Tyre Pressure

Post by **bobjebb** » Thu Apr 20, 2006 11:33 am

Just had the amber 'RR' light come on, so stopped in at Kwick Fit (You can't get better apparently)

Checked for nails, nothing - no signs of a puncture, pressure was indeed a bit low though. Anyone know why this might happen? Valve seemed OK too.

This was all after faffing about with ramps, as the first one couldn't lift her...

The manager took the job of putting it onto the ramp, amusing if not a little frightening to see the way he shot forward like a cat on fire, (he clearly wasn't expecting that, all the more amusing as he'd just pointed out his new M3 in the car park) After he was done he asked if I wouldn't mind taking it back of the ramp myself!

Anyway, any advice welcome and I'll see if it comes on again...

Post by **SimonS4MTM** » Thu Apr 20, 2006 12:28 pm

When did you last check your pressures? Pressures wil drop over time.

Post by **bobjebb** » Thu Apr 20, 2006 12:47 pm

Never. ever. I know I should. I thought these days they were pretty leakproof?

Post by **SteveH** » Thu Apr 20, 2006 1:03 pm

Have had pressure drop over time also on previous cars; another instance over the years I had pressure drop after a rather savage pot-hole but no damage to the tyre or rim, it must have tweaked the bead and then re-bedded itself as wehn I topped up the air all was good.

As a matter of interest what pressure do you run at... reccommended 40psi?

Post by **W8PMC** » Thu Apr 20, 2006 1:14 pm

The RS6 is a heavy fast saloon on only average sized tyres, so pressure changes happen fairly often.

I used to check mine weekly & all 4 often needed a top up weekly. The tyre pressure monitor is often a little keen, as every now & again it would display a warning when in fact the tyre pressures were spot on.

You may need to re-calibrate the monitor, so just top all the tyres off to the recommended levels & then reset the monitor via the DIS Menu functions. A drop of about 4psi over just a couple of weeks is fairly normal. Never heard of bigger drops over longer times, but 4-5psi is the average fluctuation.

Post by **rs666** » Thu Apr 20, 2006 1:55 pm

The other potential is what my car had. I kept losing 10 psi in nsf every few weeks, wouldn't be gradual, just go down suddenly.

Went to several tyre fitters no-one could fine the problem. Then valve gave way and I had to be trailered home from Bristol. Turns out the valve housing in the alloy wheel had corroded. So I got it replaced under warranty. Just another option.

Post by **SimonS4MTM** » Thu Apr 20, 2006 2:39 pm

rs666 wrote:Turns out the valve housing in the alloy wheel had corroded. So I got it replaced under warranty. Just another option.

Unlikely as the valve seals by way of an o ring, could be Audi fobbing you off.

Post by **rs666** » Thu Apr 20, 2006 2:48 pm

Great! It was ATS who pointed it out to me when I had all four tyres replaced!

Its due a service soon, I'll ask for confirmation.

Post by **mbedford** » Thu Apr 20, 2006 11:44 pm

The valves are steel and the valve bodies are alloy hence the threads corrode together and if a valve starts to fail, which they invaribley do over time, you find you can't remove the old valve.
I had three replaced recently because I read that if you get a puncture you should take the valve core out prior to sqeezing in that sealant gunk and then replace the valves and reinflate.
It'd be a bit of a bugger to get a puncture and find you couldn't remove the valves.
I've done 1500 miles since replaceing the valves and the pressure hasn't dropped at all. Prior to this I was having to put in about 3lb every week.

Post by **SteveH** » Fri Apr 21, 2006 7:48 am

Had new valves at 40K service as the threads had corroded; kindly replaced under corrosion warranty.

Post by **peterb** » Fri Apr 21, 2006 10:45 am

After having my wheels refurbed and new tyres fitted, I found that they were all dropping in pressure - the worst lost 20psi in two days! I tightened all the valves, and the valve inserts and now they are perfect.

None of my valve bodies seem to have suffered from corrosion, despite not having been touched for 34 months/24k miles.

BTW, tyres can't be 'pretty leakproof', unless you inflate with nitrogen. Oxygen molecules can pass through the rubber of the tyre!

Post by **stevos** » Fri Apr 21, 2006 5:25 pm

40 psi . mine rarely leak. but the tyre get eaten so quickly they dont get a chance to leak

Post by **Jeeves** » Mon Apr 24, 2006 4:02 pm

44+ of Nitrogen. Didn't know that about the valve stems or the valve removal prior to sealant, but carry a full spare and an uprated pump as the OE one will only fill to 36 PSI. Unfortunately it doesn't filter out the O2 to leave just the Nitrogen, but a bit like coffee, I get free top-ups.

Post by **mwcltd** » Mon Apr 24, 2006 4:33 pm

I am on 19" wheels with 255/35 MPS2's. With just me in I have tried 38, 40, 42 and 44 psi and have found that on our perfect British roads 42 psi is an ideal compromise and wears the tyres evenly.

Post by **SteveH** » Mon Apr 24, 2006 5:29 pm

Its funny as I ran 36psi with PZero's and they wore as if they were over-pressure; Whereas I've found the PS2's wear evenly at 40.

Jeeves, where on earth do you get Nitrogen!? do you work for BOC or something?

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