Should you pre-slime a bike tire?

Most bikers have had to deal with a flat tire. It sucks when you are miles from home or a bike shop and find yourself walking your bike back.

One quick road repair option for a flat bike tire is to use Slime bike tire sealant. Basically a goo you squirt into the tire which will seal any holes from the inside.

That’s great and all but then you need to be carrying around a bottle of that stuff which, while not a huge deal, is not ideal.

I have heard some people pre-slime their bike tires. Basically put the goo in before you get a flat. If a puncture occurs the tire just seals itself up right away.

Is this a good idea? It seems too easy to not have a downside.

Does the slime stay gooey, and sufficiently fluid that - if a puncture does occur - it will move to the area of the puncture? I would imagine that even though there is a very limited amount of air inside the tube, the extra slime would dry up and be useless.

I suppose you could insert so much slime that all areas of the tire are already covered, but then you might as well get solid doesn’t-need-air tires.

I’m also wondering if a substantial amount of goo would move the wheel’s center of gravity, and/or make the wheel significantly heavier, which would make pedalling harder.

If you’re going to buy something to try to prevent punctures, I would go with something like a Mr. Tuffy liner. I’ve used it with good success in the past. I agree that it seems unlikely that Slime would stay active for weeks or months inside the tire.

Around Sept-Oct of last year (2020) I was attempting to mulch leaves with my riding mower when I noticed a front tire going flat. Called a friend with an air bubble and after putting some air in, there was a fairly substantial hole/leak. I finished up what I could in 10-15 minutes and parked it with a jack under the leaking tire axle. I just aired it up a couple days ago and NO leaks. Checked my records, and I had put slime in it June 2018. I was impressed!

I’ve never used slime so I can’t answer the OP directly, but my go-to solution for this problem is to carry a spare new inner tube at all times - fresh out the box and (therefore) tightly rolled up, it fits neatly into a small under-saddle bag, along with a couple of tyre levers and hex wrenches for any other minor running repairs needed. That way, if you get a puncture you can just take the outer tyre off, remove the punctured tube, then (important) after checking whatever caused the puncture isn’t still lodged in the tyre, add the fresh inner tube and be on your way again in a matter of minutes. Then if the punctured tube is salvageable, you can fiddle around trying to find the hole when you get home.

Also, since switching to puncture resistant tyres, I’ve only had one puncture in about 5,000 miles of (largely road) riding - highly recommend them. They add a small amount of weight but in my opinion it’s well worth it.

I once upon a time put the slime in my motorbike tires. I never had flats (the tires wore away first) so I cant be sure if it worked or not. The theory was - it distributed itself evenly around inside tread area of the tire, so covered all areas where leaks are likely to occur. Theory also was, in a closed tire it stayed sufficiently fluid to do its job. Conveniently, it also supposedly helped balance the tire (except if the bike bike sat for a long time, then it would take a while to redistribute.)

Since I never saw the dead tires, i have no idea how true this is. The only flats I had were a valve problem and a sidewall problem. (3-inch screw stuck in half-way up the sidewall, on a month-old tire!). Goop didn’t help those.

Its weight (unsprung weight) is the main drawback. Otherwise, why not?

That said, if I was inclined to slime my tires, I’d buy the pre-slimed innertubes (guessing you’re not tubeless, because the necessary sealant does much the same job) instead of bothering with putting it in myself.

According to the Slime FAQ, you can pre-slime your tires and it will last 2 years:

I thought the whole point of the goo was to have it already in your tyres. You can get inner tubes that come with slime pre-installed.

The instructions don’t specifically say but they strongly imply that you slime the tire before hand.

I have tubeless tyres on my mountain bike. Every six months or so I replace the sealant.

I went riding in New Mexico near Alamagordo many years ago and the locals ride with Tuffy Liner AND these Airlock Presta Valve Tube | due to the acacia bushes and rocks. FWIW, landing in them is…nasty.
This was pre tubeless but sliming your tires can be a good compromise if you’re running tubeless.

When I was younger and poor, I used to carry patches and do roadside repairs. But I got so many punctures, I would have little patches all over and inevitably one or two would start slowly leaking and I was always airing up. Then one would catastrophically fail while out riding.

Now I follow the good Dead_Cat routine, including the thicker road bike tires. I mountain and road bike a lot and I still routinely get 1-2 flats per year, but I swap them for a new tube, or one with 1-2 very good patches I applied from the comfort of my garage. I toss them after that - no more 20 patches.

Edited to add: I lived for a bit in a region that had “goat head” thorns. No way to keep a tube inflated in that area. Would never move back to a place plagued with them. You have to run solid tubes or get used to riding on flat tires. Or, maybe Slime would work there? It didn’t exist back then…

I was always a ‘carry a spare tube’ (only) cyclist, and – FWIW – I took them out of their packaging, ‘opened them up,’ coated them (by hand) with baby powder, and then stored them in a Ziploc bag in my under-saddle bag.

My wife used the Tuffy liners but felt a noticeable difference, to @bump basic point (though I thought it was rotational mass more than unsprung weight ?).

ETA: I’d guess that, on a full-suspension MTB, it might be unsprung weight at least as much as rotational mass :wink:

Yeah, the answer to goatheads, and actually to all flat related questions, is to switch to tubeless. It absolutely changes the game.

For anyone who doesn’t ride enough to bother with the expense of going tubeless, Mr. Tuffy liners and slimed tubes are about the best you can do. And it’s about 10% the effectiveness of tubeless tires. Go tubeless.

Converting to tubeless does have a bit of a steep learning curve, and you may be tempted to have a shop do the work for you. Don’t. Spend a day cursing a blue streak while you learn. It’s a pain, but an absolute necessity to know how to do it yourself. After a few tire changes you’ll be an old hand at it.

There is, in fact, a problem with a pre-slimed (by you or the factory) bicycle tube. As soon as you run over something the slime cannot handle, SLIME WILL SPRAY OUT ALL OVER THE PLACE AT HIGH PRESSURE. :slight_smile:

I have only ever bought the pre-slimed tires when the normal ones weren’t in stock, and never found them to be helpful in anyway. I can see them being useful if the puncture occurs from hitting an obstruction too fast and the tube gets compressed and pinched hard enough to puncture (the infamous “snakebite”). But outside of that, if it’s a puncture from, say, riding over a thorn or other sharp object, I found the object usually gets wedged enough into the tire itself that it doesn’t come out, and it’s continued presence (still protruding into the tube) is enough to defeat the slime. This has led to what is (to me—and apparently @DPRK as well) a telltale sign of a puncture (and how useless the slime is) as I will often find myself getting sprinkled by something like a very light, intermittent mist, almost as if it were drizzling, but then the “rain” seems to be falling up and hitting me more on the undersurfaces of the face than anywhere else.

I carry a small pump and a patch kit. Works every time.


And just a couple of notes from my experience.

I worked in a shop after the military. When a car came in with a tire that needed to be replaced that had Fix-a-Flat in it, we charged more, because it was so nasty to deal with. It smelled like rotten fish, blueberries, and an old, used condom. Seriously. It is the weirdest thing I’ve ever smelled. And we were told to avoid touching it, and to wash immediately if we did. I wouldn’t think it had anything corrosive in it, so I don’t know why they said that-- maybe it had a toxin that could be absorbed through the skin.

Second is, I used to bike everywhere. I would go to state parks, camp overnight, and bike back. A four hour ride was a nice afternoon.

There are tubes, and there are tubes. Pay for the expensive ones that claim to be puncture resistant. This was when I was in my 20s, and watching every dollar. I biked a minimum of 100 miles a week, seriously. I had rain gear, I had snow gear, I could carry a lot of Gatorade when it was 95°F. Unless I had to haul something that you couldn’t strap to a bike or carry in a backpack, or had to be somewhere that was just impossibly far away, like Terre Haute by 8am, I biked.

In about 10 years of being such a serious biker, I think I had one puncture. I changed the tube myself, pumped it up with the hand pump I carried, and it took about 20 minutes, because I knew how to do it-- I had practiced.

I did carry a cheap tube as my back-up, because I carried a couple, in case I pinched one. I also carried a patch kit, because it patching was possible, it was preferable.

After I did the emergency tube change on the road, I went to a shop ASAP, had a good tube installed, and the wheel trued, also, the tire checked to make sure the puncture in the tire wouldn’t damage the new tube. Sometimes the word back was that the tire was worn enough that since they were taking it off anyway, I might as well replace it. But I trusted the bike shop. The manager was the younger brother of a good friend of mine from high school, and I was a very loyal customer-- not someone they wanted to try to soak once and never see again.

So, basically, I say “No,” don’t “pre-slime.” Carry a patch kit, a new tube, a tire tool, and a hand pump. Also, a cell phone, something that didn’t exist when I biked. And practice changing a tube before you need to do it in an emergency.

Also, pay for the good tubes that are puncture-resistant.

Having never heard of them, I checked out your Airlock tubes on that website. Not a single size is available on line. That said, I’d probably buy them when available. I hate, hate, hate getting flats. I did switch to puncture resistant tires and haven’t had a flat in 1700 miles of road riding.

There are a lot of options for self-sealing tubes actually. Slime makes some, Specialized makes the Airlock series, and it seems like every other mass-market cycling gear manufacturer (Bell, Schwinn, etc…) makes their own variant.

I, too, used to do it this way: Change the tube, then patch the old one when I had a chance. But lately, I’ve realized that there isn’t really much difference in price between a patch kit and an entire new tube, so now, I mostly don’t even bother trying to patch tubes.

Yes – I actually thought the primary use for Slime was as a flat preventative, not repair.

Seconded. I switched to Schwalbe Marathon tires just a little while ago. I ride all over NYC on my bike since the start of the pandemic. Seems like a good idea to avoid the subway.

So far so good. The streets of NYC are littered with broken glass, bits of metal, and who knows what else. No flats so far. Which, I know, isn’t proof of anything, but in the past, on other brands of tire, I’ve never gone this long without a flat.

Schwalbe’s Marathon Plus tires are advertised to be even more flat-resistant than the Marathons, but I couldn’t find them in the right size (I ride a folding bike with very small wheels).

Back in my motorcycle days, I was aware that people did this, on both tube and tubeless tires. At rallies, you’d see people offering to slime your tires on the spot. Maybe it worked, I don’t know.

The downside was said to be that, if it didn’t work, it made the tire impossible to repair, which was especially costly in the case of tubeless tires.

That seems to be true all around, for all kinds of bike parts. When I needed new tires, my local bike stores had nothing. The usual online bike parts sellers had few tires, and none in the size I needed. I ended up getting tires from a recumbent bike shop in Utah (again – the small wheels thing).

I suppose it’s due to increased demand during the pandemic, combined with trade issues with China…