Upper Rear Link Build (Reduces rear camber to improve tire wear)

I have been contacted by several people looking for information on upper rear links to reduce MS camber. I can have my local shop do another run of links which will come out less than $600 per set machined and anodized (but without bushings). My only concern is making sure people that purchase these links take full and complete responsibility for the consequences of installing these links.

Please let me know if you are interested and include that you are comfortable with the following-

You take full responsibility for the design and installation of the links. I'll ship you nice aluminum coffee table conversation pieces and then you can decide if you want to put them on your car.
If you choose to install them on your car, you will need to press out the bushings from your existing links and into the new links.
You have looked at FMVSS 126 (especially the over steer emergency maneuver test) and know that, if you choose to modify your vehicle, you will likely reduce over steer margin in Model S.

Thanks
Bill

if there is a chance of suit, there is no chance of links

I'm feeling a bit like Atlas Shrugged here.

The last talk I had with my machine shop centered around five sets. If five cars need them they can be done. There is no time frame to speak of.

Those are nice rear camber numbers and very close to my car AFTER I put the links on my P85+. It will be interesting to see if other's S60s show similar numbers. It would also be nice to see if the coil suspension cars have a higher "Standard" ride height allowing camber gain to provide the lower negative camber readings seen above. My wife's coil spring suspension S85 arrives 9/6. I have a set of arms ready for it and will, of course, have it up on a rack before I do the arms. If I see the same 1.1-1.3 type values, I will not be installing the arms.

I believe Tesla was shooting for the best possible range when they choose the non-staggered original P85 configuration. They had to go bigger on the rears when they removed bushing compliance so, yes, staggered widths is how more standard ICE mfgs and Tesla with the + package handle the need for more oversteer margin. Wider rears equal more lateral grip.

It is my personal opinion that the oversteer issue is important if you are trying to pass FMVSS 126 but is more a tempest in a tea pot for the real world. I do wish we could get a couple of cars on a skid pad and form our own opinions about loss of the rear for the standard, plus and reduced camber cars.

Also, keep in mind that I put the upper links on my P85+ so I could get to the same numbers on the stock S60 shown above. If Tesla allows that S60 to ship with those camber values they are obviously (1) within manufacturer's tolerances (as also indicated by the tolerance section of the print out) and (2) safe. Tesla seems to think -1.1 degrees of rear camber is ok and that is just what I have on my car now.

I've spent some time looking at Tesla's published alignment specifications and believe I have a better understanding of the trade offs they made to support air suspension. You can find the specs (Telsa SB-13-34-003) here - http://craigfroehle.com/posted/ModelS_Alignment.pdf


Remove the camber and the tire sits flatter. Sure, bad toe settings will still cause wear even with less camber but it will not be directed only on the inside shoulder of the tire. We also know Tesla put the camber in the rear for a reason.


From the above Service Bulletin we can see that the standard suspension rides 14mm higher than the air suspension in the rear. The coil suspension's acceptable camber range in the rear is -1.2 to -1.9 where the air suspension is -1.4 to -2.1. Both cars use the exact same suspension components and thus the difference in specification between the two is purely a function of camber gain (see below explanation).


What I take from this is that -1.2 degrees of rear camber is perfectly within specification and thus perfectly safe for MS. Lowering the car should improve safety thus an air suspended car lowered at highway speeds with -1.2 degrees of camber should be safe.


I know reducing my rear camber from -2.2 in standard ride height to -1.2 by changing the upper links was safe. However, my knowing it does not make it so. After reviewing Tesla's specifications, I believe they agree with my assessment.




Camber Gain
This term is used to describe changes in camber as a wheel moves up and down. Modern suspensions are designed such that the pivot arm for the top of the upright (assembly that the wheel bolts to) is shorter than the lower arm. As the upright moves up with respect to the car (car lowering) the upper arm with its shorter radius pulls the top of the upright in more than the longer lower arm. The net result is that the top of the tire tilts inward as the tire travels up in the wheel well. This inward movement is an increase in negative camber thus the term camber gain.

I built my own and then the OpenEVSE folks did some that they were selling to others. There have been some changes in bushings so you want to make sure you get arms that work with the particular bushings you have. The OpenEVSE people should know what you need.

Thanks for pitching in Chris... Sorry there was not enough interest to keep building them.