Dear bicycle mechanics patron,


I have two questions about tubes, which need a somewhat urgent answer, as you will see soon.


Q1: I had my front tire go flat. I thought it's a snakebite, as I was running it at low pressure to maximize traction on snow/ice. Came home and found that the "puncture" is actually a cleft near the base of the valve (Schrader). The crevice is about 5 mm long, perpendicular to the axis of the valve, and about 2 mm from the base. Given these parameters, do you think it's worthwhile to try and fix this tube, with the usual vulcanizing glue and patch? Note that the rent is rather shallow, and only the central part of it seems to get all the way through the rubber.

Q2: I have a spare 26" tube of the appropriate width. Problem is, I abhor it. It is a Kenda "Schlauch (tube) mit pannenschutz" - that is, a tube filled with some nasty goop, which theoretically would go on filling potential holes, thus rendering the tube "puncture-protected". I hate this good, because the one time I tried one of these tubes, it seemed to want to escape from the tube and fill my pump, and gunk it up. In fact, I did seem to have some issues pumping with that pump, afterwards, for a while. The question is: is there a safe way to pump this sort of tubes, and am I just paranoid, and nothing ill will happen to my pump? Is there some solvent which can wash the hardened goop away, if it does end up in the pump? (Also, is this stuff the spawn of Satan?)


The urgency comes from the fact that tomorrow I need to commute to work, and this is my winter commute bike with the appropriate studded tires. Sans one tube, at the moment.

To answer question number 1. Yes you can with a big patch ,you do run the risk of it not staying . just makes sure the glue area is bigger that the patch. (bigger the hole ,hard to keep in the air. ) ,most people just replace the tube.
To answer question Number 2. When putting in air into a tube with slime or something like it always put the valve at 12 clock and then pump air into it, that way the slime will not clog the valve and / or your pump for that matter.I found just using soap & hot water will work to clean up slime

1. it won't hurt to try to patch this as long as it is not at the bend to the stem.

2. use an air compressor that is on (like at the gas station) to inflate, the pressure should prevent any goo from going back up the pump.

A1) In desperation, I have occasionally tried fixing damages close to the stem by punching a hole through the patch and then threading the stem through the patch before glueing it down in the regular way. But as long as there is a choice I prefer to replace those tubes.
More importantly you need to figure out why you're getting damage like that. As you mention that you've run very low pressure odds are that the tire has slipped on the rim and pulled the tube with it until it tore by the valve.
This is not the oly option though, check rim for burrs while you're at it.

A2) While goop might make patching a tire more difficult it's rare that it interferes with pumping. Goop will follow the laws of gravity and physics, which tends to keep it away from the valve once installed.

Thanks bikeman715 and cyclist2000, very kind of you to help so quickly. I shall heed your advices.

And thank you, too, dabac. Yes, I have already deburred the side of the valve hole where the cleft was created. That does now, as you imply, guarantee that it won't happen again. I would hate to have to run high pressure in the front tire, since I really enjoyed the great traction I got today, but it looks as if though it's not meant to be.

1) Patching the tube will be an exercise in frustration. It is normal to put a one inch patch over a small hole so the distance from the edge of the patch to the hole is almost a 1/2 inch.
In your case, the distance from the edge of the patch to the hole will be less than 2 mm. Getting a good bond, that close to the valve stem will be difficult if not impossible.

2) If you don't like slime filled tubes, then throw that spare away. No point in frustrating yourself.

Living where I do, tubes are cheap and easy to get so I am a wasteful North American.

you can run your front tire under 20 psi of whatever the max is and not get snakebite. let say the max is 60 psi then you run 40 psi and all is good. glad to be of help.

Well, first of all - try to determine if this is the case. If you install the tube/tire with valve straight up you can then see if braking causes it to tilt or not. If it stays straight, then your tire isn't slipping on the rim.
If it does slip there are two options apart from increasing pressure.
1) put a thin layer of liquisole on the bead of the tire. This usually will increase the friction enough to keep the tire from slipping and can be really useful particularly on folding tires.
2) the hardcore-no nonsense approach is to use contact cement or tubular glue on the bead on one side of the tire. You only need one side "open" to be able to get the tube out, so although it sounds drastic the consequences are quite manageable . Tubular glue will keep the tire from slipping and it's weak enough that removing the tire when that day comes isn't too much of a chore.

Right on, guys - the great advices just keep coming! This thread is full-win!

OK, so, I will put some rubber cement on the bead of one side. Brilliant idea, actually.

skilsaw, I agree that patching this tube at the valve might be utterly pointless. I did put the vulcanizing glue in the crevice and around it, and patched it, but I have no faith in it surviving, and I'll come to the why in a moment. As for tubes being plentiful and cheap: yes my dear friend, but it's night here, and all the shops are closed, and I need to go to work in the morning. I just did not consider that my storage of these wider 26" tubes is down to only that one, dreaded "pannenschutz schlauche". As a fresh father, I tend to not have time to follow these things as assiduously as I used to, earlier. Therefore, cut me some slack, mate.

And now, to the why I have no faith that patching this tire at the valve will result in happiness: I determined, as per dabac's advice, the actual cause of the rent. I t hink I found it: the rim is a bit too deep for the valve, and it will inevitably be under some tension, once the pressure in the tube decreases - since then, the valve will tend to recede inwards. Solution: tube with longer valve. Or run a tube with high enough pressure to push the valve long enough out. I think I'll just pump up the slimy tube with the valve at 12 o'clock as per bikeman715's advice, and keep my fingers crossed

It's time to break out some money and get new tubes. "Schwalbe's schraeder tubes come with the threaded ring to secure the stem when pumping up with a floor pump or on the road pump. It cuts down on stem and near stem punctures. Hostel Shoppe online has them. Ten bucks each. bk

sorry if the tone of my email was off. This was not intended.

A buddy of mine use to say "You can have it Quickly, Inexpensively and Well Done. Which two would you like?"

No, your tone was OK. I just added a bit of levity. Seems more like my tone was off

Your buddy is a wise man.

Ladies and gents, my commute to work this morning was most instructive. It cost me a tube, but it's the price of learning, I guess.

What happened: after about 6 Km (just over the halfway in my commute) the tire went flat. I tried to inflate it, no dice. I walked those 5.5 Km to work and tried to patch my new tube. Well, guess what? The valve was almost torn off. Mind you, this is a new tube, not the one I patched yesterday (which, btw, is holding up fine).

CONCLUSION: I should have used the rubber cement on the bead on one side of the rim. Will also invest in that Liquisole dabac mentioned.


Sorry dabac, I should have listened to your advice immediately, not with a delay. Now I know better.

This not a good rule. Proper PSI is directly related to weight being carried; thus if the weight being carried is 250 pounds running 20 psi under max would be severly under inflated causing snake bite type of flats; whereas carrying weight around 150 pounds would be ok with PSI 20 less then max, and actually better then running at max.

If your running your tires too low on pressure the tube can either start to slowly craw in the tire and valve would move along with it till it is torn, or the lower pressure every time the wheel rotates to the valve at the lowest point it would force the valve firmly into the valve hole in the rim eventually ripping it.

The other weird thing, though I doubt it, is that your using a thin Presta valve in a rim designed for a thicker Schrader valve.

Also check the condition of your rim strip, especially around the stem hole.

Make sure that when you put air in your not flexing the valve back and forth as you pump, this especially happens with hand pumps where one is pumping very hard and rips or weakens the valve area due to wiggling the valve back and forth.

Don't buy cheap tubes.

I wouldn't have too low of pressure, it may be possible that the tire pressure is so low that the tire is slipping on the rim and it is pulling at the fixed stem and tearing the tire at a fixed point. is the valve stem perpendicular to the rim? or slightly cockeyed?

Yes, I think the slippage of the tire is what caused the tear at the base of the valve, so I have now glued the bead on one side of the tire, to the rim. I had a relatively safe ride home.
For what it's worth: no, the valve is and has always been perfectly perpendicular to the rim. But that doesn't mean it couldn't have been torn. I do believe, at this point, that the most likely scenario for my tube breakdown modes was, in fact, slippage of the tire.

EDIT: by "slippage of the tire", in this context I meant "slippage inside the rim", not on the road.

the rule of 20 psi less the max is for winter riding in snow so there more rubber (tire) touching the ground. if you go with max then it slid more. to keep snakebite from happening the psi should always be at 50% or more of the max psi to keep the tire from slipping.

I understood what you were saying but you did not put carrying weight into the equation. If a person is 250 pounds riding a bike with 20psi less then max, when they should be running at 10% more then max thus 20 psi less would be about 10 pounds less then max is a recipe for tire problems. Also if the person is only 140 pounds normally they should be running 20 psi less then max on dry snow free roads, so now your suggesting to drop the psi 20 psi from max which means the tire will slip. Your forgetting the weight.

I'll cut the Gordian Knot: I'm only 130-132 lbs.

I think the benefit of running tires at lower pressure in snow or ice is very questionable. I will run mine fully inflated at all times.

I was thinking the same thing, Al1943. If the snow is a thin layer on top of pavement or gravel some other hard surface then I prefer to run narrower (like 28 - 35mm) high pressure tires to running wide mtb style tires at low pressure... and if I only have wide tires I run them at top pressure or higher. High pressure allows the tire to cut down through the snow and contact the hard surface below.

If I am riding on deep or packed snow where I have no chance of staying in contact with the ground underneath I use wider softer tires as this will provide 'flotation' on top of the snow.

My current winter bike has 35mm rear tire and a 40mm wide studded tire on the front... which is a middle width and so goes against my advice.

Different strokes for different folks, as they say. For me, running the front tire at low pressure works wonders. I feel much safer than before, I feel I have better control and stability.

Your experience may and will, differ considerably, but it does not alter mine.