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Trouble with Continually Flatting Rear Tire

Old 06-29-20, 06:11 PM
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judybat
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Trouble with Continually Flatting Rear Tire

Have lurked on this site for about a year and have appreciated the collective knowledge I've found.

In the past month or so I've begun experiencing a great number of flats and can't figure out what's up. Been cycling for about a year on a Cannondale Synapse 105 that's about a 2006 model. Live in Scottsdale, Arizona. Put Continental GatorSkin tires on the bikes July last year and no flats until a month ago. Have about 1,700 miles on the tires.

When the flats first began it appeared the rim tape was shifting on the rims, exposing the spoke holes, and I noticed the holes in the tubes was on the inner side. So, new rim tape.

Good for a week or two and started flatting out again. Finally decided to replace the tires with new GatorSkins. First ride was this morning and got a flat 16 miles in.

Very frustrated. Running 25 mm wide tires at 85-90 PSI. Weight is about 225 lbs and has been consistent the past year.

My next thought is to scrap the bike and use this as an opportunity to buy a new one but I don't want to spend that kind of money.

Any thoughts?
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Old 06-29-20, 06:29 PM
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Inflate the old tube and see where the holes are. If on the inside then its the rim tape of something in the rim.

Do you check the tire before putting a new tube in?

I've ridden in Scottsdale and there's plenty of thorns so flats are not surprising.
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Old 06-29-20, 07:04 PM
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cracked rim pinching the tube?
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Old 06-29-20, 07:09 PM
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Originally Posted by GlennR View Post
Inflate the old tube and see where the holes are. If on the inside then its the rim tape of something in the rim.

Do you check the tire before putting a new tube in?

I've ridden in Scottsdale and there's plenty of thorns so flats are not surprising.
Yep, gotta find the root cause, starting with the location of the hole in the tube. Can be tedious. Might require multiple more flats to occur. Become diligent about tire and tube orientation on the wheel.
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Old 06-29-20, 07:27 PM
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Originally Posted by judybat View Post
Have lurked on this site for about a year and have appreciated the collective knowledge I've found.

In the past month or so I've begun experiencing a great number of flats and can't figure out what's up. Been cycling for about a year on a Cannondale Synapse 105 that's about a 2006 model. Live in Scottsdale, Arizona. Put Continental GatorSkin tires on the bikes July last year and no flats until a month ago. Have about 1,700 miles on the tires.

When the flats first began it appeared the rim tape was shifting on the rims, exposing the spoke holes, and I noticed the holes in the tubes was on the inner side. So, new rim tape.

Good for a week or two and started flatting out again. Finally decided to replace the tires with new GatorSkins. First ride was this morning and got a flat 16 miles in.

Very frustrated. Running 25 mm wide tires at 85-90 PSI. Weight is about 225 lbs and has been consistent the past year.

My next thought is to scrap the bike and use this as an opportunity to buy a new one but I don't want to spend that kind of money.

Any thoughts?
At 190lbs, running 25mm tires (GP5K), I start to run the risk of pinch flatting at 96 psi.

Doesn't surprise me rhat you're encountering issues. I'd increase pressure and see if that does the trick.
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Old 06-29-20, 07:39 PM
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A very good reason to patch tubes. The patches serve as documentation to location on the tire. Patches showing up around the same place (or same distance from the valve) tell you there is an issue in the tire or rim. (For this reason, always put tires on the same way. Convention is label to the drive side of bike and centered at the valve. Now you can just put the tube in the half mounted tire and search where the patched are for glass, thorns, the tiny short pieces of hair-like wire from var tires and issues on the rim and tape.)

Edit: I weigh 155 and pump 25s to 100. Pinch flats very often come in pairs, hence called "snakebites" as both sides are pinched by their respective rim. If you patch, you quickly find two holes, not one and you now know the cause.

Last edited by 79pmooney; 06-29-20 at 07:44 PM.
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Old 06-29-20, 08:11 PM
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need more psi. i'm 123 lbs and running 25mm tire on 80 psi. You need AT LEAST 105-110 psi
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Old 06-29-20, 08:43 PM
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Use a 28 tire & see if that helps.
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Old 06-30-20, 06:34 AM
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Re: Trouble with Continually Flatting Rear Tire

Thanks for the ideas.

I looked at the last three flats and all were on the inside of the tube, near where the rim tape is. I checked the wheel and rim tape but see nothing to indicate a problem. Added a second layer of rim tape.

When reinstalling the wheel I noticed that the rear wheel is very slightly out of spoke alignment although I'm not sure if this could be a contributing factor. I'll take it to get re-trued today.

On PSI, have been running the same pretty consistently for a year but will up the pressure to see if that makes a difference.

Running 25's but don't think wheel and bike will support wider without changing the wheels themselves.

Thanks, all.
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Old 06-30-20, 10:21 AM
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I've not ran across a normal road bicycle with a 25 tire have issues using a 28 tire. YMMV: Others may have exp with that particular bicycle to suggest otherwise.
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Old 06-30-20, 11:00 AM
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Definitely try increasing the PSI. I'd consider 85-90 on the low end for myself, at 125lbs.

Wider tires would probably help, but I'd take some measurements before going that route. On bikes from that era, there is often not enough frame clearance for much over 25mm (my 2010 cannot go above 23, actually.)

If you ride anyplace where trucks go, sometimes little invisible pieces of wire can get caught. If you turn the tire inside out and rub a cotton ball around, you can find them. I doubt that's the issue, but can be another cause of recurrent flats.
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Old 06-30-20, 11:26 AM
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I would leave your tire pressure alone. I'm about your size, inflate my tires to 80 psi and don't have pinch flats. 80 lbs is pretty comfortable. Gatorskins are nice but they will flat as well. I would check your tire for imperfections or something embedded or stuck in the treads. I had a piece of glass go right through a Gatorskin. Took out the glass and filled the whole with rubber cement.

Having a flat while riding is so exasperating. I have been riding Cont Gp 4000 II and Gp 5000s and no flats.
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Old 06-30-20, 11:40 AM
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It is a good idea to mark the location of the valve on the outside of the tire before you remove the tire after getting a flat. That's so you can exactly line up the the hole in the tube with both the rim and with the inside of the tire casing. This narrows down where you have to look for the cause of the puncture be it on the tire or on the rim. Carefully feel around inside the tire for something protruding through the tire casing. Look at the rim for a burr near where the hole in the tube lines up with its position on the rim. In the worst case you would be far better simply buying a new wheel rather than an entire bike.
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Old 06-30-20, 11:59 AM
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Originally Posted by VegasTriker View Post
It is a good idea to mark the location of the valve on the outside of the tire before you remove the tire after getting a flat. That's so you can exactly line up the the hole in the tube with both the rim and with the inside of the tire casing. This narrows down where you have to look for the cause of the puncture be it on the tire or on the rim. Carefully feel around inside the tire for something protruding through the tire casing. Look at the rim for a burr near where the hole in the tube lines up with its position on the rim. In the worst case you would be far better simply buying a new wheel rather than an entire bike.
I always center the tire label at the valve. No marker needed.

OP, a rim can handle a wide variety of tire widths. Wider rims is the popular tend now but many of us rode wider tires on the older narrow rims years ago without issue. 28s are right in the middle to tire widths and will go on just about anything (assuming the slightly larger tire will fit inside your frame and not run too close to the fork or rear stays or (sometimes) the seat tube.). Pinch flats from not enough pressure or tire size will always show on the rim/underside of the tire, (Look carefully for a second flat about 1 cm to the other side of the tube. That's a pinched tire "snakebite".)

Ben
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Old 06-30-20, 12:50 PM
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inflation or wheel issue, 90 psi @ 225lbs is low. I am 170lbs and run that on 25's.
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Old 06-30-20, 01:30 PM
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Sometimes you get a thorn or a thin piece of wire that ONLY goes through the tire when weight is on the wheels. In such a case it can be quite hard to find the item that's causing the flats. I take the tire completely off the rim and then flex the tire and run a cotton ball along the inside of the tire and hope it snags on whatever has punctured the tire. Sometimes I've had to do the same thing on the outside of the tire because the thin wire is protruding a bit on the outside but doesn't work its way through to the tube until after some distance riding. I now carry a small bottle of Stan's Tire Sealant in case I get a tiny hole that I can't find whilst checking on the side of the road. All my tubes now have removeable valve cores so I can get the sealant into the tube easily. I haven't needed to use it since but I bet the day I leave the sealant at home will be the day I wish I had it with me.

Cheers
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Old 06-30-20, 01:33 PM
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When I first bought my road bike with 23 tires I got a flat within two weeks. I am 150lbs and was running around 80psi. Lot's of people prediccated I got a pinch flat ( two snake bites ). Sure enough when I inspected my inner tube later it was a pinch flat. I agree with others you should be riding with a lot more psi.

I now run 28 Continental Grand Prix 5000 at 100 psi. No more pinch flats. I wish I could say now more flat tires. lol
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Old 06-30-20, 01:50 PM
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What is the replacement rim strip? Cloth tape? Stans? Replace the tire and inner tube, start there.
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Old 06-30-20, 03:17 PM
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Ride the bike to your local shop (if they're still open). Ask the friendly mechanic if he can figure out why your tire keeps going flat. (You may have worn the rubber down to where it's not very puncture resistant.) While he's in the back, go look at new bikes anyhow. It's fun, and you don't really have to buy one.
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Old 06-30-20, 04:13 PM
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Adding all the puncture resistant features, will make your tires too heavy to be satisfactory, perhaps?

there is a Tannus Tire option https://tannusamerica.com/ https://tannusamerica.com/pages/tannus-airless-tires
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Old 06-30-20, 04:30 PM
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What kind of rim tape do you use? I found that a newfangled plastic one gave me a few flats on the inner side. Replaced it with cloth based tape with correct width and the problem was gone.
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Old 07-01-20, 04:21 AM
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Might be time to consider tubeless.
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Old 07-01-20, 05:33 AM
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Bontrager rim tape, although I added a second layer of tape (Velo).

Found that the wheel was very slightly out of true and got the LBS to fix that. They're thought is air pressure, so I'll be sure to air it up higher than I have been.

Thanks, all.
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Old 07-01-20, 05:43 AM
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Originally Posted by Ross520 View Post
At 190lbs, running 25mm tires (GP5K), I start to run the risk of pinch flatting at 96 psi.

Doesn't surprise me rhat you're encountering issues. I'd increase pressure and see if that does the trick.
And/or go with a wider tire, if your frame and fork allow that.
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Old 07-01-20, 08:27 AM
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Originally Posted by Miele Man View Post
Sometimes you get a thorn or a thin piece of wire that ONLY goes through the tire when weight is on the wheels. In such a case it can be quite hard to find the item that's causing the flats. I take the tire completely off the rim and then flex the tire and run a cotton ball along the inside of the tire and hope it snags on whatever has punctured the tire. Sometimes I've had to do the same thing on the outside of the tire because the thin wire is protruding a bit on the outside but doesn't work its way through to the tube until after some distance riding.

Cheers
Great advice. This has been my experience as well. Little shards of glass and metal pieces like staples and pushpins get in the tread. Removing the tire and flexing it will eventually find these little buggers. Double flatting after you have swapped tubes without finding the cause is a tell tale sign you have some tiny piece embedded in the tire.
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