E46 M3 Caster / Steering Feel Rabbit Hole – Looking for Advice

[Solo.Spec]

Hey guys, I wanted to make a post about an issue I’ve been chasing for a while now because I feel like I’ve gone pretty far down the rabbit hole, and I’d like to hear from people who have dealt with something similar.

On the stock suspension, the steering always felt normal to me. It had decent weight, good return-to-center, and overall the front end felt natural.

The whole issue really started after I installed ST XTA coilovers.

After putting the XTAs on, I started noticing that the steering felt a little strange. It seemed lighter, didn’t return to center as strongly as I remembered, and overall just felt like it had less steering feel. It wasn’t necessarily terrible, but it was noticeable enough that I started trying to figure out what had changed.

At the time, I suspected the steering rack.

I ended up replacing the original rack with a yellow-tag rack. The yellow-tag rack was also fully rebuilt, so internally it should be in good shape. Unfortunately, changing the rack didn’t really solve the issue. The steering characteristics I was trying to fix were still there.

That’s when I started looking more closely at the alignment and, specifically, caster.

With the ST XTA camber plates, I was seeing roughly 7 degrees of caster. I started thinking that getting more caster might help give me some of the stronger self-centering and steering feel I was looking for.

I eventually switched from the ST XTA plates to Vorshlag camber/caster plates specifically because I wanted more adjustment.

Ironically, I ended up going backward.

With the Vorshlag plates pushed to their maximum caster position, my most recent alignment was approximately:

• Left caster: 6.5°
• Right caster: 6.3°
• Front camber: around -3.6°
• Front toe: 0

So I actually lost roughly half a degree of caster compared to what I had with the ST XTA plates.

I contacted Vorshlag and found out that their non-M E46 plate sits about 0.316” farther rearward and 0.5” farther inboard compared with their E46 M3 plate, which helped explain why I was running into limitations with how much rearward movement I could physically get from the M3 plate.

At this point, I’m basically trying to figure out the best way to get as much caster as reasonably possible on the car.

One big requirement for me is that I DO NOT want to cut, notch, grind, or otherwise modify the factory strut/shock tower opening just to allow the top of the strut to move farther rearward. I know some setups can gain a lot of caster if you clearance the tower, but I would really like to keep the chassis untouched.

I’ve also started looking into other ways of gaining caster, including offset FCABs, different camber/caster plate designs, and potentially different coilover setups altogether.

What I’m mainly trying to understand is:

For those of you running lowered E46 M3s on coilovers, what kind of caster numbers are you actually getting?

Especially if you have adjustable top hats, I’d be really interested to know:

• What suspension/camber plate setup are you running?
• What is your actual measured caster?
• Are you at the maximum caster setting?
• Did you have to modify the strut tower at all?
• Are you running stock or offset FCABs?
• How is your steering return-to-center and overall steering feel?

I’m also curious if anyone has gone through a similar situation where the car drove fine on stock suspension, then lost some steering feel/self-centering after installing coilovers.

At this point, I’m trying to determine whether getting back into the ~7+ degree caster range — or potentially higher — is the missing piece, or if there’s something else about the suspension geometry that I should be looking at.

I’ve already changed the steering rack, changed camber plates, played with alignment, and basically chased this thing from multiple directions. Before I keep throwing parts at the car, I’d really like to hear what caster numbers other lowered E46 M3s are actually running and what setups are achieving those numbers without cutting the strut towers.

Any input or alignment sheets would be greatly appreciated.

[bigjae46]

I'm confused...you're running the non-M plates, correct? It sounds like you had the M3 plates?

If you run the non-M plates, which I do, you get more negative camber but give up some caster. I installed 4 PS pump relief shims and the steering is nice and heavy.

[maupineda]

Contrary to what lovers say, the e46 M3 has never had great feel, directionally you want more caster but what else have you changed? Wider tires up front and more aggressive offset? These two will dilute feel a bit, also the steering guibo couple removes some texture, so a solid u joint coupler will help.

if it was me I would run factory mounts set up and confirm is what you say you remember, and from there do the offset FCAB which will add caster and remove pins if you want camber or go to CSL knuckles which will also add a bit more camber.

i have a Z4M and is mildly better but has geometry differences such as the offset fcab, solid u joint coupler and a different steering knuckle ratio. I have the black tag rack which made very little for steering feel. I have coilovers but left the top mounts factory and did not lower the car.

steering talks to me, but is more like a mumbling than an actual chat if that makes sense

[D-O]

To confirm your current results: Vorshlag plates on TCK Da's. Caster is maxed out and I am just short of 7 degrees.

At one point I had Eibachs and the stock top hats and I might have got 7 degrees out of it. I'd have to see if I still have an old alignment printout.

[D-O]

Correction - Paperwork says I get about 6.5 with the Vorshlags and I got 7 with the stock top hats.

[bigjae46]

Correction - Paperwork says I get about 6.5 with the Vorshlags and I got 7 with the stock top hats.

i get 6.5 with non-M plates and at the max caster setting. Meaning I removed the little screws on top...and didn't reinstall with loctite but that's another story 🤬

[sapote]

using the offset lca bushing is not an elegant way to gain more caster as this might cause less front tire track (if the hex end center distance is equal or more than the inner BJ relative to the car center line then for sure you have less track width using the offset bushing) . Why not use a custom offset inner ball joint which shifts the spindal forward and gain more track or less track depending which way to turn the offset ball stud.