Citroen C1, Peugeot 107, 108 & Toyota Aygo Owners Club. (Discount code for CityBugStore: C1OC)

Was checking my tyre pressures yesterday when my foot pump started leaking air around where the hose connects to the valve via a thumb lock connector. Luckily if I locked it in the other direction it stopped leaking so I was able to inflate my tyre as I lost a lot of air whilst it was leaking.

I've had it 4 years used every 2 weeks and it only cost just over £ 10 ex VAT. This time I have gone for a supposedly "better" unit the Michelin 12209 reviewed here...

https://www.autoexpress.co.uk/accessories-tyres/86069/best-car-foot-pumps-2018

This one has a screw on type of connector but a much more accurate pressure gauge which is also digital. So I'll probably overinflate by a couple of PSI then use my separate digital pressure gauge to recheck using it to let out air slowly if needs be. I am sure I'll get used to it.

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2019 Smart Fortwo Prime Premium Cabrio A453 Turbo 900cc 90hp
R-Link Evolution Sat Nav/DAB with Android Auto, Bluetooth, USB, SD & AUX
Heated Seats, Electric Mirrors, Air Con
6-Speed Dual Clutch Automatic
Rear Parking Sensors
White with 15” Alloys

You bought a good one there, I have the lower spec manual dial gauge Michelin footpump and it lasted 3 years so far. I stupidly bought one those cheapo metal pumps, but those either the metal bends/breaks or the connector doesn't seal very well. The screw on connector of Michelin is much better.

The only annoyance is the stupidly short standard valve length on our 107's tyres, makes checking tyre pressures and fitting pump valves tricky, that's why I went for screw on type.

Funny you say that, l have one of those metal ones. Do like the choice Neil has made, mines a double barrel job and a pain, have to keep lifting it up to read it. Mostly use the ones is the Petrol Stations.
Never seen any were you screw them on those, much more secure.

I've got a pump that runs off the car cigarette lighter socket... er, no, it's a 12v accessory output these days, right? Can't encourage smoking right?

Aaaanyway, I've had if for many years (maybe 20 or more) and it still working perfectly. It has a built-in pressure gauge. I just set the value that I want (readout calibrated to 0.1psi) and wait. It takes a bit longer than a pump at a petrol station, but not that much longer.

I've got one of those electronic pumps that runs off the 12v too. It was a Christmas present a few years ago before I bought my first foot pump. I prefer manual foot pumps as I don't have to start the engine to use it.

My first foot pump had a quick release thumb lock connector whearas my electronic pump had screw on as does my new Michelin foot pump. I find them a bit more fiddly to use as you lose air whilst unscrewing them, I used to lose air when disconnecting the thumb lock but not much as it was quick release.

Therefore I am going to have to overinflate to compensate for the air loss whilst unscrewing the foot pump, then I'll use my seperate digital gauge to bring it down to the correct amount. I'm sure I'll get used to it.

At least my new pump has a accurate pressure gauge which is also digital. My fronts need to be 29 PSI and rears 36 PSI. I'll probably overinflate them by 2 PSI according to the foot pumps digital gauge them bring them down to the correct amount with my seperate pressure gauge.

I'm sure I'll get used to exactly how much I'm losing when unscrewing the pump from the valve and overinflate accordingly. If I was inflating a completely flat tyre I'd use my electronic pump, all that pumping can't do the manual foot pump much good.

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2019 Smart Fortwo Prime Premium Cabrio A453 Turbo 900cc 90hp
R-Link Evolution Sat Nav/DAB with Android Auto, Bluetooth, USB, SD & AUX
Heated Seats, Electric Mirrors, Air Con
6-Speed Dual Clutch Automatic
Rear Parking Sensors
White with 15” Alloys

Checked my tyre pressures with my new pump today, it turns out that my seperate digital pressure gauge reads 1.5 PSI over what the digital pressure gauge on the pump reads.

Should I trust the £ 5 digital pressure gauge or the one on the pump, both are supposed to be accurate.

I think I'll go with the one on the pump which means I don't have to use the seperate digital pressure gauge anymore.

Unscrewing it isn't as bad as I thought and I only lose maybe 0.5 PSI which isn't a fat lot seeing as I've probably been under inflating them by 1.5 PSI all this time.

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2019 Smart Fortwo Prime Premium Cabrio A453 Turbo 900cc 90hp
R-Link Evolution Sat Nav/DAB with Android Auto, Bluetooth, USB, SD & AUX
Heated Seats, Electric Mirrors, Air Con
6-Speed Dual Clutch Automatic
Rear Parking Sensors
White with 15” Alloys

Well, I can't say I didn't tell you.

In sort of related news, my wife's car has been giving her tyre pressure warnings in the morning over the last few days. Why? Cold weather lowering the pressure in the tyres slightly. After a few miles, or starting up at the end of the day, strangely enough: no pressure warnings.

We had the same thing a few months ago when the hot spell came to an end, the car had been serviced during the hot weather so the dealer adjusted the tyre pressures then, so it was no surprise that the tyre pressures dropped by around 3 PSI when the weather got cooler and triggered the TPMS.

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2020 Aygo x-clusiv x-shift
2015 Skoda Octavia 1.4TSI Elegance estate

Sadly missed - 2006 Audi RS4 Avant

Even being 1.5 PSI under isn't the end of the world, its ok to be 1 to 2 PSI out. Moderate under inflation starts at 2.9 PSI to 7.11 PSI.

I'm actually quite happy, it was always a pain in the arse to check the pressures with my old gauge, its nice and easy with my new foot pump. It does it all, inflates the tyres and gives an accurate reading too. Screws on and off easily enough.

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2019 Smart Fortwo Prime Premium Cabrio A453 Turbo 900cc 90hp
R-Link Evolution Sat Nav/DAB with Android Auto, Bluetooth, USB, SD & AUX
Heated Seats, Electric Mirrors, Air Con
6-Speed Dual Clutch Automatic
Rear Parking Sensors
White with 15” Alloys

Agreed. Though I would say that if one corner drops by a couple of PSI, I can usually start to feel a hint of "something is off" about my car. All -round balanced deflation of a couple of PSI (perhaps due to cold weather) is, perhaps, less obvious - but it does start to become more so if it's any more than that IMO.

Anyway, it was more that I (and others) had said that it was pointless to be particularly concerned at a pressure gauge measuring differences in tenths of a PSI when it was highly unlikely that the equipment would really be calibrated to that level of accuracy and the inherent variations within the system (tyre, valves, temperature, load etc) made concerning yourself with the tiny daily variations that you were reporting pointless too. And now you now have two different pieces of equipment that vary in their readings under the same conditions by far more than the variations you were initially reporting.

Correct tyre pressures are most certainly important and both under and over inflation can have serious consequences - I'm not denying that - but there is no point worrying about variations of fractions of PSI from one day to the next with no continuing trend (as would be the case with an actual leak) when there is no practical guarantee that the equipment is calibrated to that level of accuracy and that the natural variation within the system is greater than that level of accuracy anyway (making trying to measure and adjust to that level pointless).