[lolachampcar] Performance Upgrade Efforts

[lolachampcar]

The difference between my wife's coil and my Standard Air (that has been lowered just a bit with links) is between a 1/2" and 3/4" depending upon which corner your looking at. The difference between Standard and Low on my car is around an inch to an inch and a quarter.

Given that you're not going to be able to raise the car to get around issues, I would think one inch down from stock coil heights would be a good place to start.

WRT fitting everything, it is a PITA. I was hoping to get the upper spring perches from Tesla but learned you have to buy whole damper assemblies ($550 each). I then learned the two coil springs I thought I was ordering last week (where I expected an $80 price tag) turned out to be a full front and rear damper assembly. Ooops!

I've found some M5 adjustable upper perches/plates that have a urethane isolation bushing (like stock) for $300 each including 2.5" spring perches. Another option would be stock M5 units that do not have the fancy and not needed adjustability for about $80 each but they are designed to work with the stock BMW M5 large diameter coil springs. Nothing is turning out to be cheap or easy for a 2.5" conversion.

I guess I will know more when I get my two damper assemblies (for a whopping $1100).

Thanks for the coil spring numbers. They look a lot like my wife's which is comforting.

BTW, those look like 12" by 2.5" springs. Do you remember the rate and can you share the application?

 

[Dreamin]

BTW, those look like 12" by 2.5" springs. Do you remember the rate and can you share the application?

Yes, that is the spring spec. Stock springs were 400lbs front and rear. The company did the spring testing and landed at 500lbs front, 450lbs rear.
Application is 1st gen Cadillac CTS-V.

Ignore the rear application in these write-ups as it's not a spring over shock design.
CTS-CTS-V FAQ Page: Ground control lowering kit
CTS-CTS-V FAQ: Ground Control Lowering Kit installation procedure

 

[simplesolar]

I measured my ride height. It is around 29.5 all around give or take a little. Is there a way to over-ride the air suspension software on our car?

 

[lolachampcar]

SS,

There are three ways that I am aware of-

The first is replace the fixed length links between the suspension arm and the ride height potentiometer on all four corners with an adjustable length one. In MS' case you need to lengthen the link to lower the car. I normally do not use this method as any lowering that is done adds to lowering in Low mode and thus can be problematic. However, I did do it on my P+ to lower it 1/2" for the reasons below.

The second approach is to use the factory diagnostic software to redo the vehicle ride height calibration at a lower ride height. MB has a lock out that prevents ride heights below a certain level. I believe these lock outs are tied to country version coding as I could not get US cars as low as European models using StarDiagnostics to recalibrate ride height. Of course, we have no access to this type of software for MS.

The last one that I am aware of is a suspension module. I did a couple variants of these for some tuners in US and Europe. The basic theory is that you offset the signal provided by each wheel height sensor by the amount needed to achieve the desired ride height. I then monitored the wheel speed signal on the CAN bus to remove my offset in a linear fashion as the factory software tried to lower the car with speed. This approach kept people from putting the car on its suspension bump stops at highway speed which would dramatically change the ride characteristics and thus be a safety issue.

I believe MS uses MB style linear potentiometers where one side is a rising voltage with rising ride height and the other lowering voltage. VAG cars used Pulse Width Modulation at one of two fundamental frequencies to send ride height. I do not remember off hand but suspect they did the same one side goes up on the positive pulse while the other side of the car goes down when the ride height changes. I'd have to go back and look at the code to confirm that. There is no MS wire harness information so it would be a huge PITA project to figure out how to install a Suspension Lowering Module (SLM) and to properly identify the CAN wheel speed so the offset could be removed.

 

[CanuckS#69]

What I do not want to do is expose myself to ANY liability. So far, I've provided some links to owners that I know and who know enough about cars and the risks associated with them to know if they want to make a change. I've provided some coffee table discussion pieces and they have decided to put this non-certified parts on their cars.

There's never a perfect solution to this dilemma, anyone can sue for anything, whether they are in the right or not. However, I suspect that as the installer of the part, the owner would have a hard time proving liability without implicating themselves and thus invalidating their lawsuit. Disclaimners of liability, "for off-road use only", etc. are often used by larger scale aftermarket parts companies, but I would think for your scale, you offer to make the part for the person much as any machine shop would and let them take on the liability for its usage.

 

[Gizmotoy]

There's never a perfect solution to this dilemma, anyone can sue for anything, whether they are in the right or not. However, I suspect that as the installer of the part, the owner would have a hard time proving liability without implicating themselves and thus invalidating their lawsuit. Disclaimners of liability, "for off-road use only", etc. are often used by larger scale aftermarket parts companies, but I would think for your scale, you offer to make the part for the person much as any machine shop would and let them take on the liability for its usage.

That's usually done because the part is not street legal, rather than protection from liability. Even if you went the whole way: some type of liability-limiting corporation, a waiver, and clear "for off-road use only" markings, you could still be sued. It's not likely to go anywhere, but it could still happen. That's why the best thing you can do is to separate the business and personal assets.

 

[lolachampcar]

I bumped up the length of the upper arms by another 0.040" which should equate to removing another 0.2 of negative camber. From all the alignment data in the Good, Bad... alignment thread, removing just one degree is not enough.

 

[lolachampcar]

I'd like to solicit a little help if possible. Specifically, I'm working with all air spring parts and need to source some upper strut mounts for coil springs that will work with Model S. I've ordered a front and rear spring from Tesla which turned out to be a front and rear spring/damper assembly as Tesla does not have just springs. Apparently their vendor builds up the damper/spring/upper spring perch - strut mount assembly and ships it to Tesla as a unit. I get the joy of paying $600 or so each for a $55 spring just so I can confirm the stock spring rates.

Anyway, it does not make sense to pay for a complete assembly just to get the upper spring perch - strut mount so I went looking for alternatives. Here is an E36 M5 (V8 version) front upper strut mount. The bushing hole is too large (not really a problem as it could be sleeved) and the bushing length is too long (the 52.5mm or 2" value you see on the calipers). The MS damper attachment section is 10mm OD and 22mm long. I'm going to try to work with Turner and Ground Control to identify some parts but most of these companies to not want to deal with silly projects like this. By chance does anyone have experience with different upper strut/damper rubber isolated mounts and have any suggestions of what might work? My next step was to look at the E60 M5 but I think this time I'll try to find one to do the measurements as opposed to buying the mount. Oh, and the bolt centers for the BMW E36 part was 55mm which is the same for MS.

Thanks,
Bill

 

[lolachampcar]

All measurements are in
Left Front Right Front
Left Rear Right Rear
format
Lowered P+
Low Setting
27 11/16 27 10/16
27 12/16 27 15/16
.
Lowered P+ (exact same car) AFTER Software 5.8
27 15/16 .. 28 0/16
28 3/16 .. 28 3/16
.
Standard Setting
28 15/16 28 4/16
28 15/16 29 0/16
.
S85 Coil Spring
29 6/16 29 8/16
29 10/16 29 8/16


I went back and re-measured my P+ at Standard and it is unchanged (within measurement and air height repeatability) so one data point says the firmware release left Standard untouched.

 

[Gizmotoy]

Something like 1/4-1/2" raise on low? Interesting. Not only did they change the speeds (on purpose or not), they also tinkered with the height at each level. Looks like standard is about where it used to be, though, from what I recall (about 0.62" lower than the coil).

 

[redi]

delete

 

[GSP]

I need a little help with this whole camber link thing. Specifically, I am all for a forum based effort to generate helpful parts. I'm not in the business, nor do I want to be, of making parts but I do not mind helpful projects for the greater good of the MS community.

What I do not want to do is expose myself to ANY liability. So far, I've provided some links to owners that I know and who know enough about cars and the risks associated with them to know if they want to make a change. I've provided some coffee table discussion pieces and they have decided to put this non-certified parts on their cars.

My question to all is how do I say yes to people that want to try the links without doing something stupid, picking the wrong person to send stuff to and then getting sued in the process? I realize there are releases to deal with liability issues but it has been my experience that documents are only as good as your willingness to litigate and I have ZERO willingness to litigate. Any other ideas?

Why not set up a small corporation or LLC and sell from it? Limiting libility is the reason corporations were invented. While this should protect you from creditors, better check with a lawyer about lawsuits. I believe it is easy, cheap, and quick to incorporate in Delaware. Many companies have filed their paperwork there for convenience (including the original General Motors Inc. back in the day).

GSP

 

[passion4audio]

Yes, a corp or LLC should protect you.

I'm not a lawyer (or even close) but what about having your LLC require that all purchasers sign a waiver which informs them that these products are for professional, off-road use only - and not intended for public roads, highways, etc., and that the manufacturer is not to be held liable in any way for misuse of this product?

 

[redi]

Thanks for your efforts on this Bill. Please advise on how the 250s work for you.

(sure are a lot of expert opinions and traffic on this forum from folks that don't have a MS tho. Odd.).

 

[lolachampcar]

I've made a bit of headway in characterizing MS' dampers and air/coil springs. Here is what I have so far.

The front springs are 250 lbs/in, have a free length of 14 3/8" and a 2 1/8" preload when assembled on a damper.
The rear springs are 225 lbs/in, have a free length of 17 5/8" and a 7/8" preload when assembled on a damper.
Note that the spring rates, lengths and preload values were determined using a tape measure (and my car scales on a press but the scales are accurate to a pound) and thus are not exact. They are close enough for the work I am doing.

Below are shock dyno plots comparing both front and rear coil to air dampers. It is interesting to see that the air spring dampers carry a lot more valving (resistance) in both compression and rebound. I hope to add plots of P and P+ air spring dampers when I next work on my car. It will be interesting to see how much of a change was made. As it looks now, simply moving to coil springs on a standard air car would provided a significant increase in both bump and rebound over a standard coil car. Put differently, Tesla seems to be supporting the coil cars on the spring rate and the air cars more on damper valving. This makes a lot of sense in that air cars do not need spring rate and preload in order to maintain ride height with higher vehicle loads (passengers and luggage). This also explains the difference in feel between air and coil cars.

Please forgive the lack of accuracy (return to zero and the like) as I was using a race shock dyno with a 1" measurement stroke and was not able to properly remove all movement in the mounting system (rubber bushings and bolt slop on the dampers).

View attachment Front Damper Comparison 1.pdf
View attachment Front Damper Comparison 2.pdf
View attachment Rear Damper Comparison 1.pdf
View attachment Rear Damper Comparison 2.pdf

 

[Dreamin]

Really interesting results.

It is interesting to see that the air spring dampers carry a lot more valving (resistance) in both compression and rebound. ... As it looks now, simply moving to coil springs on a standard air car would provided a significant increase in both bump and rebound over a standard coil car.

I completely follow this. Looks like the air shocks are stiffer in both compression and rebound vs the coil shocks. Air shocks with stiffer/lower coil springs would be the ultimate combo.

Put differently, Tesla seems to be supporting the coil cars on the spring rate and the air cars more on damper valving. This makes a lot of sense in that air cars do not need spring rate and preload in order to maintain ride height with higher vehicle loads (passengers and luggage). This also explains the difference in feel between air and coil cars.

I dont follow. Why not match the shock valving of both setups and also match the (effective) spring rates of the air springs and coil springs. I believe removing air decreases the volume of the spring 'bladder', lowers the car, and as a result, makes the 'spring' stiffer. So are the air shocks optimized for the lowest ride height setting?

 

[lolachampcar]

Dreamin,

Let me start by saying I've not worked on street car suspensions at all so this is uncharted territory for me.

I've not dissected the air spring to see how the internal geometry changes with stroke but my first reaction to an air spring is that, air temperature being constant, pv=nrt would dictate the characteristics of the spring. Adding or removing air would change the current neutral point (ride height) but not the rate.

WRT air spring rates, my best guess is that it is a function of the unit's geometry. I try to picture two extreme scenarios where the unit is a very large diameter and very short. A small compression would make for a huge increase in internal pressure and that pressure is actuating against a very large piston. Conversely, a very small diameter with an extremely long length yields little resistance to compression. A small movement of the piston would make but a minor increase in pressure and that increase is acting on a small piston area - thus small change in force. I liken this to sealing off the end of a very small insulin syringe and one of those big fat syringes. You can easily bounce the insulin syringe's plunger up and down but it is way more difficult to do it with the fat one.

The differences in dampers tells me that the air and coil configurations are two very different ways of supporting the car. Once you remove the need for the spring to support ride height at maximum loading conditions, you are free to pick a much smaller spring rate that is optimized for comfort and handling. I think the air is allowing the engineers to separate preload from spring rate when they design.

Not having that high a rate is what gives the air the ability to absorb all the little road imperfections. I have not used the practice myself but I know the Indy teams will routinely decrease spring rate and dramatically increase damping for some road courses where they are running high ride heights. Although not the same, Tesla may be doing something based on a similar theory. Again, I'm no street suspension guy.

I've been putting some thought into what coil springs might best be pared with air dampers. I'm thinking the best place to start would be to establish lower perch grooves on air dampers such that stock spring dampers would produce Standard air ride heights. The idea is that we already have a significant increase in damping with the air units and the normal Tesla coil spring implementation is reasonably stiff already. Of course, you could also add a few more lower perch C clip grooves for lower ride heights while you had the damper on the lathe. This would allow you to play with ideal ride heights with the new configuration.

Should 2.5" coil overs with adjustable ride heights be the ultimate goal, the Koni adjustable sleeves go right on the air dampers and 2.5" springs will land nicely on the stock Tesla upper mounts. Some long Ultra Long Travel Hypercoil springs would finish off the package nicely. I may end up here but I'm going to start with stock springs for now as I think that will be as firm as I want to go. There is also the possibility of using P+ dampers with coils as well if more shock valving is needed.

Lastly, I ordered in some new lower a-arms with the idea of putting P+ lower arms on my wife's S85. When I got them in I checked the part number and it is the old part number from my Feb. P85. Apparently Tesla, like the early sub-frame bushings, is now shipping all cars with a single specification lower a-arm bushing (which is the stiffer P+ unit). This explains why I love my wife's car so much. I thought it was just the coil spring set up but she also has the stiffer lower a-arm bushings that reduces that "wind up" feeling I get in MS when accelerating hard (breaking and re-gaining traction).

I love this company...... They just keep pounding away in the background making the car better and better. I can understand not advertising their efforts as (1) things like a-arm bushings would just make people's eyes glaze over and (2) they would have to deal with people saying "you changed it for the new cars so you have to give it to me for free". As far as I am concerned, they can keep improving and keep me guessing

 

[Gizmotoy]

Lastly, I ordered in some new lower a-arms with the idea of putting P+ lower arms on my wife's S85. When I got them in I checked the part number and it is the old part number from my Feb. P85. Apparently Tesla, like the early sub-frame bushings, is now shipping all cars with a single specification lower a-arm bushing (which is the stiffer P+ unit). This explains why I love my wife's car so much. I thought it was just the coil spring set up but she also has the stiffer lower a-arm bushings that reduces that "wind up" feeling I get in MS when accelerating hard (breaking and re-gaining traction).

Really? That's pretty great. It would also somewhat explain the wildly varying opinions on handling if they started subbing in P+ parts at some point. So to confirm, the lower A-arm bushings on your P85+ and your wife's S85 are actually the same? Could they be using the same part number for the control arm, but inserting different bushings without altering the assembly's part number?

Maybe it's just me misunderstanding, but it seems like having having that same part number from your Feb P85 would indicate they sent you the wrong part, rather than implying that they're all the same now. Otherwise your P85 would have had the bushings as well, correct? And you didn't like the way that handled, hence the upgrade to the P85+.

 

[Jason S]

I think what he's saying is that *now* the part is the same. Before (in Feb) the part was different.

 

[Gizmotoy]

I think what he's saying is that *now* the part is the same. Before (in Feb) the part was different.

"When I got them [the brand new P+ control arms] in I checked the part number and it is the old part number from my Feb. P85"
Maybe that's what he meant, but what was written makes it sound like the new part is the same as the Feb P85 part, hence the confusion.