mercalia wrote:so the morale is dont put too much strain on alloy bars? then they wont break?
No, I don't think there is a morale.
My morale would certainly be better if I didn't have to worry about putting too much strain on the bars! That shouldn't really be necessary though. However, if you're a powerful rider (or one who is taller or who likes to use wider bars), you would be wise to choose your bars carefully.
Wider bars will exert more leverage to the stem interface. I've also noticed that Nitto offer their wider bars with a special heat treatment, which I suppose, in theory, should make them more fatigue resistant, or is it just to make them more stiff? Wider bars will more likely be used be taller, more broad shouldered people, who will tend to put more twisting force through the bars.
I've had several bad experiences with butterfly bars. This started with Humpert butterfly bars that came with my Dawes Galaxy. They became distorted around the stem clamp, with scoring markes around the edges, where the stem clamped them. I actually got through 3 of these bars!!! (replaced by the bike shop FOC), before deciding to install drops. Looking back, I wonder whether my LBS may have mis-sold me the ITM road Race stem, which AFAIK, was only ever sold in 26mm (anyone know?). The butterfly bars were 25.4 stem dia.
Apart from this uncertainty, I'm pretty certain that using wide bars, such as these, on a tourer, was inducing more twisting force,and so fatigue. They also felt 'noodly' - well, the whole set up did TBH.
More recently (5 years ago :0), I built up what I call my trekking bike, or gravel bike, to use modern parlence. Because I'd enjoyed the ride comfort and position of the butterflys, I choose to try out the original Modolo Yuma Butterfly bars. This time, I've only got through 2 of these bars! This time the guilty component was a Nitto bar shim, which unbelievably, was sold with a sharp edge which scored the bars after a year of service
At ths point I deceided to use the proper 25.4mm stem.
Anyway, although I continue use these bars, the mileage they undertake is low and I don't use the bike as a loaded tourer. I will periodically check these bars because of my experiences.
One final point, I always check the edges of the stem clamp area any of stems I use. If they look at all sharp or hard edeged, I just file a little of the edges, if only to reassure me that this stem won't contribute to any wear.