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Steel? Ti? Al? Carbon fiber?(23 posts)

Steel? Ti? Al? Carbon fiber?bsdc
Oct 31, 2002 6:51 PM
Which is the best all around frame material?
Oh dear...aeon
Oct 31, 2002 7:47 PM
I'll start by assuming you didn't INTEND to post such tempting flame bait...

Anyway, you have to ask yourself: best for what? At what price point?

These are the usual stereotypes:
-Aluminum is generally stiffer at the same weight. Aluminum bikes are generally the lightest

-Steel provides a very nice ride if tuned, but cannot be made as light, and cannot be made as stiff without a weight penalty.

-Titanium can mimick the plushness of steel in a lighter, stiffer package. Also, Ti will not rust. Ti is the most common "custom" material, as it lasts a very long time.

-Carbon is kind of a wild card, in that there are so many possibilities. You can build it light, plush, stiff, aero, whatever. May not be as durable in a crash.

my favorite: bamboo.
FantasticSnyder
Oct 31, 2002 9:32 PM
Is that a functioning bamboo bycicle? It looks like a single speed. How is the ride??
or if you want to be real coolScottland
Nov 1, 2002 4:21 AM
or if you want to get more Aero.............Dave Hickey
Nov 1, 2002 4:48 AM
oooh, lugged bamboo.. (nm)dotkaye
Nov 1, 2002 9:10 AM
Web Resourcesfbg111
Oct 31, 2002 9:25 PM
http://www.sjsu.edu/orgs/asmtms/artcle/articl.htm
http://www.sheldonbrown.com/frame-materials.html
http://www.sheldonbrown.com/rinard_frametest.html

Also search this forum. Plenty of discussions and info about this.
re: Steel? Ti? Al? Carbon fiber?mackgoo
Oct 31, 2002 11:02 PM
I've ridden steel and now I'm on Ti. Ti is great but better ride? I don't think so. I'm currently drooling over either Cinelli's or Bianchi's interpertation of carbon for the "perfect" ride. I don't know, I have a feeling I'll be back to steel. I sure will have a heck of a stable though.
"Pleez esplain youself Lucy"...Ride-Fly
Nov 1, 2002 2:26 AM
expound a little more on why you think you'll be back on steel. I'm no expert on Steel vee Ti but I would think that a well made Ti frame would feel just like a well made steel frame except that you get all the extra benefits Ti has such as rust-free, longer fatigue life, made lighter for the equivalent stiffness, etc. Or is Ti not quite able to duplicate the "steel is real" feel but comes close? I ask because if I decide I am going to get a travel bike instead of a new racing steed, I have it narrowed down to a Dean Ti frame with a S&S couplings or the new Ritchey Break-Away which uses its own proprietary coupling system. Thanks and Ride ON!!!
What kind of cycling do you do?REPO42
Nov 1, 2002 2:38 AM
It totally depends on your budget and what you plan to do. If you are a triathlete. Carbon would be a better choice. Frame can be made aero and light. You do a lot of centuries, maybe Ti or steel. Go for a plush ride. If you do a lot of crits, then Aluminum or Steel...The reason I suggest steel for crits is if you race Cat5/4 you want a frame that getting destroyed in a crash due to some squirly idiot won't make you have to file chapter 11
What kind of cycling do you do?xxl
Nov 1, 2002 3:44 AM
Just curious, but why did you not suggest ti for the crit specialist?
"If you can't afford to replace it, you can't afford to race it"Gregory Taylor
Nov 1, 2002 8:03 AM
You certainly could race crits on a ti bike, but you'd be putting a very expensive frameset at risk. The few races that I've done (all Cat V) have been notable for wrecks. My "race" bike (HAH! Me, calling myself a "racer"! What ego!) is a Cannondale CAAD3 with a mix of Ultegra and 105. Stiff, light, nimble, and cheap.
What kind of cycling do you do?REPO42
Nov 1, 2002 5:20 PM
I would if you race let's say Cat2's or maybe Cat3's... Ti is awesome, but pricey. Hate to see him destroy a $2000 frame racing squirly Cat 5's. No offense to Cat 5's, but damn those crits are scarey
"Pleez esplain youself Lucy"...mackgoo
Nov 1, 2002 10:46 PM
For me the steel was a little smoother, more compliant. Certainly Ti wins with corosion resistance etc.
The bikes are both Bianchi's, TSX-UL and a Ti Mega tube exact same size and geometry.
Let me take a crack at this one....(long)joekm
Nov 1, 2002 6:27 AM
Picking a best all around frame material will depend on your point of view. However, an understanding of their material properties and the implications of those properties can be helpful in deciding what the best choice for you is. So, let me try to give an overview of some common bicycle material properties:

Steel - Modern steel bicycle tubing is very stiff and has insanely high ultimate tensile strength (UTS) and yield strength. The yield strength is the more important property because beyond that the metal can take on pemanent distortion (or "set"). These steels also tend to have a high stiffness (or "modulus") compared to their weight. As a result, you can safely make tubing with fairly thin walls without having to worry about denting or "oil canning". Furthermore, fatigue, toughness, and corrosion resistance is very good.

Because of these properties, it's relatively easy to build in vertical compliance while still maintaining stiffness at the bottom bracket, head tube, etc.

The downside is the relatively high density (around .29 lbs/ in^3). OTOH - the strength to density for the better alloys (Reynolds 853 for example) is pretty good and that will compensate for the high density somewhat.

Aluminum - Most common alloys for bicycle use appear to be 6061 and 7005. This may sound contrary to what you've heard but these materials aren't nearly as stiff as steel. However, they are considerably less dense and the "modulus to density" ratio is about the same as typical modern bicycle steel tubing. The reason that aluminum frames are stiffer than steel is that an aluminum frame can use thicker and larger diameter tubing at the same overall weight as a comparable steel frame. This gives the aluminum frame a larger cross-sectional inertia and that is what makes it stiffer.

The downside is lesser material toughness and fatigue resistance. This also makes it difficult to dial in vertical compliance without risking compromising the frame. I understand that scandium can be alloyed with the metal to offset this somewhat, but I am not sufficiently familiar with those alloys to comment on that here. I also understand that Reynolds is experimenting with an aluminum-lithium alloy. Boeing messed around with this in the mid 80's and, as I recall, it had good fatigue properties but was very expensive.

Titanium - 2.5/3 is the most common variety. It has outstanding corrosion, fatigue, and toughness characteristics. However, it's modulus to density is low as compared to either steel or aluminum. To compensate, the tubing diameters should probably be a little larger to increase cross sectional inertia. The resulting bike will not have the stiffness of a comparable aluminum bike. Attemting to optimize a titanium frame for weight could result in excessive frame flex. OTOH - The strength to density is slightly better than even the best steels and A designer could probably make an outstanding stage or century bike with this material.

6/4 Ti is considerably stronger but difficult to work. This makes it a tad expensive. Both modulus to density and strength to density are outstanding. If you can get around the workablity challenges, there is no reason that this wont make an excellent bike frame. Last I heard, you can't extrude a closed form with it (but I'm not sure of this). This would mean that tubing would have a welded seam.

Carbon Fiber - As a composite, it will tend to attenuate high frequency noise (which is why it makes a good fork). It's greatest strength and it's greatest weakness is its tuneability. Vertical compliance and lateral stiffness can be designed in fairly readily by tuning the material bending axes to what you need. However, if not done correctly, the material could also turn a lot of energy into heat. In other frames, this energy would be partially stored in the material and eventually make it to the road.

It boils down to how well the bike is designed. I
Let me take a crack at this one....(long)gtx
Nov 1, 2002 7:31 AM
a frame with vertical compliance is broken

http://www.sheldonbrown.com/frame-materials.html
Let me take a crack at this one....(long)joekm
Nov 1, 2002 8:23 AM
I think if you read his explanations and my post you'll find that we are in agreement, although he goes into more detail as he has more space to work with. He is absolutely correct in what he is saying. The last paragraph of his vertical stiffness discussion explains the frames contribution. This is the only part that is pertanant to the original posters question. And yes, he is quite correct in saying that the tires and seat have more effect. This is also why frame makers that try to dial in vertical compliance tweak the seat stays. As far as the frame is concerned, that's where you will have the best effect.

The ultimate point I was trying to make (and my original post got truncated unfortunately) is that any of the materials are capable of making an excellent bike frame as long as you work within their respective material properties. In addition, as reflected in your web site reference. Carbon fiber will require some special considerations owing to it's uniqueness and non-isotropic properties. I would concur with the author's opinion that carbon fiber is probably not the best option for a touring frame.

Finally all structures have vertical compliance, it's just a question of how much.
Let me take a crack at this one....(long)gtx
Nov 1, 2002 9:56 AM
I don't think anyone is capable of telling differences in vertical compliance between different frames. The differences are way too small. It's the princess and the pea. A friend of mine had his downtube break while riding. He said the first thing he noticed is that is frame got a lot more comfortable. The guy who started Slingshot had the same experience. Differences in ride quality and comfort come from fit, geometry, seat and tires.
You are entitled to your opinion....joekm
Nov 1, 2002 1:11 PM
I'm just discussing the various materials to answer the posters question. Although I would disagree with your princess and the pea analogy.

...seen the slingshot design, interesting.
You're on of them engineers aint' yaPEDDLEFOOT
Nov 1, 2002 7:39 AM
No question. AL is the best all around...Bruno
Nov 1, 2002 10:07 AM
economical, light, efficient. If you could only make bikes with one material AL would allow you to make cheap entry level frames and also high performance frames.
No question. Steel is the best all around...(nm;-)Spunout
Nov 1, 2002 10:56 AM
No question. Steel is the best all around...(nm;-)REPO42
Nov 1, 2002 5:30 PM
I would say steel is overmatched by Aluminum and Ti. The have narrowed the walls down of steel so much that if you barley ding it you will most likely dent the frame. Walls are way to paper thin, and you still don't get the weight savings of Aluminmum. Please correct me if I am wrong..