leaky tyres ?

[Richam]

Hope this isn't a stupid question....

I've got a 99 C43 with original wheels, I'm pretty sure they've be re-conditioned at some time in their life.

My front tyres both lose pressure at around 10psi (from normal presssure) over a week and it's getting slowly worse. I've had the car about 9 months and there was slight, barely noticeable, loss when I got it. The tyres were new then and have now done about 8,000 miles.

There are no signs of any nails or anything stuck in the tyres, but I haven't had them or the valves tested.

I wondered if anyone else had had a similar experience - is this something that happens with wheels of this age ? Could the refurbishment have done anything to affect the seal between rim and tyre ? Or is it just two coincidentally slow punctures and I should put my hand in my pocket and buy some more ?

I'd be grateful for any thoughts.

Thanks.

 

[Blobcat]

All tyres do leak, however 10psi over a week denotes a leak of some sort. Has this always done this? Have you kerbed the car?
If the wheels have been poorly repaired then there could be a problem with the seal against the rim. Easiest wasy to test is to find a friendly tyre dealer and have then put your wheels in a water tank to check where the leak is.
They could also leak if the rims were not cleaned off prior to your latest tyres being fitted.

 

[television]

Hope this isn't a stupid question....

I've got a 99 C43 with original wheels, I'm pretty sure they've be re-conditioned at some time in their life.

My front tyres both lose pressure at around 10psi (from normal presssure) over a week and it's getting slowly worse. I've had the car about 9 months and there was slight, barely noticeable, loss when I got it. The tyres were new then and have now done about 8,000 miles.

There are no signs of any nails or anything stuck in the tyres, but I haven't had them or the valves tested.

I wondered if anyone else had had a similar experience - is this something that happens with wheels of this age ? Could the refurbishment have done anything to affect the seal between rim and tyre ? Or is it just two coincidentally slow punctures and I should put my hand in my pocket and buy some more ?

I'd be grateful for any thoughts.

Thanks.

Bobcat was almost spot on, what can happen with alloy wheels is that they can corrode on the sealed area, Had my V70R done last week they slip the tyre off, wire brush the rim and apply a sealent, mine is now perfect.

malcolm

 

[Richam]

Thanks to you both for your (unbelievaby quick) replies.

On the phone to the local tyre place tomorrow then.

Thanks again.
Richard.

 

[jberks]

ditto to the above - had the same on the jeep, dropping 10psi+ per week. Tyre removed and resealed and all fine since.

 

[angus falconer]

Hi Richam,

Sounds like the others are probably correct. Chances are it's an issue with poor sealing rather than porous rims.

Having said that the previous owner of my car found hairline cracks on the inside rims of both his rears at about 4 years and Mercedes contributed to the cost of their replacement with new ones. Not sure if this meant air escaping.

One final point of weakness; they are genuinely light wheels and are easy to buckle - I did one of the rears on my prevoius one - had it straightened during refurbishment but watch out for potholes!

Congrats on the C43 by the way - are you enjoying it?

 

[television]

If the problem is the wheels in the end, as Angus says, you can always fit a tube.

malcolm

 

[Rory]

I know a lot of people are sceptical (me included) but might filling them with Nitrogen prevent this happening?

10lbs/wk does sound too much even for the bigger Nitrogen molecules though.

 

[television]

I know a lot of people are sceptical (me included) but might filling them with Nitrogen prevent this happening?

10lbs/wk does sound too much even for the bigger Nitrogen molecules though.

Hi Rory, It did not help mine, when the major outlet fitted the two rear tyres they filled with Nitrogen and one went down straight away. A little guy around the corner did it for me, only got air now in one, and nitrogen in the other.

Malcolm

 

[jberks]

I know a lot of people are sceptical (me included) but might filling them with Nitrogen prevent this happening?

10lbs/wk does sound too much even for the bigger Nitrogen molecules though.

As you say, a loss of that magnitude is too great to be explained by the loss through the tyre carcass, which is all nitrogen would prevent.

 

[geoffd]

supersize nitrogen ?

What are these nitrogen molecules supposed to be bigger than ?

Air is about 80% nitrogen and the rest is mainly oxygen which according to my copy of the CRC handbook is a bigger molecule than nitrogen.

Looks like this is one for the 'mythbusters'.

Cheers

Geoff

 

[Blobcat]

What are these nitrogen molecules supposed to be bigger than ?

Air is about 80% nitrogen and the rest is mainly oxygen which according to my copy of the CRC handbook is a bigger molecule than nitrogen.

Looks like this is one for the 'mythbusters'.

Cheers

Geoff

They are larger;
Oxygen atom size 0.14nm
Nitrogen atom size 0.15nm

That extra 0.01nanometers makes all the difference

Been through this bit before - http://forums.mercedesclub.org.uk/showthread.php?t=18105

 

[geoffd]

more myths about nitrogen

A two minute scan of the internet reveals that most of this 'nitrogen advantage' is utter rubbish and/or a money making scam. If it were otherwise, the tyre manufacturers' web sites would mention it, and they don't.

I can live with race cars or other highly specialised tyres using nitrogen (or even dry air) to eliminate water vapour pressure variations but not the rest.

Also, while a nitrogen atom might be bigger than oxygen (by about 2% not 10), a nitrogen molecule - with two atoms bonded together - isn't.

Geoff