New slick tyres and tubes - tube popped after pumping

kramlin
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New slick tyres and tubes - tube popped after pumping

Postby kramlin » Sat Dec 20, 2008 10:17 pm

Hi all,

Just got myself a pair of 1.25" Maxxis Detonators for a MTB (26") and a pack of the Innova MTB tubes (1.0-1.25").

These are the tubes: http://www.torpedo7.com.au/products/INTUBNNMT

I pumped them up with a floor pump and no matter how hard I tried, I couldn't get past 90psi. The Detonators are specified to be 100psi. The tyres already get quite firm at 20psi, I thought. The gauge seems to be correct as I checked with a hand pump which also has a guage.

So I left them at 90psi. I sat on the bike, then got off and put it on my rolling stand, and the rear tube popped!

What am I doing wrong here?

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Kid_Carbine
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Postby Kid_Carbine » Sun Dec 21, 2008 1:50 am

A common problem is that people often assemble the tyre & tube onto the rim & simply pump it up. What happens is that the tyre bead isn't concentric with the rim & the bead is pushed over the lip of the rim at high pressure.
The tyre is actually dismounting from the rim. One can easily imagine what happens to an unsupported tube at about 90psi & for those without imaginations, try it with a baloon.

It is necessary to put about 25 to 30psi into the tyre then examine the tyre at the edge of the rim. There is a moulded-in line near the wire [or Kevlar] bead of the tyre & you want to see it all around the rim, treferably the same distance all the way around the rim, ..... both sides.

If it isn't as it should be, then 30 psi should be low enough to allow you to push or pull the sidewall with your thumb to try & manoeuvre the tyre into the correct position. Once done, pump some more air in, carefuly watching any problem areas that were found.
Be ready to very quickly deflate the tube if the tyre starts to peel off the rim

Still good? Then keep pumping & keep watching. Once you are up to rated pressure, do a final check then mount the wheel back into the bike.

I still clearly remember a friend hastily mounting a new & quite expensive Michelin tube into his tyre then pumping it up to 110 psi. He managed to ride it about two bike lengths before it went .......................... KA[expletive deleted]BLAM
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wombatK
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Postby wombatK » Sun Dec 21, 2008 9:35 am

Kid_Carbine wrote:It is necessary to put about 25 to 30psi into the tyre then examine the tyre at the edge of the rim. There is a moulded-in line near the wire [or Kevlar] bead of the tyre & you want to see it all around the rim, treferably the same distance all the way around the rim, ..... both sides.

If it isn't as it should be, then 30 psi should be low enough to allow you to push or pull the sidewall with your thumb to try & manoeuvre the tyre into the correct position.

+1.
If you find you can't get them right, it could be that the tyre bead is too large. I've had Innova tyres from T7 with that trouble (but bulging rather than exploding), and if your Maxxis were specials they might be sus.

The floor pump is a strange one. Some cheaper pumps aren't rated for HP but tend to break/burst if pushed too far - have you checked the rating on your pump ?
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Spiza
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Postby Spiza » Sun Dec 21, 2008 10:42 am

I had a similar problem with the tube bursting once during pump up and 3 times after 1-2 days on the bike. I thought it may have been the brand of tube so I bought a different type and exactly the same problem. I then tried 1.5"-1.75" tubes and never had the problem again. I think the larger tubes don't like been pump up to high pressure on their maximum size.

Try 1.5"-1.75" tubes and I'm confident it will fix your problem. I'll put money on it :wink:

BTW. Check the rim tape and the pressure with an accurate gauge first :)

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Postby ForkinGreat » Sun Dec 21, 2008 12:32 pm

One trick I picked up years ago was to dust the tube & inside of tyre with talc powder. never had a pinched tube flat. You might want to take tyre, tube & rim tape or plugs off occasionally to check for moisture. Other than that, it works well. Makes mounting easier.

+1 on the staged inflation and checking. saves much frustration.

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il padrone
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Re: New slick tyres and tubes - tube popped after pumping

Postby il padrone » Sun Dec 21, 2008 12:49 pm

kramlin wrote:So I left them at 90psi. I sat on the bike, then got off and put it on my rolling stand, and the rear tube popped!

When the tube 'popped' was the tyre still on the rim, or was part of the bead over the rim edge?

I reckon Kid Carbine's diagnosis is the most likely answer, in my experience. Tubes rarely 'pop' when they are inside a correctly seated tyre. Try pumping up a 1.25" tube out of your tyre and see how big it will get without failure - as big or bigger than the average 1.75 tyre.

Refit your tyre and be diligent about the even seating of it onto your rim. And if your stand pump doesn't do more than 90 psi, maybe it's one designed for MTB use. Invest in a good Silca stand pump, reliable and long-lasting.
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Spiza
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Postby Spiza » Sun Dec 21, 2008 1:36 pm

Spiza wrote:I had a similar problem with the tube bursting once during pump up and 3 times after 1-2 days on the bike. I thought it may have been the brand of tube so I bought a different type and exactly the same problem. I then tried 1.5"-1.75" tubes and never had the problem again. I think the larger tubes don't like been pump up to high pressure on their maximum size.

Try 1.5"-1.75" tubes and I'm confident it will fix your problem. I'll put money on it :wink:

BTW. Check the rim tape and the pressure with an accurate gauge first :)

Sorry in my previous post I meant try 1.25"-1.5" (I have 1.5" slicks and using 1.5"-1.75" tubes fixed the problem for me)

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Postby kramlin » Sun Dec 21, 2008 1:38 pm

Hi guys

The pump is a Tioga floor pump that has a max psi of 160.

When the tyre popped the bead was still in the rim.

I pumped up a tube not inside the tyre and it got pretty big, a lot larger than the diameter of the wheels.

I took out the popped tube and it looks like it blew in the spot where the valve is:

Image

How would I avoid this?

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Postby cavebear2 » Sun Dec 21, 2008 2:29 pm

kramlin wrote:I took out the popped tube and it looks like it blew in the spot where the valve is:

Looks like the tyre bead has pinched the tube, ensure that this is not the case before inflating the tube by checking the tyre bead inside the rim, over the full diameter of the wheel (both sides). Near the valve this can be ensured by pushing the valve into the tyre space when putting the tyre on.

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Postby il padrone » Sun Dec 21, 2008 2:41 pm

kramlin wrote:I took out the popped tube and it looks like it blew in the spot where the valve is:

A split that huge is the result of a blow-out. You probably hadn't cleared the valve stem base away from the tyre bead properly. Pumping up the tyre would have pushed the bead up enough for the tube to protrude and blow, then the bead has fallen back into the rim.

There is no way a 1.0-1.25" tube would blow like this inside a 1.25" tyre.

kramlin wrote:How will I avoid this?

Solution: ensure the bead is correctly seated and the valve stem in particular is clear of the bead. While the tyre is flat just push the stem in away from the bead.
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Spiza
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Postby Spiza » Sun Dec 21, 2008 3:11 pm

Plenty of stuff for you to try kramlin. Please let us know what finally solves your problem :)

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Postby kramlin » Sun Dec 21, 2008 6:45 pm

Guys,

I followed your advice on making sure that the tube is seated and clear of the bead and everything seems to be fine now. One thing I didn't do before was make sure the valve was pushed into the tyre (and the tube therefore seated inside the tyre properly) when pumping.

I managed to pump both tyres to 100psi. It might have had something to do with the way the tube was seated but I think it also has something to do with the way I'm pumping now - use my body weight to push the pump all the way down to the bottom especially when it reaches higher pressures.

Did a short ride around the neighbourhood and it didn't blow 8)

My original intention with these slicks was to use the MTB as dual purpose - slicks for the road, and knobblies for the occasional trail. Given the hassle of changing tyres though, (and without a stand), maybe I need another bike! Although I dont' feel comfortable on drop bars and having both a MTB and a flat bar road seem a bit superfluous in a small house without a garage...

Thanks!

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Postby wombatK » Sun Dec 21, 2008 7:52 pm

kramlin wrote:Guys,
My original intention with these slicks was to use the MTB as dual purpose - slicks for the road, and knobblies for the occasional trail. Given the hassle of changing tyres though, (and without a stand), maybe I need another bike!
Thanks!

Nah, you just need confidence - and that comes from practice. Plenty of us use slicks on MTB's for commuting and swap for trail rides.

Just make sure you change to the knobblies a bit ahead of the actual trail ride, so you can clock up a few km on them to prove you've got it right - saves you getting stranded miles from nowhere.

I've found Tioga stuff is good quality - maybe not up to the premium brands but it should do the job as you found when you put a bit more grunt into it. 100 psi of grunt :lol:
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Postby il padrone » Sun Dec 21, 2008 8:33 pm

When I got back into MTB riding in the early 90s I had just the one bike, a rigid MTB and did the tyre swap thing - knobbies for the weekend trail ride then slcks for the commute or touring rides. I did this for 6-7 years. One thing that I found was that after a few tyre changes the bead relaxed enough that I could change tyres without tyre levers, just using my hands. Knobbies are usually easier to get off/on - it was the slicks that were tight at first. And also I didn't fiddle around with slipping tubes in or out, just hauled the whole tyre and tube off the rim and left the tube in the tyre ready to be put back on later. Tyre changes were a quick 10-15 min job.

When you can afford it, specific bikes are nice though :wink:
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Postby kramlin » Mon Dec 22, 2008 1:02 am

More problems.

I was just minding my own business, on the computer, when I heard the sound of a tyre deflating in the other room. It sounded like a valve had been pressed.

So I found the rear tyre (again) deflating - it felt like the air was escaping from the area of the tyre near the valve. The valve screw (presta) was closed though.

I removed the tube and tried to repump it, it seems there is a pinprick puncture but not near the valve. The tiny hole seems to be right on the seam of the tube.

I did run over a bit of glass today, but I kept riding and the tyre was fine. If the deflation was due to the puncture (which occurred hours before) I wonder why it only deflated suddenly now?

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Postby il padrone » Mon Dec 22, 2008 9:25 am

Sounds like a standard puncture. Patch it, check inside the tyre for glass. Glass fragments can take some time to work through the tyre carcass and penetrate your tube.

One point - you're using those Innova tubes? I've had a poor record with these and now no longer use them. Several times with these tubes I've developed a leak at the valve stem join with the tube. Unrepairable when it happens :(
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Postby RainForeverRain » Mon Dec 22, 2008 11:06 am

kramlin wrote:My original intention with these slicks was to use the MTB as dual purpose - slicks for the road, and knobblies for the occasional trail. Given the hassle of changing tyres though, (and without a stand), maybe I need another bike! Although I dont' feel comfortable on drop bars and having both a MTB and a flat bar road seem a bit superfluous in a small house without a garage...


You could always take the middle option by leaving the knoblies on the original wheels and buying yourself a new front and new rear wheel to put the slicks on.

Probably easier to swap wheels than tyres if you have to do it on a regular basis, and the wheels are cheaper and take up less space than a new flat bar.

[Edit] come to think of it, that would give you the option of running different gear ratios on the different rears - customised for road or bush use! [/Edit]
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Postby twizzle » Mon Dec 22, 2008 11:17 am

kramlin wrote:I removed the tube and tried to repump it, it seems there is a pinprick puncture but not near the valve. The tiny hole seems to be right on the seam of the tube.


On the inside of the tube, or the outside? ie., the side facing the rim, or the side facing the tyre?
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Postby Kalgrm » Mon Dec 22, 2008 11:28 am

RainForeverRain wrote:You could always take the middle option by leaving the knoblies on the original wheels and buying yourself a new front and new rear wheel to put the slicks on.

Probably easier to swap wheels than tyres if you have to do it on a regular basis, and the wheels are cheaper and take up less space than a new flat bar.

[Edit] come to think of it, that would give you the option of running different gear ratios on the different rears - customised for road or bush use! [/Edit]

This was what I was doing for a while too. To get the most out of this system, it's best to have the same hub in both rear wheels so that lateral spacing on the gears is matched - no fiddling with cable tensions to adjust the RD between wheel swaps.

If you have disc brakes, you can build up a set of 700c commuting wheels - they fit on MTB frames without issue. The disc brakes make it easy because you don't need to adjust the position of rim brake pads with different wheel diameters.

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Postby kukamunga » Mon Dec 22, 2008 11:36 am

One point - you're using those Innova tubes? I've had a poor record with these and now no longer use them. Several times with these tubes I've developed a leak at the valve stem join with the tube. Unrepairable when it happens :(

+1. Cheap - and for a good reason. You really need to be dilligent with rim tape, bead seating, even the valve hole on the inside of rim may need countersinking/deburring for a smooth transition curve for cheaper valve stems to sit and not get damaged.

Be wary - talc powder on the bead can make it slippery and cause the tyre to rotate on the rim under hard braking, causing the stem to bend and possibly split from the tyre. Probaly not such a problem with higher pressure road tyres, but certainly on fatter, lower pressure tyres.

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Postby il padrone » Mon Dec 22, 2008 3:02 pm

RainForeverRain wrote:Probably easier to swap wheels than tyres if you have to do it on a regular basis, and the wheels are cheaper and take up less space than a new flat bar.

I've tried this in the past. Different cassette wear is the killer with this if you do it for a while. One cassette will be more worn than the other and the chain will not run without jumping.

Once you have the tyres changed a few times they can be OK to swap quickly.
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Postby kramlin » Mon Dec 22, 2008 9:45 pm

Right, now.

I patched the tube - the tiny hole was at the seam. Sanded it down a bit, used the rubber cement, let it dry, then applied the patch. It seemed to inflate fine.

There was no sign of penetration through the tyre, and I couldn't find any glass or irregularities in the tyre or inside the rim.. I think it was may have been the pressure that caused it to puncture at the seam.

Then I went to dinner, came back, and found my tyre deflated. It had leaked where the patch was.

I ended up changing to a new tube. Good thing I have (HAD) a pack of 10! I'm finding now inflating to 100psi isn't as hard as it used to be, must be all the tube changing I'm doing...

Hopefully this tube will last more than 3KM and a few idle hours. Not having much luck here, although the first blowout was probably my fault...

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Postby wombatK » Mon Dec 22, 2008 10:28 pm

kramlin wrote:I patched the tube - the tiny hole was at the seam. Sanded it down a bit, used the rubber cement, let it dry, then applied the patch. It seemed to inflate fine.

But then the patch started to let go... or really wasn't all that firmly attached to start with.

To prevent this, try letting the patch cure overnight or 24 hours before pumping tube up. Seams are difficult - really important to flatten any edge. I find a razor (plastic shaving type) works better than sand-paper which tends to inflict too much thinning action on areas next to the seam, although some sand-paper roughing up is needed to take the gloss off the rubber.

Other comments here are suggesting the innova tube quality is below par. If things don't improve, maybe bin them and get some better quality tubes.
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Postby kramlin » Mon Dec 22, 2008 10:52 pm

wombatK wrote:
kramlin wrote:I patched the tube - the tiny hole was at the seam. Sanded it down a bit, used the rubber cement, let it dry, then applied the patch. It seemed to inflate fine.

But then the patch started to let go... or really wasn't all that firmly attached to start with.

To prevent this, try letting the patch cure overnight or 24 hours before pumping tube up. Seams are difficult - really important to flatten any edge. I find a razor (plastic shaving type) works better than sand-paper


Won't flattening the seam cause the rubber to part, creating a split in the tube? I found when I sandpapered the seam, the puncture at the seam actually got slightly bigger along the seam.

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Postby wombatK » Tue Dec 23, 2008 7:09 am

kramlin wrote:Won't flattening the seam cause the rubber to part, creating a split in the tube? I found when I sandpapered the seam, the puncture at the seam actually got slightly bigger along the seam.

This suggests that the rubber might have been too thin along the seam or the seam was not well formed i.e. poor manufacture. Using such a tube seems a bit of a time-waste to me, and its probably doing nothing for your confidence. I've found BBB tubes or continental tubes are quite good, if you're looking for something better.
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