Tire leak?

[Don_Eilenberger]

I seem to have one I can't figure out. Conti Road Attack, 5k miles on it - not badly worn (some center wear.. expected) seems to be very slowly loosing air - or my air-gauge is loosing it.

 

I can usually tell if a tire is getting low because my feet reach the ground easily.. so I check tire pressure. Had this happen over the weekend, and I checked pressure the other night, and found while my front was fine at 34PSI, my rear tire read 29PSI - and I'd filled them to 34/36 about a week before.

 

So - I filled it again last night to 40PSI, and then sat there, cleaned the entire tire, looking for a nail - nothing. Used a sprayer on the tire - turning it and looking for bubbles - nothing. I saw a TINY (think about 0.005") metal shiny spot on the tire - poked at it with a sharp pair of nippers - and it popped off - and no air leak where it had been. It was so small I couldn't find it after it popped off.)

 

So - I checked it again - and with the usual air excape of my tire pressure gauge - it now read 39 PSI.. and I went to bed.

 

Checked it this morning - and with a few psssstttsss from the tire pressure gauge - it now read 37.5 PSI. Checked it again - less pssssttt getting the gauge on it - and 37 PSI.

 

Digression - why do they make gauges that release about 0.5PSI every time you try to check the pressure? There's something wrong with that..

 

I think the drop I saw from yesterday to today was probably from my sloppy tire gauge technique... maybe..

 

Anyway - didn't ride it to work today 'cause of this (and a few other things..) and will check it tonight when I get home.

 

The valve stem/core don't seem to be leaking (it's a new bike..) No nails, no holes, no air bubbles I can find.

 

It's like magic is letting air out very slowly..

 

My thought now is doing something like slime.. I hate to do it, but since I'm usually involved in changing my own tires - figure I'd be the one getting gooped up when the tire comes off.

 

Any thoughts?

[Mike T]

Could be a bad valve stem with a slow leak. I've had this happen on my cars before.

[Don_Eilenberger]

Could be a bad valve stem with a slow leak. I've had this happen on my cars before.

That was my thought also.. so I did the soap/bubble test. No joy. Even tried bending it around to see if it was leaking at the base - still no joy. Wish it was that easy..

[FrankBrown]

Usually this kind of problem ends up being a bead issue. Speck of dirt or minor imperfection. Pump it up to 55-60 psi and ride it for 5-8 miles, let sit and cool for at least three hours, let air out to what you normally run it at plus 1 psi and check in 24 hrs. This may help. Good luck.

[Don_Eilenberger]

Leak was eventually found..

 

It was apparently a defect of some sort in the tire. After pressurizing it to ~90 PSI and using my laundry room sink as a dip tank - I spotted a tiny stream of bubbles coming right out of perfect looking rubber. Even examining the rubber using a 5x eye-loupe there were no apparent cuts/holes/defects in the tire.

 

I contacted Conti-North-America about it - and thanks to Greg at Conti-NA. He coordinated with BMW-NA and is arranging for me to receive a new tire - mounting and all - at no cost.

 

I'm impressed with the tire wear on the Conti RoadAttack - I measured mine and I have 4.5-5.0mm of tread depth in the center of the tire. According to Greg - it starts life with about 7mm... the tire now has 6,000 miles on it.

 

Kudos to Conti for standing behind their product! I suspect when I eventually do wear out the RoadAttacks - they will be replaced with new RoadAttacks (they work great dry or wet.. I got to really experience wet last Friday.)

[Albert]

One cautionary note here Don. There is a physical limit to which a tire can be inflated. When that's exceeded the result can be explosive. I know first hand, having had a coworker a number of years ago who lost part of his hand in just such a mishap. Tire technology has come a long way, and the tire he was working with was larger (automobile), but I still am careful not to overinflate a tire an excessive amount to this day.

[Don_Eilenberger]

One cautionary note here Don. There is a physical limit to which a tire can be inflated. When that's exceeded the result can be explosive. I know first hand, having had a coworker a number of years ago who lost part of his hand in just such a mishap. Tire technology has come a long way, and the tire he was working with was larger (automobile), but I still am careful not to overinflate a tire an excessive amount to this day.

That's quite true - and I considered that as I inflated it..

 

But 90PSI is less than is normally used just to seat the bead on a modern low profile motorcycle tire. It frequently takes in excess of 100PSI to get the bead to "pop".. so 90PSI was within a safe limit IMHO.

[duckbubbles]

But 90PSI is less than is normally used just to seat the bead on a modern low profile motorcycle tire. It frequently takes in excess of 100PSI to get the bead to "pop".. so 90PSI was within a safe limit IMHO.

Do you use any kind of lubricant on the tire bead? I have never had a tire take more than the normal operating pressure to seat the bead. Usually about half of operating pressure.

 

Frank

[Jim VonBaden]

But 90PSI is less than is normally used just to seat the bead on a modern low profile motorcycle tire. It frequently takes in excess of 100PSI to get the bead to "pop".. so 90PSI was within a safe limit IMHO.

Do you use any kind of lubricant on the tire bead? I have never had a tire take more than the normal operating pressure to seat the bead. Usually about half of operating pressure.

 

Frank

 

I have gone as high as 70 psi, but never needed any more.

 

I do not, however, doubt Don's assertions.

 

Jim

[aggieengineer]

I've been using Yamaha aerosol tire mount lube lately to do numerous motorcycle and car tire changes. I've never needed anything approaching normal pressure to seat the bead. The stuff dries nearly out of existance in a few minutes, but before it does, man is it slippery. Get some before the EPA decides it's too good for us.