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Here's the entire video, and it's all interesting. Skip ahead to the five minute mark to see the component (top suspension link) in question:
Robin
Why, exactly? Because your past experience with plastic says it's not strong? Fiber Reinforced Plastic is both lightweight, strong and flexible (and cheap) and can easily fill the need for an upper control arm.
Daniel in SD
(supervised)
Seems a little bit scary to me too. Half the problems that have scared me away from BMW and other german cars seem to be the result of plastic parts (plastic cooling system, plastic timing chain guides, plastic transfer case gear, etc.). I'm sure it will be fine. haha. On the other hand it won't be exposed to much heat there in the wheel well and it will be super easy to replace if necessary. I don't drive very many miles a year so I probably won't be the first one to break one. Good to hear it's also on the S and X and hasn't caused any problems.
More that my past experience with parts asked to do that job says those parts have always been made of steel. Plastic has its place, no doubt. But I wonder if its place is in a component that sees a lot of weather, wear, vibration, shock and (some, but how much?) stress. The upper control arms on my Spitfire (a 1200-pound car) are forged steel. Of course, they've held up for 40 years.
Not saying its the wrong choice, really. Just an unusual and noteworthy (as in, worthy of note) choice.
As for being on the S and X, I believe the engineer doing the video deep dive said the ones on Model S are made from steel. Don't know about the X.
Robin
mjgillen
Member
C141medic
Active Member
That’s funny you mention that. Years ago I had a 1970 Pontiac Lemans. One day car wouldn’t crank. Eventually discovered that the timing chain teeth were plastic and were chewed up like someone with really bad dental work. Not too hard to replace (cars were a lot easier to work on back then). But, really, plastic parts on a timing chain?
Edit: not chain, gear.
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mjgillen
Member
Same thing on my 1970 Chevy Nova. However, having the plastic gear fail likely saved the pistons from destroying the valves/head or punching a hole through the engine block which is what happened to my 71 Suburban. That engine was toast vs. the Nova which just needed a new gear installed.
Just sayin'... and of course completely off topic from the original OP's subject however that seems to be the norm here...
C141medic
Active Member
My apologies for digressing off topic. As a fellow “old folk” you know how easy it can be for us old folk to sometimes digress. Ok, enough of that and back to plastic
The same components on the BMW 3 Series are steel. They are notorious, though, for their plastic bushings failing.
Robin
Robin
Drivesolo
Member
Those are the lower control arms for a Bimmer (strut suspension). They're subjected to a lot more load and susceptible to damage from debris and their proximity to the ground. The upper control arms (double A-arm suspension) are usually well protected against damage that a lower control arm components and experience much less load than the lower control arms since the shock assembly is mounted to the lower arm. Also due to the mechanical advantage ratio (1st class lever) of the upright it might see just 1/3rd the load.
I'm not thrilled seeing that UCAs are plastic but in other common double a-arm setups they're mainly made of aluminum and have always seemed surprisingly thin to me, but they seem to work.
Daniel in SD
(supervised)
Aren't those the lower arms? I think they see a lot more stress than the upper arms and yes I'm told they should be replaced every two years if you corner hard. Very bad when the front wheel detaches! Another reason why I will never own a BMW. haha
No because he cancelled his reservation and wants everyone to join his party.
I you watch the video. The word major suspension part never made it in. Infact the words were just the opposite.
Click bait.
My mistake. I Clicked the Pic too Quick. Here's the upper left arm.
As for wanting everyone (or anyone) to cancel, nope. I came to my decision my way. You come to your decision yourself.
That keeps everyone happy.
Robin
ℬête Noire
Active Member
That just wasn't the case with my brother's '74 Nova! He drove that thing HARD, as my brother in his youth was inclined to do. Even when the gear shifter fell out, and you had to reach down inside and shift via moving the linkages around directly, it kept going(albeit as more 2-on-the-floor, 2nd & 4th, rather than the full 4, because shifting was such a PITA)....until a deer ran out in front of him when traveling at some unspecified speed and wrapped the entire front end of the car around the engine block.
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I will admit to this, though: I would have been more favorably impressed if Tesla made the windshield from transparent aluminum.
Robin
Robin
Drivesolo
Member
Maybe we're talking about different things. I'm talking about 3-series Bimmers (usually compared to the Model 3), which don't have front upper control arms. They have struts for front suspension. From what I know, that isn't a front suspension component from a 3-series BMW from the E36 - E92, might be for the F-chassis but AFIK they're still using struts.
Possibly! My experience with BMW's began and ended with an R69S.
Here's the description of the part above:
BMW 3-Series 2018, Control Arm Strut by Lemfoerder®. In order to ensure safe vehicle handling, even in the event of extreme roadholding, it is important that the movement of the wheels is transferred quickly and precisely. For this purpose, intelligently designed control arms with joints are used within the wheel suspension. The control arms assume the task of wheel guidance and frequently also transfer spring, damping and stabilizer forces.
