hans
P631
That's the reason they told me they couldn't upgrade just the LCA on my early model car (Jan 2013 delivery)
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[lolachampcar] Performance Upgrade Efforts
- Thread starter lolachampcar
- Start date
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- Driving Dynamics Model S
HyperMiler
Member
Bespoke bushings
@Lola champ:
Would a beefier custom-made polyurethane bushing be an option, sir?:redface:
Or would that be trouble with the previous subframe?
The ICE tuners swap these all the time, pu, pe, aluminum, brass, you name it ?
@Lola champ:
Would a beefier custom-made polyurethane bushing be an option, sir?:redface:
Or would that be trouble with the previous subframe?
The ICE tuners swap these all the time, pu, pe, aluminum, brass, you name it ?
The problem I have is that there is some angular misalignment associated with the bushings in addition to the rotational element. I feared (1) I would not be able to get the bolts back in the arms to re-assemble and (2) if I did, that I might create some huge stress risers when the suspension moved under load. I did have some poly bushings machined up that filled the open space in the existing soft bushings in an attempt to remove compliance. I did this at almost exactly the same time that Tesla came out with the P+ arms which solved the problem and negated the need to test the spacers.
On a side note, I actually made some upper links with high angle misalignment ball bearing joints of the type used on aircraft control surfaces and actuators. This is where I learned that upper link bushing stiffness did absolutely nothing for feel in the rear of the car. I went from gen 1 soft bushing arms to absolute zero play ball style equipped arms and I could not tell any difference. The lower a-arms, now that is a different matter. There is a huge difference between new and old arms but you can not get ball type bearings in the existing lower a-arm bushing holes.
On a side note, I actually made some upper links with high angle misalignment ball bearing joints of the type used on aircraft control surfaces and actuators. This is where I learned that upper link bushing stiffness did absolutely nothing for feel in the rear of the car. I went from gen 1 soft bushing arms to absolute zero play ball style equipped arms and I could not tell any difference. The lower a-arms, now that is a different matter. There is a huge difference between new and old arms but you can not get ball type bearings in the existing lower a-arm bushing holes.
Here is what FlasherZ had swapped out at the St Louis SC to bring his early VIN up to current suspension standards. (Don't ask for an "upgrade"; those requests were denied because ownership thought those folks were trying to do a partial P+ upgrade on the cheap.)
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HyperMiler
Member
As discussed, the cambered wheel is running a permanent turn because of its conical shape, i.e. has permanent lateral slip when going straight. 1.5 at the rear seems a good compromise, and rear camber should be higher than front camber in street applications. Can someone mathematically gifted calculate the ideal turn radius with no slip at 2 deg of camber, please?
HyperMiler
Member
So my back of an envelope calculation arrives at a natural rolling radius of that rolling rubber cone of 7187 mm.
Meaning that a tire at 2 degrees of camber is equivalent to the outer slice of a cone that is getting narrower by 12 mm for every 245 mm of width, i.e. is equivalent to a rubber cone of roughly 22 feet in length?
i.e. a 245/35 21 tire at a 2 degree camber will role a circle of roughly 44 feet in diameter if left to its own devices?
At which point slip is minimal across the entire surface patch?
And which explains while the camber thrust of forcing that cone to roll straight is quite significant.
245 *(312/12)
Meaning that a tire at 2 degrees of camber is equivalent to the outer slice of a cone that is getting narrower by 12 mm for every 245 mm of width, i.e. is equivalent to a rubber cone of roughly 22 feet in length?
i.e. a 245/35 21 tire at a 2 degree camber will role a circle of roughly 44 feet in diameter if left to its own devices?
At which point slip is minimal across the entire surface patch?
And which explains while the camber thrust of forcing that cone to roll straight is quite significant.
245 *(312/12)
Hyper,
Wouldn't the radii differential between the larger inner tire contact (shorter (relative to outer) radius to asphalt requiring higher revs/mile) patch vs. the outer smaller contact (longer (relative to inner) radius to asphalt requiring fewer revs/mile) be in constant conflict/scrubbing further reducing efficiency (increased watts/mi) along with decreasing tire life with a high negative cambered vehicle?
Wouldn't the radii differential between the larger inner tire contact (shorter (relative to outer) radius to asphalt requiring higher revs/mile) patch vs. the outer smaller contact (longer (relative to inner) radius to asphalt requiring fewer revs/mile) be in constant conflict/scrubbing further reducing efficiency (increased watts/mi) along with decreasing tire life with a high negative cambered vehicle?
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HyperMiler
Member
Yessssir, the higher the camber thrust (leading to scrubbing because of negative camber when driving straight = wheel drag) the lower the efficiency. Measurably so as I recall Lolachampcar telling from his racing experience.
Because the outer radius of the tire (from hub to ground) is longer it has the longer leverage, which is why the inner (shorter) radius is the segment of the rubber that gets scrubbed off.
This is somehow counterintuitive, because it happens even though the pressure on the inner radius is higher and the car leans on the outer radius more in turns. And it explains why even usually well behaved citizens who don't floor it at every redlight and do not go around turns on two wheels see it happening on their cars.
An additional reason adding to this could be the squatting of the rear on heavy linear acceleration (known to occur in the Model S at times:wink
which further increases negative camber and adds linear slippage forces. And linear grip is indeed reduced in higher negative camber vehicles.
This said, some negative rear camber (-1.3 to - 1.8) is good for fast turns and road safety. If the rear camber is less negative than the front, the car will eventually spin (oversteer) in turns entered at higher or excessive speed or when braking becomes necessary, and which is a very dangerous uncontrolled condition.
Because the outer radius of the tire (from hub to ground) is longer it has the longer leverage, which is why the inner (shorter) radius is the segment of the rubber that gets scrubbed off.
This is somehow counterintuitive, because it happens even though the pressure on the inner radius is higher and the car leans on the outer radius more in turns. And it explains why even usually well behaved citizens who don't floor it at every redlight and do not go around turns on two wheels see it happening on their cars.
An additional reason adding to this could be the squatting of the rear on heavy linear acceleration (known to occur in the Model S at times:wink
which further increases negative camber and adds linear slippage forces. And linear grip is indeed reduced in higher negative camber vehicles.This said, some negative rear camber (-1.3 to - 1.8) is good for fast turns and road safety. If the rear camber is less negative than the front, the car will eventually spin (oversteer) in turns entered at higher or excessive speed or when braking becomes necessary, and which is a very dangerous uncontrolled condition.
I suspected my new P85D's always low settings were not as low as Low used to be. The P85D measures (with four rims in tires stuffed in the back)-
2015 P85D with 19" rims/tires on "Always Low"
29 0/16...........29 2/16
28 14/16.........28 14/16
The following is from a post I did way back when comparing the P+ to my wife's S85 on coil springs. It looks like the new Low is the old Standard.
Here are my ride heights. My P+ has lowering links so I should be a tad below stock for both Standard and Low. I would appreciate it if others could add their ride heights so we can see if Tesla is reasonably consistent. I measured by dropping a tape measure to the ground, through the center of the wheel center cap and then used a small stick under the wheel arch to "bring out" the bottom of the wheel arch at its highest point.
.
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
.
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
2015 P85D with 19" rims/tires on "Always Low"
29 0/16...........29 2/16
28 14/16.........28 14/16
The following is from a post I did way back when comparing the P+ to my wife's S85 on coil springs. It looks like the new Low is the old Standard.
Here are my ride heights. My P+ has lowering links so I should be a tad below stock for both Standard and Low. I would appreciate it if others could add their ride heights so we can see if Tesla is reasonably consistent. I measured by dropping a tape measure to the ground, through the center of the wheel center cap and then used a small stick under the wheel arch to "bring out" the bottom of the wheel arch at its highest point.
.
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
.
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
arijaycomet
Member
I know there had been some discussions about Tesla adjusting heights a year ago from people worrying about battery damage/fire if hitting debris on the road. Somehow related to that?! Odd.... seems strange they would raise the AWD car, unless they did so to compensate for change in weight from front motor?
OT- car goes in next week for adding c-clip grooves to my S85 OE shocks
OT- car goes in next week for adding c-clip grooves to my S85 OE shocks
I think Tesla just quietly made the change to reduce the risk of battery damage...... The P85D was just my first chance to update my measurements.
Gizmotoy
Active Member
Right. There were a bunch of quick one-off measurements that indicated they raised the heights, but I'm not sure anyone else is quite as thorough as lola, here. :wink:
Hmmm... not seeing much of a difference on my P85+. Rear height measured in April 2014:
28 11/16... 29 03/16 STD
28 03/16... 28 10/16 LOW
So back in April I raised the rear to get the camber under control:
29 08/16... 29 11/16 STD
Just measured it now on 6.0 (2.0.81):
29 13/16... 29 13/16 STD
A slight difference, but not much.
28 11/16... 29 03/16 STD
28 03/16... 28 10/16 LOW
So back in April I raised the rear to get the camber under control:
29 08/16... 29 11/16 STD
Just measured it now on 6.0 (2.0.81):
29 13/16... 29 13/16 STD
A slight difference, but not much.
jerjozwik
Active Member
all this talk about bushings has me thinking. i... sort of recently took my NC miata to energy suspension in orange county to let them develop a complete poly-bushing kit for the NC miata platform. took about a week and they were very excited to get the car. if anyone in the los angeles area is interested in handing off their car for about a week or a week and a half i can get in contact with the folks at energy and see if they are interested in a model S bushing kit.
The issue with doing poly bushings is that they are not that good at handling angular misalignment. By design, the upright can tilt just a bit so the rubber bushings are needed. I just some high angle misalignment ball bearings which worked very well. I could not feel any difference in handling so I removed them and went back to the stock (later firmer bushings).
jerjozwik
Active Member
fair enough, i have to say i did not read all 26 pages, just saw the one post about poly and triggered the S development idea.
basically i used your thread as a PSA to anyone interested in southern california. :biggrin:
JPP
Active Member
Rims are on and the car is lowered. The longer upper rear links will go on tomorrow and then off to the alignment rack. All of the changes have prevented me from looking at the alignment as delivered new.
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