Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

MTB alloy handlebars and stem LOAD TOLERANCE?

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

MTB alloy handlebars and stem LOAD TOLERANCE?

Old 02-28-20, 01:53 PM
  #1  
BMarino
Junior Member
Thread Starter
 
Join Date: Jul 2019
Posts: 17
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked 3 Times in 3 Posts
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.






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.
BMarino is offline  
Old 02-28-20, 02:38 PM
  #2  
Wilfred Laurier
Señor Member
 
Wilfred Laurier's Avatar
 
Join Date: Feb 2013
Posts: 5,031
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 627 Post(s)
Liked 261 Times in 191 Posts
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.
Wilfred Laurier is offline  
Likes For Wilfred Laurier:
Old 02-28-20, 02:40 PM
  #3  
Wilfred Laurier
Señor Member
 
Wilfred Laurier's Avatar
 
Join Date: Feb 2013
Posts: 5,031
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 627 Post(s)
Liked 261 Times in 191 Posts
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.
Wilfred Laurier is offline  
Old 02-28-20, 06:18 PM
  #4  
AlmostTrick
Tortoise Wins by a Hare!
 
AlmostTrick's Avatar
 
Join Date: Feb 2006
Location: Looney Tunes, IL
Posts: 7,045

Bikes: Wabi Special FG, Raleigh Roper, Nashbar AL-1, Miyata One Hundred, '70 Schwinn Lemonator and More!!

Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 1385 Post(s)
Liked 568 Times in 317 Posts
I wouldn't worry since they're not made of cracken fiber.
AlmostTrick is offline  
Old 02-28-20, 10:43 PM
  #5  
Ironfish653
Senior Member
 
Join Date: Oct 2015
Location: Virginia Beach
Posts: 1,265

Bikes: 1997 Cannondale, 1976 Bridgestone, 1998 Softride

Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 439 Post(s)
Liked 150 Times in 101 Posts
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)
Ironfish653 is offline  
Likes For Ironfish653:
Old 02-28-20, 11:04 PM
  #6  
alo
Senior Member
 
Join Date: Feb 2020
Posts: 430
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 191 Post(s)
Likes: 0
Liked 92 Times in 70 Posts
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.

Last edited by alo; 02-28-20 at 11:16 PM.
alo is offline  
Likes For alo:
Old 02-29-20, 09:07 PM
  #7  
bluehills3149
Senior Member
 
bluehills3149's Avatar
 
Join Date: Jun 2014
Location: Brooklyn USA
Posts: 312

Bikes: depends what week it is..

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 105 Post(s)
Likes: 0
Liked 18 Times in 16 Posts
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.
bluehills3149 is offline  
Likes For bluehills3149:
Old 03-02-20, 11:47 AM
  #8  
BMarino
Junior Member
Thread Starter
 
Join Date: Jul 2019
Posts: 17
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked 3 Times in 3 Posts
Thanks for your replies everyone! It seems I was definitely overconcerned over this!
BMarino is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.