(I am sure many of you are more than aware of this already, but still worth a post IMHO)

 

So a few days after collecting my new VRS, I thought I would check the air pressure at the local petrol station, as under spirited driving it felt really squirmy and unsettled.

 

Lo and behold, when I set the garage air pump to the door-card 39 PSI (2.7bar, 225/35/19) it put a fair whack of air in all the tyres and the car rose noticeably. 

 

Handling instantly felt much better...ride a little firmer and boomier, but overall a big improvement and I did this fill again from a different garage about a week later to check pressures were still good (which they were) and to confirm the TPS settings.

 

Today I bought a proper pressure gauge (rated within 1psi) and tested the tyres again...they were still at only 35psi! (with no indicated loss from the TPS over this time)

 

I proceeded to fill to 39psi from my foot pump and the handling improved still further, with no more increase in noise or boom. Indeed, the car now seems "springier" over holes and bumps and traction from hard acceleration has been noticeably improved.

 

So it looks like the dealer were pretty lax on handover, as I estimate their pressure could well have been as low as 30...and it seems the local garages are well behind on calibrating their air gear as well!

 

Annoying really, as the handling on the limit was likely significantly compromised at these pressures, tyre wear would have been very uneven if I hadn't rectified it and I am sure my economy took a hit as well as the potential risk of damage to the wheels with the tyres so far under recommended pressure.

 

Lesson learned - buy a decent gauge and learn to trust that over anything else!

Edited 8 May, 201610 yr by Item

I've had good 12v inflators / tyre pressure readers for a few years now. My current one is digital and fully automatic and lives in one of the boot cubby holes in my car. You just plug it in then connect it up to each tyre and it inflates it to the set pressure before switching back off again. (It actually over inflates by around 0.5 bar so as to compensate for any loss of air as you disconnect it from the tyre.

 

It was on offer at Halfords when I got it and think I paid around £25-30 instead of its something like £50 RRP.

 

No need to use the one's at the petrol stations anymore. 

(It actually over inflates by around 0.5 bar so as to compensate for any loss of air as you disconnect it from the tyre.

Are you sure? That's around 7psi its over inflating which you won't loose just disconnecting the valve. Maybe you mean 0.5psi...?

I used to use a PCL mk3 tyre inflater at work(was run off plant air) but it went missing, they are about the best type you can get. I also had one I bought from Halfords that connected to my air compressor at home but when I check it against calibrated gauges at work its gauge under read by 20psi!!

I used to use a PCL mk3 tyre inflater at work(was run off plant air) but it went missing, they are about the best type you can get.

 

+1

 

I had a PCL Mk2 forever, never missed a beat until it died through abuse, like anything, you get what you pay for.

 

Not unusual for a lot of gauges to be out by 5psi or more

Yep v true....I have a Zafira Tourer with proper TPMS which tells you the individual tyre pressures.

I went to the local Sainsburys as I normally would do as I wanted to inflate the tyres to Eco pressures (hoping for better tyre wear and MPG) so inflated all to 41 psi as the OEM recommendation.

In the current weather I sometimes see the tyre pressures increase to 43 psi...and it's obvious from the infrequent variation in pressure between the wheels that each has a slightly different inflation despite being filled the same by the automated inflator at the garage.

TBF with increases in ambient temperature, different loadings on axles etc it's fine to see a variance but it's indicative that these machines are not particularly well calibrated.

Is it really as high as 39psi for the tyres.

That seems very high to me. I've been running at 33psi all round in my tsi estate.

Is it really as high as 39psi for the tyres.

That seems very high to me. I've been running at 33psi all round in my tsi estate.

Fuel cap states 2.7 bar for my estate which is 39psi. Drives great and the front tyres wore evenly down to just over 2mm right across them before I changed them.

39psi is for 19inch wheels.

34 for 17+18 inch.

Is that right ?

39psi is for 19inch wheels.

34 for 17+18 inch.

Is that right ?

 

34/35 psi yeah.

 

Depending on which conversion chart and air line gauge you use!

Having had motorbikes for 10+ years I am picky with air pressures. However it should be well known that supermarket tyre inflators and cheapo compressors from halfords are often well off the mark. My current one claims 45psi when it's actually nearer 34psi. I always carry a calibrated gauge with me, that way you can use anything to inflate the tyres and check it with something you trust!

I always have my trustworthy, 3€-worth tyre pressure gauge in my car. Never failed me and keeps reliable readings (unlike many gas station gauges).

Cars change, gauge stays: giving a good service in 6th car now