Suspension advice - with a twist (E91 M3)

[MMMM6GC]

Pic for attention!



Looking for some advice from you E9x suspension gurus. As you can see I have an E91 M3 full conversion. I'm at the point where the complete conversion (mechanical, drivetrain, interior, exterior) is complete, but as is the case with these project cars, it's the fine-tuning and dialling in which really "finishes" the build.

Specifically, I want to ask your advice on some suspension component upgrades - starting initially with rear lower control arms and front tie rods. My plan is to refresh all components - but these need the most attention as they're in the worst shape from the donor E90 they came from. Having recently had an alignment - the tech recommended I replace these as a start point (as they're pretty beat on my car),

Now I can go the straight OEM route - the rear LCA's run about $90 a piece and with black friday sales coming up, even cheaper. But are there any aftermarket/upgraded ones I should consider? Lots of choice out there but I'm not well versed on this platform so looking for advice. After doing some searching on the forum - this is a bit of a unique case so I thought i was worth asking.

Similarly for the front tie rods, a full kit from FCP is about $400 but should I consider other aftermarket options?

Some reference points:
- The added weight of the wagon body is an important factor
- I'm currently running Ohlin's R/T and the wheels are AG OEM+ style 359s, so 19x11 in the rear and 19x10 in the front
- This will be 100% street use
- Ideally as I go through and refresh the front and rear - I'd prefer to use a consistent brand
- More adjustability is important

Some options for the rear toe arms:

- Bimmerworld ($299) - hex shaped, easy adjustment
- Tuner ($350) - hex shaped, grooved and includes lockout hardware
- SPL ($450) - hex shaped, grooved and includes lockout hardware
- Dinan ($490) - hex shaped

Anything else to consider? I'm leaning towards SPL currently...

[wyatth]

For street use, I'd just go with OE (TRW in the front, not sure about the rear arms). You can add monoballs to the front arms (Dinan, GAS) but the rest don't seem all that important. The aftermarket arms make alignments easier and add range, but it doesn't sound like you need that. They also have some cases of failure.

Your car is awesome. I want that.

[CTMike]

Tremendous car! The GAS monoballs are a very popular option with no observable downside. Generally I’ve read comments that SPL parts are more race oriented than street, which may be a consideration. As far as weight - I think you can take some comfort that, afik, the components you are looking to refresh are all the same across E90/E92/E93 convertible, which adds several hundred pounds over an E92 (someone I’m sure will correct me if I’m off on that)

[MMMM6GC]

Thanks guys!

Been doing a bit of research based on what you've said and for the front tie rods - I'll really need the full assembly, not just the tie rod ends which most aftermarkets are.

Googled around and can't find TRW branded tie rod assemblies. The OEM Bmw full kit is currently $370ish on FCP sale which includes both sides Genuine BMW assemblies + 2 x Lemforder boot and nut, which is a pretty decent price tbf. Can't find the tie rod's themselves made by Lemforder. ECS have a "budget" kit for $236 with the genuine BMW rods replaced with "Hamburg Technic" who I'm not familiar with...tbh I'd pay the extra to get genuine BMW. Can't really see any other option here.


As for the rears, tons more choice here, but OE TRW arms (and hardware) are gonna be around $100/side - less than half the price of SPL.

I guess I just wanted to check I'm not missing a trick while upgrading? Appreciate your point about the cross-compatibility with E93's which are heavier so maybe it's not an issue. Just from reading it appeared these rear arms flex a lot so I thought with the heavier body (this thing squats like a mofo on full throttle) it might be worth an aftermarket option. Also - unsure - but maybe I'd benefit from extra adjustability given the non-stock setup I have to give "more wiggle room" to dial in the alignment.

If I'm overthinking it - I'll just go with OE/TRWs and the FCP OEM kit for the front tie rods!

[MineralWhiteF80]

for a street car, I would 100% go factory everything. You are not going to be stressing the OEM arms/bushings hard enough on the street to warrant the need for spherical bearings. And aftermarket arms with unprotected bearings have several downsides such as increased NVH and accelerated wear.

The only caveats would be are if you cannot achieve a desired alignment spec (caster/camber/toe), then I would buy an aftermarket option that is adjustable to get to your alignment needs.

If you absolutely want to some aftermarket items, you can do the monoball upgrade to the front thrust arms that have no downsides.

[MMMM6GC]

Cheers guys - pretty much settles it - will go for OEM all round! I can wait a week or two before ordering so hopefully FCP's black friday is a good one this year!

[Redd]

You'll be fine with OE arms. Just be aware there are some quality complaints about TRW arms since they moved manufacturing of our arms to Malaysia. Do some research.

I would also highly recommend solid rear subframe bushes. It's just a great upgrade with zero downsides.

Lastly the E93 cabrio comes with an extra underbody brace. Not sure if that will help your E91 wirh the extra weight at the rear. Just a thought.