W123 front lowering correctly. - PeachParts Mercedes-Benz Forum

rwd4evr · #1 02-28-2019, 02:43 AM

I threw a bid on a w123 300td I figured would go for 1500-2000 and won it for $610. So the 300sd is saved from the cutoff wheel. It's almost completely rust free supposedly although I haven't picked it up yet. Anyway Im super excited to return to the first Benz I fell in love with. Build plans are the ax15 5 speed trans. W126 gen 2 big brakes up front and 3.23 LSD from a euro 380slc out back.
The one thing I hated about my original wagon was the nose up attitude. The more I've learned about suspension geometry building my drift car make me worry about if lowering the w123 front on just shortened springs will ruin the front end geometry like it did on my c107. I'm not going super low but all I've seen is cut or h&r springs.
I'd love to see some lowering spindles instead. Any input on performance after lowering a w123/126 frontend? It may be a diesel wagon but it's going to be a performance oriented build. I'll probably run w126 v8 springs and kyb shocks.

fonzi · #2 02-28-2019, 08:47 AM

Sounds like I should get the 5.0 and manual trans in that SLC pretty fast so I can at least feel the fun before downgrading to the stock 5.0 2.72 LSD.

I am pretty sure the 300td (non-turbo) our back has a 3.46 rear end in it. So hopefully that will buy some time.

Lowering... as you now respect the original engineering more, and since the rear end already has stock springs, and since you will probably very often have a heavy load in the back, why not first make sure the rear end is high and stiff enough for the duty this wagon will be performing? I’ve definitely seen at least a few cars lowered focused right around how they look at the time they are lowered, only to later realize they settled down even lower in time.

With fixed control arm mounting positions, shorter springs just end up making the control arms ride around in the compressed position all the time, sideways force pushes up on the springs (more) instead of transferring all the sideways force to the subframe.

So, the spindles you are talking about... you want to raise the position of the wheels (to lower the car) without changing the suspension geometry that (let’s face it) the engineers got pretty damn right to use it on 2 of the most legendary Mercedes tanks of all time, the w126 and w123. You yourself spoke of just how well that 280se 4-speed handles the highway on/off ramps.

So if you could just raise the position of the actual axle on the spindle, that would probably be most ideal. Right?

Or, would you simply be looking for the stiffest spring that would put the static height position at the most stable position?

Obviously you don’t want to keep the existing spring rate and simply put the suspension in a compressed position kind of like riding around on an upside down wishbone with all the weight at the bottom center, the wishbone with have a tendency to compress the springs with its own weight.

The camber that has been designed into the suspension surely consider the weight of the front end of the vehicle so it reacts to the forces of a turn. Is that worth messing with?

I imagine that the w126 and w123 (and w116?) probably don’t have the performance tuning following to justify someone casting shorter spindles that would simply raise the wheel height with respect to the stock suspension.

I suspect that the challenge will be finding the shorter stiffer springs (and maybe shocks) that bring the static front end height down just enough to make you happy with its looks while not causing the springs to enter the compressed geometry until it’s needed. You don’t want to be so stuff that the car understeers, nor do you want it to oversteer. Right?

Am I following?

P.S. isn’t the level of the rear end without SLS going to affect the castor on the front wheels depending on the load on the rear end? That’s one reason I wonder if you are going to discover that the rear end may be where you want to set your “tuning” focus. You are probably going to want some heavy duty springs and shocks that will have your rear end looking quite high when it’s not loaded. All sorts of tools and wheels and maybe some significant tongue weight on the rear, and I could see the rear end easily carrying around an extra 1000 lbs on occasion. This will surely be “nose up” situations if the rear end springs aren’t super-stiff.

rwd4evr · #3 02-28-2019, 01:26 PM

It has an actual sls removal kit someone came up with. The guy said they are like Ford truck front springs or something. I may actually try to return the SLS to operational. I've found air shocks that will fit I believe, if not. Yes, you're correct on most of what your saying. I have to look at the suspension at it's correct ride height to see how much it can be lowered before affecting the geometry. The relationship of the lower arm to the ground is important. Once it goes past level and slopes downward toward the car bad things start happening. But I have seen very low performance w126 cars so I believe they can handle a fair amount of drop. The m119 powered race car in New Zealand for example. Roll center height and weight jacking effect are the important factors
. Cutting and rewelding the spindle is a possible option but I don't really want to do that unless absolutely necessary. I was hoping to find out that somebody did make a lowering spindle. Castor will be adjusted after ride height is set.