Mountain Bike Reviews Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
I just had another one of those unrepairable torn valve stem flats, about 10 miles from home. Luckily, I was about 0.5 miles from a payphone. Anyway, I've owned two mountain bikes in my life, an old school Mongoose hardtail, and now recently I upgraded to a Schwinn FS Delta_88. It is definitely the case that V-brakes can rip a tire and tube right off a rim. My old cantilever brakes had no such stopping power. The other factor I have noticed, primarily because my Mongoose is so old, is that a tire slip on a wider single walled rim is easier to forgive than a tire slip on a narrower double walled rim. In the past I would notice that the valve stem was crooked, deflate the tire, slip it back, and reinflate. No flat. On the double walled rims, the valve stem remains upright, while the tire and tube slip laterally, causing a rupture at the base of the schaeder valve stem. I have been scolded by those who say I am running with too low a tire pressure, but even having the tires hard as a rock, it still happens. Riding with high pressure, riding with talc powder on the tube, riding with roughed up rim walls, these are all bandaid solutions to the real problem, which is a rim architecture that is too unforgiving. I have opted for what I call the "relaxed fit" shraeder installation. For those of you who routinely drop from height, you may not want to try this on your nice rims. I took a 3/8th's inch drill bit, and reamed out the shraeder hole. I followed that with a 1/2 inch bit on the inside (tube side) wall only. I finished the mod by removing the burrs with a rattail file. The next time the tube slips, I should get a warning "lean" from the valve stem, which may buy me enough time to unslip the tube before it ruptures again. I run with thornproof tubes and vinyl strips, and do not see the utility of being forced to buy tubes by the dozen because of an unforgiving rim.
 

·
President, CEO of Earth
Joined
·
1,001 Posts
Do you ever use a minipump? Because those will rip your valve off every time if you arent't careful to hold the back of the pump on the power stroke.
 

·
Registered
Joined
·
1,635 Posts
how I solved that problem

funny, I only had the problem with loose-fitting Geax tires, and/or with an old pair of Mavic 217 rims that have a special hard shiny anodizing.
I tore 4 front tubes coming down from Kennebec Pass this year and made the final 20 some miles using only my rear brake because I had no more spares. My friend had 3 but they were schrader, so the next flat would have seen me coring out the presta valve hole to schrader size with my knife, not an attractive prospect.
The mate of that 217 rim is on the rear of another bike, and I had the same problem with it.
Solution: Glue one bead of the tire to the rim with Pliobond cement, available at hardware stores nationwide. Actually I first used 3M Plastic Trim Adhesive because that's what they had when I went looking the day after the Kennebec episode. It works fine. I was looking for 3M FasTak trim adhesive, which is even stronger -- I used to glue my track sewups on with it -- but the didn't have it.
Unlike the plastic trim adhesive, Pliobond says right on the label it's good for rubber, metal, etc.
You put a bead all around one edge of the outside of a tire bead, then install the tire and pump it up. You can still access the tube from the other, unglued side. And you can get the tire off, you just have to pull a bit. But it completely stops tire creep. After gluing the two offending tires, I used to stop frequently after big long descents and look at the valve stems, which were always pointing exactly at the hub just like they should be. NO creep at all.
It ain't yer V-brakes. Any brakes worthy of using will cause the same thing. It's a combination of a slightly loose tire and/or a slippery rim. Add the heat generated by a big descent and there ya go.
I use Avid cantilevers on the bike with the front creep, and an IRD Widget on the rear of the other creepy bike.

Iditabikers and others who ride snowpack a lot, and so who tend to use extremely low tire pressures for traction and flotation, discovered long ago they need to glue one bead of their tires to their rims.
There's probably a bunch of adhesives that would work. I can vouch for Pliobond, and 3M Plastic Trim Adhesive in a little black tube.
It will solve your problem.

I'm sure somebody's gonna post that talc on the tubes will solve it as well. I always use liberal talc, didn't solve it for me.
 

·
Luddite technophile
Joined
·
302 Posts
You might also consider ditching the vinyl rim strip and going with a cloth strip - gives the tube a little more purchase to prevent slippage. Also, clean the tire bead and rim hook areas to get the dust off. Good luck - I've been fighting the same problem on my wife's bike (Geax Sedona's on X317). Those two measures seem to have helped. If the problem persists, I'll pull out the glue. Higher pressure is not a good option - she's only 105 lbs. Getting rid of the tires is not an option either - she loves them. She's become much bolder on downhills with those fat tires.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #5
relaxed fit is working

After my last ride I noticed the front tire/tube had slipped. Because of the relaxed-fit holes I drilled in my rims (half and three eighths) the valve stem was cocked. I released air, slipped tire, and pumped back up. No torn valve stem. So far the system works.

Under OEM rim conditions the tire slip would not be noticed leaving the tube under constain strain. Until of course the next rupture.

I have a certain amount of loyalty to the vinyl strips as they save my bacon almost every ride due to the native puncture vine (goatheads) that dot the So Cal landscape.

What I am saying is that I have "a" solution to the problem. Gluing tires to rims seems too agricultural a fix.

kgginslc said:
You might also consider ditching the vinyl rim strip and going with a cloth strip - gives the tube a little more purchase to prevent slippage. Also, clean the tire bead and rim hook areas to get the dust off. Good luck - I've been fighting the same problem on my wife's bike (Geax Sedona's on X317). Those two measures seem to have helped. If the problem persists, I'll pull out the glue. Higher pressure is not a good option - she's only 105 lbs. Getting rid of the tires is not an option either - she loves them. She's become much bolder on downhills with those fat tires.
 

·
Registered
Joined
·
1,635 Posts
same tire

kgginslc said:
You might also consider ditching the vinyl rim strip and going with a cloth strip - gives the tube a little more purchase to prevent slippage. Also, clean the tire bead and rim hook areas to get the dust off. Good luck - I've been fighting the same problem on my wife's bike (Geax Sedona's on X317). Those two measures seem to have helped. If the problem persists, I'll pull out the glue. Higher pressure is not a good option - she's only 105 lbs. Getting rid of the tires is not an option either - she loves them. She's become much bolder on downhills with those fat tires.
The Sedona was the front tire that resulted in my 4 flats descending from Kennebec Pass.
I like it too. Big as anybody else's 2.5. And the 2.0 Geax in back rides more like a 2.2.
I use reinforced strapping tape for rim strips.
I've even gone so far as to try roughing up the rim bead with a dremel.
Glue works for me.
Another benefit is when you have to fix a flat, the tire stays on the rim, most loose-fitting folding tires want to come completely off the rim and fold up. I know racers who only run wire bead tires because they're quicker and easier to deal with. Haven't heard of anyone gluing one bead for the same reason. Seems like it would be a good idea.
 

·
Registered
Joined
·
1,635 Posts
mr. tuffys

southern_pacific said:
After my last ride I noticed the front tire/tube had slipped. Because of the relaxed-fit holes I drilled in my rims (half and three eighths) the valve stem was cocked. I released air, slipped tire, and pumped back up. No torn valve stem. So far the system works.

Under OEM rim conditions the tire slip would not be noticed leaving the tube under constain strain. Until of course the next rupture.

I have a certain amount of loyalty to the vinyl strips as they save my bacon almost every ride due to the native puncture vine (goatheads) that dot the So Cal landscape.

What I am saying is that I have "a" solution to the problem. Gluing tires to rims seems too agricultural a fix.
You're talking about Mr. Tuffy or similar puncture preventive strips that keep goatheads out.. He's talking about rim strips that cover the spoke holes in the rim. Totally different thing.
No clue what "too agricultural a fix" means, never heard the word used in that context.
Glue, which prevents the creep, seems a more elegant, and effective, fix that boring a bigger hole in the rim, which does not prevent the creep, only allows it to progress further before something bad happens. Or so it seem to me.
I found my remedy, don't really care if anyone else uses it, long as I don't have to loan out my tubes when somebody else's valve rips out.
 
1 - 7 of 7 Posts
Top