No problem, I will let you know as soon as I have the information.

Later, Steve

 

Steve,
Disabling PSM is easy. You just need to disconnect the connector going to the pre charge pump under the brake fluid reservoir. I just had my shop wire an on/off switch in the wire going to the connector so that I could turn it on or off without having to remove any of the covers and pulling any plugs.

 

Do you have a permanent PSM error message on the dash?

 

The yellow "PSM OFF" circular light at the base of the dash will be illuminated. This is the same light that you get if you turn off PSM via the dash switch. When you start the car you will also get a "PSM failure, drive to workshop" (or something like that) in the central display. Your can just clear that by tapping the column stalk and it goes away. The PSM dash switch will be inop without any lights illuminated. There are no permanent messages stored in the ECU and if you turn the PSM back on (by plugging in the pre charge pump connector or the master switch in my case) everything is back to normal.

 

I wonder if there is a way to install a resistor in the plug that will make the ECU believe it's still connected?

 

Don't know. But if someone figures it out I'm all ears.....

 

The more I look the crazier this gets.

Take a look at the varience between spring rates and their wheel rate percent.

STOCK
Front: 188lbs. 54.9%
Rear: 343lbs. 45.1%

PSS10's
Front: 260lbs. 52.8%
Rear: 515lbs. 47.2%

KW 2-way Club Sport
Front: 340lbs. 43.7%
Rear: 970lbs. 56.3%

H&R RSS Club Sport
Front: 340lbs. 48.5%
Rear: 800lbs. 51.5%

JRZ Double Adjustable (Vivid Racing Recommendation)
Front: 400lbs. 64.0%
Rear: 500lbs. 36.0%

From 36% to 56% rear wheel rate.

In most cases, the front to rear swaybars aren't sized to significantly alter the wheel rate percent of the springs.

Maybe someone from Vivid Racing can shed some light on this.

Later, Steve

 

That's exactly my contention Steve. The sway bars are so puny that their ability to alter spring wheel rate is extremely limited especially when you compare changing the swaybar setting from one hole to another or going from a 21.7mm stock bar to a thinner 20.7mm GT3 bar that is basically the same stiffness on the third hole as the stock bar and at full stiff only marginally stiffer than stock. The adjustable sway bar allows you to fine tune your suspension on a well set up car, nothing more. A setting that works on one track may not work on another. You may only be changing the spring wheel rate a few pounds or so at best. Thats why I find it amusing when people proclaim how they feel such a profound difference from just sway bar settings on the street which doesn't really provide you with a repeatable testing environment like a track would. I believe alignment setting like camber changes, spring rate changes, shock settings, tire sizes, and tire pressures will have a MUCH greater effect on the handling of the car than simply changing a sway bar setting that may add 10 ft/lbs. of change to your spring wheel rate. At least that is what my testing at the track bears out. Flame away....

 

The swaybars aren't typically making a significant change, but the setup I'm getting ready to run does make a difference.

My current setup with PSS10's and a GT3 rear bar on the next to the softest setting give me a total rear wheel rate of 46.8%

Simply replacing the GT3 rear bar with an H&R rear bar on the middle setting will change this to 55.3%.

FYI this would take a 195lbs. increase in rear spring rate to have the same effect.

Basically the bar CAN have a large effect, it just doesn't appear that many setups make that big of a change. Maybe I'm out of my mind making the change.

Oh well, it's less than $300 and I've definitely made bigger mistakes than that.

Later, Steve

 

I was referring to the stock v. GT3 bar which are both very similar in stiffness. The H&R bar is huge (24mm v. 20.7mm) compared to the GT3 bar and on top of that it's solid so its much much stiffer. Not even the same ball park.... That will make a noticeable difference I would imagine will all things being equal.... I like the H&R bar on my set up but I've never run any others to compare it to so it will be interesting to hear what you find out in your case.

 

A rule of thumb is that if you can't tell a difference after taking a few corners when you moved the swaybar links a hole or two, don't even bother with fiddling on swaybars, or anything else for that matter. Invest money in driving instruction and spend time driving the car until you do build up a basic level of "feel".

Short about swaybars, to simplify a little bc this thread really went where nobody really should ever have to go;
In racing, swaybars are essentially nothing more than a fine-tuning tool used to hit a perfect oversteer/understeer balance for a given car, track, set of tires and driver. That's all the swaybars are supposed to do. Over a 90 minute stint, tires change, fuel load changes and a bit of adjustment even while driving is very helpful, and those are really minor adjustments (that's why serious GT cars have adjustable bars with links to the ****pit so the driver can change as he goes), but they make a huge difference on the laptimes. If for example rear tires are getting a little hot you can dial in a little push for a lap or two to ease the strain on the rear tires, then adjust back and get active again for maybe a last lap push. It's part of strategy and very important if you want to be competitive to the finish line.

So back to the point of a fine tuning-tool. When the car is as good as possible on the spring rates and frequencies front/rear, and with the shocks valved right, perfect rideheight and aero balance, then the swaybars can dial balance the final tiny amount yet while making AS LITTLE impact as possible to an already well setup car.

In less ideal cases in racing and with heavier cars, mainly typical for OEMs making cars for the road, one can use swaybars to add cornering stiffness (less roll - feels sporty, reduce camber change due to suspension travel), but without having to use a megahard spring which wouldn't be practical to sell to the customer.

Back to OP, there is really not with more than spending a minute on choosing swaybars.

First rule is to get a matching set unless you have a bastard car and need something custom with a non-matched set.
H&R or Eibach are specialists and make very good application specific products.
Done.

 

We have developed a proper bolt on solution several years ago.

Here is a link to the product , let me know if you need more info.

http://www.gmgracing.com/store/index...l-bar-set.html

 

+1000

Except I got good results from just adding a rear H&R sway bar and putting it on full stiff. But we went up gradually from full soft over the course of a few sessions and I could feel the difference in every notch (I think 4 on the H&R rear car). HUGE difference.

If you don't feel a difference, you probably aren't testing the limits of the setup. And it's not likely to happen on the street.

Knowing what I know now, I may have tried a front bar with some rake changes in addition to the rear bar. I just did not want to add any understeer back as no one at the time could tell me if how much the other bars were or werent stiffer than the stock one.

 

I agree with Carl and Dez. I have my GT2 rear sway 2 away from soft, and the car is over steery ( my driving style) as is. What got me there was not the swaybar but my whole suspension as a unit. It's a package. The swaybar just gave me 1) a slightly more predictable rear end at the limit, of what the car will do lap after lap.

I disagree with Carl in another thread where he stated that you need coilovers for the car to handle good. Most people will not achieve the capabilities of what coil-overs give them let alone know what to do to fine tune them for certain tracks/roads or whatever. It will only make it more difficult for them learning how to drive. When I had my ruf springs, I would go faster then guys on Motons/JRZ/KW's you name it and slicks in GT3's, people whom had 100' of track days. Start with a base, fine your driving style, get an someone that knows how to align your car --do that. Do lower springs as you will not have to deal with the headache of fine tuning compression and rebound. Because trust me, as Carl knows as he is part of the MB group every road surface is different and 99% of people wont have a clue how to adjust the swaybars let alone coilovers.

So my suggestion to the OP is get an alignment. I can suggest one to you that I like that makes the car lively in the rear end, but that is my driving style. You will get bad wear unless you are driving in the mountain roads. You will get about 10k for the rear tires like I do.

 

I spoke with some who has an extensive background in roadracing 911's and got his opinion on this discussion. Keep in mind he has worked with the TRG and Brumos Rolex teams recently.

He agrees that in general you will need rear spring than front spring on a street car, but there are several instances where a significantly higher front spring rate is necessary (sometimes even higher than the rear spring rate).

Apparently our cars lose front grip as the front moves up and down. Sometimes it's necessary (depending on the track) to keep the front end planted and reduce this up and down motion.

He did say however that the rear swaybar would be significantly stiffer to maintain the balance as the front spring rates are increased.

So, I'm still going to go with the H&R rear bar and stock front bar with my PSS10 coil-overs.

Later, Steve