Slon Workshop E46 M3 Carbon Front Triangulating Reinforcement Kit

[Obioban]

Yea, but isn't the entire point of living in a god forsaken winter hellscape to save money so you can do cool shit? Like to make your M3 the best it can possibly be, for those precious few moments you have to enjoy driving it?

Also, snow driving is the best driving, so long as nobody else is around.

[jet_dogg]

I understand his point. $5k buys a lot of parts, mods, tunes etc on other cars. This particular part is more of a sign of the "excessiveness" that the E46 M3 platform is evolving into (excessively priced NLA or maintenanceparts, excessively priced mods, excessively priced entry point) and the excessiveness continues to rise, kinda more into Porsche territory. Pretty hard to justify $5k for a big dog single item strut brace even if it massively improves the car when you can spread that $5k out and do more bang for the buck improvements on other cars.

Dude isn't ballin with a new manual Supra because he unwisely spends his mod money, that's for sure.

Five bands ain't shit when you got six cars.

[tnord]

I was intrigued by this until I saw the price tag. There are certainly scenarios where you can rationalize it's purchase (if I bought a different car, I'd be burning $5k in sales tax alone), but that much money would be better spent elsewhere on my particular car. I feel like this is one of those things you should buy once everything else is done.

[Sprp85]

How would the benefit of the CF roof compare to the brace? (Weight reduction/perhaps some increase in rigidity?)

I would guess the final cost would end up being similar, around ~$5k?

[CrisSilberGrau]

How would the benefit of the CF roof compare to the brace? (Weight reduction/perhaps some increase in rigidity?)

I would guess the final cost would end up being similar, around ~$5k?

The inclusion of the roof bow with a slicktop brings the chassis rigidity to that of the CSL, about 18,750 Nm (units unsure going from memory). and if youre going from sunroof to CF you lose about ~50lbs off the top of the car and gain at least 1in of head room. The CF roof install is a lot more involved and the car would have a ton more down time depending on the speed that you go and how many other "while youre in there" things you decide to tackle. Price comparison might be similar, in my case id have to do new windshield, cowl, maybe rear too, roof rails, insulation, adhesives, etc etc. adds up. If I were to choose one right now I'd do the roof, more benefits for the driver in terms of room, im 6'3" and even with Nogaros im not 100% comfortable.

Both are endgame mods/additions. I think Obioban can delve deeper into the weight benefits of the brace vs the roof. From the looks of it, the performance benefit is definitely on the strut side vs the roof. ~20% frontal rigidity increase is pretty insane, you pay mega do re mi in the racing world for a fraction of that. Goes to show you how much more is left in this chassis performance wise.

[Bry5on]

It’s about 3% less body roll from going from sunroof to CF roof, I modeled this in my build thread. I’d bet that the strut brace would be the more noticeable of the two modifications. Reason being that the strut brace is likely to have a larger impact on steering feel since it stabilizes the strut towers and front longitudinal crush rails.

While I didn’t do a CF roof, I did go from a roof rack setup to no roof rack, which was heavier than a sunroof and reduced body roll by 5%, by the math a bigger change.

Maybe Slon will also test torsional stiffness change of adding the roof so we can have some objective data to go from.

[IamFODI]

Interesting to think of penalty-free chassis stiffening and weight reduction as endgame mods. They're literally the first things I'd do on any car. 🤷♂️

[repoman89]

CF roof isn’t a noticeable change on its own IMO. It’s barely a 1% change in weight and a marginal increase in rigidity from BMW’s numbers. Maybe if you’re incredibly highly attuned to your car on the track you could barely perceive a difference at the cornering limit, since the lost weight is up high. Definitely not on the street. I do have a Karb roof on my car so not just saying this because poor and jealous.

The increased headroom is great and the weight loss per dollar is also surprisingly good as a component of an actually noticeable 5-10% weight reduction.

[Nate047]

Interesting to think of penalty-free chassis stiffening and weight reduction as endgame mods. They're literally the first things I'd do on any car. 🤷♂️

Not really though, if we're being honest. Take a completely stock E46 M3, and list the first $10k of improvements. Those items are definitely not going to be a roof and CF strut brace. You'd do wheels, tires, brake pads, suspension. Assume the car has the big 3 already done, and is refreshed already so that doesn't even include any bushings.

The brace and the roof come later when the curve of cost vs benefit starts to flatten out, which is where OP's car is at after years of ownership, setups, and trying different things.

[Obioban]

How would the benefit of the CF roof compare to the brace? (Weight reduction/perhaps some increase in rigidity?)

I would guess the final cost would end up being similar, around ~$5k?

The CSL is only stiffer than the M3 coupe because of the CF roof.
CSL: 18,750 nm/deg
M3: 18,500 nm/deg

So, the CF roof is good for a ~1% increase. The reality is probably a bit more favorable than than, because the lighter you car is the less stiffness it needs (as in, less forces acting on it to bend it).

As above, the benefits of the CF roof are really lowing the CoG and increasing head room. I actually do think you can feel the difference if you're coming from a sunroof car (I did), but it's certainly not as dramatic of a change to driving experience as this brace. That said, being able to fit in the car with a helmet without reclining was a HUUUUUGE upgrade for me.

Price is similar if you're paying for labor. If you're DIYing (which I would not do again on the CSL roof-- it was probably the worst project I've done), the roof is cheaper.

Interesting to think of penalty-free chassis stiffening and weight reduction as endgame mods. They're literally the first things I'd do on any car. 🤷♂️

Subframe, vanos, rod bearings are my day 1 "mods"

CF roof isn’t a noticeable change on its own IMO. It’s barely a 1% change in weight and a marginal increase in rigidity from BMW’s numbers.

1.5% weight change from stock!

I think it's the lower CoG that's noticeable, more than the absolutely lightness. But, 50 lbs is nothing to sneeze at-- very easy to detect a small female passenger in the car from the driver's seat, and that's only ~2.5X the roof weight.

[repoman89]

1.5% weight change from stock!

I think it's the lower CoG that's noticeable, more than the absolutely lightness. But, 50 lbs is nothing to sneeze at-- very easy to detect a small female passenger in the car from the driver's seat, and that's only ~2.5X the roof weight.

Agreed, that’s why I did it as a component of dropping weight off the car. Personally I didn’t notice it on its own but do notice 3-4x the 50 pound difference of the roof from say a passenger, as you say.

[heinzboehmer]

(which I would not do again on the CSL roof-- it was probably the worst project I've done)

Bet you're really looking forward to installing the rear wall then

[usdmej]

Interesting to think of penalty-free chassis stiffening and weight reduction as endgame mods. They're literally the first things I'd do on any car. 🤷♂️

it's the price relative to the cars worth that makes it an end game mod it seems

similar to buying a small starter home and the first thing you do is to add a 3 car garage with lift to it. i mean, it makes sense to me, but most people would defer that mod to later on down the line

[Obioban]

Bet you're really looking forward to installing the rear wall then

It was drilling out the spot welds that I really hated.

[tnord]

as expensive as this is, I've been of the opinion for a while now that every real upgrade/maintenance item this car needs, if done correctly and completely, pretty much comes down to $5k.

full exhaust? $5k
suspension with bars and endlinks? $5k
brakes? maybe not quite $5k but it's not far off.
RACP with full rear end refresh? might be even more than $5k, that's the one I haven't done yet.
VANOS+bearings with new engine mounts, gaskets, and I did the cooling system at the same time. $5k.
Airbox with MAP conversion, maybe DME update, and a tune? $5k.

ok maybe that's a bit of an exaggeration but that's what it feels like.