Sport And Biking Talk: When should you replace your carbon handlebar?

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.

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 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.

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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