Contemplating steel over alloy!! - The Unofficial BMW M5 Messageboard (m5board.com)

Sebring NL · 25th June 2007, 13:47

Gentlemen,

As you know I am about to upgrade the Sebring to 345mm floaters.

As I understand correctly, the lower suspension arms on all 6-speeders are steel over my current alloys.

I figure it has something to do with weight of the caliper/rotor combo?

Anyways, some thoughts please.

W

farrell · 25th June 2007, 14:00

Hi Wout
I think that there was an initial drive by BMW with the 3.6 to reduce unsprung mass on the front suspension.

Option1
That went out the window with the Boat anchor calipers & discs whose diameter rival that of Simonals trouser belt.
The unsprung mass went out of the window.
The cost of the vehicle piece parts grew.
BMW just snatched a few Deutchmarks back on the profit ratio possibly by going to steel arms

Option2.
Use steel arms with its greater mass & density for a given size to better damp vibration & peak torque loads under braking.

Thinking cost myself.

Cheers
Faz

Stevie · 25th June 2007, 17:08

Quote:

Originally Posted by farrell

discs whose diameter rival that of Simonals trouser belt.

Think you're confusing those with the new 460x36mm option Sir.....

davidoli · 25th June 2007, 17:21

An unbelievably sexy looking set of brakes !

farrell · 25th June 2007, 18:05

Wow
Somebody pinch me

They must be phenomenal....
19" rims anyone

Lottery winners please form an orderly queue here.

Farrell

Mmm-Five · 25th June 2007, 20:50

I think even 19" rims might be a tight fit

but how badly do I want them

stevie sam · 25th June 2007, 23:25

Beautiful looking caliper if I may say so!!!!

Simonal · 25th June 2007, 23:39

Quote:

Originally Posted by farrell

Option1
That went out the window with the Boat anchor calipers & discs whose diameter rival that of Simonals trouser belt.

Oi

Quote:

Originally Posted by Stevie

Think you're confusing those with the new 460x36mm option Sir.....

That's more like it!

Phlem5 · 26th June 2007, 02:02

Wout, I would do the same if I was in your shoes. Alloy / steel arms have been discussed before and I think cost saving of the steel arms v's the weight saving (approx = to having a good sh1t of a morning) of the Alloy arms, make's it a big thumbs up for Steel.

T Bone · 26th June 2007, 02:15

Hey Wout, if you plan to track the car with the bigger wheels & brakes, I definitely would go for steel arms.

As you may know steel is resilent and don't wear under normal loads. Steel flexes. Almost all aluminum alloys bend to some degree with any amount of force so aluminum alloys have a lifespan. But since you are subjecting the suspension to higher unsprung mass, the alloys may wear out even quicker.

When we were tracking the 944 Turbos, the guys who lowered their cars bought the steel control arms. Control arm collapse was a significant issue with the 944 Turbos.