2011 FLHTK, new to me a year ago. New rear Dunlop American Elite with the bike. Has a little under 5K on it now. Pressure held fine over the winter, down a couple pounds when I finally got out to ride in early April - added back the couple pounds to run at 40psi where I normally do. A week or so later, checked it again before first 2-up ride of the season. Good to go, still at 40.

Fast forward to last saturday - (3 weeks or so after last pressure check / 2-up ride). Went on a short ride to grocery store - had a moment where bike felt a little squirrely in a tight-ish 30mph turn - but road surface was patched and uneven, and my line wasn't quite right and passed over the joint between old road and newer patch - chalked it up to rusty riding. When walking back to the bike after the store, the rear tire did look somewhat low - but didn't have a pressure gauge with me, so I rode home. Should have checked it when I got home, but didn't. Then yesterday I finally had a chance to ride to work - pulled the bike out, and checked the rear. it was down to 8 psi. HOLY $#!T. Figured I had to have picked up a nail or a screw or something.

Didn't have time to do a thorough check before work, so pumped it back up (to 34 psi, cause that's what I got to, being aggravated), and took the truck. Got home, it was still at 34. Pumped it the rest of the way to 40, and left it overnight. Still at 40 this morning. Finally got a chance to put it up on the jack and really look it over - turned it over 5 times, can't find a single sign of damage/puncture/debris in that tire. It DOES feel to the hand like it's got some mild uneven wear. Don't think it was like that last year, but honestly wasn't paying that much attention. Took it out for a a few miles today, seems to be holding pressure, and I can't feel anything odd. My guess is I've been running at least somewhat low for the past couple weeks (causing some mild choppy wear). I did not really feel anything dramatically bad in the way of handling though.

What the heck could have caused a fairly rapid deflation (40psi to 8psi over roughly 3 weeks) besides a puncture? Outside air temps are a little warmer than 3 weeks ago. Front tire is still where I put it (well, acutally 0.5psi higher). What the heck else could cause this? Nobody has access to the bike to let air out of the tire (it's locked in my shed). I'm stumped??

Any suggestions on things to check? At this point, my plan is just to monitor pressure before and after every ride, and only do short distance / low speed stuff until I re-build some confidence in the tire.

Thanks

Dan

 

Bike up on a jack, spray bottle with soapy water, spray the wheel, turn slowly and observe.
Check stem and valve core, too. The bubbles will show it. Inflate to 40. Check treads, too.
Some small leaks will leak more depending on how it is parked. Heck, if you have to, put a big container of water under the tire and lower some of the wheel into the water.
You will find it. Some leaks can be very tiny.

 

Dirty / worn schrader valve. It seals, except when it doesn't.

if you rode it much at 8 psi, I'd be concerned about the tire carcass. Particularly the sidewalks.

 

A couple years ago I kept losing pressure real slow .
Kept looking & found both tires had been plugged by
previous owner . Bike only had 4,000 miles on it when
I bought it . I was not happy .

 

was just being a *****? Maybe somebody let the air out? Cut somebody off or have a crazy loud exhaust? On good terms with your neighbors? I guess I'm just naturally skeptical, esp since it appears to be holding air now.

Ben

 

Replace the valve core anyway. Cheap and easy and the most likely answer
to intermittent air loss. Things happen. The universe is just reminding you and all
of us to check tire pressure. You can no longer tell by looking. 8 psi. Been there.


Every vehicle I have has a gauge handy.

 

I second the valve. Although you have a peculiar situation, all things considered the valve would be the first suspect.

Although I admit, my first thought was an old movie and I can't remember the name or even the storyline except that there was this accountant type geek who had a neighbor that loved to screw with this guy. Knowing that he (the accountant type) would meticulously keep track of his mileage, the neighbor would siphon gas from his car one week, only to put it back in sometime later, after the accountant would have refilled and checked his mileage. The accountant was totally frustrated as one week he would get 32 miles to the gallon, only to check the next week and down to 12 miles to the gallon. Then a week or two later back up to 36 or whatever.

So does you neighbor have access to your bike?

 

Thanks for this - now that you mention this I recall my father doing this with a bicycle inner tube once. This will be my next step, to try to verify no leak in tire. Will check valve stem as well, but as mentioned below, gonna replace the core.

Anything I can look or feel for to indicate trouble here? Apparently thanks to my complacency, it could have up to 200 or so miles on it at anywhere between 40 and 8 psi. My assumption (maybe incorrect) is that I'd feel much more unusual behavior from the bike if the tire was at 8 psi while riding. No interest in doing a controlled experiment to find out now though.

Fairly certain this isn't my case, as the tire was new when I bought the bike.

Going to do this. Definite complacency on my part for not checking tires more frequently - got lulled into it by previous good behavior of tires, along with how much of a PITA it is to check on this bike compared to previous ones. I normally carry the gauge with me, but pulled it off the bike (along with the rest of the toolkit/raingear/etc. that rides in a kit in the right bag) to make room for the stuff I was picking up at the store. Going to change my approach, and split a small 'always aboard' toolkit out of this.

LOL, If I had a neighbor who wanted to get back at me, that would work for me too - I track fuel mileage every tank. Pretty sure its the FP3 that's currently putting a dent in my fuel economy, however. A couple stops at public places, and one trip to work (with the bike parked in the equipment shop) are the only times someone other than me would have access. While I have no way to rule it out, I also have no particular reason to suspect anyone is trying to mess with me. Bike is locked up in shed at home, so even if neighbors had a problem, they don't have access. Fairly recent (6 months) new neighbor on one side who keeps to himself, other side they've been there since we have, and are friendly. I'm gonna stick with it being mechanical for now....

 

Make sure you use valve stem caps. The centrifugal force of the tire rotating can push the valve partly open causing an ever so slight leak at speed.

I bought a "FOBO bike" TPMS. I haven't got to use it since the bike is apart for engine upgrades. You can see, on your phone, what you tire pressure is. You can set high and low pressure alarms. Just my attempt at being more diligent about my tire pressure. I hate laying in the driveway checking it before heading out.

 

I need to check my smooth laced wheels as they are always low. Couple pounds every few weeks and drives me crazy and been this way since new.

The front is easy enought to add but the back is a pain and definitely installing 90 degree stems next set of tires