Performance Springs: Mixing models? ( T1/T2/T3/T4)

[thicc3]

QQ for those who've been E82 owners much longer than I have - been scouring the forums and getting the part # for doing the M Performance suspension upgrades.

Problem is, my VIN came back calling for the T2 (31-33-6-788-892 fronts, 33-53-6-788-899 rears) which would be great if the rears were in stock anywhere... looks like i can get the fronts although they may take a month to ship.

BUT - the T1 (31-33-6-788-891 fronts, 33-53-6-788-898 rears) are much easier to get.

If you were in my shoes, would you mix T2 front with T1 rear, or just go T1 all around?

i know its weight based on options, i have a 128i manual with only options being adjustable and heated seats, and sunroof... I cant imagine there is too much weight diff between 128 models unless you got AT vs MT.

[ShocknAwe]

Can't say. It's just spring rates though. Doubt there's a length difference. You could even (and this is what I would 100% do, is get the front springs you want and then get custom length and rate linear swift springs for the rear and use a height adjusting collar mount for them.

Your front spring will mitigate most of the harshness by sticking with the BMWP spring and then the custom rear rate will help you balance the chassis weight transfer better.

$0.02

[tpl.mallon]

I wouldn’t mix T1/T2.

Those spring classes are weight-matched from BMW, so mixing them front/rear can throw off balance (rake + handling). Even small differences matter since they’re designed as a set.

For your spec (128i manual, light options), T1 all around is probably closer to what the car actually needs anyway. T2 is usually for slightly heavier configs.

If it were me, I’d just run T1 front + rear and call it done rather than wait or mismatch.

[thicc3]

yeah I am leaning toward just doing the T1 - worst case it is a little "softer" but my goal is a OEM+ feel with minimal drop.

Plus - swift, eibach, etc. are always going to be around. The M Perf. springs seem to be rapidly disappearing so might as well try while I can

[PureE92]

I did t3 front and t5 rear, enjoyed it before lowering the front by putting Megan springs and cutting the rear springs a bit.

BMWP Front Springs
Length: 345mm
T1 - 133lb - 31336788891
T2 - 146lb - 31336788892 (4.0 effective turns, 12.4mm wire)
T3 - 160lb - 31336788893 (4.0 effective turns, 12.7mm wire)
T4 - 176lb - 31336788894 (Officially supplied for E9x only)

BMWP Rear Springs
Length: 310mm
T1 - 390lb - 33536788898 (8.5 effective turns, 13.7mm wire)
T2 - 420lb - 33536788899 (8.5 effective turns, 14.0mm wire)
T3 - 454lb - 33536788900
T4 - 490lb - 33536788901 (Officially supplied for E9x only)
T5 - 530lb - 33536788902 (Officially supplied for E9x only)

[thicc3]

Welp - bad news is the T1 are also out of stock and seems like the T3 might also be that way...

Bummer, really wanted to stick with OEM but it be like that sometimes. Seems like the H&R OE Sport are the closest in drop length to the M Perf. springs so we'll see.

[cerealwars]

Careful - can't remember which brand (might have been H+R?), but one of the major names can yield a pretty severe rake. I'd recommend checking out installed photos on a similar car before pulling the trigger.

[ZHPizza]

OP I don't remember where I got this info, but I had these estimates in my notes for my lightest-spec 128i M Sport (manual, no sunroof, no I-drive, manual seats).

BMW Performance Springs
31 33 6 788 891 T1 FRONT 135 (est 10mm drop)
31 33 6 788 892 T2 FRONT 146 (est 5mm drop)
31 33 6 788 893 T3 FRONT 160 (est 0mm drop)
31 33 6 788 894 T4 FRONT 178 (e9x)
33 53 6 788 898 T1 REAR 390 (est 10mm drop)
33 53 6 788 899 T2 REAR 420 (est 5mm drop)
33 53 6 788 900 T3 REAR 460 (est 0mm drop)
33 53 6 788 901 T4 REAR 495 (e9x)
33 53 6 788 902 T5 REAR 519 (e9x)

I ended up buying T1 front + rear, but never installed them. I believe I still have them packed away somewhere, so let me know if you do some more digging and decide that's what you want to do. Lots of good discussion on these springs were had by the UK owners on the babybmw forums.

[cerealwars]

I found mine through a WTB post. I was hoping to find someone who hung onto their OE parts when upgrading, and it worked!

I just wanted 128i sport pack springs. Transmission and sunroof didn't matter to me, but I didn't want 135i springs because I figured that would introduce a front/rear bias. The labels on the springs went from C4f/C1r to D3f/L2r. Three years later, couldn't be happier with them.

[thicc3]

Originally Posted by cerealwars

Careful - can't remember which brand (might have been H+R?), but one of the major names can yield a pretty severe rake. I'd recommend checking out installed photos on a similar car before pulling the trigger.

Yeah i saw a bunch of these threads - from what i could tell the almost cartoonish rake came from the Sport and Super Sport lines that slam the car. After some probably wonky math it seemed like the OE Sport from was within 1-2mm drop in the rear of the M Performance so its close.

wa128's pics in this thread are what convinced me to go with the OE Sport for anyone else who lands here in the future wondering the same: https://www.1addicts.com/forums/showthread.php?t=343630

Worst case - I hate it, create a WTB thread, and then play the waiting game

[ShocknAwe]

Keep in mind a lot of springs are designed with the RFTs in mind. Even with super stiff summer perf tires you can go fairly high in spring rate before it feels rough.