Chromoly v carbon frame

[steve jobs' pancreas]

Apart from the weight difference, is one frame better than the other in terms of road riding (keeping all other components the same) ?

In particular I'm thinking in regards to impact absorption of the bumps and ripples in the road surface, would one type of material be more fatiguing than the other ?

 

[Liberty555]

That's a bit like asking if a hard tail is better than full suspension. There is such variation between good bikes and great bikes!

Put it this way. They are now bringing out carbon frames with compliance and dampers like the Domane and others. A GOOD steel frame can ride beautifully but that's not true of every steel frame. Different grades of steel are used etc. Steel can provide lovely vibration damping too. But it's generally heavier.

Try both. Then decide. You won't get a feel for how they ride on a forum.

 

[mtb101]

weight for weight - carbon fibre is much stiffer (compared to alu and steel) and most modern CF frames have less flex in bb area and across bars (so sit on seat and check lateral movement at bars), stiffer bb means less power loss & more response and stiffer front area means better handling especially if going hard on descent, carbon can have built in flex points such as rear stays. also carbon don't transfer road buzz like alu and to a lesser extent steel.

cf can in theory last forever if there's no chemical reaction (like when you bond alu to cf), no UV and no impact or break in structural integrity.

Steel has built in weaknesses where welds are and of course is prone to oxidization.

most steel frames I've seen don't have press fit bb so less material around bb area and don't have enlarged head tube area for larger fork.

of course most steel frames are not aimed at elite racing (not anymore), more all rounder.

my steel frame bike is my second bike for more cruiser rides.

 

[rangersac]

Very much frame dependent, but my (limited) experience is that carbon absorbs high frequency buzz better than steel, however steel is more compliant over ripples and larger bumps.

 

[The Duckmeister]

As others have said, it is very frame dependent in terms of grade of steel, tube profiles (for both) and layup (carbon). As a very general guide, steel has good low-frequency compliance; it irons out the bigger bumps, but the trade-off is that it bends more under power, so it's not as efficient. Although considerably better than aluminium, high frequency damping isn't fantastically great, so you get a somewhat buzzy ride.

Carbon is basically the opposite. It's incredibly stiff under low-frequency bumps, so a lot more of your power is used to make it go, but its high-frequency vibration damping is second to none, thanks to the resin component of the composite. Being plastic it has some compressibility and a lot of springiness, so it really soaks up the buzz. That compliance also helps take the edge off bigger bumps too.

 

[Joly Joe Rider]

stiffer bb means less power loss & more response

Hate to inform but this is complete nonsense. For their to be a loss of power due to bending of material there would have to be plastic deformation. In the force levels that an average cyclist makes, your bike would have to be made of chocolate to cause plastic deformation. If you seriously believe all the marketing hype put forward by the bike manufactures about the superior stiffness of their latest frames, year on year, we should be using CF bike frames to make bridges!

CF's great quality isn't that it is super light weight - My own TT bike that I built the steel frame for, only weighs 7kg. Thats complete with HED3 wheels and all aluminium components.
Nor is it that it is exceptionally stiff. What CF offers us is directional stiffness. In other words we can make a frame stiff where it needs to be (for handling) and less stiff where we want it (any thing that transfers energy into your butt)
It also has fewer constraints with regard to shapes and is far cheaper to reproduce once we get to production stage.
An added benefit as stated is that CF has better vibration insulation properties over both steel and ally frames.

Ally frames are stiff because they have to be- Otherwise they will fatigue and fail.

 

[spoozbucket]

Hate to inform but this is complete nonsense. For their to be a loss of power due to bending of material there would have to be plastic deformation. In the force levels that an average cyclist makes, your bike would have to be made of chocolate to cause plastic deformation. If you seriously believe all the marketing hype put forward by the bike manufactures about the superior stiffness of their latest frames, year on year, we should be using CF bike frames to make bridges!

CF's great quality isn't that it is super light weight - My own TT bike that I built the steel frame for, only weighs 7kg. Thats complete with HED3 wheels and all aluminium components.
Nor is it that it is exceptionally stiff. What CF offers us is directional stiffness. In other words we can make a frame stiff where it needs to be (for handling) and less stiff where we want it (any thing that transfers energy into your butt)
It also has fewer constraints with regard to shapes and is far cheaper to reproduce once we get to production stage.
An added benefit as stated is that CF has better vibration insulation properties over both steel and ally frames.

Ally frames are stiff because they have to be- Otherwise they will fatigue and fail.

It's more of a feeling, I know going from a light weight flexy crank to a stronger heavier crank makes my bikes feel like they accelerate quicker, same again going from a Cr-Mo frame to an alloy frame. I went the light weight route on a MTB once and the bike felt horrid so I just bolted the strongest parts I could to it and the bike felt so much more lively even though it was over a kilo heavier.

 

[Joly Joe Rider]

It's more of a feeling, I know going from a light weight flexy crank to a stronger heavier crank makes my bikes feel like they accelerate quicker, same again going from a Cr-Mo frame to an alloy frame. I went the light weight route on a MTB once and the bike felt horrid so I just bolted the strongest parts I could to it and the bike felt so much more lively even though it was over a kilo heavier.

Yeah most definitely.
You can get similar results by maintaining the gear inches but varying the size of the Chainring/sproket combo - this affects chain tension which in turn flexes the frame more or less.
As you apply pressure to the pedals the frame deflects, storing energy. As the pedal moves down to the 6 O'Clock position, the force you apply weakens and the stored energy is returned the system. This gives unique characteristics to certain bikes - A torsionally stiffer frame will return the energy faster and sooner. This would suit someone with a high cadence for example (maybe - I've yet to see an empirical peer reviewed study - until then its just 'in theory') . So sure choose these things because it feels better.

Just want to add as well that both of the road frames I have made are from the 'least stiff' steel tubing columbus make - small diameter and wall thickness down to .5mm. At no point have I found either bike to behave badly due to the frame not being stiff. In fact both descend like demons. Also note that bolting strong parts onto a frame isn't making the frame stiffer. If anything, stiffer parts will make the frame deflect more. If you do a google search of Bicycle Quarterly they did a very good write up on frame stiffness. It included a double blind test, in which both cyclists agreed that the more flexible bike was the better bike.

I get a nervous twitch every time I see a (road) bicycle manufacturer start rambling on about frame stiffness - its complete BS. In terms of bending due to pedal input, the only people frame stiffness will affect is Track sprinters and BMX racers. For BMX the frame is so small that I can't ever see stiffness being a problem and for the Sprinters its a about confidence not loss of power.

If you look at the modulus of elasticity vs Specific gravity only - you could make a bike (or anything for that matter) out of Steel, Titanium, Carbon Fibre or Spruce, with similar stiffness and weight. The difference would be in both packaging (that would be a lot of spruce compared to Steel) and yield strength and HF vibration qualities.

I believe, the reason for that massive looking structure we are seeing in CF bikes around the BB, are less to do with 'performance' and more to do with reliability.
CF, unlike steel, when it fails does so with not much warning and its nearly always a show stopper. On the other hand Steel will either yield or crack around welds. Even then the crack propagation is slow and tell tales will show up in the form of creaking and rust stains. CF is sensitive to the speed that loads are put through it