Tube diameters

[Dakkar]

In the mid to late 90's frame builders started building bikes with wider diameters to create a stiffer ride, so I have read. Does anybody know if there is a noticeable difference in how a bike rides with different or larger tubes. Is there bend or waver when hammering down on the pedals with narrower steal tubes and if there is, is it a bad thing anyway?

I have heard that there was one brand on Vitus frames that was famous or notorious for bending when placing pressure on the pedals. Was this unique to Vitus are are all frames prone to this?

Thanks in advance.

 

[monty dog]

Prior to the advent of over-size tubing, there were a number of frame notorious for their flexibility - particularly those made from bonded aluminium such as Vitus, Alan as well as early bonded carbon frames.
A lot depends on the weight of the rider - I much prefer the ride of Columbus SL because I only weigh 60kg and find some the over-size / stiffer tubesets pretty harsh in comparison.

 

[AndyPA]

The larger diameter tubes like columbus genius had very thin walls and were lighter so nicer to ride but suffered from rot later in life.All Alans and vitus frame were soft but very comfortable to ride,o and the fork ends always used to drop out

 

[hamster]

From an engineering point of view, it's advantageous to use the same weight of metal as thinner, larger diameter tubes for increased stiffness.

The trade-off is that thinner walls increases the risk of denting (think coke can) and of course durability - rusting is more likely to prove fatal.

Also, placement of braze-ons such as gear bosses becomes critical as cracking can propagate easily from stress concentrations.

The mid-90's weight fad also led to over-thin frames which were great on paper but traded stiffness for weight saving.

 

[AndyPA]

Columbus Genius traded nothing in stiffness ,the tube butts were shorter and it was heat treated making it stiffer and lighter than say Columbus slx.
The nicest steel frame I rode was a tig welded Columbus Genius, but the tubes rotted from the inside out 10 years down the line.