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Finish Line FiberLink Tubeless Tire Sealant works very well, sealing quickly at setup and staying sealed whatever happened over several months of testing. I did have one strange issue early on which I never got to the bottom of, but it was never repeated.
The strange problem was the fibres (or fibers, if you prefer simplified English...) clumping together into a single ball, which obviously meant they were no longer available to wash into holes and clog them up. This latex sealant cures in air and plugs small holes like any other, and the fibres – made from kevlar – are there to reinforce larger plugs by interlinking.
Checking the sealant after a month revealed a single large ball of fibres in each tyre. However, having filled the same tyres on new rims with a fresh dose from the same bottle of FiberLink, I had no such issue again. Even after more months than I care to admit, because I should have submitted this review ages ago, there was no further balling of fibres.
And yes, I followed the instructions each time, vigorously shaking the bottle for about a year (approx) and never using CO2, even though that's allowed in an emergency. I also used a measuring jug to get the dosage just right, rather than the guide lines on the sticker, which may or may not be accurately stuck.
Two other testers were using FiberLink during the same period, and neither had any problem with the fibres balling together. I don't know what I did wrong – and presumably a large puncture would have defeated my first installation – but anecdotal evidence says this issue is rare.
Actually, I never had a single (noticeable) puncture during the test, even with the fibre failure, despite my wintry lanes being seriously dirty, crap-strewn and cracked, and there being thorny hedge clippings all over them at one point as well. Honestly, they'd probably puncture wooden clogs if you walked around here.
I also never suffered any large tyre stabs or tears either, to see how the kevlar threads did at blocking larger holes (though Finish Line makes no 'seals Xmm holes' claims anyway).
I found very little sign of FiberLink drying out after around three months. Basically, this stuff does just what you want: it goes in easily, seals immediately and the tyre never went flat while I was riding (or any other time, for that matter). Oh, and it doesn't particularly smell, either.
For a large chunk of the test it was around or below freezing, with highs of perhaps 10°C, so low temperatures don't seem an issue.
This Finish Line setup did lose a bit more pressure than tubes when left for a while in the shed – say 15-20psi where a tube would drop 10 – but the losses were consistent across both wheels, and over any given number of days too.
At £12.99 for 240ml this bottle works out as 5.4p per millilitre, which is slightly cheaper than most of what we've tested lately – if not the cheapest option out there.
For comparison, the clothes-staining (read our review) Pirelli Cinturato Sealant is good and works out at 8p per millilitre (£9.99 for 125ml), while Squirt Seal Tyre Sealant (review here) is 6.6p (£9.99 for 150ml) and Momum Gum Tubeless Tyre Sealant is 6p (200ml for £11.99).
However, something like Weldtite's Tubeless Sealant can beat all these quite easily at 4.6p per millilitre – it's £10.99 for 240ml.
As always, though, there are useful savings to be had by buying larger bottles, and all these products are available that way.
In Finish Line's case, FiberLink also comes in a 960ml bottle for £39.99 (4.1p per millilitre) or a workshop-sized plunge-pool of a thing that's 3.8L and £119.99 (3.1p)
Strange but unrepeated balling issue aside, this sealant works very well for its reasonable price.
Gets the job done without fuss, lasts well and is reasonably priced
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road.cc test report
Make and model: Finish Line FiberLink Tubeless Tire Sealant
Size tested: 240ml
Tell us what the product is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Finish Line says: "Finish Line FiberLink Tubeless Sealant is built with Kevlar to deliver faster and stronger seals."
Tell us some more about the technical aspects of the product?
From Finish Line:
* 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
* Mountain Bike Tires
* Gravel Tires
* Road Tires
Tell us how the product performed overall when used for its designed purpose
Tell us what you particularly liked about the product
Seals quickly and reliably, price is good, resists drying out too fast.
Tell us what you particularly disliked about the product
Dosage guide marks on label aren't hugely accurate, particles can ball up together.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
It's good – this is at the cheaper end for a quality sealant.
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Use this box to explain your overall score
This just got on with the job, sealed quickly and didn't lose much pressure between rides. I did have an issue with the fibres balling up together, but only on one setup out of two, and two other reviewers running this same sealant had no problems with that at all. Overall the performance is good.
About the tester
I usually ride: Vitus Zenium SL VR Disc My best bike is:
I've been riding for: 10-20 years I ride: A few times a week I would class myself as: Experienced
I regularly do the following types of riding: general fitness riding, mtb,