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Front control arm question Re: Slotted bolt use Vs Non-slotted
GLK350 4matic 2010:
I installed new front control arms (Febi/Bilstein). It did not come with hardware so I ordered a new bolt kit which comes with a slotted bolt, 2 washers and a nut. I could not find a non-slotted bolt anywhere online. I ended up using the slotted bolt and reuse the old round washers with the new control arm. I know the slotted bolt is to make adjustment to camber/caster but I'm just using it straight through without trying to make any adjustments. Also the new upper control arm (torque strut) has Slotted bolt "Repair Kit" Original arm with oval opening vs new arm with round opening
just a round hole for the bolt vs my old arm that has an oval opening for the bolt. So I guess I'm just asking is that a problem using the slotted bolt and round holed arm? Its all torqued to 120nm so it isn't going anywhere.
It must be an optical illusion, but the new arm looks shorter than the old one.
My "project" 2012 didn't have a slotted hole in the compliance bushing end, either. So I just bolted the new one in and called it a day. I used the original hardware as well (since I wasn't trying to adjust caster). Was there a problem with the old hardware? Those bolts look like they could hold a battleship together, so unless they're horribly rusty or otherwise damaged, I can't imagine replacing them, particularly with a new set of hardware that will likely make it possible to mess up the front end alignment.
I can kind of visualize how the "kit" allows some slight caster adjustment, by rotating the "notch" against the corresponding "notch" in the chassis, with the slot in the bolt riding into the opposite notch. That would - if I'm visualizing correctly - allow for two slightly different caster angles - one slightly higher, one slightly lower. I suppose if you're not going to adjust caster, you just use flat washers instead?
FWIW, I created the video below for a similar thread, just last night. It shows the attachment of the arm to that point, which might be helpful for others to understand how those "notches" in the chassis might work...
2006 Alfa Romeo Brera, 2010 GLK350, 2018 BMW 640i GT, 1997 Subaru SVX, 2012 Moto Guzzi Norge GT8V
The control arms on my 2010 did not have an oval hole. I think they wore that way. Notice how thin the metal is on the ends of the hole. You must have had a lot of noise and movement in that arm.
Last edited by Silver Shadow; Jun 8, 2024 at 05:15 PM.
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
Originally Posted by habbyguy
It must be an optical illusion, but the new arm looks shorter than the old one.
Agreed. I would use a bolt long enough to feed thru BOTH the new and old arm thru-holes, then check they are of even length, to the swivel bolt (ball and socket) end.
Last edited by calder-cay; Jun 8, 2024 at 05:36 PM.
Good idea, I'm waiting on the left side to arrive by USPS so I'll double check but in the meantime I verified the fitment at RM European where I ordered all the parts.
It must be an optical illusion, but the new arm looks shorter than the old one.
My "project" 2012 didn't have a slotted hole in the compliance bushing end, either. So I just bolted the new one in and called it a day. I used the original hardware as well (since I wasn't trying to adjust caster). Was there a problem with the old hardware? Those bolts look like they could hold a battleship together, so unless they're horribly rusty or otherwise damaged, I can't imagine replacing them, particularly with a new set of hardware that will likely make it possible to mess up the front end alignment.
I can kind of visualize how the "kit" allows some slight caster adjustment, by rotating the "notch" against the corresponding "notch" in the chassis, with the slot in the bolt riding into the opposite notch. That would - if I'm visualizing correctly - allow for two slightly different caster angles - one slightly higher, one slightly lower. I suppose if you're not going to adjust caster, you just use flat washers instead?
FWIW, I created the video below for a similar thread, just last night. It shows the attachment of the arm to that point, which might be helpful for others to understand how those "notches" in the chassis might work...
I didn't reuse any of the old hardware as I was concerned about doing that. I don't know if MB directly instructs replacement of hardware but I guess I felt better using new.
Just replaced the same parts on my 4-matic. You RWD guys don't know how easy you have it! It's a whole different ball game with a half shaft and CV joint in the way...
I personally have and do re-use hardware, unless it is not in obvious good condition. Though it probably is a good idea to buy new, im cheap.
They have the regular bolts at the Mercedes dealer $10.50 each if you want. I go to my local MB parts dept frequently since the prices arent bad on the small items and dont have to pay for shipping.
Pretty sure that bolts stretch when tightened to the correct setting (includes the correct torque plus the extra degree setting). I usually get new bolts to avoid a bolt being over stretched.
Pretty sure that bolts stretch when tightened to the correct setting (includes the correct torque plus the extra degree setting). I usually get new bolts to avoid a bolt being over stretched.
The issue is when it gets stretched beyond its elasticity limit. If it isn't then it should (will) return to its original length when loosened. Just because they specify angle torque doesn't mean it's a "torque to yield" application. If it is, they will always specify a maximum length measurement, or always require replacement. The advantage of angle torque is that the measured torque is much lower than the final torque, where the introduced errors from friction are lower, so the preload on the bolt is much more consistent.
Oh, just one more thing... Before you reach the elastic limit, the torque required to tighten the bolt further continues to go higher. Once the elastic limit is reached, the torque required to further tighten the bolt begins to level out or even decrease (then you've gone too far...)
Comes down to what you are comfortable with. I've bought new bolts for a job and not ended using them since the old bolts looked fine. I also torque everything down, so I feel comfortable I'm not over tightening anything down.
Granted I have 1/4", 3/8" and 1/2" Pittsburg torque wrenches from Harbor Freight so I dont think they are 100% accurate. I bought the 1/2" one and it never worked right out of the box and finally recently exchanged it for another one. I keep that one in my trunk for my wheels.
Speaking of wheels, I'm pretty sure they are the original lug bolts and they still hold the wheels on fine.
When I get around to replacing a leaking front cv axle boot I have a new axle bolt i'll use. I know those things are really on there and take alot to remove, so figure a new bolt wont hurt. Suspension hardware in general I replace if theres any rust or corrosion.
I personally have and do re-use hardware, unless it is not in obvious good condition. Though it probably is a good idea to buy new, im cheap.
They have the regular bolts at the Mercedes dealer $10.50 each if you want. I go to my local MB parts dept frequently since the prices arent bad on the small items and dont have to pay for shipping.
Thanks for parts #'s. I called the local MB dealer and they didn't have any of the bolts but they did have the nuts for 16.00 each. I was like dude what?
IMHO, those nuts, bolts and washers could outlast five cars. Serious hardware that I wouldn't be able to hurt without a six foot breaker bar (and room to swing it). I honestly can't imagine ever having a problem re-using the hardware unless it's a rust or accident issue.
That MB dealer is a rip off. The nuts are $5.50 and the washers are $3.50 at the one near me. If the part isnt in stock I just pay for it then they get it within a day or two.
I was under my car yesterday and from the looks of the hardware I would probably re-use the front control arm bolts, but the rears are another story and covered in rust.
So simple trick that helped me: Reuse the old washer and nut to help hold the wrench in place.
I updated all my bolts to the 21mm flange bolt and 21mm flange nut. When you are ready to fasten everything down, you can temporarily use the old washer and nut to hold the wrench. This makes it pretty much impossible to round off that nut or slip off. I don't have a lift so this helped out a ton.
One of these 21mm zero degree flat box end wrench also make the job way easier.
The non-slotted hardware is floating. It doesn't matter which side has the wrench and which side has the torque wrench. Even if you use the camber adjustment hardware, you still need to counter hold the bolt otherwise you can deform the tabs.
This is the passenger control arm (right side) 204-330-84-11; the frame has a protrusion that holds down a cable harness. It is awkardly in the way. I'm also using a compact 3/8" click torque wrench with a 21mm socket instead of a longer 1/2" drive size.
There's literally no reason to torque the first stage on the nut side unless you want to make things harder for yourself.
For the other control arm 204-330-80-11, the sway bar link is in the way. The threads of the bolt protude significantly about 25mm which also negates the use of shallow sockets on a torque wrench. In this scenario you can choose to unbolt that mount and use a deep socket or just torque it on the bolt side where you have miles of clearance.
Lastly, "by the book" I would need to get another alignment since the hardware was removed and replaced. If you are converting over the to camber adjustment bolt you would have the alignment technician do all this. However I am deferring it since the alignment I got last month was perfect and I'm due for tires soon.
The friction of the bolt shank in the bushing invalidates the torque reading. The torque wrench must be applied to the nut.
Yeah sure, look at post number one. That huge slot in the factory bushing sure puts a ton of friction there. You drop a bolt in either bushing hole it spins freely.
Originally Posted by PaulEdisto
If you are using the camber adjustment hardware, you should torque it on the nut while it is on the alignment rack. If you are using the regular hardware you can torque it from either side, whichever makes your life easier. If you are doing it on the ground like me, setting the torque on the bolt side is less frustrating.
Not really sure why you are giving so much shade. Go buy some nuts & bolts and try it out for yourself.
FWIW, I just this moment received some cool new tools that I think are perfectly in line with this thread. The depth of the ratchet plus socket is the show-stopper, so when I saw these, I knew I had to have them. I'm sure I won't use them often, but when they're needed, they should be gold!
They are billed as "Low Profile Socket Lever" on Amazon ($14 for the set of three). This would work for the bolt / nut in question, by bracing it up against something solid, or I suppose slipping an extension tube over the handle if necessary.
Full disclosure - I got these free in return for a review, but get nothing / zero / nada for a post like this, which I'm doing just because I think they're cool enough y'all would love to see them. ;-)
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