Bicycle Mechanics - Pinch Flats
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05-28-07, 03:34 PM
I'm running 26x1.25" Panaracer UrbanMax tires on my bike and am having serious problems with repeated pinch flats. These occur when I hit big bumps at speed. I'm not getting any puncture flats (yet). Although I like the faster ride and reduced rolling resistance of these tires, I've been getting repeated pinch flats using the 1.1-1.4" tubes. The rims are Performance Loco brand and are fairly wide for such skinny tires. I can actually feel the wheel "bottoming out" when I hit a bump at speed and this is when the pinch flats happen. The tubes that correspond to this tire size are really thin and fragile. What is the downside to using a 1.5-2.0" tube with this tire as long as I'm able to get it in the tire without pinching it? It's also quite possible the tires are just too skinny for the wide rims and this will keep happening. Does any one have advice on tire/rim compatibility and how to avoid pinch flats in general, besides the obvious "don't hit bumps" advice?
05-28-07, 03:36 PM
You don't mention how much air pressure you are using, Try increasing aby about 5-10 PSI, this should help, maysbe even stop pinch flats. If your wheel is bottoming out you need more air cushion.
05-28-07, 04:10 PM
I'd try using a wider tire. I've often thought that 1.25 is a pretty narrow tire for many mountain bike rims.
05-28-07, 04:27 PM
I'm running the recommended max, 80 psi.
RG, which tires would you recommend for commuting on pavement? Specialized Armadillos at 1.5 inches are wider and take 80 psi, but they are overpriced. They don't roll nearly as smooth as the Panaracers. Also, every Armadillo tire I've ever had on my bike ended up with the tread shredding off from the casing before the tread was completely worn. That can be quite the showstopper when it causes a puncture in the middle of nowhere. You can patch a tube but you can't really patch a tire. Having said that, the Armadillos are excellent for puncture protection from glass and other road debris.
To get rid of the pinch flats you'll have to either go higher pressure or go with wider tires. Since you've already maxxed out the pressure, looks like it's time to shop for new rubber.
Presuming that new rims are out of the question, perhaps some 1.5 inch tires would be better. Conti Contact Sport is a good flat resistant tire.
05-28-07, 06:03 PM
I am very surprised you are pinch-flatting on these. Are you getting out of the saddle or taking a little weight off the bike on these potholes? I have never pinch flatted on 26 inch tires ever, and I have not had any problems on 700x32's either (and I am not a light guy). Are you sure these are pinch flats and not a puncture from a spoke poking through a bad patch of rim tape or a peice of debris in your tire or something? Does it look like a little snake bite on the tube, or something else?
05-28-07, 06:20 PM
Joe Dog, did you ever run tires as skinny as mine on relatively fat rims? I"m pretty sure that is the issue. I could run more pressure but that would exceed the manufacturer's recommended maximum for the tire. The flats do look like snake bites, although there is never any puncture through the tire and the potholes that flat the tubes are usually ones that I hit while seated. I also put weight on the bike, up to about 20 pounds and I weigh over 190 lbs. This sucks because I only have maybe 200 miles on the tires and already have six flats.
05-28-07, 07:55 PM
Not sure what you mean by "fat rims" - I ran 26 x 1's on what I think were pretty standard mountain bike rims (Cannondale mountain bike from the late 1980's). From your description is does sound like pinch falts, so I have to say you are probably right about that and my assumption that it was something else is probably wrong. I used Tom Slick's very successfully. I would think the Panaracer's would be pretty good tires - probably equal to the Tom Slicks.
I get out of the seat anytime I can to take a pothole (and I "think light" as well). I would make that a habit, but otherwise I guess I don't know what to tell you. I would not go much above the recommended PSI on the side wall - the tire could probably take it but the ride would probably be pretty bad. I guess if it were me, I would get the widest, slickest, highest pressure tires I could find and run those.
Sorry for your bad luck - hang in there and hopefully you will get the combination dialed-in soon.
05-28-07, 08:26 PM
I'm running the recommended max, 80 psi.
RG, which tires would you recommend for commuting on pavement?
I'd try something that's about 1.5" and has a kevlar puncture resistant belt under the tread.
05-28-07, 08:28 PM
You havent said how wide your rims are. If the inside width is 21 mm the min width tire you can run is 1.375". If it is 23 mm, you cant go below 1.625". If you dont ride the bike on serious off road trails (rocks and tree roots) a new rim on the wheel that gets the pinch flats wont be very expensive.
05-28-07, 08:58 PM
Even if you are 80 PSI, I'd go 10 more.
05-30-07, 03:06 PM
I bought a set of Geax Roadsters with Kevlar. They are nominally 26x1.5" but they sure look fat for that width. I used to run Specialized Nimbus Armadillo 26x1.5" tires on my bike but the tread literally flakes off the casing once the tires get worn and the tires are ridiculously expensive. This same tread flakiness happened on every single Armadillo I've owned. The Geax Roadsters next to the Armadillos look way fatter, even though they are both supposedly 1.5 inch tires. I'm not sure where they measure the width on tires but if you put this Roadster next to the Panaracer it looks at least twice as wide. These tires work okay so far, with no flats and no bottoming out but they are heavier and have way more rolling resistance than the Panaracers. I'm running 80 psi, which is 5 psi more than the recommended maximum pressure. Anyway, I'm a commuter so I can't be changing flats every day and I'm willing to sacrifice a little performance (grudgingly).
05-30-07, 03:33 PM
If there's a hole or rock big enough to cause pinched flats, they're big enough to be seen. Don't hit potholes or rocks...
Most people make the mistake of looking way ahead at the horizon like they're driving a car. Problem with this is you don't see stuff that's only 10-feet in front of you. So keep your neck & head at a 45-degree angle and look from 30-75ft ahead of you (reduces neck & shoulder pain as well). Then you'll see the stuff that you're about to run over. To look up and watch for lights & cars, just roll your eyeballs up, but keep your neck & head in-line with your spine.
05-30-07, 03:42 PM
Seems to me you're more likely to get pinch flats with wider tires than narrower ones... combination of pressure rating and geometry.
05-30-07, 05:15 PM
Sounds like the tire is too narrow for your rims. I have some old school wide MTB rims (28mm exterior width) from the late 80's and I run Ritchey Tom Slicks 26x1.4" and that is as narrow as I'll go on those rims.
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