[F87source]

Originally Posted by M Fifty

Good picture. This is what I meant when I said that the unsupported length of the BMW CF brace was clearly not a problem given that in front end impacts it was the bracket that failed first. So it's pretty good in compression as well as tension.

You still don't understand the difference between rigidity and tensile strength. The brace clearly has massive tensile strength to the point where the bracket fails first, however that doesn't address anything about rigidity or the ability to transfer it.


The longer the lever arm the more susceptible it is to flex, hence why a long piece of wood will bow in the middle vs. a shorter piece of wood which will not bow. Bolting down the brace in multiple places shortens the lever arm reducing any mechanical advantage reducing flex and increasing its ability to transfer forces to the brace making it more rigid. This is basic physics....

Originally Posted by M Fifty

Yep those are where the BMW Aluminium brace attaches to - and the CF part bolts to it. My point was that the Turner Braces don't. HTH?

The turner brace does bolt to the strut tower, take a look at the bracket where the stock brace bolts to. It's welded to the tower...

Originally Posted by M Fifty

Also bollocks.

Your favoured product needs to mount in exactly the same way as the M4 brace for this to be even remotely true, plus when was the last time you flew on a steel aircraft? To match the stiffness, the steel item will end up heavier.

Maybe if you clarify what you mean by wheelhouse? The M2 isn't a ship, so doesn't have a rudder...

1) You don't understand the direction of movement of the strut tower do you? When the tower moves towards each other or away from each other the best bracing position is between the towers, that offers the best way to transfer forces. The m4 aluminium brace is angled and cambered so all the force are now acting on an angle to the brace in a direction where there is less material reinforcing it making it weaker - this being the joint.

A stronger material doesn't necessarily brace better than a weaker material if it takes the forces in the wrong direction. The stock aluminium m4 brace has to take forces for every direction, and its design isn't strong in every direction. If the strut towers are moving up or down all the forces go to the joint which isn't reinforced well.


You also need to remember a tubular item is stronger in design because it can take forces in all directions, whereas a flat piece is stronger in the axis of its thickness. So in some directions the m4 brace is strong in some directions it is weak, a tubular piece is stronger in more directions.


2)

a) Youngs modulus, which is taken into account by cross sectional area (so size) per unit area steel is far more rigid than aluminium: https://www.thefabricator.com/thefab...0of%20aluminum.


b) Yes you get a weight penalty but the rigidity is 3x higher, so depending on aluminium grade the strength to weight ratio vs. a steel grade may not make up for it.


Also density is a contributing factor. Aluminium has a lower density than steel, so a same size object is lighter but not stronger. For example an m8 aluminium bolt is the same size as a grade 12.9 steel bolt, it is lighter than the steel bolt but it is many factors weaker. When braces are made size is taken into account too, so for the same size piece steel is stronger despite a weight penalty.

Why do you think critical components are not all aluminium? Roll cages, crank shafts, rods, etc. Because to make aluminium as strong it has to be too big. Even steel wheel bolts are better than titanium wheel bolts, because for the same size titanium isn't strong enough.


Planes are aluminium because the strength to weight ratio is strong enough to satisfy the fuslage requirements. But take a look the landing gear isn't aluminium. Ships aren't aluminium, because it would take really thick sheets of aluminium to meet the strength requirements.


Weight isn't the only question, design matters too.


So in summary a similar size item steel is going to be heavier but it'll be stronger. The only way aluminum gets stronger is if it's the same weight but that means it'll have to be much bigger than the steel part. In terms of weight vs. strength of aluminum vs. steel it is so dependent on grade of either material and design. So its hard to say how much weight you'd be saving with aluminum to get a similar strength.

In a space sensitive area the weight trade off for a tubular steel part like the afe part would be worth it over aluminum because it'll be so much stronger.


Either way the stock part is the stock part, a pretty damn good design but I believe an aftermarket strut tower brace will easily outperform it. Especially the afe brace, that thing is a beast.



c) I explain explicitly what the wheel house is in my review.

Originally Posted by M Fifty

I'm aiming for where the goalposts appear to be in your posts?

You bring on new unrelated topics each time I answer.

Originally Posted by M Fifty

It certainly doesn't - as you say. Whether the aftermarket products highlighted here are more effective than the M235i Racing items reused on the F8X M3/M4 and M2C (as asserted by the OP) - rather than merely being cheaper - is my issue with the OP.

I also have doubts about the cost effectiveness of the aftermarket products highlighted here compared to the BMW items as they are bolted in locations that appear to offer less bang for the buck and major on the cosmetic aspects. If they attached to the strut towers using the mounting points for the strut tops and then tied in the mounting points for the corner braces, that would be a compelling alternative offering.

HTH

The corner braces are more for wheel house bracing, not solely strut tower. The carbon m4 brace doesn't even attach to the wheel house region so how can it even come close to providing more rigidity for this area. Add in a strut brace made specifically for the movement of the strut towers (in a material far superior than aluminium such as carbon) then it will out perform the bmw solution.

Originally Posted by M Fifty

Looking through RealOEM (which does have a number of errors), the earliest F8X (M3/4) came with a CFRP front brace with the part number 51618061631 (weighing 2.295 kg). This is listed as being used from 03/03/2014, which is inconsistent with the launch date of the various models. It is however listed as superseding 41008417085 (weighing 1.862 kg) but that is only listed for the M235i Racing from 11/01/2013.

This suggests that the brace predates the M3/4, even though the dates don't match.

So, there are now two scenarios:
1. BMW developed a chassis bracing system for motorsport use which they subsequently adapted for use on road cars for marketing reasons.
2. BMW developed a chassis bracing system as a marketing device, and subsequently used it for motorsport applications (but tried to make it even lighter and subsequently replaced it with a stronger item).

In the former case they will have prioritised effectiveness (so a trade off between weight and stiffness) while minimising cost. Using it on road cars was primarily a marketing solution (as said road cars would be unable to exploit the benefit), but it wasn't cost prohibitive and did actually work.

In the latter case, the marketing solution would have prioritised bling while minimising cost. While wishing to maximise the marketing potential, it would only ever have been used for motorsport if it provided a benefit that couldn't be realised more cheaply using other means.

In both cases, had just beefing up the corner braces yielded significant benefit, we could reasonably expect to see something like the Turner items on the M235i Racing (or just thicker versions of the wriggly tin items rendered in steel or aluminium), as there would be a compelling cost/benefit and weight reduction benefit compared to what they did come up with for marketing or motorsport use.

Having fitted the BMW supplied uprated parts on three cars now (R53, E46, F87), the difference can be felt in the steering while turning when going over camber changes and rumble strips at both low and high speeds. So, they are doing something.

If you can't feel any difference when using products from other suppliers, that doesn't mean they aren't making an improvement to your car's handing, but away from a track day with data-logging - how would you know?

But, they are significantly cheaper than BMW's solution, and - in concert with additional strut bracing - might result in a difference you can feel rather than only measure with data-logging on track.

HTH.

Parts availability is always lagging behind chassis availability. The m3/m4 was in production long before the m235ir (and thus designed even earlier), so clearly the parts came from the m3/m4...


The corner braces were only released with the cabriolet models and were designed to meet a budget target. Why would bmw spend even more making molds and tooling when they could reuse the f8x bits.


BTW as I said before as a total package the m4 brace offers better performance. It is only when you add strut tower bracing the corner braces become better, as it more effectively braces the wheel house.