Aluminum Vs Steel

[FRpilot]

i want to start a debate between aluminum and steel parts. which one would you guys prefer and why? i know that aluminum is lighter than steel, but how strong is that stuff? my friend said aluminum is better than steel for certain parts. what i'm talkin about is suspension and bracing parts in particular. for example, would you rather have an aluminum strut tower bar or steel? how bout do-lucks tension gauge set and floor support bars. they have aluminum and steel versions. wouldn't steel be better since it should be stronger and thus stiffer for bracing? what im worried about is aluminum crumbling up under pressure. i would love to have a lighter car, but im not sure if aluminum is strong as steel for bracing purposes. how bout aluminum coilover casing vs steel. i was looking into zeal functions and they offer the b6 (steel) and s6 (aluminum). which one would you guys go with?

[RBS14]

Roll cages are steel for a reason. To hell with metal... just go with CF. hahaha

[transient]

Well, I'm by no means an expert in this area, so feel free to correct me, but here's my understanding.

Steel is ultimately stronger than aluminum, but it also tends to be more flexible at the same time. Therefore something like a strut tower, which doesn't take a huge amount of stress, but needs to be very stiff, is much better suited to aluminum than steel. Aluminum also has the benefit of being resistant, if not impenitrable, to rust. It's much lighter weight as well.

One must not forget, however, that the engineering of a part has as much to do with the structural integrity of something as the material that it's made from.

[wpayne]

I think transient put it very well. I too *think* that if the component can be engineered efficiently in a way that the structural rigidity/shape/etc is not compromised or where the component is not be pushed pass it's stress limit(like the tower bar) with it's given use, then go with aluminum. Have the advantage of it being lighter too.

If what you need is strength or where aluinum just won't do, go with steel(stainless of course).

edit: Then again, I gues there are sometimes(can't think of one now) where you need a little flex, a little give, to absorb some of the stress. I guess thats why you use steel when you need more strength. Okay, nevermind.

[240racer]

Originally posted by transient
Well, I'm by no means an expert in this area, so feel free to correct me, but here's my understanding.

Steel is ultimately stronger than aluminum, but it also tends to be more flexible at the same time. Therefore something like a strut tower, which doesn't take a huge amount of stress, but needs to be very stiff, is much better suited to aluminum than steel. Aluminum also has the benefit of being resistant, if not impenitrable, to rust. It's much lighter weight as well.

One must not forget, however, that the engineering of a part has as much to do with the structural integrity of something as the material that it's made from.

aluminum corrodes, but it's not called rust, because it's not iron oxide.

one must also not forget that almost every part you buy for your car is made more for how well it will sell then how well it will work. IN other words I bet not one of those strut bars has had an engineer do calculations on them. They are big enough that they look stiff and small enough that they look and feel light, that's it. if it matters then you need an engineer to do calculations, if not, then it doesn't matter what matterial it is anyway.

Just to further confuse the issue, which is stiffer a 1" tube of steel or a 1" tube of Al (same ID)?

[s13rookie]

steel is stronger, by far. try milling through aluminum and than try milling through steel. no contest. but if done correctly, an aluminum part can be lighter and stronger

to make it simple look at it like this

say you have a 1" diam tube, made of steel at a .125 wall thickness.that weighs 10lbs, and can support 1000lbs

you can have an aluminum bar, 1" diam., .275 thick, supporting 1000lbs, but weighing only 9 lbs

yes my numbers are a bit off, but for the sake of illustration

does that mean i would prefer an aluminum engine block to an iron block? not really, i would however prefer aluminum wheels to steel

[s13rookie]

also thou, flex is not ALWAYS a bad thing.

i used to be a big bmx'er. had a few alum frames, but most were good ol chromoly(4130). i was happy in the exchange between a few less pounds and stiffness versus a few extra pounds and a bit of flex, ecspeccially if a lil bit 'o flex would save you from snapping a head tube gusset