A nail punctured my rear wheel tire today while riding. My question is, how do you know if you need to replace a tire or simply repair it with a tube repair kit?

The hole looks pretty nasty. The cap part of the nail entered the tire, leaving an L shaped hole.

My concern is that water might get into the wheel in wet conditions.

  • I got bored of fixing punctured/flat tubes and bought much better (like bullet-proof) tires (which are designed for touring).
    – ChrisW
    Jun 11, 2012 at 12:49
  • I had a very small hole in a road bike tyre that used to cause a puncture every 200-400 km. Took me four punctures before I figured it out. Hole was perhaps a millimetre, but it was round, not a cut so the tube just poked through. I patched the inside of the tube in the end.
    – Criggie
    May 10, 2016 at 8:25

8 Answers 8


From personal experience, I'd say a larger-than-usual hole in the tire could have these undesireable side-effects:

  1. The tube might get a bit exposed, and the day-to-day rolling over the hole might wear it down until the tire eventually flats out. Chemical aggresion from road grime or mud could also be involved.
  2. The fabric of the tire might get damaged to the point there is a visible bulge. This not only causes a bump while rolling, but most importantly is a weak point that might lead to tire explosion and and accident.

Most of these somewhat larger punctures damage mainly the rubber and not so much the tire fabric (plies). If that is the case, a simple cautionary patch on the inside (with a regular tube patch) is enough to warrant peace of mind.

If the tire is bulging around the hole when it is inflated at the pressure you use, that is a warning indicating the tire is probably too damaged. A larger or stronger patch might be used inside the tire, and some regular observation to see if it stabilizes or grows is needed, but most probably it would be better to get it off the bike (which is very sad when it is a relatively new tire).

Hope this helps


Generally, if you are using an inner tube in the tire, you should replace the tire if there is more than a 2 millimeter cut in the tire casing. Not in the rubber, mind, but it the threaded cloth casing that your rubber bits are laid on to.

I personally err on the side of replacement rather than risking a serious injury from a blow out at a bad time, so I usually replace when there is a 1mm or larger cut in the casing.

Or if I put a new tube back in, and the hole is large enough to see the tube.


Generally, you repair tubes, not tires. From your last sentence, it sounds like you are indeed talking about the tire.

As it is with the tube, the real answer is "Size Matters". In this case, both the size of the hole and the size (okay, type) of the tire. If I was looking at damage to a road tire "slick", the hole you describe would likely having me change tires. On a cross or MTB tire I might try a repair. In addition to using a tube patch, I'd also glue the "L shaped hole" back together with superglue.

If there's any safety doubt, change tires. The closer to the side of the tire, the higher chance this could cause a lack of integrity while riding.

Never hurts to get a second opinion at your LBS either. Smaller shops will tend to give you a straight answer rather than just going for the sale of a new tire.

Ride Happy!

  • Thanks, sound advice! I am going to open up the wheel and further inspect the damage. After a second look it seems to be easily repairable with a tube repair kit.
    – TheOne
    Jun 10, 2012 at 20:06
  • 2
    I would use contact or rubber cement in lieu of super glue. Superglue isn't flexible when dry and will eventually disolve in water.
    – mikes
    Jun 10, 2012 at 20:11
  • 1
    Mike, I agree with rubber cement for the interior patch, but getting the sides of the hole (the "L") together to prevent further ripping I think might be better with superglue as rubber cement needs to dry and application on parts that naturally touch doesn't always work (you would have to hold them apart until they dried). Ideally, flexible superglue, but since its a rubber installation, you would get quite a bit of stretch from the surrounding rubber. I actually "treat" small gravel holes in my slicks this way and seems to work well (I do use a 'flexible' superglue now that I think about it)
    – Ken Hiatt
    Jun 10, 2012 at 21:42

Always BEST to just replace the tire, but... I have ridden my tires with a gash of an inch or longer. I couldnt recommend it to everyone (legal issues) but I do it all the time. I take an old tube, cut about a 2 inch section out of it (so you have a 2 inch long tube, not just a patch), wrap duct tape around it then duct tape that onto the inside of the tire.Duct Tape Patch

It will poke out the cut a little, but as long as you have a decent tire, your chords will keep it from ripping more.

  • 1
    Good idea for an emergency and the chords in the duct tape probably help, although they'd be much sparser than those in the tyre. Obviously you'd still be risking a blowout, so I'd take it easy (re speed and traffic) with this kind of repair. Feb 27, 2013 at 8:13
  • You are correct. Better safe than sorry. (Me personally, I rode this tire here for over a year in this condition, in skateparks, at high speeds (and altitudes), until the tread wore thin. I trust it, only because I trust the brand of the tire, tough as h*ck! (unless you gash it on a piece of metal))
    – BillyNair
    Nov 27, 2015 at 16:17
  • Other suggestions for materials to use as a boot I have heard: cut up a section of an old tire, cut up a Tyvek mailing envelope.
    – Weiwen Ng
    Aug 15, 2021 at 18:20
  • This is only a temporary repair. You could also just buy Park Tool TB-2 instead of making your own tire boots.
    – juhist
    Nov 13, 2022 at 10:58
  • yes, I cant recommend keeping this permanently, but... this was a new tire, only a week old when I got the gash, and after I did this repair, I rode it until it was bald. Not just ride around town, I ride skateparks, so this stood up to backflips, 360s, 15-20 foot airs, all with 65-80 PSI in it. I cant say people SHOULD do it, but it was done and more than worthy of an emergency fix if you need to get it home. As for the Park Tools Patch, that looks cool, but I never tried them, but I might if I get a gash soon
    – BillyNair
    Nov 15, 2022 at 14:36

I've never heard of repairing a bike tire. Maybe if it were tubeless you could plug it, just as you do on your car. But if not...I guess if you're just cruising around town give it a shot. If you are pushing the limits on this thing, buy a new tire. Worst case you blow out and slide under a truck (or into a tree maybe if we're talking mountain biking?). Best case you end up flatting over and over b/c the now non-smooth inner wall of your tire constantly wears down the tube. When inflated, tubes are very thin and very easily punctured or worn through. Dropping $50 on a decent tire might seem annoying, but if you hurt yourself riding on busted gear, you'll regret having 'saved' that money.

  • In the old style patch sets (at least here) there used to be a patch of fabric just for that. To glue inside a tire to protect the tube when the tire was damaged. I never used it, most people I know never used it either.
    – Willeke
    Aug 9, 2015 at 11:03

My opinion matches zenbike's: when in doubt, replace the tire. My riding is 99% on the road. If your flat is due to a small thorn hole, and you have removed ALL of the thorns, or is a puncture from exposed rim or stem hole burs, you can mitigate those by filing, rim tape, etc. If it is from a nail, tack, or larger puncture (like yours), I feel unsafe letting it ride again - my experience is that it wears another hole in the tube or worse... eventually.

I prefer to retire the tire (sorry, couldn't resist the pun) from outdoor riding and then using it for indoor trainering. While the indoor trainers do wear the tire's outer treads quickly, at least you can get a flat, not worry about falling off, and you don't have a long walk to a replacement.

  • 2
    There's no need to replace a tire because of a simple puncture that did not damage a significant amount of cord in the tire. May 27, 2013 at 0:15

I am not sure if this is going to be accepted as a comment or an answer, so apologies in advance and any superuser please feel free to amend it appropriately

I had a condition a month ago when I braked hard, hit a pothole, somersaulted on the road, and my inner tube had a proper burst with cracks on my back tyre. I would say replace your tyre, get something like a 1200 mile puncture-proof tyres (Schwalbe ones are good) for about $40 (guess). Living in a country like UK where you can never rely on the weather, I always get my tyres replaces in case I have a nasty crack. Rain will destroy my tyre anyway, so no point using those clever crack-repairing glues. Speaking of which, for cracks like 2-3 mm you can use those glues to do the job. They are not too bad, considering that you are not riding somewhere really really hot where your tyre pressure is also affected by the temperature. If you are in a place where rain doesn't really affect your riding, you could probably get away with it.

My suggestion is "Replace your tyre if possible" because your safety is not bigger than your cash :)

If your bike was a Road bike (can't remember), definitely replace the tyres. Road bikes are different animal and with about 120 psi on on wheels, you don't want a cracked and damaged tyre supporting the super-pressurised inner tube!


If the rubber cut is large, replace even if the inner casing is fine

I just realized I'm really stupid today.

I have a Schwalbe Marathon Plus Tour Hs404 700x40c and it is quite resistant, allowing me to do a bit of gravel in between roads on my touring.

On May 2021, I got my first flat on it. It was a perfectly shaped pointed stone, with a very flat base which managed to make it through. I had ridden a Schwalbe of the same type for about 2 years by then, and I know it was a rare occurrence.

After I removed the stone, it left a cut of about 6mm on the exterior rubber. But the inner casing looked fine, and unless I pressed it with my hand, the cut was not very visible, so I decided to continue riding it.

Then today on August 2021 I was doing some other repair, and I noticed that a another stone was stuck in the exact same place! Luckily this one didn't puncture.

But this drove the message home. So soon after the flat, another stone was stuck in there, and I know that tire is quite resistant.

If there's a significant cut on the rubber, replace the tire, obviously. This one was likely a close call for me getting another flat in the middle of nowhere and spoiling a ride or worse.

The stone before I removed it:

enter image description here

The hole when I'm pushing it open:

enter image description here

The inner casing, apparently intact:

enter image description here

Repair strategies

Criggie mentioned in the comments that it should be possible to repair in some cases, which hadn't crossed my mind, so I had a look for it.

The following video from GCN actually explains how to repair even the inner casing by sewing it, but inner casing repair is not a job that would be worth my time on my 35 dollar tires.

They then repair the rubber cut with a product known as "SHOE GOO", which was originally intended to keep shoes of skateboarders going longer, and is readily available.

I ended up buying this one labelled "Shoe Goo II" (it has to be better than the original one, right??): https://www.amazon.co.uk/Shoe-Goo-Crystal-Permanent-Adhesive/dp/B08P5V9GQV I haven't tested the patched tire on the road yet, but the result seems solid and might actually prevent further stones from sticking in.

Here's how the result looks like, with me pressing to open the cut, and it just did not open. I didn't do a perfect job, added a bit too much of it I think, but I'm guessing the excess will just be scrapped off while riding and shouldn't be an issue.

enter image description here

  • In your case, the tyre has a cut that does not penetrate through to the tube. I'd start by gluing it shut from the outside, by flexing it open, lay in some tube vulcanising fluid, wait 10 minutes, then relaxing the tyre and folding it back on itself to close the cut. Then an hour later I'd install the tyre like normal. Second option would be to make the cut wider by trimming with a knife, or taking the triangle tip off that block of tread. For some reason, the road surface you ride in is finding that cut where it doesn't find the other tread lines.
    – Criggie
    Aug 15, 2021 at 18:55
  • If the cut was all the way through., I'd expect the tube to herniate out and blow out. I've experienced that before, a puncture every 150-200 km in the same spot, and it was invisible until the patches started accumulating in the same spot. Good answer though.
    – Criggie
    Aug 15, 2021 at 18:56
  • @Criggie nice, I'm going to try that vulcanising fluid. What brand do you use? youtube.com/watch?v=s0FxUqlXba8 says amazon.co.uk/dp/B07VDV1HMJ should work. Aug 15, 2021 at 19:52

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