Stuff I don't like that have made cars unbalanced and unruly in the corners:

DIY setup changes including off brand struts, springs, or mismatched sways. The worst handling Boxsters ever have been DIY "tuner" setups by someone who thought they were making the car faster. If you want success in AX or TT, I ALWAYS recommend using a highly experienced shop with a history of putting cars on the podium. It just works.

YMMV
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Old 09-26-2017, 05:24 PM   #7
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What autocross racing series or sanctioning body are you competing under, or plan to compete under? If you are serious about doing well in competition, my recommendation is to be mindful of whatever rules apply in your racing series. Making the "wrong" modification (e.g., in SCCA solo, putting aftermarket springs on a car which is otherwise "street" class compliant) can easily throw your car from competing in a class where it could have a chance of winning to a class where it has no chance.

If you don't really care about competing successfully, feel free to disregard. In any case, have fun!!
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Old 09-26-2017, 07:42 PM   #8
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Thank you all for your input and advice. A little more on my plans and thoughts. I'm on a limited budget so I will be doing little things as time and money permit. Jakeru, currently I'm just competing within our PCA region where I run in class C. At times, we participate in SCCA events where I am in STU. I would like to win occasionally but I'm never going to nationals or anything like that. Just trying to improve myself and get off the bottom of the rankings.

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Originally Posted by jakeru View Post
What autocross racing series or sanctioning body are you competing under, or plan to compete under? If you are serious about doing well in competition, my recommendation is to be mindful of whatever rules apply in your racing series. Making the "wrong" modification (e.g., in SCCA solo, putting aftermarket springs on a car which is otherwise "street" class compliant) can easily throw your car from competing in a class where it could have a chance of winning to a class where it has no chance.
Topless, as I mentioned above, I just want to do some little things to improve the handling. I don't want to make my 986 a track car, I enjoy cruising in it as well. I will probably go for new struts when my stock units wear out. One set I may go for are the Koni FSD.

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Sorta depends on how far you want to go with it. My 986 was in development for 10 years and I have spent a lot of time riding right seat in other peoples cars, both novice and top national drivers.
Thanks for the chart Steve. What should I assume that I would have installed on my car? The standard suspension for a 3.2L or the Sport M030 bar for a 3.2L?

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Here's a chart with the sway bar stiffness, that also includes the stiffness for the Eibach bars:
Thanks Tommy for the link. I'll have to seen if the p/n's are applicable to a 2004S

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Originally Posted by tommy986 View Post
This page has chart for early cars through 2002.
Thanks TRK. Good advice. And it follows my budget & plan. I think I'll go with the Front sway bar. One other thought I had was to change out the bushings on the car. Would that tighten things up as well?

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Originally Posted by The Radium King View Post
stiffer front sway bar. will reduce body roll and improve turn-in. will not detract from ride quality. m030 (there used to be a great chart that showed the relative thicknesses of the various bars) is good option that doesn't require special drop links. or a 996 gt3 front sway bar - will require aftermarket drop links, but is adjustable. don't use H&R - too stiff, too heavy.

don't mess with the rear (yet); the boxster tends to get tail happy quick when you start messing with it.

also look at alignment - as much front camber as possible, keep rear about half degree less. the amount of adjustability (or lack thereof) will ensure that you won't get so much camber that your car gets darty or your tires start wearing funny.

i think when you say 'stabilisers' you mean strut braces which are different - they are there to keep the top of your struts from pulling apart under hard cornering - don't think you are there yet.
Thanks Ciao, if you read all my other responses, you'll see I want to move in baby steps for these items as I build up more seat time to improve the nut holding on the wheel.

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Originally Posted by Ciao View Post
Great question. For street use I like the S setup. There will be sacrifices in quality ride in street use when beefing up the suspension for track use. Other variables are how much money are you willing to spend and what street sacrifice are you willing to give up?
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Old 09-27-2017, 07:31 AM   #9
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Originally Posted by eicheldp View Post
Thanks for the chart Steve. What should I assume that I would have installed on my car? The standard suspension for a 3.2L or the Sport M030 bar for a 3.2L?
If you look under your front trunk hood you should see a sticker with option codes, if you have the code 030 you have the sport suspension, and if not, you have the regular suspension.

If there is no sticker (for example there was a fender bender and the car got a new hood at some point) you could also look at the part number on the rear sway bar, it should be visible if you get down on the ground behind the car, and compare it with the part numbers on one of the sites with a parts lookup and diagrams.
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Old 09-27-2017, 07:57 AM   #10
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Originally Posted by eicheldp View Post
Just trying to improve myself and get off the bottom of the rankings.
I would suggest that your best investment is in yourself!

Find a competent driving instructor and then get as much seat time as possible. A purely stock Boxster is incredibly capable and there isn't much point in improving the car unless your driving skills can take advantage of the car improvement. In fact, it can be a hinderance.

The best gauge of progress is to track your lap times and compare to equal cars. If you're not at the top of that list, then its not the car that is holding you back.

I did around 25 track days before I improved my original Boxster beyond better brake pads and performance tires. You'll know when you are better than the car and when the car is what is holding back your performance. THEN upgrade the car.

I still follow this lesson to this day. Even after three seasons of racing Spec Boxster, I am not at the top of the leader board so I will continue to focus all of my efforts on improving my driving skills first and foremost.
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Old 09-27-2017, 09:07 AM   #11
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I would suggest that your best investment is in yourself!

Find a competent driving instructor and then get as much seat time as possible. A purely stock Boxster is incredibly capable and there isn't much point in improving the car unless your driving skills can take advantage of the car improvement. In fact, it can be a hinderance.

The best gauge of progress is to track your lap times and compare to equal cars. If you're not at the top of that list, then its not the car that is holding you back.

I did around 25 track days before I improved my original Boxster beyond better brake pads and performance tires. You'll know when you are better than the car and when the car is what is holding back your performance. THEN upgrade the car.

I still follow this lesson to this day. Even after three seasons of racing Spec Boxster, I am not at the top of the leader board so I will continue to focus all of my efforts on improving my driving skills first and foremost.
^^^^^This.^^^^^
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Old 09-27-2017, 11:39 AM   #12
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Agree with Thstone. On a limited budget leave the suspension alone and run stock class. Mount the freshest tires that are competitive in your class, get a performance alignment to make the most of your contact patch, and get a top driver in your right seat for coaching. "Tuner" suspension changes will make no difference in lap times at this point. Always tighten the loose spacer behind the steering wheel before making changes to the car.
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Old 09-27-2017, 12:14 PM   #13
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Looking at pictures of your car and thinking that it is leaning too much is normal. But body lean is also a good thing, as it provides good feedback. Some of the most difficult cars to drive quickly have really stiff set-ups, which tend to feel fine until the suddenly let go, because they don't give progressive feedback (especially for a novice).

Lots of good advice in the posts above, especially the bit about working on the driver first.
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Old 09-27-2017, 04:56 PM   #14
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[/QUOTE]
I did around 25 track days before I improved my original Boxster beyond better brake pads and performance tires. You'll know when you are better than the car and when the car is what is holding back your performance. THEN upgrade the car.[/QUOTE]

Thstone, Topless, Rattan and Racer Boy,
Thank you for your advice. I think i'll save save some money to devote to lessons instead of parts. I hope I can get to the point where I can recognize that the car is holding me back. (Or that this old man lives that long )

One question, where is a good place to look for an instructor for AX? I reside in eastern PA.
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Old 09-27-2017, 07:06 PM   #15
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Evolution all-day autocross school may be coming to your nearborhood at some point...
The Evolution Performance Driving School - Building Champions since 1993 - Autocross, Driver School, HPDE, License

Your local SCCA region may also have educational events, or instructors who can ride along and critique your driving, or drive you car while you watch and observe and learn.

I'm also just curious, what modification(s) did you make already which put you into SCCA Street Touring Unlimited class?
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Old 09-27-2017, 07:22 PM   #16
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I did around 25 track days before I improved my original Boxster beyond better brake pads and performance tires. You'll know when you are better than the car and when the car is what is holding back your performance. THEN upgrade the car.[/QUOTE]

Thstone, Topless, Rattan and Racer Boy,
Thank you for your advice. I think i'll save save some money to devote to lessons instead of parts. I hope I can get to the point where I can recognize that the car is holding me back. (Or that this old man lives that long )

One question, where is a good place to look for an instructor for AX? I reside in eastern PA.[/QUOTE]

Looks like you are in PCA Zone 2. Find an active AX region near you and contact their CDI. Let him know you are interested in improving your AX skills and would like to work with a qualified instructor. He will direct you from there.
AUTOCROSS « Porsche Club of America, Zone 2
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Old 09-28-2017, 06:31 AM   #17
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Originally Posted by jakeru View Post
I'm also just curious, what modification(s) did you make already which put you into SCCA Street Touring Unlimited class?
Jakeru,
The only modification I have made was changing wheel diameter and putting on some spacers and summer performance tires. I put it all in the thread below. Everything else is stock.
http://986forum.com/forums/boxster-racing-forum/67760-wheel-fitment-spacers.html
I went back to the SCCA classifications and I saw where my car is listed under STU class, but I also read the opening paragraph of the class that allows for suspension and engine modifications.
What confused me was the C street list of applicable cars, where it states "Boxster (986 chassis, all) (1997-2004)". It doesn't call out the S version specifically as they do for other classes for different models. I guess I'm in the wrong class.

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Looks like you are in PCA Zone 2. Find an active AX region near you and contact their CDI. Let him know you are interested in improving your AX skills and would like to work with a qualified instructor. He will direct you from there.
AUTOCROSS « Porsche Club of America, Zone 2
Topless,
I looked at the other regions listed on the link you provided, it seems that Reisentoter (my current chapter) is the most active for Autocross. I'll check within the club, but I will also check with the SCCA.
Thanks
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Old 09-28-2017, 07:36 AM   #18
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I think the "all" in "Boxster (986 chassis, all) (1997-2004)" means base and S models. However I think STU is a better class; If I run SCCA autocross again I will run in STU since the mods that I have done for HPDE move me out of the street class (used to be B Street for the 986 Boxster S)
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Old 09-28-2017, 07:54 AM   #19
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I think the "all" in "Boxster (986 chassis, all) (1997-2004)" means base and S models. However I think STU is a better class; If I run SCCA autocross again I will run in STU since the mods that I have done for HPDE move me out of the street class (used to be B Street for the 986 Boxster S)
But with no engine or suspension mods wouldn’t CS be more appropriate for my situation?
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Old 09-28-2017, 07:58 AM   #20
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SCCA street class accommodates aftermarket wheels with a few allowances... see section 13.4:
http://cdn.growassets.net/user_files/scca/downloads/000/019/208/2017-01-30-Solo-Rules-complete-reduced.pdf?1485811400

Quote:
Any type wheel may be used provided it complies with the following:
13.4 WHEELS
A. It is the same width as standard and as installed it does not have an offset more than ±7.00 mm (±0.275”) from a standard wheel for the car. The resultant change in track dimensions is allowed.
B. Wheel (rim) diameter may be increased or decreased 1” from the standard part.
Wheel spacers are permitted provided the resultant combination complies with the offset requirements of this Section. On vehicles supplied with an OE wheel spacer, the wheel spacer shall be considered as a part of the wheel. Wheel studs, lug nuts, valve stems (including pressure-relief types), and/or bolt length may be changed. Wheel bolts may be replaced with studs and nuts but the number of fasteners may not be changed. Tire pressure monitoring sensors may be removed.
Centerlock/Spline Drive/Knock-off type hubs may be converted to lug type hubs provided the resultant combination complies with the offset require- ments of this Section.
With how many different size "standard" wheel options and sizes Porsche made available on these cars (although FYI I believe in stock class, you may be confined to looking at those available for your 2004 "S" spec), along with the +/- 1" wheel diameter and +/- 0.275" offset allowances on top of those, SCCA street class leaves some pretty significant leeway for legally changing our wheels!
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