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Steel vs. Aluminum in flexability

PB Forum :: Dirt Jumping & Street
Steel vs. Aluminum in flexability
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flag nwatkins
Posted: Jan 27, 2008 at 14:14 Quote
BMX8000 wrote:
Man NS has the sickest website ever.

What makes it even sicker is NS stands for no-shit. (just figured that out yesterday)
flag dandriller
Posted: Jan 27, 2008 at 14:16 Quote
Steel is a little more flexible compared to Aluminum. Steel is more forgiving when it comes to bumps on the trails, but aluminum is lighter.
flag fugger
Posted: Jan 27, 2008 at 14:21 Quote
4130 Chro Mo Steel...!
It holds up to the sledge hammer test...
<Photo does not exist: 1606864>
Aluminum does not...
flag Charmander-mtb
O+
Posted: Jan 27, 2008 at 14:33 Quote
Titanium!!!! It flexes like steel and weighs less that aluminum!!! .....its just really really expensive
flag srobinson
Posted: Jan 27, 2008 at 16:36 Quote
fugger wrote:
4130 Chro Mo Steel...!
It holds up to the sledge hammer test...
snip
Aluminum does not...

A steel frame would have a nice bend right there. Aluminum has less flex and is more likley to break, steel, felxier and more likely to bend. Nearly and Cro-mo/steel/chromoly bike are made out of 4130 so don't let that confuse you. As far as riding goes I can't really feel much of a difference between the two, I think it would be more important to be messing with wheel lacing and tire pressure to absorb the impact.
flag shacabahalla
Posted: Jan 27, 2008 at 16:51 Quote
Charmander-mtb wrote:
Titanium!!!! It flexes like steel and weighs less that aluminum!!! .....its just really really expensive

Titanium does not weigh less than aluminium

Some aluminium frames are designed to be more flexy than others.

Titanium is renowned for its abilty to cut the out trail buzz.

Your best bet if your back is on the way out, is stop ridin hard or switch to a full suspension bike
flag ricar
Posted: Jan 27, 2008 at 20:38 Quote
Cro-mo welds melting??????? I have never heard of that before. Also since ALU is heat treated at about 300 deg and cro-mo at over 1000, I seem to have trouble beliveing an Alu frame would make it down a hill. Alu is NOT weaker than steel (not that it's stronger) BUT it is lighter and stronger by weight. That means a 2lb tube of cro-mo will not be as strong as a 2lb tube of Alu. The problem is, Alu work hardens. That means when it flexes the molecular structures bind and the tube will become very stiff. Continued flexing will break the structures and the tube will develop hair line cracks. These cracks are only visable with processes like magna fluxing. Leading to another problem with Alu, method of failure. Aluminium has a tendancy to tear (bad). So manufacturers have to design a frame that will not flex, so it will ot work harden, and not fail. So Alu frames are designde to be stiff. Cro-mo is more forgiving of flex and has a safer failure mode, generally cracks develop and the frame feels weak, ot only one tube will break and the other will bend. 4130 tubing is required to bend at room temp without cracking. Also cro-mo is better suited to abrasion than aluminium which in the street world is a good thing. In the end do you want a stiff frame or more flexable frame? Alu does not suck, it just depends on weather it fits your needs. Also the life expectancy of a steel frame is MUCH longer than Alu. As far as racing frames, Alu is 3 months, steel is 3 years. This of course does not include other versions of steel (like the super hard tubes from reynolds) and different Alu's now available for bike frames.
flag dandriller
Posted: Jan 28, 2008 at 5:28 Quote
Somebody paid attention in science class!
flag spongebomb
Posted: Jan 28, 2008 at 5:45 Quote
that was probably the most usefull comment on pinkbike tup
flag BMX8000
Posted: Jan 28, 2008 at 6:55 Quote
spongebomb wrote:
that was probably the most usefull comment on pinkbike tup

thatguydave wrote:
Somebody paid attention in science class!

I would definitly agree on that.
flag doctorz
Posted: Jan 28, 2008 at 7:11 Quote
Steel tensile strenght ratio is higher and more resilient than aluminium if you make a huge drop the recoil will depend on how well the bike is structure and weld as for alu it will collaps at his weakest point i had steel bike all my life and never had a problem with them ever and ive weld steel for over 15 years so i know how to set up geometry to make them last as for your original question it all depend how you land if your going to injure your back i sau use your leg better and do so exercise there where its needed

pound for pound steel is lighter when its custom drawn compare to alu my buddy bike is heftier than mine and we both have the same set up( same parts) his weight 51pnd and mine 48 pnd
flag huckoveraduck
Posted: Jan 28, 2008 at 8:35 Quote
ricar wrote:
Cro-mo welds melting??????? I have never heard of that before. Also since ALU is heat treated at about 300 deg and cro-mo at over 1000, I seem to have trouble beliveing an Alu frame would make it down a hill. Alu is NOT weaker than steel (not that it's stronger) BUT it is lighter and stronger by weight. That means a 2lb tube of cro-mo will not be as strong as a 2lb tube of Alu. The problem is, Alu work hardens. That means when it flexes the molecular structures bind and the tube will become very stiff. Continued flexing will break the structures and the tube will develop hair line cracks. These cracks are only visable with processes like magna fluxing. Leading to another problem with Alu, method of failure. Aluminium has a tendancy to tear (bad). So manufacturers have to design a frame that will not flex, so it will ot work harden, and not fail. So Alu frames are designde to be stiff. Cro-mo is more forgiving of flex and has a safer failure mode, generally cracks develop and the frame feels weak, ot only one tube will break and the other will bend. 4130 tubing is required to bend at room temp without cracking. Also cro-mo is better suited to abrasion than aluminium which in the street world is a good thing. In the end do you want a stiff frame or more flexable frame? Alu does not suck, it just depends on weather it fits your needs. Also the life expectancy of a steel frame is MUCH longer than Alu. As far as racing frames, Alu is 3 months, steel is 3 years. This of course does not include other versions of steel (like the super hard tubes from reynolds) and different Alu's now available for bike frames.

about the melting - you missed the part where I said I was taking the piss! lol
flag doctorz
Posted: Jan 28, 2008 at 10:29 Quote
4130 is not the weakess but tone of the hardess to weld you need a high end mig to weld this nasty steel by far one of the best steel there is even once its heatreated
flag goodbyepinkbike
Posted: Jan 28, 2008 at 11:08 Quote
not sure but u'd b best to get a full sus for ur back. tho it will be no good for street.
flag doctorz
Posted: Jan 28, 2008 at 11:45 Quote
you have a point there are many type of rear suspension that could be good for street

 


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