Question about Thrust Arm

Shisou · 10-13-2020, 11:27 AM

So I took my F30 (328xi) in to Brooklyn BMW for scheduled maintenance...I purchased this vehicle with a CPO a few years back and still had the maintenance warranty on it so a vehicle check/diag is included in the visit.

However, upon retrieval, I was given an inspection report that pointed out a few things:

1. I need wheel alignment.
2. The thrust arms are leaking.

As far as the wheel alignment, I knew this was probably necessary, as I took an extremely long drive upstate and through New England a few weeks ago and needless to say I hit a few bumps and there is a noticeable drift.

However, according to the mechanic the thrust arms are "leaking". I wasn't aware these things could leak but based on the pic they sent me, it does in fact look like it's leaking some sort of fluid.

Dealership says it's $1100 for this (yikes) so immediately I recalled reading posts (while lurking of course) that suggested ordering the parts myself and then taking it to trusted mechanic would be far better for my pockets.

I've been looking on tunersport and FCP for the parts but I'm kind of confused on what to order exactly, wondering if anyone can help:

https://www.fcpeuro.com/products/bmw...-kit-lemforder

OR

https://www.turnermotorsport.com/p-5...-control-arms/

Or...am I just completely wrong all around?

And yes I'm a noob...but I figured this is a decent place to get a second opinion. Any advice would be appreciated.

pauli18c · 10-13-2020, 12:02 PM

I would definitely upgrade them if they need replacing. Lots of info on how much of a difference they make.

Millway is another great option (probably the route I'll be going eventually)

https://www.millway.se/front-control...0-x-drive.html

ktw · 10-13-2020, 01:34 PM

The OE thrust arm bushing is a hydraulic bushing that contains fluid to help dampen noise/vibrations. It is quite common that they fail and fluid begins to leak out after ~50k miles.

Lemforder is an OE manufacturer of the arms, so the first set you linked would be an OE replacement. Note that xdrive thrust arms differ from RWD--make sure you get the right ones. The lower control arms do not have the same type of hydraulic bushing, so you are probably fine replacing only the thrust arms unless inspection shows wear specifically on the LCA bushing or ball joint.

As pauli18c noted, upgrading the thrust arms to a non-hydraulic bushing can improve steering response at the expense of some NVH. Monoball bushings seem to be the best rated option around here. Millway and VAC Motorsport both make monoball options.

Shisou · 10-13-2020, 02:49 PM

Quote:

Originally Posted by ktw

The OE thrust arm bushing is a hydraulic bushing that contains fluid to help dampen noise/vibrations. It is quite common that they fail and fluid begins to leak out after ~50k miles.

Lemforder is an OE manufacturer of the arms, so the first set you linked would be an OE replacement. Note that xdrive thrust arms differ from RWD--make sure you get the right ones. The lower control arms do not have the same type of hydraulic bushing, so you are probably fine replacing only the thrust arms unless inspection shows wear specifically on the LCA bushing or ball joint.

As pauli18c noted, upgrading the thrust arms to a non-hydraulic bushing can improve steering response at the expense of some NVH. Monoball bushings seem to be the best rated option around here. Millway and VAC Motorsport both make monoball options.

Interesting

So the entire control arm doesn't necessarily need to be replaced, just the "bushing"?

FYI, here's what the BMW tech showed me

pauli18c · 10-13-2020, 03:07 PM

Quote:

Originally Posted by Shisou

Quote:

Originally Posted by ktw

The OE thrust arm bushing is a hydraulic bushing that contains fluid to help dampen noise/vibrations. It is quite common that they fail and fluid begins to leak out after ~50k miles.

Lemforder is an OE manufacturer of the arms, so the first set you linked would be an OE replacement. Note that xdrive thrust arms differ from RWD--make sure you get the right ones. The lower control arms do not have the same type of hydraulic bushing, so you are probably fine replacing only the thrust arms unless inspection shows wear specifically on the LCA bushing or ball joint.

As pauli18c noted, upgrading the thrust arms to a non-hydraulic bushing can improve steering response at the expense of some NVH. Monoball bushings seem to be the best rated option around here. Millway and VAC Motorsport both make monoball options.

Interesting

So the entire control arm doesn't necessarily need to be replaced, just the "bushing"?

FYI, here's what the BMW tech showed me

correct. the bushings can be pressed out and back in with a shop press

ktw · 10-13-2020, 04:26 PM

Yep, only the bushing needs to be replaced. Depending on the shop rate to press out/in bushings, it may be the same price or cheaper to just get new Lemforder arms w/ bushing pre-installed though (and as a bonus you get a new ball joint on the wheel carrier end).

therealm3 · 10-13-2020, 05:12 PM

I will add that these are a pretty easy DIY too if you are inclined to do so. Or have a friend who is and you buy some tacos and beer.

I swapped on Turner mono ball thrust arms my self and am happy with the improved steering response. They did add a fair amount new vibrations and rattles to my car when on rough pavement though. I live with it or turn the music up. The steering improvement was worth it to me. If that isn't something you care about, then just buy some OE replacements and get and independent shop to put them on for you.

FaRKle! · 10-13-2020, 06:02 PM

Quote:

Originally Posted by therealm3

I will add that these are a pretty easy DIY too if you are inclined to do so. Or have a friend who is and you buy some tacos and beer.

Yup!

smrtypants44 · 10-14-2020, 12:03 AM

I did the turner motorsports monoball arms and it made a big difference in steering feel.

Couple notes about my experience:
Turner sent the wrong size bolts for my car ('17 F32)- my OEM bolts went through harmonic weights that added to the length of them

Also my passenger side was a PITA to do- the battery cable goes right across the bolt head for the bushing.

10-13-2020, 11:27 AM	#1
Shisou Registered 1 Rep 3 Posts Drives: BMW F30 (328xi) Join Date: Oct 2020 Location: Brooklyn, NY iTrader: (0)	Question about Thrust Arm So I took my F30 (328xi) in to Brooklyn BMW for scheduled maintenance...I purchased this vehicle with a CPO a few years back and still had the maintenance warranty on it so a vehicle check/diag is included in the visit. However, upon retrieval, I was given an inspection report that pointed out a few things: 1. I need wheel alignment. 2. The thrust arms are leaking. As far as the wheel alignment, I knew this was probably necessary, as I took an extremely long drive upstate and through New England a few weeks ago and needless to say I hit a few bumps and there is a noticeable drift. However, according to the mechanic the thrust arms are "leaking". I wasn't aware these things could leak but based on the pic they sent me, it does in fact look like it's leaking some sort of fluid. Dealership says it's $1100 for this (yikes) so immediately I recalled reading posts (while lurking of course) that suggested ordering the parts myself and then taking it to trusted mechanic would be far better for my pockets. I've been looking on tunersport and FCP for the parts but I'm kind of confused on what to order exactly, wondering if anyone can help: https://www.fcpeuro.com/products/bmw...-kit-lemforder OR https://www.turnermotorsport.com/p-5...-control-arms/ Or...am I just completely wrong all around? And yes I'm a noob...but I figured this is a decent place to get a second opinion. Any advice would be appreciated.
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10-13-2020, 12:02 PM	#2
pauli18c Lieutenant 211 Rep 519 Posts Drives: 2017 340i RWD M Sport Join Date: Jun 2019 Location: Chicago iTrader: (4)	I would definitely upgrade them if they need replacing. Lots of info on how much of a difference they make. Millway is another great option (probably the route I'll be going eventually) https://www.millway.se/front-control...0-x-drive.html __________________ 2017 340i M Sport Alpine White / Coral Dorch Stg2, CTS catless, xHP, Custom E50 Tuned by Shoup
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10-13-2020, 01:34 PM	#3
ktw Private 55 Rep 77 Posts Drives: '14 f31 328i xDrive Join Date: May 2019 Location: North Bend, WA iTrader: (1)	The OE thrust arm bushing is a hydraulic bushing that contains fluid to help dampen noise/vibrations. It is quite common that they fail and fluid begins to leak out after ~50k miles. Lemforder is an OE manufacturer of the arms, so the first set you linked would be an OE replacement. Note that xdrive thrust arms differ from RWD--make sure you get the right ones. The lower control arms do not have the same type of hydraulic bushing, so you are probably fine replacing only the thrust arms unless inspection shows wear specifically on the LCA bushing or ball joint. As pauli18c noted, upgrading the thrust arms to a non-hydraulic bushing can improve steering response at the expense of some NVH. Monoball bushings seem to be the best rated option around here. Millway and VAC Motorsport both make monoball options.
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10-13-2020, 04:26 PM	#6
ktw Private 55 Rep 77 Posts Drives: '14 f31 328i xDrive Join Date: May 2019 Location: North Bend, WA iTrader: (1)	Yep, only the bushing needs to be replaced. Depending on the shop rate to press out/in bushings, it may be the same price or cheaper to just get new Lemforder arms w/ bushing pre-installed though (and as a bonus you get a new ball joint on the wheel carrier end). __________________ F31 328i xDrive, EBII
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10-13-2020, 05:12 PM	#7
therealm3 Lieutenant Colonel 630 Rep 1,649 Posts Drives: F30 340 MSport Join Date: Aug 2006 Location: CA, USA iTrader: (7)	I will add that these are a pretty easy DIY too if you are inclined to do so. Or have a friend who is and you buy some tacos and beer. I swapped on Turner mono ball thrust arms my self and am happy with the improved steering response. They did add a fair amount new vibrations and rattles to my car when on rough pavement though. I live with it or turn the music up. The steering improvement was worth it to me. If that isn't something you care about, then just buy some OE replacements and get and independent shop to put them on for you.
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10-14-2020, 12:03 AM	#9
smrtypants44 Captain 518 Rep 895 Posts Drives: 2017 440i Join Date: Jul 2015 Location: Tulsa, OK iTrader: (2)	I did the turner motorsports monoball arms and it made a big difference in steering feel. Couple notes about my experience: Turner sent the wrong size bolts for my car ('17 F32)- my OEM bolts went through harmonic weights that added to the length of them Also my passenger side was a PITA to do- the battery cable goes right across the bolt head for the bushing. __________________
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