Should I use slime-filled inner tubes or anti-puncture lining?

I've never tried an anti puncture lining, so can't comment on those. But my experience with slime tubes is that you still get a puncture and now also have the added hassle of slime all over everything.

The correct solution to this problem is to use proper tubeless tyres and sealant, however even though this is now a well established technology for MTB, may well be difficult and expensive to get setup initially (might need new rims).

I put the Tannus Tire Liners in with my tubes.

They are very lightweight, but do not compress easily, so if there is a puncture, you can still ride on them to get back:

I'll report back on their true performance, if I ever get a flat, but I put these in my tubeless tires & rims (swapped out the stems) because they provide greater puncture protection, do not create a mess, and do not leak after long storage like the tubeless sealant can.

There are a number of solutions cyclists use to manage punctures:

1. "Patch whenever needed"

This is for the vast majority of conditions the optimal strategy. The strategy is based on the observation that punctures, although possible, are relatively rare. A cyclist can ride several thousand kilometers without getting a puncture. If the tires are made more puncture resistant, this will increase their rolling resistance. The rolling resistance means that 5 minutes of saved time patching punctures can actually require 5 hours of extra time needed to ride the distance.

However, there are some situations where this "patch whenever needed" strategy is no longer optimal. For example, in northern climates where roads can have a layer of ice in them, they spread a particularly sharp form of gravel to reduce pedestrian accidents due to falling on slippery ice. The gravel bits can be thin, sharp and as much as 15 millimeters long. Many of these areas also erroneously combine pedestrian paths with bike paths, instead of placing the cyclist in the optimal location on the right side of the road. Often times, riding on the right side of the road is illegal if there's a bike path or shared use path nearby. Thus, cyclists have no option than to ride on the sharp gravel distributed on the shared use paths. Especially when the snow and ice melts, the roads have only a wet layer of this sharp gravel directly on pavement. The water acts as a lubricant, reducing the friction between the tire rubber and sharp gravel bits. The sharp gravel bits always puncture the tire rather than "puncturing" the pavement because the tire is softer than the pavement. In these conditions, it's often cold, wet and dark, and punctures repeatedly happen once every 100 km. Thus the "patch whenever needed" strategy is no longer optimal.

2. Tubeless tires

Tubeless tires seem to be a particularly fashionable technology nowadays. They attempt to solve punctures but fail in that. Tubeless tires still have punctures.

A tubed tire setup requires one to carry only one spare inner tube plus a patch kit. This prepares the rider for practically anything. When a tube punctures, simply install the spare tube and patch the punctured tube which becomes the new spare tube. A tubeless setup relies on the theory that a messy sealant can seal punctures. It seals only some punctures, and often a lot of air escapes before the puncture is sealed so it may require re-pumping when having a sealed puncture. Because of the huge mess, tubeless tires cannot be patched so whenever there's a puncture that wasn't sealed, one needs to install an inner tube. To prepare for both rear and front punctures, the cyclist needs to carry two spare inner tubes as opposed to only one. The size of the emergency toolkit practically doubles because the spare tube is by far the largest component in the emergency toolkit.

Tubeless tires also don't work with the very best of rims that have double eyelets. Thus, with tubeless tires one can only use unreliable and/or needlessly heavy rims because double eyelets are needed in rims to distribute spoke tension across both the inner and the outer walls.

Tubeless tires also make the rider feel safe due to not having to think about pinch flats. A bit later, the rider who didn't worry about pinch flats suffers rim damage, which is something that cannot be repaired with roadside tools easily. The rider using tubed tires, having learned to avoid pinch flats, has also learned to avoid rim damage, and rides more carefully, thus not damaging the rim.

3. Tubeless sealant in inner tube

One can actually get the sealing benefits of tubeless tires when using inner tubes. Simply put the tubeless sealant inside the inner tube. The problem is that it makes a huge mess, making patching the inner tube impossible.

4. Slime in inner tube

There are several inner tubes that have a slime that's supposed to seal holes. It has the same problem as tubeless tires, namely that they don't seal all holes. Also when patching is needed, the slime has made a huge mess making patching impossible.

5. Tire with thick rubber

One solution is to use a tire that has a puncture protection belt that's supposed to work due to its thickness. For example, Schwalbe Marathon Plus tires are 7.5mm thick. To puncture the 7.5mm thick tire and 1.5mm thick inner tube, an object 9mm long is needed. Unfortunately, the sharp gravel used in northern climates repeatedly punctures this 9mm thick system. The thick rubber somewhat increases rolling resistance too. So it makes you slower while not preventing punctures.

6. Tire with some tear-resistant fabric

Because it has become today impossible to sell tires that are not puncture protected, manufacturers needed something that doesn't increase rolling resistance much but can be sold to unsuspecting cyclists as a "puncture protection" technology. Thus, nearly every tire, even high-performance ones such as Continental Grand Prix 5000, has a tear-resistant fabric. It doesn't do what it claims to do, namely to eliminate punctures. Well, at least it doesn't increase rolling resistance much so it's not harmful either.

7. Stiff liner

These stiff liners are usually around 1mm thick. They work by being stiff as opposed to rubber that isn't. So even if there are hazardous objects that can puncture the tire otherwise, the last 1mm bit of protection can actually prevent some objects from puncturing the inner tube. The stiff liners are sold in varying widths and can be cut to size.

One problem with these stiff liners is that the ends damage the inner tube. After 1000 km of use, the inner tube repeatedly punctures at the ends of the liner. It is practically impossible to cut the liner so that the ends touch each other. Either the liner is too long or too short. So you get 1000 km of trouble free riding and then a puncture, with no obvious cause of it in the tire. Upon closer inspection, the puncture happened exactly at the ends of the liner. Upon even closer inspection, the sides of the stiff liners have also started to damage the inner tube.

To make the stiff liner less harmful to inner tubes, it's possible to cut it slightly longer than needed and taper the ends of it using a piece of sandpaper so that one tapered end is on top of the other tapered end. This can reduce the punctures caused by the ends of the liners. The sides of the stiff liner can also be protected by adding several thick layers of duct tape which can reduce the probability of inner tube damage at the sides.

However, this effort is not worth it because there usually is a better solution:

8. Thick soft armor

Thick soft armor is sold at least by Tannus. It is over 10mm thick in the middle so it works against punctures not by its stiffness but by having such a thick layer that most objects (yes, even including the sharp gravel used in northern countries) can't penetrate it. Having over 10mm thick armor may sound heavy but actually a typical liner weighs only about 200 grams per tire because the material is foam-like.

The problem of soft armors are several, however. First, it requires strong thumbs and a bit of effort to install. Secondly, it is not available for odd-sized wheels. (Got a Brompton? You have to use the stiff liner instead of the better armor as armor isn't available.) Thirdly, it requires one to switch to a smaller inner tube than one usually uses with a given tyre, so one has to re-purchase the whole stock of inner tubes one has.

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My opinion: in most cases, the best strategy is to patch whenever needed. In the cases such as sharp gravel used in northern countries, one needs to decide between armour (use it if at all available for your wheel size!) and liner (you have to install it carefully and protect it with duct tape to prevent it from puncturing the inner tubes automatically in 1000 km).

I'm by no means a "pro" or even that prolific on my bike any longer, but, if you're changing tyres and tubes, check into the puncture resistance of your tyres - I found the properly resistant ones to be almost miraculous compared to "standard puncture resistance" (and my goodness, non-resistant tyres will get punctures if you look at them wrong!). See what the side protection is too - most tyres are pretty good on the main central rolling area, but get worse up the sides - a good MTB tyre should have taken the likelihood of a side puncture into account.

Secondly, as noted elsewhere, the slime only fixes small punctures. A small thorn or similar probably qualifies, but if it's got through a puncture resistant tyre, it's probably not a small thorn. As noted, slime also tends to find its way out of the holes and into everything else which makes patching or just replacing the tube a cleaning job as well as everything else (any valve work, including the little bit of air that escapes when you take the pump off it, also spits out some slime).

Most "serious" cyclists I've ever asked don't like tyre liners. I've tried them, and if poorly fitted you can really feel them as you ride (on hard surfaces, especially). There's an inevitable seam between ends of the liner (if you use something like this: https://www.wiggle.co.uk/panaracer-flataway-tyre-liner-1), and that causes a bump in the rolling of the wheel, but if you can fit them really carefully they do indeed provide a pretty solid layer against punctures (I'd go as far as to say an almost impregnable barrier). However, they don't protect you against punctures where there's no liner - so if the liner's just on the running edge of the tyre, then the sides are still vulnerable. Fine if you're rolling over broken glass, but not so good in the thorn bushes.

I've never had a tubeless bike tyre, so can't comment about those. A bit like disk brakes though, I'm sure they're very good if you've got a pro bike team support vehicle nearby - if not, you've got to cover that function yourself. If you're a bit lazy or less than diligent about fitting and maintenance then maybe not so good.