Handlebar Fatique?
 

RE aluminum bars: Clearly a lot of stress is placed on the bars at the edges of the stem. For this reason, should they be replaced after a certain # of miles? Or just removed & checked (a pain).?

I'm wondering too, because I noticed mine seem to flex a little more after a recent crash. Not sure if I just didn't notice it before. Is there anything to check for?

You'd have to remove the bars & look for small stress cracks where they go into the stem. In your case i'd replace the bar, period. Why take a chance? Bars & fork are 2 parts i don't want to fail on the road!

Cyclepath is right. The fork, stem, and handlebar should all be carefully examined after any such incident and replaced if there are any doubts regarding their integrity. This is especially true for aluminum and carbon which are more prone to catastrophic failure than steel or titanium.

I've cracked a stem and a handlebar and bent a second handlebar. The stem faceplate started coming apart near the end of a very long ride and I'm so thankful that it wasn't in the middle of a technical descent. I also cracked the carbon fork after a crash on my road bike. The fork was carbon reinforced aluminum and didn't seem to flex any more than it did previously but the tiny crack kept growing. The fork was replaced very soon thereafter.

Bars are not a wear item. They will last forever in normal use. If they are bent, however, then replace to be on the safe side. If you have a quill stem, tighten it so that you can just rotate the stem in the steerer tube by hand, so that if you crash, the bars will move there is less strain on them.

Aluminum has only so many stress cycles in it, unlike steel. Of course the bar is sleeved to minimize this, but i still don't know if it can safely be ridden for a lifetime, especially since the manufacturers don't expect anyone to do so....

Bar failure == instant endo.

If you are familar with what to look for, examine the bar for bends or cracks. If not, have someone else do it... riding along and having a bar in your hand that is not attached to the stem really, really sucks.

That's the hard part for me. I had just bought the bar a few weeks before the crash, so I hadn't gotten used to its characteristics and how much flex is normal for it (being lighter than my stock bar). I inspected it thuroughly, and there are no cracks or inconsistencies with its shape. Not even a scratch. I know it got struck on one side as the bar tape got torn, so maybe I should play it safe. Just hoping not to have to beg the wife to let me buy yet another part.

If you crashed and the bars appear bent even slightly it's safer to go ahead and replace the bars. But I rode on a slightly bent Cinelli bar for about 6 months and even raced on them like that and never had a problem...but again let me stress that for safety reasons if the bars are bent you should replace.

If the bars have not been bent and their not creaking then those bars are probably still good; there is no set miles as to when to replace. Some manufactures do have a set miles when to replace their bars but that is more for legal purposes so that in the remote case a bar broke due to fatigue they can't be held liable. But I have never seen a bar fail due to fatigue; in fact my friend who weighs 240 pounds (6'4" muscular build) broke 2 Vitus's, 2 Kliens and 3 Cannondale frames from over powering them (all at the bottom bracket area) but never a bar.

I have another friend who has an old early 70s era racing bike with the original bars and their still good!

My current bike has a Nitto bar that has over 20,000 miles on it and it's still good, my previous TTT bar had over 50,000 on it and was replaced only because it got scuffed and I didn't like the scuffs! By the way I use to live in California and rode into the mountains all the time, so the added stress of climbing steep grades never seemed to effect the bars.

Lighter bars will have a tendancy to fail sooner and flex, but my above mentioned TTT bars and previous to that the Cinelli's (the ones that I rode bent for 6 months) were light racing bars and they never failed; so how to determine if and when a bar will fail is tough question

That is reassuring.

Well, no.

All materials have limited stress cycles; steel just has a higher resistance to fatigue than aluminum.

The key word is stress cycle. If the bars are not being stressed to their limits, as I don't think they are in normal riding, then they should last a lifetime.

Aluminum doesn't like being bent, however, so bars definitely should be inspected after a crash and replaced if they are not straight.

Lastly, quality does matter. Better bars will likely be made of stronger alloys which might make a difference in the really long run.

As to stems, I dislike aluminum quills; too much flex and I've seen them break for no apparent reason. Once I discovered Ritchey Force (cro-mo, made by Nitto) I never never considered Al stems again.

Again, as with the bars, I've never seen AL quills fail as a result of fatigue in normal cycling or even racing. I have seen some quills eventually being unable to securely tighten inside the head tube, but you begin to notice this with slight movement but never sudden failure. Again for all the same reasons I posted in my previous post never saw a quill fail.

BUT...please note, quill stems AND more rarely bars can fail in professional track bike racing. Nitto does make a line of track bike quills and bars that are made of Cro-Mo and are designed to take the power of a track bike racer; but most folk here on this forum will never track race professionally. The same can be said with clipless pedals, pro track racers do not use clipless pedals because they overpower the clipless system and their feet will not stay on the pedal thus they use a double strap clip style pedal to hold their feet.

So if your generating so much power that even clipless pedals won't hold you then your stems and bars may be subject to breaking, otherwise your bar and stems are more then just fine, just as they were in the old school racing days.

Have no fear your bars and stems will hang tough with you.

Thanks froze. The bar does not seem bent, which is why I am probably just paranoid at watching the bar flex slightly when I apply a lot of pressure on the hoods. It is a lighter bar that I bought in May (TTT Forgie at 228g) so it probably just flexes more than the heavy monster I replaced.

It ain't worth it. Replace the gear, then you will not worry about it. You seem to think your wife would be upset if you impacted the finances a bit more. You had better believe that she would be even more upset if she thought you were risking serious head injury because of the $'s involved- then she might blame herself. You are replacing this stuff for her. You are still going to ride. You might watch the pay it forward thread here on BF.

BTW. I've seen the bars fail. One was on Lolo Pass at the campground west of the summit. One of the group was an aircraft mechanic and she somehow managed to put the bar together with I do not know what, maybe scotch tape and used clarinet reeds or pieces of tree bark or something. The damaged bike was RIDDEN over the pass and down the other side into Missula. Adventure Cyclist took on a whole new meaning.

I've replaced 3 bars this year on my BMX, partially because of the stresses I run them through, partially because I like to try new things.

I believe the poster was referring to road bikes, thus jumping stresses applied to bars while BMXing probably wouldn't occur on a road bike...what do you think?

The stresses would not be that great, altho we do have a lot a bad pavement here...do MTB & BMX bars have greater wall thickness?

I checked my MTB bars and they appear (I didn't mic it) to be a tad thicker then my road bike bars...BUT that could be due to my MTB bars being inxpensive bars.

The wife would rather me not ride at all, but I don't have the "eat anything, do anything and still live to be 105" gene. It's ok, though, she approved the bar purchase, and said she trusts me as long as I don't go overboard. So no new Serrotta, but do you think a new Colnago is overboard? :D

Doesnt say anything about a road bike, could have been a MTB.

Thats what I think.

Depends upon which limit you're talking about: fatigue, yield, ultimate? Both steel and aluminium have an ultimate limit, the point at which a part breaks. Steel happens to be a higher ultimate limit for the same size, but it's about the same as alloy for the same weight.

Same with yield limit, steel will take a higher load to take a permanent bend for the same size as aluminium. But when you make the parts of the same weight, steel will yield at roughly the same load.

However, steel DOES have a fatigue-limit whereas aluminium DOES NOT. There's a load-level below which steel will NEVER fail. There is no such limit with aluminium, no matter how low the load, eventually it will fail.

If you crash bad enough to bend a bar, DO NOT BEND IT BACK!!! You've already overcome the yield-limit in one direction (one side of the bar), don't double the stress and bend it back in the other direction, you'll have introduced cracks TWICE!

All failures start as cracks on teh surface, so it's easy to inspect. The scratches from twisting a bar through a stem is usually a very common spot for propagatings cracks and when these cracks join, SNAP!

The modern style of bar is bulged in the centre rather than shimmed. I think that using a shim is better, the strip of metal can absorb score markes without affecting the bar tubeing and the stress of the clamp is spread over a wider area, esp if the shim has a feathered edge.
What advantage does a bulged, shim-less bar have?

It doesn't make annoying creaking sounds since there aren't multiple pieces to rub against each other. I think the shimmed bars were 3 piece, actually. Right side, left side, and the shim that held them together.

Cheaper to manufacture.

I've broken two handlebars, one in a crash, one just starting from traffic lights...

Did you read this before you sent it?