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Tesla Driveline Vibration issues and fixes. “Aim before firing”

Tesla premature tire and half shaft repair fund

If you have ever owned a Tesla model S or X of the first generation 2012-2020 you will experience and expensive fix in your future. At some point you will need front half shafts. (CV Joints). The symptom is the front of the car shaking violently under heavy throttle. Typically the car drives fine at normal loads but with heavy throttle the vibration appears. This is inevitably the front half shafts wearing and wobbling out of round due to the high torque loads. Yes, there is a service bulletin and yes there are new parts, but there are still issues.

Tesla S/X (2012-2020) Front Half Shaft Assemblies that are Vibration Prone

Here is some relatable stock car racing knowledge. Once upon a time N-car changed the rules about ride heights. They used to require cars to have high heights in the garage and during inspection. 8″ high in the rear! This was a problem as cars needed to be low for best performance, but not too low they hit the ground. Many tricks were used to achieve this and it usually required huge libraries of very expensive springs to achieve. Eventually the rule making body changed the rules and allowed cars to go out at any height they wanted. Teams quit making their cars high in the garage as it was an unnecessary complication. Yay, money saved on springs that could be spent in other areas!

The unintended consequence was the cars started randomly vibrating! (oops)

Mini Stock car for reference. (If you need a house then call the person on this one)

We narrowed down the shaking to the driveshafts. Weird. This was crazy. The new lower heights actually made the driveshafts more straight. Things should be better! Logic no longer applied. What could have changed? We didn’t change our parts. We still have the same transmissions, the same driveshafts and the same rear ends. What in the world was going on? Many teams were confused, including the sanctioning body.

The parts didn’t change. The rules changed. With the new rules race cars did not travel vertically like they used to.

Previously the cars had huge height changes every time they would go out on the track. This 8″ of vertical travel would result in an longitudinal inch movement of the yoke in and out of the transmission. This frequent large movement would inevitably lubricate and work the splines of the yoke. This movement would keep the yoke splines properly engaged and wear more evenly.

Without normal slipping the slip yoke was wearing faster and allowing orbiting.

Without height changes, there was no longitudinal change on the yoke splines. This caused the yoke to wear faster in one spot as it always ran in the same spot. 900hp of heavy load is hard on components. In the corners of the track the car would see a torque reversal. As the pieces wore, on this reversal the yoke would get the splines out of whack and orbit a bit. This orbiting was causing mind shaking vibration to the point that shifter handles started to break off the transmission. (This is a very bad thing for a race car driver… not to mention the handles)

Through no fault of their own there was a new “normal” causing many drivers to drop out race after race. There was a behind the scenes race to engineer a solution to the problem.

This was a complicated problem. Many prominent teams spent millions on this issue. It took months for many teams to figure out where the vibration was coming from and curiously what was actually causing it. Luckily we were on it and things were better for us quicker than others.

So… Back to the Tesla. There is a very similar phenomenon occurring on these front half shafts. Once they are worn, they can orbit and you get a case of the shakes.

Let me say this. Almost never is there a problem with the rear shafts. Why is this? What is the big difference between the front and rear of the car? The rear has more power? Shouldn’t it wear first?

Wear is a function of overall angle and torque on the half shafts. Overall angle? Yes the angle has a much bigger effect than the overall power. The front tires steer. The back tires do not. This is the main reason why the fronts are usually the culprit. Yes there is more overall angle on the front caused by the geometry and the front ride height but the big culprit is steering and the jack shaft.

This is why even when lowered those that have lowered to “save their half shafts” continue to have problems with their front shafts shaking. It’s the overall angle and high torque with high steering angles that are causing the most wear. The issue has more to do with the driver than the ride height.

Our advice is to not go crazy when pulling out into traffic or when making hard turns. Simply, “Aim before firing” is good advice. You can save your money for more tires instead of half shafts.

The Tesla half shaft fixes are improvements but are not really fixes. Hang in there. We are working on a better solution.

Tesla does have their newer vehicles encourage lower heights more. It is a trade off to save the half shafts (to some degree) but it does have the effect of radically sacrificing tires… Save your tires with our camber arm kits for 2012-2020 Tesla S/X vehicles or our palladium camber kit for 2021+ Tesla S/X.

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Tesla S&X “CAMBER IS FINE”

They say “camber is fine” at the service center. It may be fine, but why can’t it be better than fine? Why can’t it be awesome? We say there is no reason it can’t be awesome.

Tesla Model X

You get more usable grip, higher efficiency and better tire wear with our camber upgrades! If you have a 2012-2020 S or X you need our MACSBOOST camber arm kit. If you have a 2021+ refresh you need our MACSBOOST Palladium camber kit. Every Tesla S or X vehicle ever manufactured suffers from the same “fine” camber. That makes over 1,000,000 vehicles that are “fine” and could potentially be made awesome.

Tesla Model S

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Tesla S & X Alignment Woes or WOAHS

For those new to the Tesla S and X, you may be on your first set of tires. What comes next is the inconvenient truth. You may not understand until you drive a few more thousand miles. For now, read on.

The rear suspension of these vehicles is largely not adjustable yet is very dynamic. Toe is the only factory adjustment. Camber is not, but camber does change with ride height. That is the camber angles and heights are interrelated. You find yourself being told you need tires and an alignment. Here we go.

Before working on your vehicle, the alignment tech tells the vehicle to change height. The vehicle goes through a dance and ends up somewhere in spec. We can guarantee that this height is never the same twice. It is close.. But inevitably not exactly the same each time. This is not a flaw but the reality that the vehicle has to be able to cope with ride height changes on uneven ground. Most road surfaces are in fact not even and thus it has to have a reasonable bit of height roll and variance that it can call “acceptable.” It should be a bit more repeatable on a flat surface like an alignment rack but there is a large tolerance there. In addition, what occurs on a flat rack will be different when it levels itself on uneven surfaces like your home driveway or work parking lot.

Planes and Automobiles

To define a plane, you only need 3 points. When you introduce the fourth point, you now have 4 separate planes or 4 solutions to the problem… A 4 wheel car is overconstrained. With real world road surfaces almost never being perfectly flat, how does the car handle these situations?

With 4 different possible planes, which one is correct? If you are getting confused, don’t worry so is the car. Things just need to be “close enough” for it to be happy. As a human you will see 4 sensors, one on each corner. How can we simplify 4 sensors into 3 points? Internally the rear sensors are averaged and treats their outputs as one. (generally speaking)

Four sensors can give you four different solutions for ride height. What to do?

This variation in ride height or roll, heave or tilt plays a part in the geometry of the suspension. For the rear, more travel will result in more camber. Specifically if a car is tilted, one side is lower than the other and you end up with differing values on each corner. The stock suspension components are very repeatable and “not adjustable” as you have heard time and time again. Most of the variation comes down to the tolerances on the vehicle height, not actually from differences in the components. These height variations are driving the differences in cambers.

Rear camber imbalance is most often caused by the vehicle not sitting level while being measured.

Countless Tesla owners have been not only to Tesla, but have been to 3rd party alignment shops and are begging service advisors to please help them. They get their car aligned not once, not twice but countless times. The end result is the same. Tire wear is so bad that you can’t believe it is that bad. Yet every time you hear the same “it is within spec.” Camber is “not adjustable.” While technically true, it is not the whole truth.

They may not be able to help you at first. But we can give you good advice. Instead of concentrating on the symptom, attack the cause first. Instead of measuring camber, find the flattest surface you can and measure from the ground to the lifting pads. If heights are different from left to right, you are probably on to the first issue you need addressed. Unfortunately it will require a Tesla service visit to perform, but get an SC appointment and ask them to calibrate the ride height. Tell them what you found and specifically have them level the car better left to right.

tesla model x height specs.  we recommend the macsboost palladium camber kit

This could solve your left/right issue, but you still need to address the “more than optimal” overcamber in the rear for low or “normal” ride heights.

Tesla Plaid set to very low with reduced yet high performance cambers.

Lucky for you, MACSBOOST offers high quality parts that are all you need.

For first generation up to 2021 (AC rear drive motors) you need a camber arm kit.

MACSBOOST Tesla S X Camber arm set

For refresh 2021+ vehicles you need a palladium kit.

MACSBOOST Tesla S X Camber Kit 2021+ Palladium

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Why does the Tesla S and X have too much camber?

Elon is a genius. Shouldn’t these vehicles be perfect from the factory? To answer this you must ask yourself for what situation are they perfect for. Is it everyday driving, or is it for breaking records on high speed tracks?

For the curious, the stock suspension of the Tesla S and X (and refresh 2021+) is designed to have 1.5 degrees (rear camber) in mid ride height. This is the typical setting for cars like an M3 Bmw. This sounds reasonable for a high performance vehicle, correct? The gotcha is camber is something that changes with ride height and Tesla S/X have air suspensions that allow many vertical inches of adjustment. There are 5 settings with mid height being logically in the middle. Mid height sounds normal, but it is not. Low is the new normal. On refresh vehicles it won’t even let you drive mid level above 55mph. In low, camber increases to 2+ degrees. This is quite extraordinary for a “normal” alignment. However if you want to set a record lap time with a bone stock, unmodified vehicle, this is what you do. https://insideevs.com/news/532116/tesla-models-plaid-record-nurburgring/ While an awesome feat, it does not come without tradeoffs in straight line traction and tire wear.

The problem is 1.5 is itself a very aggressive setup. but that’s not where the cars normally drive. This means 2+ degrees is really the nominal everyday camber. This is well into a region of diminishing returns and is devastating to tire wear or even tire reliability. When tires fail, drivers are told they are not running enough tire pressure when they burn up a sidewall. They are told You have to run the maximum tire pressure just to prevent it. Again, higher pressures are bad for grip. Where did that sidewall heat come from anyway? (it came from your batteries, lol). This is far from ideal and your tires are begging for mercy. It’s time to stop the insanity.

So, what is the tesla “spec” for camber? If you want to call it a spec, it is anything between -0.5 and -2.5 degree. In that region the alignment machine will give you a green light. That is just like saying there is no spec. Everything from a Dodge caravan to a race setup Corvette should fit within that metric. Good thing for Tesla there is no stock adjustment, so just about any reading is ok. That’s ok, MACSBOOST is here to help.

The Hunter Tesla S/X rear alignment Specs Shown. Camber is -.5 to -2.5 degrees! Nearly anything goes for camber. Rear toe of 1/16″ out to 7/16″ total toe in all falls within specification of green. Shown toe is typical of independent suspension rear toe alignments.

Car setup is all about tradeoffs. While it would be nice to have one setup to rule them all, a magic best setup for all conditions or every corner does not exist. Every alignment setup is a compromise in some way or another.

There is no one size fits all car setup. It is all about compromise.

It is in our opinion (and those of our expert peers, championship autocrossers, racing team engineers and tire experts) that the stock setup is simply overboard when it comes to rear cambers and daily driving. Yes it is better to have high cambers for very high speed road course tracks… And maybe for best numbers through a high speed slalom course but that’s about it. A setup of this kind sacrifices straight line and even moderate turn traction and is quite awful on tires. They are making major sacrifices for this edge use case and are needlessly filling landfills with tires.

But the PLAID is the quickest production car ever? Shouldn’t it have a setup optimized for drag racing? No, it doesn’t. It can go faster. The major limit of the plaid drive train is grip. It has more power than it can use. Tire types, pressures, alignment all have a huge effect on grip or acceleration. You would think Tesla would have acceleration in mind when working on their alignments. Apparently no, when you have more horsepower than anyone else Tesla can afford to sacrifice grip to be able to brag about other superlatives. https://greengarageblog.org/14-negative-camber-pros-and-cons This also means.. If you add grip, it will go faster!

It does not take much imagination to look at your leaning tires to see the trapezoid shaped contact patch with uneven contact pressure. Obviously this is not ideal for maximum grip. This is not ideal for efficiency either. When rubber flexes it makes heat. Heat added to the tires comes straight from your batteries.

Don’t know what contact patch is? See what goodyear says: https://www.goodyear.com/en-US/learn/tire-basics/tire-contact-patch?

Simply put, while awesome for a fast, twisty race track, stock camber is simply too excessive for anything else.

The MACSBOOST Palladium camber kit is designed to realign your camber to a more real world setting. Camber is reduced by .8 degrees. Straight line rear grip is noticeably improved. Tire life is increased dramatically. Performance is still inline with a typical camber spec of a 3 series BMW in low. As a bonus, if you go to very low, camber increases to over 1.5 degrees comparable to the spec of an M3 or an AMG GLE 63. This sounds like a win-win because it is. You still get M3 level grip on demand and most of the time you are running an optimized street setup with drastically better tire life.

Lastly you don’t want to spend a lot of money, you want high quality and you don’t want to take a lot of time to perform the fix. Good news, George, we have you covered there too. The kit components are precision cut stainless steel and should outlive all the other parts on your Tesla.

Finally, one of the biggest benefits of our kit is the ease of install. Both sides can be installed at home, with a jack on a driveway, in 30 minutes with no re-alignment equipment. Not that this is our recommended way to install, but it is that easy and you can do as good of a job as any pro. With our kit and instructions If your rear toe is good before this kit, it will be in the same place after installation.

Click on the link below to purchase our kit for the 2021+ palladium generation Tesla S/X camber kit.

If you have an older, first gen S or X, we have you covered there too. Check out our MACSBOOST adjustable S X camber arms. (These will require an alignment visit, or realignment of toe with measuring devices, unlike the palladium kit) You can purchase directly at the link below.

Mac McAlpine – President of MACSBOOST.com and Lead Performance Guru
Motorsports Instrumentation/Mech Eng/FSAE Advisor/Electric Drivetrains/Asst Professor at UNC Charlotte
Former R&D Engineer for Michael Waltrip Racing (9 years)
Former Engineer for Pi Research / Cosworth Electronics