MTB alloy handlebars and stem LOAD TOLERANCE?
 

Hey what's up fellow cyclists!


Just ended a customer service chat session with Bontrager customer service but unfortunately there wasn't a clear answer for this. I hope someone here either with a similar situation as mine, or with materials engineering knowledge can shed some light on this:


A couple years back I bought a set of alloy Bontrager RL stem (100 mm) and handlebar for my hardtail mountain bike.


https://cimg2.ibsrv.net/gimg/bikefor...bd54153070.jpg



Now, as I also use my bike for commuting duties, I sometimes carry loads hanging from my bike's handlebar. The most I've carried is 10 kg (5 kg on each handlebar end). Most of the times I'm only carrying say 3 kg on only one side.


I've grown a bit concerned that by doing this I may be surpassing my handlebar's or stem's (or both) weight tolerance, and as I also ride my bike on trails, I want to make sure I haven't compromised those components' safety by carrying excessive loads on them when commuting. I don't want the handlebars or stem snapping on me during a fast descent.


I asked Bontrager customer service what weight carrying or load limit do the RL handlebar and RL stem have, but their only answer was:
"we rate them as able to handle all normal riding conditions of a rider up to 300lbs, as that is the max weight limit for our bikes. Unfortunately we do not have a specific weight limit for our stems, nor we do specifically test them for bike packing or hauling purposes"



So what is your opinion on this? I would suppose the load forces applied on a handlebar are pretty big during trail, big step descents, and they are manufactured to perfectly sustain without fatigue those forces, but then again I really don't know how does that compare to loading a CONSTANT weight of more than 5 kg on the bars' ends.



Thanks for reading!


EDIT: My body weight is 84 kg.

If you are adding loads to your bars that are anywhere close to the loads put on by a rider near the bike's rider weight limit, you will have more trouble just riding than with durability.

Yours is kind of like the oft-asked question 'does it damage a bike to hang it upside down' by the wheel - if the wheel cannot support the weight of the unladen bike, I wouldn't dare try to load my carcass and luggage around on it.

PS. If the bike is a few years old and you have ridden it hard many times, it isn't a bad idea to swap out the bars (and maybe stem) just to be on the safe side. I don't think carrying a grocery bag on the bars is going to cause any problems, but your 64kg body pushing down on it thousands of times per season might eventually cause it to weaken.

I wouldn't worry since they're not made of cracken fiber. :D

BMarino To answer the OP question as simply as possible; Constant loads will cause the bar to bend (very, very slowly) Peak loads will cause it to break, suddenly.

298g, 7000-series aluminum. Seems like a decently strong handlebar. Not anything crazy like the old 140g Scott AT-1/LF, or the Answer HyperLite.

Changing your bars every couple of years as a preventative measure seems a little excessive.
If you're really concerned about it, get a 'Downhill' bar instead of a 'Trail / XC' bar, like I did here (link)

Carrying things on those handlebars will definitely not break them.

The greatest force on the handlebars comes when riding the bike and running into a pot hole, or something else which results in a sudden stop. Your entire body weight pushes on the handlebars.

They should not break if a rider of 300 lbs or 136 kg runs into a pot hole.

So unless there is something to indicate something is wrong, I would not be concerned.

I have never bent or broken handlebars. I have never replaced handlebars, and I never would unless there was something to indicate a problem. I ride bikes make for Western riders. The handlebars have all been made of steel or aluminum.

I did say those handlebars. In S E Asia, most people ride ladies bikes, which are not designed to be as tough as mountain bikes. I have seen these bikes with bent or broken handlebars. Sometimes the rider may be a 40 kg schoolgirl.

Here's some of the stuff I've loaded onto my handlebars while riding (and we're talking vintage road quill stem and 25mm bars which are weaker than fat MTB stems/bars)
-people sitting on them.
-multiple grocery bags (about 20lb/10kg each side).
-40lb/20kg bag of cement ridden 5 miles.
-A 80lb/40kg Pioneer SX1980 receiver (the biggest baddest vintage receiver ever made and found on the sidewalk).

so yeah, stems and bars are pretty strong.

Thanks for your replies everyone! It seems I was definitely overconcerned over this!