01 325 Ci Front Struts

It's pronounced "chassy." Brakes, suspension...things that make the car fun or a death trap
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Adam
Posts: 2240
Joined: Wed Oct 23, 2013 9:50 pm

01 325 Ci Front Struts

Post by Adam »

It's going to be a new car soon. I didn't take take that many (or good?) photos, but it's all pretty self explanatory if you're familiar with Macphereson strut front suspensions.

The struts weren't leaking yet, but did make an audible squish/hiss sound when going over bumps. Based on how they performed, it's likely that the internal seals were compromised, resulting in minimal bound/rebound damping. Since this is a "modern" car, the bump stops are integral to the strut assembly. The OEM ones were toast. You can also see several spots where the paint/coating was flaking off the factory springs.
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These are pinch-bolt style struts for maximum European-ness. There's plenty of rust, as you can see, but after struggling with the first one before applying heat, I went right to heat on the second one and it came right apart.
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Sway bar endlink
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Here's a shot of all the things. You can probably get the strut out if you unbolt the rear control arm mount and swing it in some, but that sounded like a pain (and the factory manual doesn't say to do that), so I popped the ball joint and tie rod end off to separate the spindle from the control arm. Once you do that you can slide the spindle right off the strut.
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For maximum annoyance, taking the upper mount nuts off caused 2 of 3 to spin the studs in the strut which makes it hard to remove. I solved that by cutting the nut in half with an angle grinder with minimal damage to the car. Should have used more penetrating oil.
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Here's what non-ruined stuff looks like.
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For replacement stuff I went with the same Bilstein B4 parts as the rear. For springs, I bought the replacement ones for the factory "sport" suspension, rather than the standard ones for marginally more damping and the same for the bump stops (not sure if the foam is harder or not). The control arms I did earlier are the later "ZHP" replacement ones w/o the rubber outer ball joint isolator (pressed into control arm). In typical German car fashion, I also replaced all the things including the hardware. The bolt/nut cost was only ~$12 (pinch bolts, strut mount nuts), so not a huge cost compared to the rest of the parts. The mounts/plates/washers were a bit more expensive, but the old stuff was mostly rust, so not much of a choice there.

The only remaining thing in the front end to upgrade is a larger front sway bar. This car as the 23.5mm bar which keeps the car fairly flat during cornering, but isn't quite as aggressive as the 26mm one from the M3 (or apparently 27mm on the convertible). Supposedly there was a ~25mm bar available on some of the cars. The M3 bar can be retrofit to the non-M3 cars but requires some shenanigans due to the different strut setup in the M3 and the different end link type. Maybe some time in the future when the links/bar bushings need to be replaced I'll consider some sort of upgrade. Aftermarket stuff is unreasonably priced (to me) at ~$500/set.

I've been driving on it for a few days now. Here are some words:
Pros:
- Much more controllable bump performance over terrible roads at normal speeds
- Firmer front end feel, but not sure how much is the stiffer springs vs. the not-worn-out stuff

Cons:
- Still under-damped when driving aggressively
- You do need to get an alignment after replacing these, I'll do it later cause it isn't terrible (very mild pull to the left at highway speeds)
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