Suspension springs interchangeability - PeachParts Mercedes-Benz Forum

juanesoto · #1 08-11-2009, 07:13 PM

Hello folks!! I've been out of the forum for a while...

Luckily, I'm having some free time now, so I can catch up on the forum!

Anyway, I've been wondering about suspension springs interchangeability. Since some of the forum members couldn't get in the Vogtland group buy due to several reasons, I'm starting this thread to gather all of our knwoledge to figure out if there are some Mercedes springs that are similar to the W123 springs. If we find out the model series, then we can look for updgraded springs upon each ones needs. We might even be able to figure out which factory springs from other models might work, so the members with a low budget like me can look for them at the Pick N' Pull...

In my particular case, I would like to adjust the ride heigth of my car to get about 1 to 1.5 deg negative camber in the rear and some forward rake (correct me if I spelled something wrong) by lowering the front a bit. Also stiffer springs would be a plus to match the C-class rims and tires I'll be installing soon.

Now, back to business, according to the service manual, there were several spring sets for the W123 depending on the application. I compared some early W126 and W123 springs, and there was no visible difference in their dimensions, except some length differences not greater than 5 mm. I'm pretty sure they have different rates but I don't have a way of testing them.

Also, even though the W123 and W126 springs have the red and blue marks, according to the service manual most springs had both markings on the same part number... I really don't know a way of finding out the part number of each spring AFAIK...

Any thoughts?? What about other class springs?

If late W126 springs fit in the W123, that would make things a lot easier, since you can get H&R springs for the late W126...

juanesoto · #2 08-11-2009, 07:15 PM

BTW, I created the thread in the Diesel Board because I'm interested in my particular application. If someone feels this should be somewhere else, let me know to request the change...

Sev · #3 08-11-2009, 07:35 PM

i think you created the thread in the right location.

i have also asked this question, and got less than receptive responses from people who are touchy about this subject.

i can tell you you're definitely on the right track here. this is what i want to do myself with w126 springs. to sum up the total of my knowledge on this subject, i think your best bet for lowering springs using stock springs from a w126 would be to use 560sel springs for the front, because the 560sel was the heaviest model in the w126 chassis, and therefore has the stiffest front springs. you are correct when you look at the color marks on the springs that were painted on by the factory, because those marks indicate the weight of the car for which the springs were rated.

for the rear, you don't want to get 560sel springs, because, in N. America, at least, the 560sel came stock with the SLS. therefore the springs in the rear are a bit softer, to accomodate the SLS valve and SLS shocks. that is, if the w126 is the comparably the same as the w116 and the w201, which I think it is.

therefore for the rear, you want to get springs off a non-SLS 500sel, or a 420sel. you can then take the used front spring off your w123, and assuming it has not sagged more than is normal for a 30 year old car (say, due to rust, if rust causes excessive sagging), and put the used w126 spring right next to it, and cut the w126 spring to the desired height to create a cheap lowering spring.

the next question is, what kind of shocks do you get. if you cut the springs more than about 40mm (because most aftermarket lowering springs lower the car anywhere between 40 and 60mm), you will need to get shocks with a shorter travel distance for the piston. if you can't get that, you are stuck with Bilstein HD shocks, which will blow prematurely, and cause a 'bottoming out' effect if you cut the springs too much.

therefore, it's best to decide how much you want to lower the car first, and buy and cut your springs and buy your shocks accordingly.

Sev · #4 08-11-2009, 07:36 PM

here's my discussion of w123 sport shocks:

w123 sport shocks

juanesoto · #5 08-12-2009, 10:36 AM

Thanks for your reply Sev. To be honest with you, I'm not planning to lower the car that much, 1 inch max. I really like the ground clearance the car has. I just want to give it a more "sport" touring look to match the rims I got (see pics) from a C230. They are 7J15 ET 37. I'm putting some Bridgestone Potenzas G3 in 205/60R15 on them. I'll post some pics after the paint job is done. I'm painting them Graphite Gray with 3 fine pearl additives in Jade Green, Terracota Red and White Mica. The samples turned out very nice.

Back to the springs, your hypothesis sounds right... Do you know if the 506SEL springs have the same overall diamenter of the W123 springs? The difficult part wil be getting those particular springs...

About the rear springs, I've seen some W126 HD springs available in peachparts. My guess would be that those might work pretty good in the W123. One might have to cut a coil or maybe two, to get the right height, but I'm pretty sure the ride will be stiffer. I know there has been a broad discussion about cutting springs and how they will be overloaded due to the increased load per coil, but consider this: you will be cutting a HD spring designed for a much heavier car with a higher load rating, so there's quite big "security" factor left even after properly cutting 1 or 2 coils... Just my 2 cents idea...

As I said before, my goal with this thread is building a knowledge base to improve the handling of the W123 without breaking the bank and with more options to select from regarding handling and ride quality. Hopefully some spring expert might chime in...

Sev · #6 08-12-2009, 10:35 PM

Quote:

Originally Posted by juanesoto

Thanks for your reply Sev. To be honest with you, I'm not planning to lower the car that much, 1 inch max. I really like the ground clearance the car has. I just want to give it a more "sport" touring look to match the rims I got (see pics) from a C230. They are 7J15 ET 37. I'm putting some Bridgestone Potenzas G3 in 205/60R15 on them. I'll post some pics after the paint job is done. I'm painting them Graphite Gray with 3 fine pearl additives in Jade Green, Terracota Red and White Mica. The samples turned out very nice.

Back to the springs, your hypothesis sounds right... Do you know if the 506SEL springs have the same overall diamenter of the W123 springs? The difficult part wil be getting those particular springs...

About the rear springs, I've seen some W126 HD springs available in peachparts. My guess would be that those might work pretty good in the W123. One might have to cut a coil or maybe two, to get the right height, but I'm pretty sure the ride will be stiffer. I know there has been a broad discussion about cutting springs and how they will be overloaded due to the increased load per coil, but consider this: you will be cutting a HD spring designed for a much heavier car with a higher load rating, so there's quite big "security" factor left even after properly cutting 1 or 2 coils... Just my 2 cents idea...

As I said before, my goal with this thread is building a knowledge base to improve the handling of the W123 without breaking the bank and with more options to select from regarding handling and ride quality. Hopefully some spring expert might chime in...

the offset on that wheel is too high. you'd best stick with the CLK wheels off a CLK320, for example. these are the light, polished wheels with the correct offset for a w123, and weigh only 13-14lbs each. it's lighter than the original bundt wheels that are either 14x6 or 14x6.5, and they measure 16x7 with a low offset. they have been proven to fit a w123, and will increase your performance a bit, and are a bit larger diameter than the ones you're looking to put, but look SUPER nice on a w123 if you ask me. i'd go with those.

with only a 1" drop, guess you'd have no problems sticking to the stock shocks or bille hd's

juanesoto · #7 08-13-2009, 06:29 PM

Sev, I understand what you mean about the offset. However I installed one of the rims in the front to check tierod clearance and it looked quite right. It was reduced about 13 mm, leaving about 7 mm of clearance. However, since the new rims are wider, the outer face of the rim is about 13 mm further towards the outside of the car. So far that's fine with me. I might get some concentric spacer in 10 mm to get more tie rod clearance.

Back to the original matter, I came across aset of springs of a 1991 500sel W126 non-SLS. According to some spec charts, this particular W126 has a curb weight of 4785 lbs. I beleive my W123 has a curb weight of about 3900 lbs (I need to confirm this). This means the springs in this W126 are about a 23% stiffer, in rough math. Considering my car is almost 10 years older and my springs are "worn", swaping the springs should be a good improvement, right???

I just need to figure out if I should give it a try or keep looking for the 560sel springs. The gut is asking $135 for the 4 springs from the W126. Should I go for it?

juanesoto · #8 08-13-2009, 06:32 PM

BTW, I really thought this thread would get more attention. Where are all the great minds I've seen here? Will this be just Sev and me discussing?

The idea is to figure out the magic mix of suspension parts from other Mercedes series that will let us improve our W123's from junkyard parts...

charmalu · #9 08-14-2009, 01:39 AM

Well since this title is spring interchangeability.

I used 240D front springs under my 85 300D to lower the front
after the 240D manual trans swap.

these lowered the front by 1 1/4 inches

also used the 300D one nub spring pads.

Charlie

juanesoto · #10 08-14-2009, 10:37 AM

Thanks for the info Charlie! Did you had any bottoming problems using those springs? Any increase in the body roll?

winmutt · #11 08-14-2009, 11:04 AM

If you are looking for performance you want to get the thickest springs and lop a coil or coil and a half off. Last time I checked they were quite affordable. If you want to replace the rear springs I would HIGHLY recommend getting the progressive rate rears if they are still avail. You may need to contact Classic Parts to get them from Germany.

juanesoto · #12 08-15-2009, 04:00 PM

Thanks for the input Winmutt. You're right about the springs. However if the springs are too "hard", will the shocks be able to control the bounce and the rebound?? (please excuse if I misused a term or concept)

Now that you mention the progressive springs, I'm wondering if the 560sec had progressive springs in the rear from the factory?

An update on my new rims. I got them back from the paint shop and they turned out really nice. They still need to be polished, but I'm very happy so far. The rim measurements are 6.5J15 ET37. In a previous post I made a mistake and wrote the measurments wrong. The tires I got are Firestones FH900 in 205/60R15. I did some test driving and they perform really nice. Lots of grip in braking and cornering. I'm attaching some pictures. What do you folks think??

juanesoto · #13 08-15-2009, 04:00 PM

Two more pics. The car is a bit dirty, but i'm happy with the way it looks...

Some additional info. I had to use 5 mm spacers because the tie rods were a bit too close to the front rims. They didn't touched the rims, but were very very close so I went the safe way putting the spacers.

Steering is bit heavier when the car is stopped, but other than that the car feels great. I just need to solve the ride height issue. The rear is definetely seating too low and the front is seating too high...

juanesoto · #14 08-15-2009, 08:44 PM

I found some interesting info. These are 3 spring brands that make springs for the W126 along with their respective part numbers

intrax 50.1.013 380SE/SEL/SEC/300SD/500/560SEC NSL
50.1.022 420/500/560SEL NSL

eibach 2508-140 All SEC/SEL SL

h&r 29559 All SEC/SEL NSL
52759 All SEC/SEL SL

*NSL:No self leveling SL:Self leveling

Since we already know W126 springs fit the W123, we just need to find out which W126 has the closest weight to the W123 weight. Done that, we'll have a source of "performance" springs... Thoughts?

Brandon_SLC · #15 08-16-2009, 02:17 AM

Weights of w123 and w126 are simmilar. In Euro form,your 82 is listed at 1625KG, while the 260SE was 1570kg. IIRC the 300SD weighed about 3650lbs, which was heavier than a 300d of the same year.

When both cars were new my impression was that the w126 had a smoother softer ride. So, I don't understand why the weight being similar would give you performance springs. I've driven 560SECs and they seem to handle a lot better. Maybe that is the place to look???

I've wondered the same thing about spring rates. Many manufacturers vary spring rates depending on options. But I see springs for sale that say they fit many years and models of the 123. But there's a big difference in weight between a low optioned '78 240D and an '85 300DT. So, I've often wondered if those "1 size fits all" springs are going to give anywhere near factory original ride quality.