When should you replace your carbon handlebar?

If you have to ask the question, it's probably time for a replacement

Company Spotlight Components
It’s just a scratch. Promise.

It’s just a scratch. Promise.

A few weeks ago one of our testers binned it on a review bike. He fell hard enough his parents felt it was necessary for him to undergo a cat scan. In addition to smacking his head, he also suffered lacerations and bruises to his face and arm. Once we figured out he’d be fine, it was time to assess the damage to the bike. No one’s sure what happened, but we know the bike went full tilt boogie into a tree. In the process, the brake lever assembly cracked and left gouges in the handlebar (despite everything being torqued to spec).

See? Not that bad.

See? Not that bad.

Replacing the brake and carbon bar with similar products would cost roughly $500. When faced with that dilemma, I wonder how many consumers would choose to keep riding the scratched up bar. Carbon is supposed to be stronger than aluminum, right?

Turns out, there’s no good information online regarding when you should replace your carbon handlebar. There are plenty of myths, but no facts. To find out more, I reached out to a half-dozen different handlebar manufacturers. Virtually every brand came back and said they could not respond to our questions on the record, except one.

Renthal sponsors an impressive cadre of professional motocross athletes, including standouts like Ryan Dungey, Ryan Villopoto, Ricky Carmichael, Jeff Emig, and Jeremy McGrath. In the cycling arena, they sponsor Aaron Gwin, Troy Brosnan, Jared Graves, and Richie Rude.

Renthal sponsors an impressive cadre of professional motocross athletes, including standouts like Ryan Dungey, Ryan Villopoto, Ricky Carmichael, Jeff Emig, and Jeremy McGrath. In the cycling arena, they sponsor Aaron Gwin, Troy Brosnan, Jared Graves, and Richie Rude.

Renthal is a UK based company which manufacturers motorcycles accessories, including handlebars, sprockets, and grips. Their components are sold as OEM spec by a range of iconic brands that includes Honda, Suzuki, and KTM. Founded in 1969, they entered the MTB market roughly five years ago.

Renthal manufactures a full range of carbon and aluminum handlebars in 31.8 and 35mm diameters.

Renthal manufactures a full range of carbon and aluminum handlebars in 31.8mm and 35mm diameters.

Here is what their engineering team had to say (as relayed by Ian Collins, the cycling product marketing manager) regarding handlebar replacement:

Mtbr: How do the properties of aluminum and carbon differ in terms of fatigue life?
Renthal: In metallic parts fatigue occurs as a crack propagates through the grain structure until it reaches a critical length and the part fails. Generally in composites, the mechanical properties of the material degrade under cyclic loading until it fails. The actual fatigue life of the two materials can’t be directly compared, as it depends as much on the construction of the component as the material it is constructed from.

Mtbr: Is there a standard for strength or fatigue life that all handlebars must pass? Does it differ for aluminium or carbon handlebars?
Renthal: EN14766 & ISO 4210 are applicable testing standards which Renthal parts are tested to. Regardless of material, there should be no visible cracks or fractures in any part of the handlebar. For carbon fiber handlebars the peak deflection during the test should not increase by more than 20% of the initial values. We also ensure Renthal handlebars exceed the EN BMX drop test standard. Although this is not a requirement, we recognize the importance of impact testing mountain bike handlebars.

Renthal uses sensors placed on the ends of each bar to help tune the flex characteristics of their bar.

Renthal uses sensors placed on the ends of each bar to help tune the flex characteristics of their bar.

Mtbr: Can you please describe some of the testing procedures you use? What are these tests designed to emulate?
Renthal: We test to EN14766 and conduct our own performance field testing. We also test the specific flex for a given load for every handlebar. We set this specific flex as this determines the ride-feel of the handlebar on the trail. We arrived at our specified specific flex and given load through extensive R&D field testing with data acquisition equipment. All the tests ensure that the handlebar is safe to use for all riding conditions and has the desired riding characteristics.

Mtbr: Should you replace your carbon handlebars after a certain amount of time? How about aluminum?
Renthal: Speaking only for Renthal handlebars, if the product is used as intended there is no reason why it should be periodically changed unless it has been damaged in a crash or some other abuse. This is the same for aluminum or carbon fiber handlebars.

Both sides of our carbon bar suffered from cosmetic damage to the surface. Was it anything more than that? It’s hard to say without an X-ray imager.

Both sides of our carbon bar suffered cosmetic damage to the surface. Was it anything more than that? It’s hard to say without an X-ray imager.

Mtbr: If you crash on a carbon bar, what clues should you look for to determine if the bar might be compromised?
Renthal: Typically damage will be evident on the exterior surface. Due to the nature of carbon, if a bar’s integrity has been compromised, it is likely to be obvious as broken fibers or delaminated layers may be exposed. Since this is not true of every incident, our advice is always to replace a carbon handlebar after a crash.

Mtbr: There’s a myth that states you can use a coin to determine if a frame/component is cracked by tapping around the damaged area. As you tap, if there’s a discernible change in pitch, the item may be broken. Is there any validity to this method?
Renthal: It is certainly true that a change in a parts stiffness will cause a different pitch ‘tap’ to be heard, however, without knowing what that sound was before any potential damage it is hard to categorically identify damage, particularity if the damage is so minor that it is not visually identifiable. It is not recommended to rely on this method of inspection.

Have you replaced your handlebar after a big crash as a safety precaution, or would you run it if had surface scratching like our test kit?

For more info, visit www.renthal.com

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  • Farmer Ted says:

    I don’t know that I’d call that ‘surface scratching’. The damage goes through the exterior gel coat and into the carbon structure to at least some degree. As financially painful as it might be, I’d probably replace that bar. It may be fine and last forever, it may not. The problem is that if it fails catastrophically lading a jump or some other big hit, you’re going down with it and there’s really no way to tell if and when it will fail beforehand.

    There are places out there that will repair carbon fiber parts but in the case of a handlebar, it may be cheaper just to buy a new one since, with a little bargain hunting, they can be had for $100-150 vs a damaged carbon frame which would cost thousands to replace.

    If you really wanted to be redneck, you could cut the bar down so that the grip clamps to the inside of the damaged area. This should put less stress on the damaged area. You’ll also be running a narrower bar that still may be compromised for strength.

    I’m to the point in my life where I’m just going to spring for the new part. It’s a lot cheaper to fix a bike than it is to fix a human. The risk of a structural part failing just isn’t worth it for me.

  • tyrebyter says:

    That’s why you buy bars from people who actually make them: Renthal.

  • Ibissess says:

    I think just about any bar should be replaced if the crash involves both brake levers being torn off & a CAT scan.

  • Matt says:

    “Since this is not true of every incident, our advice is always to replace a carbon handlebar after a crash.”

    …. Thanks?

  • steve says:

    It’s not a myth, it’s an approved method of determining delimitation. But I come from aviation, and the method typically applies to larger panels, and it’s highly subjective. On a piece so tightly constructed as a handlebar, I can’t see a tap test determining anything useful.

  • peper says:

    Most carbon bar makers will offer a crash replacement at about 1/2 cost. However fleabay carbon all bets are off.

  • mdilthey says:

    Good on Renthal for answering in such a complete way.

    If I crash hard on something, that part may see a second life on a beater commuter or cruising-around-town bike. No sense risking life and limb.

    This is also why I like steel/titanium handlebars. They’re a little more resilient to damage and won’t catastrophically fail all at once. You might get a bad bend, and that’ll tell you it’s time to go shopping.

  • Moondogg says:

    I busted a set of carbon bars landing off a small jump at high speed. They just snapped. Turns out my dropper post clamp had been crushing the carbon. This was my first carbon bars, and I bought a torque wrench so that I could be sure I was tightening all my components to spec. I think the torque settings for brake levers, dropper controls, etc. are too high for carbon bars. I replaced my bars with same model, but now I torque to just tight enough I can’t spin the component without some force.

    Following torques specs is good, but so is common sense. Avoid over tightening anything attached to your bars.

  • Greg Jetnikoff says:

    If you raqdius the bar clamps and anything clamped to them , Easton’s at least seem to last a VERY long time and crashes.
    I am using 2 sets of Easton ultralights that I bought in the very early 2000′s. Crashed MANY times. Keep using them because they are the inch centres and I hate the ridiculous harsh stiffness of bar bars. They have a bit more flex to reduce the stiffness and pounding. Getting hard to get small clamp size stems. Except for Downhill ( and now maybe Enduro) fat bars is one of the great pieces of stupidity of the MTB industry. I have a compressed verterbrae in my neck and simply cannot ride on fat bars as my left arm goes numb. When I can no longer get stems and my thin centres are gone, I will have to give up MTB.

  • Greg Jetnikoff says:

    NO edit…Above should read “stiffness of fat bars”

  • Dan says:

    Try a carbon Chromag BZA 800mm 35mm riser bar. I can watch the bar flex just pushing down on it. Hope thats just how they are made.

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