[vilord]

I'm installing a set of Bilstein B6 shocks and struts that've been on a shelf in my garage for the last few years. My car is an e91 XI, so the front coils are already a high rate spring, but not sure what to use for the rear.

I'm not interested in lowering the car at all, but do want a firm ride especially when carrying a load or if I hook back up the tow bar.

Currently mounted on it are xi wagon rear springs marked C7. The previous owner installed B4 rear shocks, not sure if the springs are original or swapped, but original would make sense with B4's. They have 130k miles.

In addition I have a set from a 2013 convertible, marked F5, with only 65k or so on them. My understanding is that F5's were also specified for a wagon with a tow bar, but I haven't a clue whether that information is accurate.

I know the D springs are sport, and shorter, so I don't want those.

Any idea how I could figure out which of the C7 or F5 springs have a higher / more progressive spring rate? And which would be a good match to a B6 setup?

Thanks all!

[edycol]

Don't forget stiffer lower mounts. Monroe is good upgrade.
Not sure though about springs. You could leave current and see how it works. I have B6 with regular springs on E90 xDrive and track car.

[vilord]

I went with upgraded lower and upper mounts for the shocks in the rear. The rear lower I ordered (back in 2020) appears to be a lemförder part (monroe for upper) but is definitely still more rigid than the OE that is coming off.

Just double checked and my fronts were I2 (with one of them broken in half), replacement used fronts are I1. I wish there was a cross reference of wth all these letters relate to.

[vilord]

Well, I guess I'll be using the F5's...

[vilord]

Did a whole lot of digging and found that some of the aftermarket catalogs have identifiers for the coil spring codes. I did discover that the F5 rear springs I'd ordered are wrong, they will be 10mm shorter than the equivalent xdrive spring (Cn) would have been.
Have no idea what's going on up front, as those springs had what appeared to be I1 on them, which should be an xdrive spring, too soft... but they act like a non-xdrive heavy duty spring. Maybe I read the barcode wrong, the rest of the tag fell off long ago.

I was working on things for my wagon, thinking of installing my tow hitch again. Here's what I came up with, hope it comes in handy for folks in the future trying to map from spring code to part numbers, etc. Non-wagon spring codes to part numbers are still correct, even if the application isn't useful because of the different curb weight.

First number is the suplex part number. Spring codes from catalog: https://www.suplex.de/suplex-katalog/?lang=en

Lookup which part number by options:
https://cats.parts/bmw/E91N/51081/all/springs

Wagon Front, std suspension, AWD:
06365 - L1/I1 -> 31 33 6 769 915
06366 (lesjofors 4008529) - L2/I2, L3/I3 -> 335 manual transmission, all 328 -> 31 33 6 769 916, 917
06367 (lesjofors 4008547) - L4/I4 -> 335 automatic transmission -> 31 33 6 769 918

Wagon Front, std suspension, RWD:
06262 - C2
06263 - C3
06264 - C4 -> 328 manual -> 31 33 6 767 367
06265 - C5 -> 328 automatic -> 31 33 6 767 368
06266 - C6 -> 335 manual transmission -> 31 33 6 767 369
06267 - C7 -> 335 automatic transmission -> 31 33 6 767 370
06268 - C8 -> 31 33 6 767 371

Wagon Front, sport suspension, RWD:
06369 - D2
06370 - D3, D4 -> 328 manual -> 31 33 6 767 375, 376
06371 - D5, D6 -> 328 automatic, 335 manual -> 31 33 6 767 377, 378
06372 - D7, D8 -> 335 automatic -> 31 33 6 767 379, 380
06373 - X2, X3

Wagon Rear, std suspension, AWD (340mm):
Lesjofors 4208462 is for C5 & C6
Lesjofors 4208463 is for C7 & C8
06345 - C6, C7 -> without towbar, 14.25mm -> 33 53 6 767 341, 342
06355 - C8 -> with towbar, 14.25mm -> 33 53 6 771 355
06356 - C9 -> extra load, 14.5mm -> 33 53 6 771 356

Wagon Rear, std suspension, RWD (330mm):
Lesjofors 4208456 is for F2, F3, F4
06351 - F2 -> early / no options, 13.75mm -> 33 53 6 768 250
06352 - F3, F4 -> without towbar, 14mm -> 33 53 6 768 251, 252
06353 - F5 -> with towbar 14.25mm-> 33 53 6 768 253
06354 - F6 -> extra load 14.5mm-> 33 53 6 768 254

Wagon Rear, sport suspension RWD (315mm):
06358 - K2, K3 -> early cars without towbar
06359 - K4 -> early cars with towbar, late cars without towbar
06360 - K5 -> late cars with towbar