Tyre Losing Pressure

[Dave Ford]

My front Tourance (2009 1200 GSA) loses pressure during a day's riding. For example, last Sunday I went to RAF Waddington air show, a round trip of only 130 miles. Full pressure when I left home - down to 19 psi when I returned. In an effort to find the leak I've had the wheel and tyre underwater (even pressurised to 50 psi) - not a sign of a leak.

All suggestions, even sarcastic ones, gratefully received!

 

[oldrascal]

My front Tourance (2009 1200 GSA) loses pressure during a day's riding. For example, last Sunday I went to RAF Waddington air show, a round trip of only 130 miles. Full pressure when I left home - down to 19 psi when I returned. In an effort to find the leak I've had the wheel and tyre underwater (even pressurised to 50 psi) - not a sign of a leak.

All suggestions, even sarcastic ones, gratefully received!

My first thought is to question your method of taking your pressures. I say this because I decided to buy a Draper foot-pump with pressure gauge to more easily check pressures before riding. After a month of using the pump where there was no pressure drop, I started to notice a 5-8lb drop in pressure from the front tyre. I even started a thread on this forum where answers such as 'faulty valve' or 'porous rim' were offered.

Anyhow, I decided that it was a good opportunity to change to better tyres so I got a pair of Trail Attacks . Well, sod me, the same thing continued but with even more pressure being lost. So I started to suspect the foot pump and bought a Michelin one instead. Result.....no more pressure loss.

So, it could be your pump or gauge.......or porous rim or buggered valve. Just got to take it methodically.

 

[Slowdown]

My first Tourances 'leaked' - not as much as yours, but I still needed to top them up every week. The second set were better, but still leaked a bit.

The Avon's I've got now hardly leak at all.

I guess some do and some don't

 

[Spout]

Check the valve by covering with spit.
Even a small leak will bubble the spit, and if the leaks more you wont be able to cover with spit.
Valves can leak at speed (centrifugal/petal? effect). So try another valve cap to see if this stops it (one of those with rubber in not just the plastic ones). If so, then replace your valve.

 

[Slowdown]

Check the valve by covering with spit.
Even a small leak will bubble the spit, and if the leaks more you wont be able to cover with spit.
Valves can leak at speed (centrifugal/petal? effect). So try another valve cap to see if this stops it (one of those with rubber in not just the plastic ones). If so, then replace your valve.

Good point - I've heard that decent metal valve caps can hold substantially more pressure than valve stems. Even if its rubbish, they do look good and aren't much from Halfords....

 

[Dave Ford]

My first thought is to question your method of taking your pressures. I say this because I decided to buy a Draper foot-pump with pressure gauge to more easily check pressures before riding. After a month of using the pump where there was no pressure drop, I started to notice a 5-8lb drop in pressure from the front tyre. I even started a thread on this forum where answers such as 'faulty valve' or 'porous rim' were offered.

Anyhow, I decided that it was a good opportunity to change to better tyres so I got a pair of Trail Attacks . Well, sod me, the same thing continued but with even more pressure being lost. So I started to suspect the foot pump and bought a Michelin one instead. Result.....no more pressure loss.

So, it could be your pump or gauge.......or porous rim or buggered valve. Just got to take it methodically.

It's definitely losing pressure. While riding I thought I could detect a reluctance for the bike to turn into bends, but suspected it was my imagination. Then when it came to push it, it was immediately noticeable.

I can see and feel the tyre is notiicably softer - in fact it's almost impossible not to notice. Inflate tyre back to correct pressure amd handling is back to normal.

Will try replacement valve and cap....

 

[Tomcat]

I had a similar slow leak on the rear tyre of my Aprilia - tried the soapy water trick to identify the source, and replaced the valve, all to no avail. In the end I fixed it with a bottle of tyre slime (or something similar - the stuff that fixes punctures). It has worked fine, no loss of pressure since.

 

[STUBBS]

have you any damage on the rim sounds as though the tyre is dropping pressure whilst flexing on the rim

 

[diplomaticdanny]

Used to lose pressure all the time on my car alloys until I had them filled with Nitrogen, tyre pressure monitor goes off once in six months now. Have since had my 06 GSA tyres filled with nitrogen, excellent.

 

[Wapping]

Used to lose pressure all the time on my car alloys until I had them filled with Nitrogen, tyre pressure monitor goes off once in six months now. Have since had my 06 GSA tyres filled with nitrogen, excellent.

Cue, What nitrogen? thread

 

[velofelo29]

Given that you are losing that much pressure in a day then that should be visible. I mix Stergene with water to make a soap solution (don't use washing up liquid as they are full of salt and exremely corrosive) brush this all over the tyre and valve and wait Do not over inflate the tyre as this can actually seal a small leak. Try not to overbrush the solution during the application rather try and paint it on. You will see the leak appear as froth. At this stage I would discount a porous rim, from memory these rims appear to be rolled and welded from extrusion, hard to imagine any leak possible with that method.
Best of luck, let us know what you find.

 

[Rocky Mountaineer]

have you any damage on the rim sounds as though the tyre is dropping pressure whilst flexing on the rim

The front tyre on my 2009 1200 GS has been leaking since new, the mechanic noticed it when he did the 600mi service. Whenever it was left on the main stand it dropped to 1.7bar and this week, after being away for 3 weeks, it dropped to 1.2 bar. BMW checked it at 600mi service, again when it was in for a replacement seat (warrranty claim, faulty), and again when I was in to pick up the new gear (Streetguard 3).

Mechanic had another look at it again this morning, and discovered that there is a flat spot defect across the casting. Apparently not common, but it happens. It's been frustrating to have to keep checking / refilling your tyre on a new bike...hopefully sorted now.

Warranty rep said it could be due to hitting a pothole, as can happen with low profile tyres on BMW cars. Nope, haven't hit a pothole and the stock GS tyres can't really be classed as low profile. They've got the bike overnight, until they can get another wheel. They've loaned their F800GS to get me home (rather liked it, but still miss my bike).

Fingers crossed, but something to check for if you are losing front tyre pressure for no other reason.

 

[JJH]

Cue, What nitrogen? thread

If I remember correctly 70% of the athmosphere is nitrogen 20% oxigen and other gasses carbondixoide beeing one-its a long time since I did a self contained breathing apratus course. Or a spelling course. I dont understand thr benifit of nitrogen - if the atoms are bigger and dont leak as easy then a slow leak should still leave 70% in the tyre. I dont go for that and nobody has ever explained why nitrogen should be used even people selling the stuff.JJH

 

[NeilDD]

Nitrogen in tyres

The reason that many racers will use Nitrogen is that it is more thermally stable, so when your tyre warms up the pressure doesnt change

Neil

PS
the only reason I know about this is cause I used to do drag racing 7.2 secs at 196 mph for 1/4 mile)

 

[2 wheel humvee]

I had a similar problem,took the wheel off and layed it flat on the floor and sprayed the tyre bead area with soapy water,result-dozens of "leaks" on each side, cure? take off the tyre and remove the stringy bits of rubber left from the tyre moulding process,presto hey

 

[tonkatoy]

Another one for the collection.

A mate of mine with an FJR had a very similar problem. We spent ages painting soap solution all around the tyre and the rim. Nothing. I blobbed a bit on the top of the valve. Nothing. Figuring we must have missed something we went all round the tyre again. Still nothing. Then we looked at the valve again and it had a collar of bubbles. The pressure was leaking out between the rubber bit of the valve and the metal bit.

Took it to my local friendly bike/tyre place for a new valve. "Seen quite a few of these" he said. Two contributory factors - 1. Metal valve cap - cause enough electrolytic corrosion between the cap and the metal valve body to make them a bit hard to undo. Result is that the metal part of the valve tends to twist in the rubber it is normally bonded to and break the seal a little (or a lot). The other is tyre shops charging you for a new valve but not fitting one.

When he took the old valve out he twisted the valve cap and lo and behold the metal part of the valve came away in his hand. Scary ! That could have popped out at umpty mph and a suddenly flat front tyre doesn't bear thinking about.

Now new valve and no problems.

Incidentally this all started quite suddenly. We assume it was just the act of twisting the cap off to check pressures one weekend.

Solution (in this case anyway) - Use plastic caps, they're perfectly adequate. If you must use metal use WD40, ACF50 or vaseline on the threads to reduce the chance of them seizing.

 

[Montrose Sun]

I had the exact same thing on my 2009 GSA with the exp's - bloody annoying it is too!!!

Its still happening to me with the new anakee 2's but to a lesser extent - and its still bloody annoying.

 

[Engineer]

The reason that many racers will use Nitrogen is that it is more thermally stable, so when your tyre warms up the pressure doesnt change

Neil

PS
the only reason I know about this is cause I used to do drag racing 7.2 secs at 196 mph for 1/4 mile)

We did the whole Nitrogen discussion a few months ago - it is nonsense really. Just some pseudo-science invented by someone who thought they could make a fast buck.

It is used in aircraft tyres to reduce the risk of fire, but does not have to be Nitrogen, just any inert gas will do - and it is not more thermally stable, the pressure of all gases changes with temperature pV=nRT innit!!

 

[Rocky Mountaineer]

The front tyre on my 2009 1200 GS has been leaking since new, the mechanic noticed it when he did the 600mi service. Whenever it was left on the main stand it dropped to 1.7bar and this week, after being away for 3 weeks, it dropped to 1.2 bar. BMW checked it at 600mi service, again when it was in for a replacement seat (warrranty claim, faulty), and again when I was in to pick up the new gear (Streetguard 3).

Mechanic had another look at it again this morning, and discovered that there is a flat spot defect across the casting. Apparently not common, but it happens. It's been frustrating to have to keep checking / refilling your tyre on a new bike...hopefully sorted now.

Warranty rep said it could be due to hitting a pothole, as can happen with low profile tyres on BMW cars. Nope, haven't hit a pothole and the stock GS tyres can't really be classed as low profile. They've got the bike overnight, until they can get another wheel. They've loaned their F800GS to get me home (rather liked it, but still miss my bike).

Fingers crossed, but something to check for if you are losing front tyre pressure for no other reason.

Sixty miles south in the cold, wet rain on an F800GS to pick up my 'fixed' 1200. Exchanged keys, cup of hot tea, then jumped on bike. Warning light on as I left the car park. Low front tyre. Funny, that. That's what I brought it in for. Turns out they replaced the wheel but not the valve. Guess what? Valve's leaking, but they have to order one.

Sixty miles north in the cold, wet rain on an F800GS...sigh.

(note to self - Frank Thomas winter gloves have had their day, soaked. Buy new e.g. winter sale at Hein Gericke). Cold, wet hands are not fun.

On a good note - I stayed dry and warm-ish inside my Streetguard 3 suit, SIDI boots are still comfy. Good performance considering the heavy rain and huge HGV spray on some sections of the road.

 

[Ogmios]

no - i already have my coat, thanks.

Cue, What nitrogen? thread

i want to fill mine with Nitrous Oxide...

just for a laugh.