W169 New front springs - need to match the height at the rear

[GLK]

I've had an emergency front springs replacement, after OSF one split in half.

Unfortunately, Mercedes advised the wrong part number, and when we found out, it was too late to order the right ones, as there were none in the UK - a week or so wait, to get it from Germany...

So, I now have 5 yellow dots springs, instead of 1 dot ones at the front, and they are considerably higher.

I was never too obsessed with lowering the suspension, particularly as this is a small and tall car anyway, and the actual ride quality is better, plus I don't have to worry as much about stupid speed bumps, and suchlike - I'm sure you can see where this is going - I'm not going to replace the new OE front springs, however I want to match the new height at the rear.

Hence, the question: how do I determine which part (how many dots) do I need for the rear?

For what it worth, my own calculations on EPC were spot on - I got 183 points for the front = 1 yellow dot, part number A169 321 1604 (and that's what was on the car). Part given by Mercedes for my chassis was A169 321 2004 (5 dots).

Now, I believe the rear ones are A169 324 0804 (3 yellow dots), as I have 129 points here.

Is there any way to determine how many 'extra' points do I need? The front ones are the top (or bottom if you wish) of the scale for my sports suspension and 18" AMG wheels, shall I go for the same - tallest one for the rear - A169 324 3504 (1 yellow / 1 yellow)?

 

[grober]

In theory any spring rate should be matched with its corresponding damper /shock absorber which will have specific compression and rebound characteristics. Sports shocks may also have a shorter effective travel which should not be exceeded. While comfort and ride height will be increased other handling characteristics may get worse. For that reason I would recommend sticking to the original spec springs if using the old dampers.

 

[GLK]

Thanks Graeme, the springs are listed for my chassis in EPC*, and there's only one part number for shocks, so it is reasonable to assume they are compatible.

It was suggested, by someone who knows a lot more about these, than me, to go for a matched set of sporty lowering springs and shocks, which I might still do later on (budget constrains at the moment).

* I found it rather counter-intuitive (I wanted to say "stupid and lazy", but am too polite) that, there are six part numbers listed for both front and rear springs, under full VIN search in EPC. Surely, the car left the factory with only one type fitted, and this is what should show up in EPC, not all available options for this type of suspension!

 

[grober]

Having had a quick shuffty at the EPC I have to agree its far from clear. Its all to do with Mercedes points system which varies from car to car dependent on ancilliary equipment fitted. In older fore and aft engined models there was one calculation for both front and rear springs but now there appears to be two- front and back- maybe its a fwd thing! What's not clear either is the starting point for the calculation based presumably on the exact engined model being dealt with. Oh and there's a chassis no change in there as well!

 

[GLK]

Yup, it's a mess - don't understand why the entire generic points table has to be combed through, when the exact chassis number should have eliminated options, not specified for the build!

The starting point is basically the Baumuster - 169.333, so for the front it's 168 points, then CVT - 11; a/c - 3; CDC - 1 = 183 giving me A1693211604 in 180-187 bracket.
The rear, as you said, got its own table, starting with 122 and adding CVT - 1; Sound system 532 - 1; Spare tyre - 3; Luggage cover - 1 = 128, so A1693240804 in 121-130 range.

Surely, these complex calculations could have accompanied the datacard and be available on EPC, upon entering the VIN?!

It was suggested I use the reverse calculation - to see what would have given the now fitted springs' part number, and use same starting point and options to get the corresponding rear spring p/n. I have done that and got either the A1693243204 or 3504 (not all options present in both tables, and the thresholds do not match).
I'd probably go with 3204, as it doesn't look like there's any precision in this process