"Twitchy" steering with new PS2s
#31
08-17-2010, 01:43 PM
I had Porsche reset the steering sensor, they charged $60 to do it, and it didn't help at all. I'm waiting to receive my flash back from Switzer and hoping he can deactivate the steering sensor that way, otherwise, I've gotta figure out some other solution as I'm not giving up the beautiful 19'' wheels! Thoughts?
Last edited by MikeR397; 08-17-2010 at 01:45 PM.
#32
08-19-2010, 02:47 PM
Join Date: Oct 2009
Location: Charlotte, NC
Posts: 41
Rep Power: 16 
To the contrary, you will find your "hot setup", in terms of performance, on an 18" wheel and tire setup. This is why if you ever desired to buy real racing slicks, you can only find them in 18" sizes. We actually just did some preliminary tire testing for Hoosier with their first ever set of 19" racing slicks.
The reason for this sizing is because it provides you with more sidewall in your tires. What most people don't realize is that the tire's sidewall actually functions as a spring. By specifying a different tire heights you can have a huge impact on your vehicle's performance. On REAL race slicks you can even specify different spring rates for the tire sidewalls. This is a huge part of developing grip. By running a larger wheel, you have reduced the amount of tire side wall you have to work with. This will result in less grip and worse tire wear characteristics!
You say your ride height is ~2" below stock. If it is just for looks on the streets, then this wouldn't be too much of a problem other than bad tire wear and having to watch out for every obstacle imaginable. We generally lower cars about 1" lower than stock. This brings the cars closer to the GT3 ride height, which will be better for the track. GT3s can lower themselves further than standard street cars because they have different uprights. When you lower your car by such a great deal, you have a large impact on the car's overall suspension geometry and travel. Normally camber plates are used to gain camber for track cars, not correct a problem caused by something else.
Without knowing exactly whose sway bars you have I cannot comment on what they are doing for your car. HOWEVER, sway bars have a HUGE impact on the handling performance of your vehicle. After your tire they are the next most important part of you suspension. The wrong ones can slow you down(it feels fast because they make you so lose that you are constantly wrestling the car) but the right ones can decrease your lap times by seconds. Here's a post I made in another thread...
"Sway bars are the MOST IMPORTANT part of the suspension setup after your tire choice. The sway bars you install on your car will determine the driving characteristics of your vehicle more than any other suspension component.
Having an appropriate sway bar will determine how well your car enters turns/stays planted through the middle/ and how early you can get on the throttle on turn exit. Sway bars have an even greater impact than either LSD or coilovers; these components are used to fine tune the car after the proper balance has been found using sway bars.
This isn't just what we "think" is correct. This is what we know to be correct from years of PROFESSIONAL RACING. In that time racing we were able to win the 2004 Grand Am Series championship as well as winning the 2006 24 Hours at Daytona after finishing 2nd in 2004 & 2005. Developing a Sway Bar set that makes a vehicle easier and more fun to drive while reducing lap times takes an ENORMOUS amount of R&D in real racing environments.
The TPC Racing Adjustable Sway Bar set was designed to give the driver a vehicle that inspires confidence everywhere on track; giving the driver the ability to brake later/maintain higher cornering speed/ and allow get on the throttle sooner. These bars were designed to take away the vehicle's tendency to oversteer at the limit. Instead, we find that the ideal setup is to leave the car slightly on the tight side. This really allows drivers of all skill levels to drive the cars fast without the fear of the back end coming around.
I feel like a broken record; I've talked about this so many times. But sway bars really are the most important upgrade when creating a fast track car; I cannot over-emphasize this enough! When it comes for sway bars, you get exactly what you pay for. With TPC Racing Adjustable Sway bars, you get a PROFESSIONAL RACING QUALITY parts. The bars we sell our customers are the exact same ones we sell to pro race teams."
The reason for this sizing is because it provides you with more sidewall in your tires. What most people don't realize is that the tire's sidewall actually functions as a spring. By specifying a different tire heights you can have a huge impact on your vehicle's performance. On REAL race slicks you can even specify different spring rates for the tire sidewalls. This is a huge part of developing grip. By running a larger wheel, you have reduced the amount of tire side wall you have to work with. This will result in less grip and worse tire wear characteristics!
You say your ride height is ~2" below stock. If it is just for looks on the streets, then this wouldn't be too much of a problem other than bad tire wear and having to watch out for every obstacle imaginable. We generally lower cars about 1" lower than stock. This brings the cars closer to the GT3 ride height, which will be better for the track. GT3s can lower themselves further than standard street cars because they have different uprights. When you lower your car by such a great deal, you have a large impact on the car's overall suspension geometry and travel. Normally camber plates are used to gain camber for track cars, not correct a problem caused by something else.
Without knowing exactly whose sway bars you have I cannot comment on what they are doing for your car. HOWEVER, sway bars have a HUGE impact on the handling performance of your vehicle. After your tire they are the next most important part of you suspension. The wrong ones can slow you down(it feels fast because they make you so lose that you are constantly wrestling the car) but the right ones can decrease your lap times by seconds. Here's a post I made in another thread...
"Sway bars are the MOST IMPORTANT part of the suspension setup after your tire choice. The sway bars you install on your car will determine the driving characteristics of your vehicle more than any other suspension component.
Having an appropriate sway bar will determine how well your car enters turns/stays planted through the middle/ and how early you can get on the throttle on turn exit. Sway bars have an even greater impact than either LSD or coilovers; these components are used to fine tune the car after the proper balance has been found using sway bars.
This isn't just what we "think" is correct. This is what we know to be correct from years of PROFESSIONAL RACING. In that time racing we were able to win the 2004 Grand Am Series championship as well as winning the 2006 24 Hours at Daytona after finishing 2nd in 2004 & 2005. Developing a Sway Bar set that makes a vehicle easier and more fun to drive while reducing lap times takes an ENORMOUS amount of R&D in real racing environments.
The TPC Racing Adjustable Sway Bar set was designed to give the driver a vehicle that inspires confidence everywhere on track; giving the driver the ability to brake later/maintain higher cornering speed/ and allow get on the throttle sooner. These bars were designed to take away the vehicle's tendency to oversteer at the limit. Instead, we find that the ideal setup is to leave the car slightly on the tight side. This really allows drivers of all skill levels to drive the cars fast without the fear of the back end coming around.
I feel like a broken record; I've talked about this so many times. But sway bars really are the most important upgrade when creating a fast track car; I cannot over-emphasize this enough! When it comes for sway bars, you get exactly what you pay for. With TPC Racing Adjustable Sway bars, you get a PROFESSIONAL RACING QUALITY parts. The bars we sell our customers are the exact same ones we sell to pro race teams."
That said, I do think it handles better now than with the stock wheels and Pirellis now that the alignment was corrected. I'm sure, from what you have said, that there is still plenty of room for improvement, so I'll probably end up bringing it to a PCA affiliated race car suspension shop near my house for proper tuning from here. Overall I'm pretty happy with it for now though.
Fortunately, it doesn't scrape the front lip spoiler too badly or bottom out at all so I'm in decent shape there. I may do a DE event here and there or an autocross, but my intent is to have an optimized street car, not a track car.
Thanks again very much for the info!
#34
08-19-2010, 03:07 PM
I'm glad to hear that the alignment fixed the twitchiness. You didn't mention the toe, but that makes a big difference as well.
The spec on tire pressures is 36F/44R. I have found that this gives pretty reasonable handling and tire wear on my car. YMMV.
Beware on the camber plates: they may or may not actually help you, depending on why your camber cannot be adjusted. There isn't a lot of extra room in the shock tower. On my car, the strut interferes with the body before the max on the adjustment slots.
Try doing a search on the ride height. There was a thread where Mikelly (since banned) explained how and where to measure. He pulled some of his posts, but it may still be there.
Jon
The spec on tire pressures is 36F/44R. I have found that this gives pretty reasonable handling and tire wear on my car. YMMV.
Beware on the camber plates: they may or may not actually help you, depending on why your camber cannot be adjusted. There isn't a lot of extra room in the shock tower. On my car, the strut interferes with the body before the max on the adjustment slots.
Try doing a search on the ride height. There was a thread where Mikelly (since banned) explained how and where to measure. He pulled some of his posts, but it may still be there.
Jon
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