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Negative Camber in the Rear and Expensive Tires
- Thread starter lolachampcar
- Start date
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- Driving Dynamics Model S
Insure your tires and wheels against road hazard damage sounds like it's just a road hazard plan--and an expensive one at that (at least for the 19" tires and wheels). Also it's unlikely you will be able to choose the replacement tires. I'm not sure I want to be stuck forever on the OE tires that came on my car--they certainly aren't the tires I would have chosen. The 21" plan might be worth it if you break a lot of 21" wheels--the question will be what is considered abuse (and not covered).
justaddsun
Member
Fwiw, I've used the Hankook Ventus V12s on my AMG and did not notice any decrement in performance vs the stock Pirelli P Zeros with similar or slightly improved tread life (regardless of what the wear ratings were). They cost way less than the Contis and WAY less than the Michelins, so running costs should go down.
The other option for tires would be to go with an ultra high performance all-season tire -- which does compromise performance but tread life goes way up. I suspect most MS drivers would not care about the performance loss in day-to-day driving. My $.02.
Sent from my Nexus 7 using Tapatalk 2
The other option for tires would be to go with an ultra high performance all-season tire -- which does compromise performance but tread life goes way up. I suspect most MS drivers would not care about the performance loss in day-to-day driving. My $.02.
Sent from my Nexus 7 using Tapatalk 2
dockt
Wow, I normally go to Nittos to control cost but those Hankooks are CHEAP. P Zeros normally stick so that it quite a recommendation.
Wow, I normally go to Nittos to control cost but those Hankooks are CHEAP. P Zeros normally stick so that it quite a recommendation.
justaddsun
Member
Yes, the 21" Hankooks are 35% less than Contis and a whopping 65% less than Michelins
. What's more they ranked second in a Car & Driver performance tire shootout, where the benchmark was the Mich PS2s : caranddriver.com/comparisons/hankook-ventus-v12-evo-page-10Sent from my Nexus 4 using Tapatalk 2
The calculations are correct on the upper suspension arm. I was able to go from -1.9 to -0.9 degrees of negative camber with a modified link.
I was also able to adjust rear toe back within specifications (and beyond) so there is NO need for new toe arms; only top link arms are needed.
It is time to make a set of proper arms. Tesla uses rubber arm end bushings that have a particularly large inner sleeve made from aluminum. This serves to reduce the amount of rubber making the bushings less compliant and doing a better job of controlling the suspension. Regretfully, Tesla only sells the arms with bushings and not the bushings themselves.
Does anyone know where to get these?
http://www.lolachampcar.com/images/Tesla/Rear%20Suspension/Up%20Rear%20Arm%20bushing.pdf
http://www.lolachampcar.com/images/Tesla/Rear Suspension/Bushing.JPG
I was also able to adjust rear toe back within specifications (and beyond) so there is NO need for new toe arms; only top link arms are needed.
It is time to make a set of proper arms. Tesla uses rubber arm end bushings that have a particularly large inner sleeve made from aluminum. This serves to reduce the amount of rubber making the bushings less compliant and doing a better job of controlling the suspension. Regretfully, Tesla only sells the arms with bushings and not the bushings themselves.
Does anyone know where to get these?
http://www.lolachampcar.com/images/Tesla/Rear%20Suspension/Up%20Rear%20Arm%20bushing.pdf
http://www.lolachampcar.com/images/Tesla/Rear Suspension/Bushing.JPG
Adjustable link made and new arm measurements verified with pics here-
http://www.lolachampcar.com/images/Tesla/Rear%20Suspension/adjustable_length_control_arm_fo.htm
Drawings for V1 arms released to the machne shop.
http://www.lolachampcar.com/images/Tesla/Rear%20Suspension/adjustable_length_control_arm_fo.htm
Drawings for V1 arms released to the machne shop.
V1 arms back from the machine shop and dropped off to be anodized. I'll get them back tomorrow about lunch time and, depending upon the alignment guy's schedule, should have them in tomorrow as well
http://www.lolachampcar.com/images/Tesla/New%20Upper%20Arms/new_upper_rear_model_s_suspensio.htm
http://www.lolachampcar.com/images/Tesla/New%20Upper%20Arms/new_upper_rear_model_s_suspensio.htm
pilotSteve
Active Member
@lolachampchar - what a great project you are doing! At some point would you mind summarizing the trade-offs in handling/wear/drivability that these mods would make to our cars? And is this worth doing for a non-perf model that someone likes to drive in a sporting way around nice twisty roads on weekends?
Also what are you thoughts on how your project relates to the new Tesla performance suspension kit that may or may not be retrofittable?
Thanks!
Also what are you thoughts on how your project relates to the new Tesla performance suspension kit that may or may not be retrofittable?
Thanks!
I would also be deeply grateful for some commentary about the advisability of such a change for people who drive high-performance cars (all 85's IMHO, though I have an MSP) in a "spirited" manner and who expect to eat tires like crazy. I consider myself a competent driver even when traction is at the margins, but I don't have track experience and I'm certainly no pro.
Would you (off the record, of course!) consider that there is any significant loss or reduction of safety for such drivers if this mod is performed? Or, to put the question a different way without saddling you with all the responsibility for the answer: what should I learn and how should I educate myself in order to make this choice wisely and safely for myself?
Lastly, and though it's a separate question: could anyone suggest a place where we could take Teslas to learn more about their handling at the edges of the envelope, how to handle and manage a loss-of-control or emergency reaction, practice breaking the rear end loose by excessive application of power, and so on? I wouldn't just be looking for a track, but also for someone to provide me with some education and training in this field. Partly for safety if things go to pot, but also partly just for fun.
It achieved the desired result. The arms removed about one degree of negative camber and there was sufficient adjustment in the stock toe links to get the rear toe back to zero.
(I'm looking at -0.4 and -1.3 being an average of -0.85 across the rear of the car.... I started with a spread across the rears)
(I'm looking at -0.4 and -1.3 being an average of -0.85 across the rear of the car.... I started with a spread across the rears)
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I've not spent a lot of time with modern road suspension and thus it was interesting to see that they are using rubber bushings on all ends of the suspension arms. The rotating movement at each end of the rear suspension arms is taken up by "flexing" the rubber annulus between the inner and outer sleeves of the bushing. There is not "bearing" function that lets the arm rotate freely. This is an inexpensive way to achieve rotation and provide vibration isolation. Tesla uses larger inner aluminum sleeves which reduces the rubber annulus an increases bushing stiffness over cars like MB and BMW. That being said, the lower control arm bushings are HUGE which makes sense given they carry most of the load. They also introduce flex that would otherwise not be there. I've not checked on this but I would imagine bushings would be one of the major differences between a five series and the M5.
I wanted my first pass to be conservative so I (1) added a little more meat all the way around the parts I made and (2) used the stock bushings. The next step is to machine some urethane bushings. Suppliers are a dime a dozen (http://prothane.com/). These would remove a lot of the flex in the upper arms which would not be that noticeable. I suspect the big gains would come from doing the lower arms and the drop link (that second link forward outboard of the lower control arms). This is where you will sense movement and it will be in the form of an uneasy, nervous or "slimy" feel in the rear when under load. My plan is simply to order these parts from Tesla when they become available. The sway bars could also use some attention. I will likely use Tesla's unless they are stupid expensive. Like bushings, sway bar benders are a dime a dozen and Addco is just down the street from me. Lastly, the dampers could use more bump and rebound. I've looked into having the stock units revalved and most air suspension shops only deal with the air springs (the failure point) and not rebuilding the dampers. The easiest thing to do would, again, be to buy Tesla bits. If not, Bilstein Performance in California might be willing to do them. Tesla should be cheaper here.
Now for the zillion dollar question and this will only be my opinion. I believe BMW, MB, Audi and the like put a lot of negative camber in the rear of a car to save people's butts. The go to survival instinct when you get into a corner too fast is to lift off the throttle. Lifting transfers weight from the rear of the car to the front (assuming rear wheel drive) and induces over steer. You lift because you are scared and the lift becomes a self fulfiling prophesy. Putting more negative camber allows the car to roll weight onto the outer less loaded part of the contact patch when lifting while turning thus giving more margin of safety. Camber is also used to control the contract path on race cars but I really do not think that applies to street cars. I think manufacturers simply use it to add margin at the expense of tires.
I have no problem with street cars and over steer. With exception of a very small number of cars that are more neutral (Carrera GT comes to mind), almost all street cars will push (under steer) when you lean on them. Removing some rear negative camber to make the tires last longer simply removes a little bit of that built in push. I've not wailed on the tail of my MS yet (just drove it home from the alignment shop) but I can not imagine MS is any different. I suspect it will be almost if not equally willing to have the fronts start to plow. In short, it is an absolute no brainer for me and thus my willingness to dive right into having arms made.
Lastly, the single most valuable exercise I have ever found for learning car control is a wet skid pad and someone in the passenger seat that knows CPR. I'm not talking heart attack CPR here but the Correct, Pause, and Recover steps that form the ability to catch the rear end of a car when it gets impatient wants to go first. The amount of input required and length of pause are all related to the mass and polar moment of the car. MS is a beast so I imagine you could have a bit of a conversation during the pause portion Watching Montoya in the Parabolica will give you a good idea of the other end of the spectrum. Anyway, it is super cheap fun. Get a few guys together, rent a skid pad for a morning, spray some water on it then go have fun. I normally leave with sore stomach muscles from laughing so much. Making it a wet skid pad even keeps tire wear down.
The direct answer is, get comfortable with the rear of MS on a wet skid pad and I think you will come to the same conclusion that going from -2 to -1 degree of negative camber is a no brainer. I'll bring my car for reference and I doubt there will be much, if any, real difference.
I wanted my first pass to be conservative so I (1) added a little more meat all the way around the parts I made and (2) used the stock bushings. The next step is to machine some urethane bushings. Suppliers are a dime a dozen (http://prothane.com/). These would remove a lot of the flex in the upper arms which would not be that noticeable. I suspect the big gains would come from doing the lower arms and the drop link (that second link forward outboard of the lower control arms). This is where you will sense movement and it will be in the form of an uneasy, nervous or "slimy" feel in the rear when under load. My plan is simply to order these parts from Tesla when they become available. The sway bars could also use some attention. I will likely use Tesla's unless they are stupid expensive. Like bushings, sway bar benders are a dime a dozen and Addco is just down the street from me. Lastly, the dampers could use more bump and rebound. I've looked into having the stock units revalved and most air suspension shops only deal with the air springs (the failure point) and not rebuilding the dampers. The easiest thing to do would, again, be to buy Tesla bits. If not, Bilstein Performance in California might be willing to do them. Tesla should be cheaper here.
Now for the zillion dollar question and this will only be my opinion. I believe BMW, MB, Audi and the like put a lot of negative camber in the rear of a car to save people's butts. The go to survival instinct when you get into a corner too fast is to lift off the throttle. Lifting transfers weight from the rear of the car to the front (assuming rear wheel drive) and induces over steer. You lift because you are scared and the lift becomes a self fulfiling prophesy. Putting more negative camber allows the car to roll weight onto the outer less loaded part of the contact patch when lifting while turning thus giving more margin of safety. Camber is also used to control the contract path on race cars but I really do not think that applies to street cars. I think manufacturers simply use it to add margin at the expense of tires.
I have no problem with street cars and over steer. With exception of a very small number of cars that are more neutral (Carrera GT comes to mind), almost all street cars will push (under steer) when you lean on them. Removing some rear negative camber to make the tires last longer simply removes a little bit of that built in push. I've not wailed on the tail of my MS yet (just drove it home from the alignment shop) but I can not imagine MS is any different. I suspect it will be almost if not equally willing to have the fronts start to plow. In short, it is an absolute no brainer for me and thus my willingness to dive right into having arms made.
Lastly, the single most valuable exercise I have ever found for learning car control is a wet skid pad and someone in the passenger seat that knows CPR. I'm not talking heart attack CPR here but the Correct, Pause, and Recover steps that form the ability to catch the rear end of a car when it gets impatient wants to go first. The amount of input required and length of pause are all related to the mass and polar moment of the car. MS is a beast so I imagine you could have a bit of a conversation during the pause portion
Watching Montoya in the Parabolica will give you a good idea of the other end of the spectrum. Anyway, it is super cheap fun. Get a few guys together, rent a skid pad for a morning, spray some water on it then go have fun. I normally leave with sore stomach muscles from laughing so much. Making it a wet skid pad even keeps tire wear down.The direct answer is, get comfortable with the rear of MS on a wet skid pad and I think you will come to the same conclusion that going from -2 to -1 degree of negative camber is a no brainer. I'll bring my car for reference and I doubt there will be much, if any, real difference.
I believe it is great that you are providing information on th suspension of the Model S. However, until we have a way to control (turn on/off) the Stability Control, which is always on then this is kind of an academic argument and benefit if added. Of course we can 'pull fuses' to deactivate certain functions of the car, but that is not what was intentended when the car was designed.
From my experience so far, the Wet Skidpad experience would be a bust with the Stab control on.
From my experience so far, the Wet Skidpad experience would be a bust with the Stab control on.
Nickjhowe
Member
Super interesting thread.
lolachampcar - now that you've done all the research, what would it cost someone to do what you've done?
lolachampcar - now that you've done all the research, what would it cost someone to do what you've done?
There are two elements. The first are the water jet cut links with anodizing. The second is coming up with the bushings. I bought a link from Tesla to verify my original math so I used the two bushings that came with that arm along with pressing out two from one of the arms from my car. I asked a few people at Tesla for the name of their bushing vendor and was unable to get anywhere. No real surprise there as most manufacturers are not keen to provide their vendors contact info.
My bill for one offs went something like
$450 for the links
$80 for the bespoke bushing pressing tooling
$220 for the Tesla link that supplied the first two bushings
two hours of my time to swap them out (including press and install time for the bushings) and reset the toe to something that was good enough to get me to an alignment rack
$125 for a 4 wheel alignment
I weighed that against Pilots at $520 each..... part of the no brainer equation for me.
The ideal would be a set of arms that already have bushings such that the alignment shop could swap out the links then do an alignment without having to move the car. This would allow the owner to keep the original arms just in case. The stick in that ointment is getting the $10 bushings by buying $220 suspension arms; seems kind of stupid.
Lastly, Lloyd I think you would be surprised at how the back end can be persuaded to come around even with stability control. If you ask with enough authority, the braking action of the stability control can even be used to make the static to dynamic or stuck to sliding transition. Granted, it is not as easy as an ebrake but I think you could get the job done as stability control does its best work with power on over steer. I could very well be wrong here but it seems like it might be a fun exercise. Anyone played in the snow yet to get the back to hang out without using power? That would be a similar environment.
My bill for one offs went something like
$450 for the links
$80 for the bespoke bushing pressing tooling
$220 for the Tesla link that supplied the first two bushings
two hours of my time to swap them out (including press and install time for the bushings) and reset the toe to something that was good enough to get me to an alignment rack
$125 for a 4 wheel alignment
I weighed that against Pilots at $520 each..... part of the no brainer equation for me.
The ideal would be a set of arms that already have bushings such that the alignment shop could swap out the links then do an alignment without having to move the car. This would allow the owner to keep the original arms just in case. The stick in that ointment is getting the $10 bushings by buying $220 suspension arms; seems kind of stupid.
Lastly, Lloyd I think you would be surprised at how the back end can be persuaded to come around even with stability control. If you ask with enough authority, the braking action of the stability control can even be used to make the static to dynamic or stuck to sliding transition. Granted, it is not as easy as an ebrake but I think you could get the job done as stability control does its best work with power on over steer. I could very well be wrong here but it seems like it might be a fun exercise. Anyone played in the snow yet to get the back to hang out without using power? That would be a similar environment.
Ok, I've got a couple hundred miles on the car since the new arms. Both straight line acceleration and acceleration under lateral loading are as before the links. For me, the matter is closed.
I'm talking to some owners about getting them some links. I most certainly do not want to be in the link making and selling (for profit) business. I'm happy to help if I can but I like being retired
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