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w123/w126 suspension interchange/upgrade
R-3350 Offline
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Location: Western NC USA
#1
w123/w126 suspension interchange/upgrade
i got on a tear recently looking into upgrades to solve the boat like characteristics of my 85 300d in a tight corner. as i live up in the mountains of NC it can be "interesting" on my way to work every day depending on which route i take and road conditions. so far i have looked at the sls conversion spring set that along with the second gen W126 brakes should help some however that still leaves the shocks and the front springs lacking a known good upgrade. the bilstein B4 HD shocks are slightly better but im looking into fitting something more aggressive. i have no issue driving something loud and harsh for extended time, as my other daily is a 86 F-250 with the 6.9IDI strait piped under the cab (which has the added benefit of dis-encouraging people to ask for rides or to borrow either car).
the question i have is how interchangeable are the various suspension components such as springs and shocks between the W126 and W123  cars? the W126 ran much longer and more performance options were available. so there is a slightly larger after-market which if compatible would solve some issues. there are also at least two companies i have found making coil-over kits for the W123 body. however i have not seen any reviews or found any proof that they do in fact work. (https://www.otakugarage.com.au/product/m...coilovers/) (http://pbbrakes.com/street-coilovers-kit...n-kit.html). the final question i have is directed to anyone who has worked with more race oriented equipment. how difficult do you think it would be to adapt the standard 5.5" or 2.5" universal springs to fit inside the spring stock perch with a hight adjuster? also what is the stock spring rate on a w123 sedan spring?
12-02-2016, 10:38 PM
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CRD4x4 Offline
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#2
RE: w123/w126 suspension interchange/upgrade
I can't speak to the interchangeably of w123 & w126 parts but it's known that w123 wagon sway bars, springs and brakes are larger than sedan and are a simple bolt-on affair.
That's where I'd start before going to a newer chassis for parts.
12-03-2016, 07:14 AM
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R-3350 Offline
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#3
RE: w123/w126 suspension interchange/upgrade
the w123 estate has a larger front sway-bar but everything else is the same with one exception in that the rear brake calipers are about 1-2mm bigger pistons. the w126 brakes are a direct swap for first gen and second gen if you have 15" wheels or bigger. my issue is the lack of significantly stiffer suspension components that would fit without extensive work. it looks like the w126 shocks are the exact same as the w123 and billstein has a B8 sport package for the w126 that is still available. the B8 shocks are designed for lowered vehicles so thats an option for anyone interested in lowering while maintaining proper shock valving. as for springs the w126 has slightly taller springs but the same width (475mm hight average in front vs 450mm for the w123). so it looks like im going to go for the sls delete springs in the rear with a 1.5" drop and a set of 300sd front springs cut to 1.5/1.75" drop. as for shocks im looking at the koni reds as i would like the adjustability they offer vs the bilsteins. i would like the lower valving the B8 shocks offer but im afraid that the stiffer rear springs and shocks might make it oversteer too much and would prefer to be able to dial in more or less as needed. otherwise that still leaves the rear sway-bar as an issue with no clear solution now that the 16mm version is NLA. has anyone looked into swapping in a universal torsion bar set up? i feel that you could find one the proper length and then its just a matter of making arms that would work with the stock fittings.
12-04-2016, 03:32 PM
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atypicalguy Offline
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#4
RE: w123/w126 suspension interchange/upgrade
(12-04-2016, 03:32 PM)I don\t know of anyone who has looked seriously at that. I do think that there are probably some bars that will fit. Someone is going to have to take a measuring tape to a junkyard and look at some sportier models to find a more modern merc bar with similar dimensions.The front seems like a pain, but it is so much larger than the rear and the cars were typically set up to understeer as a matter of principle. Stock rear bars on the w124 wagon can be increased from tiny stock size up through the e420 at 16.5 to the e500 at 18 and even larger and it only seems to improve handling, so I would think the w123 would be similarly tolerant of a rear bar upgrade. If it oversteers you can always go back.I think I have seen someone just make a bracket with stacked bushings and run two bars to the same links. This might be the easiest solution if there is space in the rear. R-3350 Wrote: the w123 estate has a larger front sway-bar but everything else is the same with one exception in that the rear brake calipers are about 1-2mm bigger pistons. the w126 brakes are a direct swap for first gen and second gen if you have 15" wheels or bigger. my issue is the lack of significantly stiffer suspension components that would fit without extensive work. it looks like the w126 shocks are the exact same as the w123 and billstein has a B8 sport package for the w126 that is still available. the B8 shocks are designed for lowered vehicles so thats an option for anyone interested in lowering while maintaining proper shock valving. as for springs the w126 has slightly taller springs but the same width (475mm hight average in front vs 450mm for the w123). so it looks like im going to go for the sls delete springs in the rear with a 1.5" drop and a set of 300sd front springs cut to 1.5/1.75" drop. as for shocks im looking at the koni reds as i would like the adjustability they offer vs the bilsteins. i would like the lower valving the B8 shocks offer but im afraid that the stiffer rear springs and shocks might make it oversteer too much and would prefer to be able to dial in more or less as needed. otherwise that still leaves the rear sway-bar as an issue with no clear solution now that the 16mm version is NLA. has anyone looked into swapping in a universal torsion bar set up? i feel that you could find one the proper length and then its just a matter of making arms that would work with the stock fittings.
08-09-2018, 04:24 AM
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Granfatherglock Offline
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Location: Richmond, VA, USA
#5
RE: w123/w126 suspension interchange/upgrade
Holy thread resurrection!

This is obviously a thread about junkyard upgrades and parts compatibility, but figured I'd share. I've tossed around the idea of using nascar style splined sway bars with custom arms. It may be seriously overkill, but with some R&D I believe it could work for the front as well. The biggest concern is custom length splined sway bars are expensive.
08-09-2018, 06:07 AM
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atypicalguy Offline
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#6
RE: w123/w126 suspension interchange/upgrade
I'm considering doing a run of upgrade bars, like IPD did for the volvo 240. It would be high smiles per dollar stuff.
10-29-2018, 07:52 PM
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winmutt Offline
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#7
RE: w123/w126 suspension interchange/upgrade
My W123 was pretty stiff without being terrible. Miss it.
1987 300D Sturmmachine
1991 300D Nearly Perfect
1985 300D Weekend/Camping/Dog car
1974 L508D Motoroam Monarch "NightMare"
OBK #42
11-02-2018, 02:54 PM
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atypicalguy Offline
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#8
RE: w123/w126 suspension interchange/upgrade
(11-02-2018, 02:54 PM)winmutt Wrote: My W123 was pretty stiff without being terrible. Miss it.

Interesting. My wagon seems to roll a bit more than I would like. The front bar is already huge. Everybody seems to think a larger bar works wonders on the w124 series cars; unfortunately the 500e bars are nla so the next stop seems to be the e55 bar.

Anyway I recently aired up my stock 195 series tires and it stopped howling on the sweepers on sunset. It actually impressed me yesterday. No drama. It rolls, but then sets up and goes around the corners without any alarming tendencies.

I may go with a set of the ebay 15" bundt wheels to reduce sidewall flex a bit. Either that or the BBS 3 piece, but I always thought that looked sort of like lipstick on a frog Smile

I think my tires are shot anyway, so it may be time to splurge. I think there is even a set of Fuchs 15" on ebay right now.
11-29-2018, 09:27 AM
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