F700 tyres deflating whilst bike is in garage, is it a feature of the TPMS?

Discussion in 'Parallel Universe' started by farqhuar, Mar 9, 2019.

  1. farqhuar

    farqhuar Human guinea pig

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    Hmm, now this is an issue which I have never experienced before on other bikes, but the F700 is my first, and only bike with TPMS.

    If I don't ride it for a month I can almost guarantee the TPMS light will be flashing and the tyre pressures will have dropped. It seems to happen about twice as often for the front, as it does for the rear.

    I don't believe it's a tyre leak (Anakee IIs), but most likely a TPMS issue. I suspect it may even be the way the TPMS works (constantly leaking a small amount of air in order to measure the pressure) as it has had this issue from new.

    Any others with similar experiences, or do I have a dud?
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  2. SnoDrtRider

    SnoDrtRider I've been lost here before...

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    I check my tire pressure pretty much weely on our bikes with a gauge (no TPMS) and they are usually down a pound or two. There are no detectable leaks.
    I have a very accurate digital gauge that is part of the filler so little or no air is lost switching from the air chuck to the gauge to check.
    Bikes are more prone to detectable pressure changes do to the smaller volume of air vs a car tire and car tires are known to set a TPMS warning code when the weather gets colder due to pressure changes.
    Here in the NE USA people are lined up at the air pumps when we get a cold snap.
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  3. Tigershark48

    Tigershark48 Been here awhile

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    My F700 has been in winter storage for more than three months. I did not get a low pressure TPMS error just starting it up on the centerstand. I can’t test it at the 30 km/h speed trigger point due to ice and snow on the roads, but will check again this spring. However, my measured pressures right now are 26 front and 29 rear. This is no surprise sitting that long in the cold garage. Never aired them all last summer and never got an error, but I also rode it several times per week.

    My wife’s new Highlander just got a TPMS code a week ago when wind chill dropped way below zero. She was just leaving and said it went away ten minutes down the road. I checked pressures the next day and all four were down to 32 psi with the book recommending 36. I aired them all back up to 36 and no more errors.
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  4. Pilotuh1b

    Pilotuh1b Been here awhile

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    If you set a tyre mid summer it will be low mid winter regardless of any other changes. If you’re somewhere with seasonal temperature changes.

    Pressure=temperature/volume

    Volume stays the same so if temp goes down pressure goes down.
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  5. SnoDrtRider

    SnoDrtRider I've been lost here before...

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    A tire can even change pressure from being in the sun. Cold vs Hot tire pressure on a car/truck can vary 4-5 PSI or more depending on the size of the tire.
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  6. Pilotuh1b

    Pilotuh1b Been here awhile

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    Yep. The obvious one is driving to the service station to check the pressure. The difference between the pressure at home cold and the station is likely a few psi.
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  7. farqhuar

    farqhuar Human guinea pig

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    Thanks guys. I agree re seasonal temperature changes but where I live there is minimal difference between summer (29C / 85F) and winter (21C / 70F) averages.

    On my other vehicles I check pressures regularly but probably only need to add air once per year, if that. The wife's Lexus also has TPMS but the TPMS light only ever comes on after a tyre change (and usually because the replacement tyre has a higher, NOT lower, pressure than its predecessor).

    I'm still convinced the BMW TPMS is actually causing the deflation.
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  8. SnoDrtRider

    SnoDrtRider I've been lost here before...

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    The TPMS does not use or disperse any air monitoring the pressure... it is all done internally within the tire.
    All materials are somewhat porous and will allow gasses or liquids to escape, it just depends on the size of the molecules of the contained substance vs the size of the spaces between the molecules of the container.
    The rubber seals that mount the TPMS to the rim would be my first suspect in a leak. Rubber deteriorates due to ozone and the sun and being in your location I would assume plenty of sun exposure.
    Coming up in the automotive industry we were alway taught that a new tire gets a new valve stem or tube. I have my tire guy always install new stems when I get tires and when I install new tires on our bikes they always get new tubes... especially the street bikes.
    I haven't had any vehicles with TPMS yet but I am about to find out with the new bikes.

    Another good idea that has been used the past decade or so is using nitrogen instead of air to fill your tires as nitrogen is more stable and less prone to leaking than the oxygen that is in the atmosphere which is 21% oxygen.
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  9. SnoDrtRider

    SnoDrtRider I've been lost here before...

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  10. farqhuar

    farqhuar Human guinea pig

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    Yeah, but......

    My bike is 4 years old, it has travelled less than 13,000km (8,000 miles) and is always parked in a darkened garage (which is even more temperature stable than outdoors). It stills runs the original tyres and has had this problem since day 1 - I do own several bikes and the F7 gets ridden relatively infrequently compared with the others, however, I also have a 16 year old bike in the garage, with 10 year old tyres and which hasn't been ridden in over 12 months, and its tyre pressures are only down 1psi since I last rode it (yes, I just checked).

    I agree, perished rubber seals are a potential problem, and I always replace valve stems when changing tyres, but the tyres on the F7 are the originals. I have also carefully inspected the tyres and can confirm no nicks, cuts or penetration by foreign objects.

    If it's not the TPMS the only other options are crap porous rims (which wouldn't surprise me given the general poor quality of BMW products), bad tyre valves or poor tyre to rim sealing.

    Still seems odd to me that this problem should be unique to this bike, and losing more pressure on the front wheel (6psi loss up front compared with 3 psi at rear).
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  11. farqhuar

    farqhuar Human guinea pig

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    Interesting article, obviously US centric as TPMS is not mandatory down under.

    The statement "All vehicles made after Sep. 1, 2007 must have a tire pressure monitoring system (TPMS) to alert the driver to a low tire pressure condition. " is also interesting. Given that most motorcycles do not have TPMS, does this mean that the authors of the article do not class motorcycles as "vehicles", or is it, once again, sloppy editing? :lol3
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  12. flei

    flei cycletherapist

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    FWIW, the front Mitas E-07 tire on my F650GS (798cc twin, same as the F700) which is fitted with aftermarket TPMS , would slowly lose air. I tried and tried to find the source of the leak (looked for a nail, changed out the valve core, soaped up the tire, ran it without the TPMS, etc. etc. etc.) but could not find any leak. I finally took off the wheel and brought it to my mechanic; it took him a long time to find the problem; the leak was the result of a very slight imperfection where the bead of the tubeless tire met the rim (there was no rim damage); he cleaned up the inside of the rim and that fixed it.
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  13. SnoDrtRider

    SnoDrtRider I've been lost here before...

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    Yes some info in that article is a bit unreliable but the main idea is that the TPMS valve stems do need and should receive servicing when changing tires.
    Question: Have you ever brought this issue up with BMW?
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  14. SnoDrtRider

    SnoDrtRider I've been lost here before...

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  15. B_C_Ries

    B_C_Ries Long timer

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    The problem with Nitrogen is that it is harder to get than air and since checking tire pressure always results in some loss, people will often end up checking their tire pressure less often. I'm content with air in my tires and I have a small harbor freight air compressor so that checking and filling tires is always convenient for me.
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  16. SnoDrtRider

    SnoDrtRider I've been lost here before...

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    I use air myself... I have 3 compressors between my HF 21 Gallon in the garage and the two contractor compressors I use for my nail guns, etc.
    I have an Aluma trailer that sits most of the time that had Nitrogen from the factory. I've had it for 4 years and never needed to add Nitrogen even though I check it before every use.
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  17. bykergrrl

    bykergrrl Been here awhile

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    I've had my 700 for several years - w/TPMS - even when the bike sat for 8 weeks when I had a broken wrist there wasn't any significant pressure loss in the tires.
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  18. farqhuar

    farqhuar Human guinea pig

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    Good to hear you have had a good experience.

    Yes, I suspect this is most likely the issue. In my experience with Bee eMs, of all varieties over 47 years of riding, the wheels are their achilles heel. Doesn't matter whether they are steel or alloy, spoked or solid, the rims bend or fracture, spokes snap and they struggle to retain air.

    No, I have had the run around with BMW Australia trying to get previous bikes fixed (G650 Sertao EFI issues) and I don't have confidence in their ability to acknowledge a problem, never mind fix it. :D
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  19. morfic

    morfic Been here awhile

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    My original set Anakee III seemed to lose pressure in the front, not the back which had two plugs in it.

    New Anakee III seem to hold pressure front and back just fine.

    Same rims, same TPS, actually I'd need to find service ticket to verify if valves were or were not replaced.
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  20. Tigershark48

    Tigershark48 Been here awhile

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