Flat tire again, torn valve stem again

I have a DRZ400S that I commute to work on and have had four flats in the last year, two on the front, two on the back and each time the tube has torn right at the valve stem.   Needless to say I am getting tired of fixing flats, i could understand if I am offroad and going places where I shouldn't be but on the pavement, really?    I am running a MT21 Perrelli on the front (previously had a 606 but didn't like the offroad ability or how it wore, it also had a flat once same MO) and a 606 Dunlop on the rear.  I am running various heavy duty tubes with same result.  Has anyone else had this issue?  I have about a 3 mile trip to work on asphalt and ride in temps from 35 - 100F.  All the offroading I have done and had no flats, always on the pavement.  I typically run about 18-20 PSI on the front and 15-18 PSI rear.  Any ideas?

Maybe you should buy a rim lock. With that pressure I can't imagine the tire is slipping on the rim but if your pulling the valve stem loose that would be my guess. Also if you ride it with a flat I think out will pull the stem loose from the tube so are you sure the stem is the reason for the flat or is it happening after you get a flat?

you shouldn't be slipping tires at that PSI  but I bet your air psi is less than you think after a week or so

 

I did rim locks and HD tubes to avoid that  issue

Edited by Zimman

I don't think heavy duty tubes help the valve stem rip situation.  I can see that tire creep might be worse with traction on pavement.  I also suggest rim locks.

Sorry for the stupid question but what is a rim lock?

 

I had bead locks on my Jeep but for the DRZ, I can't picture it.

 

Thanks

Tire pressure is probably to low I went through 4 tubes one back tire

A rim lock (or bead lock) is an internal wedge that holds the tire bead against the rim but only in a 2 to 3 inch long location.  Usually 1 or 2 rim locks are used for any off road low pressure use.

It's also a good practice not to tighten the valve stem nut down to the rim but instead leave it up near the valve cap.

In which case if the tyre slips on the rim the valve will go diagonal before it rips itself out of the tube.

A pre inspection before riding will give fair warning and can be rectified before total failure. 

Some of our local riders have moved away from HD tubes for this very reason. They seem to be much less tolerant to tyre creep, standard tubes will stretch more so allow more creep before tearing away from the valve.

 

Rim locks would help

Don't tighten up the valve nut

Some also elongate the valve hole with a file to allow the valve to tilt more when needed.

 

The other thing to remember is that HD tubes require more pressure to exert the same force on the tyre, I increase my pressure by approx 2 psi for HD tubes. 

How often do you check your tire pressure? I had a string of flats from ripping the valve stem off, front and back, but I found that checking pressure regularly and frequently solved the problem.

i think your tire gauge may be lying to you. 18-20 psi there is a LOT of holding pressure on the tire. i've never seen a tire rip the valve stem, or slip on the wheel at pressures above 15 psi, without rim locks. 

 

WITH rim locks, you can run it down to 5 psi (that's five) and more than likely suffer a pinch flat (snakebite/compression/whatever) but still not spin the tire on the rim and rip the valve stem. 

 

this has nothing to do with regular, heavy duty, or super/ultra heavy duty tubes. it's simply a low pressure condition, with no rim lock. 

 

loosening the valve stem nut will help prevent tears when working on the tube/tire or increasing / decreasing air pressure for trail conditions. 

 

ALWAYS use a valve stem cap. doesn't matter what it is, plastic, chrome, poker dice, but something to prevent dirt from infecting the seal and lowering your air pressure. 

 

everyone i've ridden with that didn't use rim locks, tore a valve stem. 

 

everyone that did, did not. 

I check them about once a month and ride it about every day. I will have to start checking more often and increase the pressure a little.

Every time I check the tube it is perfect except for the torn valve stem.

I always used the HD tubes off road but beginning to think they are not pliable enough for on road. I hav e a light weight used Dunlop in there now since that is all I had in the shop.

WITH rim locks, you can run it down to 5 psi (that's five) and more than likely suffer a pinch flat (snakebite/compression/whatever) but still not spin the tire on the rim and rip the valve stem. 

 

 

​I never run with less than 12psi in the rear but have had the tyre slip - not enough to cause harm but enough so you can see the valve is now leaning.

 

ALWAYS use a valve stem cap. doesn't matter what it is, plastic, chrome, poker dice, but something to prevent dirt from infecting the seal and lowering your air pressure. 

 

I don't recall anyone suggesting the PO runs without a valve cover?

 

HD tubes are more rigid and so don't give as much - it's easier to tear a valve out of a HD than it is a thin tube in the rim.

We've even had a spate of HD tube disconnecting from their valve for no known reason - no slippage at all and no puncture that can be seen, we put that down to manufacturing defect.

What brand/model of tube do you recommend because I need to get some ordered to have on hand.

HD tubes are more rigid and so don't give as much - it's easier to tear a valve out of a HD than it is a thin tube in the rim.

We've even had a spate of HD tube disconnecting from their valve for no known reason - no slippage at all and no puncture that can be seen, we put that down to manufacturing defect.

 

 

i'm not sure why you considered the advice of using a valve cover anything other than advice to do so. there was no suggestion otherwise, until you brought your own interpretation. 

 

 

 

 

tire+tube slippage vs rim = torn valve stem

 

doesn't matter if the tube 1 inch thick, or .001" thick, if the tube spins on the rim, it's going to tear the valve stem. if the tube does not spin on the rim, it does not rip. 

 

 

 

if you know of a study that shows HD tubes ripping more often, with rim locks, i'd really like to see that, cause I'm perplexed as to how it's possible. 

i'm not sure why you considered the advice of using a valve cover anything other than advice to do so. there was no suggestion otherwise, until you brought your own interpretation. 

 

No offense intended so please don't take any.

It was just that you stated it in capitals, as if you were trying to hammer home a point, a point that wasn't being challenged or even discussed.

i'm not sure why you considered the advice of using a valve cover anything other than advice to do so. there was no suggestion otherwise, until you brought your own interpretation. 

 

tire+tube slippage vs rim = torn valve stem

 

doesn't matter if the tube 1 inch thick, or .001" thick, if the tube spins on the rim, it's going to tear the valve stem. if the tube does not spin on the rim, it does not rip. 

 

if you know of a study that shows HD tubes ripping more often, with rim locks, i'd really like to see that, cause I'm perplexed as to how it's possible. 

 

The point I was making is that some slippage is tolerated, I often have a little slippage and so do others that ride in my area. Maybe it's the amount of water we ride in... We just let the tyre down, slacken the rim lock and roll the bike around, that can cure it. Sometimes we'll break the bead and force the tyre to move to correct slippage, this is more the case with very stiff walled tyres.

 

The belief among us is that HD tubes are more rigid at the valve joint and thus can't tolerate as much slippage as a standard tube. It may also be that riders are not allowing for the tube being thicker thus inflating to higher pressure.

 

I also know of no study of this effect..., but doesn't mean that it isn't so, does it?

1 The point I was making is that some slippage is tolerated, I often have a little slippage and so do others that ride in my area. Maybe it's the amount of water we ride in... We just let the tyre down, slacken the rim lock and roll the bike around, that can cure it. Sometimes we'll break the bead and force the tyre to move to correct slippage, this is more the case with very stiff walled tyres.

 

2 The belief among us is that HD tubes are more rigid at the valve joint and thus can't tolerate as much slippage as a standard tube. It may also be that riders are not allowing for the tube being thicker thus inflating to higher pressure.

 

3 I also know of no study of this effect..., but doesn't mean that it isn't so, does it?

 

 

 1 think i'll go take a look at mine, nope, valve stem is lined up nicely. are you tightening your rim locks before or after inflating the tube? 

 

2 i don't get the higher pressure part. what are you saying ? 

 

3 i think we're doing this part now. kinda. :)

. It may also be that riders are not allowing for the tube being thicker thus inflating to higher pressure.

 

 

The thickness of a rubber tube has no affect on air pressure, 20 PSI will always be 20 PSI regardless of the thickness of the tube.

Tyre construction on the other hand is a whole different story, especially when you get into tubeless tyre construction.

When I said I often have some slippage that is probably an exaggeration, what I should've said is that I have had slippage, occasionally. Others have too as they post on our local riding forum about it.

 

Rim locks - When I fit a tyre I heavily doose it with lube (car shampoo & water 1:4 mix), then inflate to between 40 to 60 psi, that normally seats the tyre bead properly, I then leave the tyre overnight if I have time, just to make sure it's fully seated. Then I tighten the rim lock and let the pressure down to 16 psi.

Maybe I should air down to 16 and let it settle before tighten the rim lock, or maybe I shouldn't leave it at high pressure over night?

 

Running the HD's at higher pressure is just physics.

First assumption is that the inner tube does not fill the entire space within the tyre & rim until it expands.

If the above is correct then the only pressure acting on the tyre's inner face is the pressure which is in excess of what is needed to inflate the inner tube.

One of our guys compared the pressure needed to make both a standard and a HD tube start to swell in open air, he noted there was several psi difference between them.

Think of it as the pressure needed to inflate a normal inner tube vs that needed to inflate a hot water bottle.

 

I'm doing both tyres tomorrow afternoon (if all goes to plan) and I have both types of tube so I'll do a comparison and report back.

Edited by DrzDick

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