Stem and Bar Service Life

[I Want Sachs?]

No crashes, and just riding the miles away. Is there a fatigue life to aluminum stem or bar? How about carbon?

How frequent (mile/time) do you retire the cockpit for brand new ones?

How about for MTB?

[Seramount]

one of my bikes is a 1992 model with original Al bar / quill stem.

after ~80K miles, they're pristine looking, so see no reason to retire them.

but, I have seen photos of some Al bars that were seriously corroded from sweat. they looked like they could fail at any moment...

seems like a visual inspection would alert you to most problems before they became too dangerous.

[ultraman6970]

No manufacturer will give a date for carbon stuff, that would mean to shoot themselves in the foot :D

No magazine will say that, but clearly they can say that a 32 mm wide tire is faster than a 19 mm one :P

Have a stem and handlebar that I bought new back in 1984 or so.

[bicycletricycle]

I think it is not possible to make generalizations here.

Lightweight components will have a shorter service life all other things being equal.

Traditional quill stems seem to last for a very long time. Well built Threadless stems are more likely to have a thread stripped than a catastrophic failure in my experience. Again lightweight units can be more of a problem especially those which are entirely machined from billet instead of pre formed by a forging process. I have seem some cracked Deda newton stems and a few cracked thomsons. This is not to say that a machined stem can't be made to last, it just seems like they may need to be a little heavier to make up for the lack of grain alignment.

Obviously corrosion , deep scratches and dents can cause some problems as well.

Most components have some kind of reputation, best to judge the components you have by what other people have experienced in the field in combination with what kind of life they have had.

[bicycletricycle]

Carbon is interesting, the resins will break down in uv. Parts painted with an opaque color will get much less uv damage.

Other than the uv problem, a properly designed part can last for a very long time, just like metal components. Obviously Lightweight parts will be less durable.

I think a big difference with carbon components is there ability to deal with damage from impact, abrasions and incorrect installation (over tightening fasteners) also corrosion around molded in metal fittings. These seem to be more of a limit than the fatigue life of the structure itself.

[Mikej]

I would say regardless of light weight or normal or heavy duty which really doesn't mean anything to me (I work with non-ferrous castings and pressed vessels for a living) as well as plastic mold injection vessels that are basically at every water source in the municipal water service. I would say that a forged stem, a welded ti, aluminum, steel or a molded carbon stem will have an infinite longevity. Sure they can break, but there is no industry rating, so they are actually meant to be in service for an indefinite amount of time, under normal circumstances and occurance, which is the catch. Same with tubing for handlebars, you won't see a frame or rim or hub bearing or seat post with or really any part of a bike with a "throw this away after 5 years" because there is no way to know the actual usage of any componant, so the are made to last. Sure there s a warranty, but that is not indicative of length of duty. Also use your head and replace any suspect parts after crashing or mis-installation or adjustment.

[bikingshearer]

Ah, don't worry about it. The bar or stem will let you know when it's service life is over. :eek:

[scpknees]

no idea on life span of stem/bars. I just go 12000 -15000 miles as long as no crashes occur then I trash them. I look at it as cheap dental insurance.

[soulspinner]

no idea on life span of stem/bars. I just go 12000 -15000 miles as long as no crashes occur then I trash them. I look at it as cheap dental insurance.

Not a bad idea...........

[Pastashop]

With aluminum bars, when you notice them bent slightly across the flat portion (i.e. across the top), it's time to replace. Used to be easier to tell with conventional 26.0 mm clamp dia bars, but the idea is the same.

Aluminum doesn't have a critical stress value, so it fatigues with every cycle, forming new dislocations and cracks and experiencing some creep / yield. Consequently, you'll see some deformation before failure.

Usually, as Mikej noted, parts are over engineered for a very long fatigue life on a bike, but a lot depends on how you ride, wham equipment, and where.

Two extreme cases:

1. Large diameter Ti or Al tubes frame with non-heat treated, 44 cm wide, light ITM bars in a short Salsa steel stem, driven by a 200 lb sprinter riding gravel roads on 28 mm tires pumped to 110 psi. This would call for replacement rather often.

2. 135 lb climber or a skinny tubed Gilles Berthoud that "planes", heat treated, 38 cm wide Nitto bars in a long Nitto Pearl stem, 32 mm tires at 50 psi, riding along paved roads of Southern France. This would call for replacement... pretty much never.

Carbon (properly protected) and steel bars will last indefinitely, as long as they're free of stress risers, or the critical stress is not exceeded. If it is, steel will deform gradually (i.e. with a warning), while carbon would just snap without a warning.

[joosttx]

Every 5 years is my rule.