I am about to begin a complete front end overhaul. One of the forum members mentioned the need to purchase mercedes bolts for both the upper and lower control arms to have on hand in case they are needed.

Does anyone know the bolt size for upper and lower control arm bolts for a W123?

I don't know either size but recall that the lowers are not standard hardware, they have cams/eccentrics on the bolts to move the arm for alignment purposes.

The uppers as I recall are standard hardware.

I doubt you'll need upper bolts but think you will want new lower hardware.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Use quality parts and don't tighten anything suspension related until weight is on the wheels.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Note some of the aftermarket lower control arm bolts have different treads. However, if you buy the kit it comes with Nuts to fit them.

Also note that the inside where the rubber bushings go of my lower control arms was so heavily rusted I got a used set on eBay. But I was still able to reuse the Bolts. The nuts are self locking and likely you are supposed to replace those but I just use Loctite on them.

Also bot the upper and lower control arm bolts (the ones that go through the bushings) should be torqued with the wheels on the ground with no support under the vehicle.

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84 300D, 82 Volvo 244Gl Diesel

I just did the bushings on my lower control arms.
I bought Lemforder for everything but the bushing for the guide rod to LCA.
The Febi part was 1/3 the price of the MB one and people seemed to have good luck with it.
The bolt that comes with the Febi kit has a shorter neck that does not fit
all the way through the two halves of the bushing.
I just cleaned up and reused the original bolt with the longer neck.

Attached Thumbnails

   

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

I located my two new brand new in the box Lemforder bolts with the cam/eccentric design. I'm trying to figure out what size bolt to order from mercedes for the upper control arms. Is it size M10X35?

You don't need the size unless going to a hardware store or there are 2 sizes for your vehicle. This site has them available.

That said, calipers and a metric thread gauge work. You can use an open end wrench and thread gauge if you know that the bolt in-hand is metric.

I'd give you the measurements but car is on the wet ground.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

My understanding is there are different grades of bolts with regards to steel strength. Hardware man at home depot told me that home depot does not stock automotive grade bolts.

They actually do if you look at the marks on the head of the Bolts. For united states threads they have up to grade 5 which is 3 hash-marks/lines on the head of the bolt and the similar metric one which you have to look the numbers on the bolt head. The metric one similar to grade will have an 8.8 on the bolt head.

Home Depot does also carry bolts with no make on the head which are of course not stated at all for automotive use.

I would think it would be their Nuts that would be suspect unless the lable on the Nuts has a grade on them. Look for the Nuts in a plastic bag. That would have the info on it. Nuts in a bin may not be labeled or labeled properly.

One of the pdfs has the Metric info.

Attached Files

	Torque chart-Tension Chart for A307 Gr5 Gr8 Gr9.pdf (76.0 KB, 45 views)
	TorqueCharts.pdf (70.2 KB, 120 views)

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84 300D, 82 Volvo 244Gl Diesel

I seem to be unable to locate the actual mercedes-benz bolt here on peach parts or pelican parts. I did, however, find some upper control arm bolts complete with part numbers on several competing websites but they do not list the bolt or bolt part number for the W123.

MB part number N 000960 012315, the size is listed here as being Grade 10.9, M12X1.5 and 85 mm long.

Available from dealer$hip, belmetric, and elsewhere on the web.


The nut is MB part number 913004-020003 (it superseds the old MB part number N 913004 012009), just in case you need that part as well.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Thank you for posting the part number and the sources to obtain the bolts from. This will help me greatly in getting my front end suspension refresh into gear.


Wrench on!!

It helps to call peachparts when you can't find something. I haven't tried lately but they used to have people that had a good idea of how these cars worked. Unfortunately, the days of Roy sourcing parts are long gone.

The local Ace Hardware has a really good supply of metric and other fittings.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.