joethebmxer

I need help with my senior project. I have chosen the subject of bike frames. My thesis statement is Chromoly frames are better than Aluminum. I could use any help that anyone could give me. I would prefer links to sites where I can recieve information but i would also like peoples opinions. Thanks.

twahl

"Better" is a very subjection frame of reference. People prefer whatever frame material they prefer based on what priority they place on the characteristics of each frame material. Some of those are flex and stiffness, vibration absorbtion, durability, weight, etc. It would be very difficult to say which is better without knowing what you are looking for.

Which is better, a chainsaw or and X-acto knife? Depends. If I want to cut a tree down, the X-acto isn't going to do the job. If I want to cut delicate plastic model parts from the sprue...well the chainsaw will just tear things up. So which is better?

SpongeDad

go to Road forum, search for "steel"

Ziggarat (Ziggurat?) posts a fair amount on the wonders of steel.

DannoXYZ 

Check out: https://www.matweb.com . Nothing new here... refer to these threads:

Steel vs. aluminum
looking for new bike advice
beryllium bikes?
Rivendell makes a good arguement for steel!
What material do you think is best?
So What is the state of carbon and where is it going?
WOW!! Reynolds 953 stainless steel
Can't stop carbon revolution.
Is carbon really stronger than steel?
Best frame material /configuration for climbing?
What's so real about steel?
Steel Bike Choices
materials
What happened to Titanium?
ti vs al
Cannondales too stiff?
If you ride a carbon bike.
Just a tally of frame failures...
steel is real, but...
Steel (ChroMo) vs. Aluminum
Custom ti bikes: round tubes or fancy-pants shaped tubes?
Steel frame weights
A story about carbon forks
When weight doesn't matter, is carbon still better than steel?
Half Carbon/Half Steel frame?
Titanium.......Bastard Step Child?
Anyone ride aluminum..and like it?
carbon vs aluminum
steel bike vs. aluminum ?
6061 aluminum vs. 7005 aluminum
Aluminum: wear out?
Steel vs everything else
Carbon Fiber fragility
How durable is carbon fiber?
Bike Materials of the Future
Pros riding Steel
Carbon v. Ti
steelframes-lugged vs. butted?
TI, Carbon or AL - which is STIFFER ?
Steel vs. Aluminum
Aluminum as frame material - Reached its peak?
carbon fiber bike?
Frame Material
Ti or Carbon for light rider?
Ever Broken Carbon Fiber?
Carbon Bikes
Why are forks often made of different materials from frames?
Ti vs. Carbon
Anyone ride aluminum..and like it?
Steel bikes - Light As You Wanna Be
Flexible Frame?
carbon vs aluminum
What's stronger, a 3lb steel frame, or a 3lb aluminum?
Steel Frame Life
aluminium frame failures-- myth or fact?
Aluminum or Carbon - Which is stiffer?
Steel Bikes
How does Titanium ride?
Steel, Carbon, Aluminium or Titanium Frame??
Ti vs Al vs Steel need help thanks
Why would Alum feel better than Steel?
Carbon Conspiracy....
Is Aluminum stronger than Steel?
If steel is real, then what is carbon fiber?
has anyone seen ti crack?
biased against steel?
tell me about the different frame materials, please.
materials
Titanium or Steel?
Frames made from air hardening alloy
Steel, Aluminum, Titanium, Carbon - What's the difference in the ride!
Full Carbon Bikes
frame materal
Titanium Frames
Aluminum + carbon frames: better ride?
Aluminium, Ti, or Carbon
Good read on frame metallurgy
Steel vs. aluminum w/carbon fork
How much does a frame REALLY matter?
frame material
What kind of materials do you prefer?
steel bike vs. aluminum ?
Titanium vs. Carbon Fiber
Are aluminum bikes THAT uncomfortable?
Alloy vs Carbon
CANNONDALE VS TREK. (the debate begins)
Carbon fiber vs Steel vs Aluminum vs Ti
Titanium vs. Aluminum Frames
Titanium, steel, aluminum, carbon?

stapfam

Chromoly normally has a bit of give in it and Aluminium is stiffer. Other than that you have to look at the use the properties of each material have and where they are Better than the other//or which do people prefer to ride. Then you have the different bikes mountain or road. Then the style of the rider and/or the age of the rider.

I am a Mountain biker and want a frame to be stiff. Aluminium for me so why do I keep a 10year old chromoly framed bike that gets used a lot? Then why get an ultra stiff alloy frame and put suspension on it? And finally- Chromoly and aluminium are old hat with all the new materials around so why choose either of these in the first place?

Good luck with your project but whatever result you come up with- just talk to the wrong biker and you can be shot down.

supcom

https://sheldonbrown.com/frame-materials.html

cuda2k

lol... nice list Danno!

xlntRider79

You're never going to be able to justify a broad statement like that, but you could make an effective paper by being more specific. If you're into BMX, you could narrow your topic to "Chromoly is better for better freestyle BMX because" then you could focus on the material properites which make it more durable such as:
More elastic, can flex to abosorb big hits
Higher fatique strength, can take more big hits
Can be bent back when tweaked in a crash (can take more plastic deformation before break)
Tubes won't buckle when lightly dented (higher fracture toughness)
Easier to weld/repair when damaged because chromoly air-hardens vs. aluminum which needs to be heat treated
etc, etc...

wsexson

You could certainly come up with enough points in favor of steel and against aluminum to write a paper with your thesis, but as a blanket statement "cromoly is better for bicycle frames than aluminum" is bunk. There are amazingly good frames made from each, and utter crap made from each. IMO both steel and aluminum are fantastic materials to make a bicycle frame. Talented designers and craftspersons can maximize the benifts and minimize the weakneses of each material.

DannoXYZ 

Exactly, material properties are irrelevant as geometry, design and construction quality makes a much, much more significant contribution to the final-product. Here's table summarizing the basic properties:



You can use this to come up with some comparison-metrics between the material-properties alone, like:

Stiffness-to-Weight Ratios
105 - chromoly 4130
100 - magnesium ZK21A-F
103 - aluminum 6061-T6
100 - aluminum 7005-T6
98.0 - aluminum 7075-T6
89.5 - titanium 3Al-2.5V
92.6 - titanium 6Al-4V
98.6 - stainless 321
97.5 - stainless Gall-Tough+
659 - beryllium S200F
668 - beryllium SR200

In this case, both chromoly and aluminium are identical. Frames of equal-weights will have equal stiffnesses in both materials. Or you can analyze based upon:

Yield Strength-to-Weight Ratios
184 - chromoly 4130
402 - magnesium ZK21A-F
379 - aluminum 6061-T6
421 - aluminum 7005-T6
716 - aluminum 7075-T6
448 - titanium 3Al-2.5V
679 - titanium 6Al-4V
208 - stainless 321
701 - stainless Gall-Tough+
524 - beryllium S200F
751 - beryllium SR200

This will let you make comparison of frames of equal-weight or equal-strength. Aluminium outpaces chromoly by a significant margin. For the same strength, aluminium will be lighter than chromoly. Or for the same weight, aluminium will be many times stronger. Chromoly's day as the premiere frame-material has long passed. Modern high-strength stainless-steels on the other hand...

Check out Damon Rinard's FEA analysis of frame structures:
Finite-Element Structural Analysis: A New Tool for Bicycle Frame Design
12 High End Frames in the EFBe Fatigue Test <-- actual testing of frames to failure

Note the cycles these frames were subjected to before they broke. Note the frames with the lowest number of cycles at failure. Then note the frames that did not fail at all after 200,000 stress cycles...

tech23

Specialized E5 Bithches.....nuf said

tech23

Yield strength means F*** All, If you make an aluminum bike deform plastically by riding it you are one strong, fat, heavy sum beatch

DannoXYZ 

Hitting pot-holes and deep drainage ditches can load the up the frame with 4-5 Gs, 600-900lbs of force. By the time you hit an aluminium frame hard enough to bend it, the chromoly will have been completely twisted into a paper-clip!

jur

Danno you're a star mate. I want a beryllium bike. To hell with the consequences.

MichaelW

Bog std chromoly is hardly a cutting edge material. The specialist heat-treated steels outperform chromoly by a huge margin. Check out the reynolds website for the specs.