Road Cycling - cro-mo frame flex?

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Patriot
08-16-04, 10:43 PM
I have an older Centurion Ironman, with a Tange #1 cro-mo steel frame. I really like this bike, but I have noticed that in lower gear, when I give a good power stroke going up hill, the crankcase flexes back and forth so that the chain rubs against the front derailer from side to side.
Is this a major problem? Their are no cracks or damage to the frame that can be seen and is tight otherwise.
Instead of upgrading this bike with newer/nicer components, I thought maybe a newer frame would be better. I like the thought of a carbon frame, but do they flex even more? Maybe an 853 steel frame would be better.

Any suggestions?

nutbag
08-17-04, 01:10 AM
Ah, this is one of those things us "retros" don't like to talk admit :D

As far as I know, it can sometimes it can just be crank flex.

If you look down at your chain-ring when you are just cruising along a flat rode, you may notice that the rings move a little from side to side. I don't exactly know what this is, but I'm sure it's accentuated during sprinting and sprinting up hills.
khuon
08-17-04, 02:04 AM
I like the thought of a carbon frame, but do they flex even more?

Carbon fibre can be made to flex as is evident by the Softride beam. However it can also be laid up to be really stiff. It all depends on how it was constructed, the layup and the particular design goals for that element. The only way to really tell is to ride it. My carbon frame is fairly stiff... stiffer than most carbon frames. However, it also damps vibration very well making it ride very smooth. When combined with a good solid set of wheels, it makes for a very responsive bike but one that doesn't punish you over the long run.

Dahon.Steve
08-17-04, 07:11 AM
I have an older Centurion Ironman, with a Tange #1 cro-mo steel frame. I really like this bike, but I have noticed that in lower gear, when I give a good power stroke going up hill, the crankcase flexes back and forth so that the chain rubs against the front derailer from side to side.
Is this a major problem? Their are no cracks or damage to the frame that can be seen and is tight otherwise.
Instead of upgrading this bike with newer/nicer components, I thought maybe a newer frame would be better. I like the thought of a carbon frame, but do they flex even more? Maybe an 853 steel frame would be better.

Any suggestions?

An older chromoly frame will flex but this is not necessarily a bad thing. A frame that's very stiff like Alu will not flex but it will be a harder ride overall.