Finish Line FiberLink is a latex-based tubeless sealant with added Kevlar fibres that does a great job of sealing punctures of various sizes. How does it compare against the very best tubeless sealants? Read on for the final verdict.

With multiple uses from body armour and high-strength cables to folding tyre beads and puncture protection for bikes, a few companies are now using Kevlar fibers – or fibres for us this side of the Atlantic – as a method of creating a particle to block and seal a puncture.

 

Finish Line FiberLink Tubeless Sealant – Technical details

The Finish Line FiberLink is a natural latex-based solution, which may be an issue for those with a latex allergy. Finish Line does produce a non-latex and ammonia-free sealant option but we did not have this available to test.

The sealant is available in three sizes with a smaller 8oz (240ml) that should be enough for two off-road tyres, a larger 32oz (940ml) and a workshop-sized one-gallon (3.8-litre) bottle.

Finish Line claims it can seal punctures up to 8mm and it also claims it is low odour, although I found it to be the strongest-smelling liquid of all we have tested (it’s got a very strong latex and ammonia smell). The smaller bottle has a nozzle sized to fit over a Presta valve stem with the core removed but the larger bottles come without this nifty feature.

The sealant needs to be shaken well before pouring into a tyre. You can see the small black Kevlar fibres, which are supposed to clog within the latex solution and dry quickly in the event of a puncture.

In the event of a puncture or simply when installing a tyre, the use of CO2 is not advised by Finish Line as this can often cause the solution to dry up quickly. Finish Line suggests that it can be used in an emergency but it will reduce the effectiveness and should be replaced as soon as possible.

Finish_Line_Fiberlink_Tubeless_Sealant_Inside.jpg
Finish_Line_Fiberlink_Tubeless_Sealant_Inside (Image Credit: Matt Page)
Finish_Line_Fiberlink_Tubeless_Sealant_Inside.jpg, by Matt Page

Finish Line FiberLink Tubeless Sealant – Performance

To test sealant performance, we created a standardised puncture test to assess each contender. The same exact tyre on the same rim for each sealant. The tyre used was a Halo GXC, measuring 47mm. Tyre sealant was added in the amount suggested by the manufacturer, and the tyre was inflated to 40psi. This pressure was chosen to give a realistic tyre pressure for all areas of off-road riding. A digital tyre pressure gauge was used to ensure that the pressure was identical on each test. After that, the tyre was rotated sufficiently to ensure that it was distributed evenly throughout the tyre. The tyres were all punctured by driving a 3mm nail through the carcass. The wheel was rotated to assess if the sealant had successfully sealed the hole. If the sealant worked, the test was repeated using a 5mm diameter nail, and if successful on the larger hole the remaining air pressure was measured with a digital pressure gauge and the result was recorded.

Finish Line FiberLink Tubeless Sealant performed well and, while there was some spray of sealant released on both 3mm and 5mm punctures, both were sealed quickly, with the larger 5mm puncture, losing just one psi of pressure.

Over several months within the tyre, the sealant has lasted well with very little drying out. While some of the Kevlar particles have stuck together, most of the fibres were well spread throughout the solution.

Finish_Line_Fiberlink_Tubeless_Sealant_Fibers.jpg
Finish_Line_Fiberlink_Tubeless_Sealant_Fibers (Image Credit: Matt Page)
Finish_Line_Fiberlink_Tubeless_Sealant_Fibers.jpg, by Matt Page

Finish Line FiberLink Tubeless Sealant – Verdict

Finish Line FiberLink is available in three sizes: a small 240ml bottle (£13), a larger 940ml bottle (£30) and a huge one-gallon (3.8-litre) bottle aimed more towards bike shops ( £130). There are a few other sealants available in workshop sizes such as the 5-litre options from Peaty’s (£125) and Muc-Off (£130).

The smaller bottle is more competitive in price with only a few options cheaper for the same size, such as Halo Fibre-Tech costing £8 for a 250ml bottle, and the 940ml bottle is on-par with many others with Vittoria Universal Tubeless sealant, Peaty’s Holeshot and Muc-Off also £30.

Finish Line FiberLink has a strong and distinct odour that I found off-putting and the latex-based solution could be a problem for anyone with an allergy. However, for those who can handle the smell, the sealing performance is excellent and longlasting.

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Test report Finish Line FiberLink Tubeless Sealant review £30.00

Accessories – misc

Product purpose: 

Finish Line says:
Finish Line FiberLink™ Tubeless Sealant is built with Kevlar® to deliver faster and stronger seals.
FiberLink™ represents a new standard for tubeless bicycle tire sealant. Developed with Finish Line’s proprietary FiberLink™ Technology, this ground breaking pro latex formula seals quickly, ensures maximum seal integrity and delivers optimum longevity.

What is FiberLink™ Technology?
Kevlar® fibers work synergistically with fast-acting natural latex to seal punctures as they occur. Free-flowing latex cures rapidly to create an adhesive seal which is reinforced with interlinking Kevlar fibers.

Features & Benefits:
• Pro latex formula utilizes FiberLink™ Technology
• Kevlar® fibers ensure strong, long-lasting seals
• Low viscosity is ideal for race conditions
• Fast-acting natural latex reduces air loss
• Optimum longevity between refresh cycles
• Low odor and easy to setup

Build extra: 

Finish Line lists:

Common Applications:
• Mountain Bike Tires
• Gravel Tires
• Road Tires

Tire Dosage Guide:
• Road – 2-3oz
• CX, Gravel, 26″, 27.5″ – 3-4oz
• 29″ – 4-5oz
• 29+ – 5-6oz
• Fat – 7-8oz

CO2 Compatibility:
CO2 can be used with FiberLink™ Tubeless Sealant in an emergency when a pump is not available. However, the CO2 will reduce the sealant’s effectiveness. For best practices, we recommend refreshing FiberLink™ soon after introducing CO2 to it.

Product construction 


Product performance 


Product durability 


Product durability extra: 

Some signs of the Kevlar particles balling up, but most remaining within the fluid

product value 


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Overall performance: 

Very smelly but offering good puncture performance and lasts well over several months in the tyre.

Product likes: 

The performance during puncture tests, and how long it has lasted.

Product dislikes: 

Limited bottle sizes are available, and quite smelly.

Enjoy: 

It performed well in the puncture tests, and I would have confidence to use it in my bike

Buy: 

Perhaps, although there are other good performing sealants available in a larger bottle with a less pungent smell.

Recommend: 

Maybe

Conclusion: 

Despite claims of a low odour, I found the opposite with Finish Line FiberLink having a very strong and smell that you would associate for a latex sealant. This was however one of the only downsides, and puncture performance was impressive, and longevity within the tyre with little evidence of drying up.