OEM shocks - CR springs - Autocross

Old 07-06-2011, 08:39 AM
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OEM shocks - CR springs - Autocross

With the stock RE50s and VSA off, at Autocross an í06 S2000 has some serious understeer. The SCCA STR class allows 255 tires all around. 255s all around would be great for AutoX, but not optimal for daily driving.

Trying to keep costs to a minimum Iíve been looking at the most cost effective way to upgrade the í06 suspension. So it would be usable at AutoX with 255s all around and near stock tires on the street.

This article is available on the KW Suspension website and provides a lot of information used to make these decisions (http://blog.kw-suspension.com/wp-content/uploads/2010/06/scc-s2k-shootout.pdf ).

Based on the article which tested the shocks (page 52), the CR has higher compression dampening up front than an AP2, but, equal rebound dampening. On the rears the CR has equal compression dampening to an AP2, but, greater rebound dampening. Based on this and reading some posts on the different S2K sites, Iíve decided that the CR springs front and rear, but, keeping OEM AP2 shocks is a viable option, basically CR coilovers.

I was thinking CR sway bars front and rear was a way to go, but, from feedback on the other sites, I was steered to the Saner Front Sway Bar, as the best way to deal with 255s all around. Itís over twice the cost of the CR front sway bar, but, is adjustable.

So as of right now the best value upgrade looks like the Saner Front Sway Bar ($300), OEM AP2 shocks (free), CR springs front and rear ($330), which leaves the rear sway bar. Feed back on the other site was to keep the rear sway bar as soft as possible (í06 rear sway bar free). This is true for 255s all around (17X9 TRMotorsport C3 rims, and 255 Starspecs $1350 after rebate), but, would result in even, more understeer when running street tires. So, I did a chart comparing front and rear sway bar stiffness through the years. Based on this Iím thinking that the best rear sway bar to use with the Saner Front Sway Bar might be the í00-í01 rear sway bar ($115). It would keep the car most balanced when the Saner bar was set to soft, and when set to hard give a ratio equivalent to the Saner bar set to soft and the í06 OEM bar (a recommended setup on another S2K site).
Year - Front Sway Bar - Rear Sway Bar - Ratio
00-01 - - - - 393 - - - - - - - - - 427 - - - - - 1.09
02-03 - - - - 300 - - - - - - - - - 396 - - - - - 1.32
04-05 - - - - 300 - - - - - - - - - 311 - - - - - 1.03
06-07 - - - - 300 - - - - - - - - - 311 - - - - - 1.03
08-09 - - - - 354 - - - - - - - - - 311 - - - - - 0.87
CR - - - - - - 392 - - - - - - - - - 362 - - - - - 0.92
Saner Soft - 566 - - - - - - - - - 427 - - - - - 0.75
Saner Center 644 - - - - - - - - 427 - - - - - 0.66
Saner Stiff - 739 - - - - - - - - - 427 - - - - - 0.58

Would the very stiff sway bars front and rear produce undesirable handling?

Another even less expensive option would be front and rear CR springs ($330), OEM shocks (free), CR front and rear sway bars ($230), and disconnect the rear sway bar when running the 255s all around.

Appreciate any and all feedback.

Thanks
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Old 07-06-2011, 10:58 AM
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I'm no expert at suspension settings, Tom, but my '08, which supposedly had revised dampening and/or springs rates and now with 14K miles on the clock, feels nicely balanced.

Most of my driving is spirited around town. I have a feeling a lot has to do with the rear tire wear (have about 25% tread left, fronts have about 60% left). I can get the rear to move around quite easily in corners with throttle, while the fronts stay planted. Neutral or oversteer on demand. Good fun.
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Old 07-06-2011, 01:57 PM
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i would go to a few events with your stock rear swaybar and see how the car feels.

i would expect that running 255s all around would result in more understeer with a much stiffer bar up front. that being said, i agree that the 00-01 rear bar would be best.

also, why are you considering cr springs? are they not stiffer up front and softer in the rear than regular ap2 springs? this would add to understeer.
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Old 07-06-2011, 04:12 PM
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The current understeer comes from the 215s up front and 245s in the rear.

The 255s all around should result in substantial oversteer as you have a lot more tire up front (grip) compared to the stock setup. This is why the big front sway bar is needed.

The CR springs are about 25-35% stiffer front and rear compared to the stock '06 springs.
Calculated Spring Rates per http://www.mccanless.net/Characteriz...rings_rev1.pdf
Front '06 262 lb/in - CR 384 lb/in
Rear '06 269 lb/in - CR 343 lb/in
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Old 07-07-2011, 03:22 PM
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this is true.

im saying that running the nonstaggered tire sizes along with the stiff front sway bar will result in substantial understeer without the addition of a stiffer rear swaybar..

the cr springs will contribute to understeer aswell as the fronts are stiffer.

Last edited by ls1->s2k; 07-07-2011 at 03:24 PM.
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Old 07-07-2011, 04:26 PM
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Well here's what I ordered:

CR springs front and rear (keeping AP2 shocks)

Saner Front Sway Bar (Moddiction is running a group buy on S2Ki - Red - $275 free shipping - price could drop to $265 with enough orders)

'00-'01 AP1 rear sway bar

That gives me a bunch of different options.

Saner Bar has 3 settings:

Soft setting 566 lbs/in
Center setting 644 lbs/in
Stiff Setting 739 lbs/in

I have 3 different options for the rear sway bar:

Rear sway bar disconnected - 0 lbs/in
'06 AP2 rear sway bar - 311 lbs/in
'00 AP1 rear sway bar - 427 lbs/in

I figure between those 9 combinations I should find 2 of them that will work one for staggered street and one for non-staggered AutoX.

I really don’t have the opportunity to push the car on the streets here in Ohio. Anything with curves has a reduced speed limit. It’s not like California where you could go up to the mountains and legally have fun. So, what I end up with for street driving is less critical than Autocross, provided the street setup doesn’t have totally funky handling.
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Old 07-07-2011, 04:38 PM
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You might consider looking for '02-03 rear shocks. They sell for cheap on craigslist and ebay since nobody seems to want the stock AP1 suspension parts. The '02-03 had 309lb rear springs. Very close to the 343lbs of the CR, the stiffest of all non-CR rear suspesion. I would think the valving would be very close to the CR.

For fronts you're pretty much out of luck. The stiffest there is the '08-09 and that's still 100lbs lighter than the CR.

Just a thought.
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Old 07-08-2011, 08:01 AM
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Originally Posted by Silverstone_Ryan View Post
You might consider looking for '02-03 rear shocks. They sell for cheap on craigslist and ebay since nobody seems to want the stock AP1 suspension parts. The '02-03 had 309lb rear springs. Very close to the 343lbs of the CR, the stiffest of all non-CR rear suspesion. I would think the valving would be very close to the CR.

For fronts you're pretty much out of luck. The stiffest there is the '08-09 and that's still 100lbs lighter than the CR.

Just a thought.
Thanks for the suggestion, I'll keep my eye out for a set.

This quote from the Science of Speed site makes me feel a little better about the course I'm taking: 'retaining the very advanced factory suspension dampers that in our experience offers better performance than most aftermarket coil over dampers.'

I'm taking a gamble and will probably end up with a couple hundred dollars of parts in the end that don't work. But, given that people are dumping $2600 into just springs and dampers for Autocross, if I get any sort of competitive performance out of what I'm doing I'll be happy.

My plan is if the current shocks don't work, or when they wear out to buy the CR shocks at that time.

I'm having fun, and each time I run I'm trying to learn a little for more driver modification.
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Old 07-08-2011, 11:16 AM
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Originally Posted by TTMartin View Post
I really donít have the opportunity to push the car on the streets here in Ohio. Anything with curves has a reduced speed limit. Itís not like California where you could go up to the mountains and legally have fun. So, what I end up with for street driving is less critical than Autocross, provided the street setup doesnít have totally funky handling.

having fun is illegal regardless of locale

hope you find a balanced setting
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Old 07-20-2011, 03:33 AM
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My STR autocross update.

I ordered 17X9 TR Motorsport C3 on all corners.

I went with 245/40 Starspecs all around.

I was originally planning on getting 255/40s. But, after reading that you really didn't get increased grip, but, rather better thermal properties out of the 255s for more consistent tire performance, I opted for the 245s. The short runs of autocross mean that the greater heat build-up in the 245s is less of an issue than it would be if I were tracking my car. Also, the lower profile of the 245/40 over the 255/40 will mean slightly more torque. edit: and the 245/40s are each 2 lbs lighter.

I have the first week of August off work, I'll get everything installed except the sway bars, as I probably wont have the Saner bar by then.

Last edited by TTMartin; 07-20-2011 at 03:41 AM.
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Old 07-20-2011, 06:06 AM
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FWIW, on the track, not autocross, that on my AP1 12K springs on the front and 9K springs on the rear worked best and I like the 10k front and 8K rear combination on my current AP2. On the AP1, the alignment sweet-spot was

Front
Camber - 1.5 d /-1.5 d
Caster +6.8 d /-6.8 d
Toe -0.03 in /-0.04 in
Total Toe -0.07 in

Rear
Camber-2.5 d /-2.4 d
Toe 0.08 in /0.10 in
Total Toe 0.18 in

It's not really street-able but it handled like a go-kart.
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