Frame preference: aluminum or steel?

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10/27/2012 6:29 PM
Edited Date/Time: 10/27/2012 6:30 PM

Hellion posted this in another thread and I figured it would be a decent discussion topic: "I wonder why everyone thinks aluminum frames are the way to go. Listen to guys who test bikes for a living, and some very well known pros who have said they prefer the forgiving nature of a steel frame." Obviously, there are pros and cons to either frame and it ultimately comes down to personal preference. So, what is your preference and why?

When KTM stuck with steel frames for their 350 and 450 it kind of made me question the general consensus that an aluminum frame is superior to a steel frame. This past year during the Phoenix supercross, Ricky Carmichael was speaking very highly of the benefits of a steel frame on slick and hard pack track while Dungey was out front. So much, that I kind of got the impression he prefers steel frames over aluminum.

I really do not have enough riding experience on an aluminum frame dirt bike to have much of an opinion. I have developed a strong preference for steel frame mountain bikes over aluminum due to the flex, which has kind of caused me to question replacing my steel framed YZ125 for a newer aluminum framed version.

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10/27/2012 6:37 PM

Went from an 09 Kx450f to a 05 Kx250 and I exponentially prefer the steel framed smoker. Feels like going from driving a pick up to a sports car.

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" To hell with them. When history is written they will be the sons of bitches - not I. "
Harry S. Truman

10/27/2012 6:39 PM

Good Thread dude,

Hmm, for me (not being fast enough to know a difference)

I will say i like the rigidity of the aluminum frames on milestones vet track and comp edges vet track. I also like the feeling of the big frame on the inside of my boot... why i have no idea lol

Now my steel frame 2001 yzf feels more plush all the way around. Not suspension wise, it just feels more forgiving if that makes sense.

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"Life is Too Short To Last Long"

10/27/2012 6:41 PM

I know I really enjoy the handling of my 02 yz, as well as the 03 rm I had. To me my suspension is a bigger factor than my frame, but I'm sure the faster you are the more it comes into play, unless your talking early aluminum Honda frames which anyone would hate.

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10/27/2012 6:52 PM

I have bikes in both metals that I like. My 03 CR125 handles great. My 12 250sx and 95 CR250 steel frame bikes are both phenominal handling bikes. I think the older, lower bike just might turn best. the B kit forks and Ohlins shock don't hurt either.

[LINK TO IMAGE]
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21 TC125
09 CR500AF
08 Ducati Hypermotard
03 CR125
05 YZ125
95 CR250
83 Husqvarna 125XC

10/27/2012 6:55 PM

I prefer the steel frame. Not that I'm fast enough to "feel" the difference when riding, but the bike is more comfortable to ride to me. Seems thinner and easier to corner, if that makes any sense.

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10/27/2012 7:02 PM

My opinion is the only bikes the average person could try and compare would be the '02-'04 YZ's and '05+ YZ's because I believe they have the same geometry. All other AF's are way too different geometry and suspension wise than their steel frame counterparts.

Even the steel framed YZ's had smaller forks (46mm open cartridge) and softer springs compared the AF's (48mm closed cartridge).

To say I liked my '02 YZ 250's steel frame better than my '09 CRF 450's aluminum frame doesn't hold water to me because there way too many other variables that make these two bikes different than just the frames.

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10/27/2012 7:15 PM

I'm not a engineer but there doesn't seem like there could be any more room than an inch of play in a steel frame. It seems like that amount could be made up in the suspension somewhere. My decision comes down to which one will last longer without the welds becoming compromised. Having said that, I have only ridden an aluminum frame and can't say that I would know the difference in aluminum and steel.

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10/27/2012 7:23 PM

I went from a 02 RM125 to 06 YZ125 to 07 RM250.

The YZ was way to stiff and rigid even though the suspension is consider the best out there (SSS).

Since getting the rm250 I haven't look back once.

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10/27/2012 7:29 PM
Edited Date/Time: 10/28/2012 5:58 AM

steel is easier to modify or fix for a custom fit or after a crash.
Aluminuim doesn't flex as much and the hours it takes to scotch brite the rails to tune it aren't worth the work.

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10/27/2012 7:29 PM

anyone who isnt an experienced test rider or a fast pro couldnt tell the difference imo

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10/27/2012 7:43 PM

exsarg wrote:

anyone who isnt an experienced test rider or a fast pro couldnt tell the difference imo

Like I said that does depend on the generation of frame though.

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10/27/2012 8:25 PM

slipdog wrote:

My opinion is the only bikes the average person could try and compare would be the '02-'04 YZ's and '05+ YZ's because I ...more

Slippy droppin some knowledge, how ya doin brudda? Dude i was using google to search my website/server for a pic, check out this thread that popped up, holy OTB Batman!

Bonds OTB

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-OC
"Feed The Bull"
Twitter: @ocscottie | Facebook

10/27/2012 8:28 PM

exsarg wrote:

anyone who isnt an experienced test rider or a fast pro couldnt tell the difference imo

X2.

However, I noticed an ENORMOUS difference when I got my '05 YZ125 (it was my 7th YZ125 since 1997.) YZs are very stable and don't usually turn as well, but the aluminum frame woke that bike up. It was still solid as a rock in a straight line, but now it was more flickable and turned better. That bike was 10 pounds lighter than its predecessor, so that couldn't have hurt!
For those reasons, I prefer the aluminum framed YZ 2-strokes. I have never noticed the "harshness" of aluminum vs. steel.

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Braaapin' aint easy.

10/27/2012 8:30 PM

exsarg wrote:

anyone who isnt an experienced test rider or a fast pro couldnt tell the difference imo

I disagree. Ride an aluminum road bicycle and then a steel or carbon. The aluminum will beat you to death. I hopped on a aluminum crf off of my steel yzf and didn't like it. Tried a 02 cr250 and didn't like the rigidity either.
,

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10/27/2012 8:32 PM

I recall KDub once talking about being able to tell if his bike had a skidplate on it or not, and even what it was made out of! ill have to ask Izer for more about that, think it was on DMXS and it was one of the most interesting stories i have ever heard.

Can you imagine being able to tell such small differences, and details? I was blown away by it, wish i remembered it more clearly.

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-OC
"Feed The Bull"
Twitter: @ocscottie | Facebook

10/27/2012 8:47 PM

Steel. feels better and its less material and just as strong as aluminum. the downside to steel is rust. aluminum doesent & stays clean for the most part,
Photo

2005 KX250F

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Run what you brung, and hope you brung enough,"

"when in doubt throttle out!" Braaap

10/27/2012 9:09 PM

Al frames, especially Hondas, have been "softened" to feel more forgiving &...ultimately more like steel. Meanwhile, steel frames, namely KTM, have been made stiffer; yet, still VERY forgiving.

I'm gonna test an Ubber new "steel" 500 this week; so, we'll see (2013 chassis/500cc 2t).

I've been fortunate enough to have REALLY well suspended modern thumpers; so, I really dig the modern Al chassis...

As I get more involved in some new "Development" work that's Very Influenced by some ol'school guys that INSIST that KTM's new frames are awesome...well...we'll see...

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Nobody ever told me, I found out for myself. You've got to believe in foolish miracles. It's not how you play the game, it's if you win or lose. You can choose. Don't confuse. Win or lose. It's up to you!

10/27/2012 9:15 PM

Hint: there's a real Teaser on this subject posted in the LaPorte thread...

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Nobody ever told me, I found out for myself. You've got to believe in foolish miracles. It's not how you play the game, it's if you win or lose. You can choose. Don't confuse. Win or lose. It's up to you!

10/27/2012 9:31 PM

ocscottie wrote:

Slippy droppin some knowledge, how ya doin brudda? Dude i was using google to search my website/server for a pic, check out ...more

Hahaha, I was doing fine 'till I clicked on your link! Now my head, wrists, ankles and shoulder hurts... And I haven't even ridden in a few months. dizzy

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10/27/2012 9:46 PM

steel for sure. I've rode KTM for a while now and when I stepped on my buddies KX I couldn't believe how much more that aluminum frame beat me up.

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10/27/2012 10:41 PM
Edited Date/Time: 10/27/2012 10:41 PM

Fuck do i know, i have been riding steel KTM frames for as long as i can remember.
The only 'big 4' bike i had was an 2005 r6.

The steel framed bikes that i have riddin' never gave me that 'klick' handling wise that i had with my KTM's.
it all comes down to personal preference i guess. It's quite funny all the japs hop on the same boat though.

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10/27/2012 10:59 PM

Aluminum, and they def stretch out after a few good sessions

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10/28/2012 1:06 AM

I had the 04 YZ 250 2 stroke and the 06, and while both bikes were awesome, to me they felt very different out on the track. As you'd expect the 06 was noticeably more rigid. In most situations I preferred the 04's steel frame, I had an especially good feeling with that bike whereas my 06 was just OK, never terrible though.

Again neither is bad these days but personally I think steel is an inherently better material for the job of an MX bike frame. It's strong yet can flex, whereas it seems the manufactures once had to go to great lengths to work some flex back into their aluminium frames. The weight savings don't exist either - KTMs steel 450 SXF frame is the lightest frame in the class.

Steel is also easier to weld if necessary and usually easier to work around.

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10/28/2012 4:45 AM

got to be the steel frame for me rode cr's on them and then changed to the ali frame gen1 frame and hated it so rode the steel frame till 02 then switched to the newer ali frame and although better the power wasn't good so went to a yz again steel framed then on to the yzf250, in 06 onto a rmz and i couldn't get it to turn aswell so tried a 06 yzf with the ali frame and it would get me all out of shape on certain jumps at times never could tell what it was going to do.

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10/28/2012 5:54 AM

I spend a lot of time on bicycles, and unfortunately most of my spare coin goes to moto. So, when I made a bad choice of getting an aluminum framed bicycle I was stuck with it for a few years and I hated it compared to my chromoly frame. There is for sure a difference in feel of the two materials. Ten years down the road and the aluminum frames have been tweaked enough that they are not near as harsh as they were at first. But they are still a pain in the ass to work on, just getting to everything takes so much more work. I'm sure the japanese manufaturers aren't going back, probably ever. I just hope KTM stays real. As the bike geeks say "steel is real".

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10/28/2012 6:20 AM
Edited Date/Time: 10/28/2012 6:26 AM

An aluminium frame is pretty much always stiffer than a steel frame.

To get the same strength with aluminium you need more material, this means larger tubing, castings, forgings etc.

Larger tubing means a higher stiffness because of its higher area moment of inertia.

Using advanced aluminium alloys an aluminium frame can be a lot lighter (6065, 7075 in T6 annealed condition), because of their higher specific strength. This also brings down the stiffness because you can use smaller tubing.

But remember that proper engineering meaning clever placement of materials can make a steel frame very light.

Note that stronger alloys aren't stiffer, there is no change in the Youngs modulus.

Steel generally is more resillient, which means it can take more energy and still return to its normal shape. This also is a factor for handling.

Note that both steel (KTM uses 25CrMo4 steel) and aluminium frames need to be carefully heat treated after welding. After repairing these frame you need to properly anneal and stress relieve the frame to achieve proper strength.

A lot of homegrown poorly converted frames (change in stress concentrations, flex charasteristics, not properly annealed) hold up because most people aren't fast enough to really stretch a frame to its limits. But this can happen if you are.

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10/28/2012 6:34 AM
Edited Date/Time: 10/28/2012 6:43 AM

Last year of the steel frame yz had 48 mm forks.
Al is cheaper to make because they can use castings. Also machining costs are lower because Al is softer.
Al is more difficult to weld , but this is not a factor on a production line.
Young's modulus for Al is 69 Gpa , steel is 300 gpa, Ti 105.
If two beams are the same dimensions in cross section and are loaded the same, the lower modulus beam will flex more.
Even though Al should be more flexy due to the lower E mod, the frames are always more rigid than steel.
Al does not have an elastic yield point. It begins plastic deformation as soon as it starts bending. The frame must be designed to be rigid because any amount of flexing would fatigue it.

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10/28/2012 6:54 AM
Edited Date/Time: 10/28/2012 6:58 AM

unknownmxr wrote:

Last year of the steel frame yz had 48 mm forks.
Al is cheaper to make because they can use castings. Also machining costs ...more

I am not trying to be an ass, but some things you state are incorrect.

Aluminium is not cheaper to produce per se. Aluminium can be a pain in the ass to machine because aluminium sticks to your tools, many cutting tools for aluminium are polished to reduce this effect. There are more factors to consider which make up price of a frame.

The Youngs modulus for steel is between 200 and 210GPa.

Aluminium does have an elastic yield strength like steels, it is considered a linear elastic material. The magnitude of its yield strength depends on your alloy and annealed state.

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10/28/2012 6:57 AM

can someone explain this to me, people say stiffer suspension or frames is better in sand but riding at dyracuse which i believe is about nasty as sand can get, it feels to me like the bike is wandering and cant do anything?

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