Inflating tyres in my own garage (no 50p required)

[TooMany2cvs]

Nobody's linked to this thread yet?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

If you're stopping short of a full-fat compressor (and the <£100 ones the Aldidl twins punt out periodically are excellent for the money), then the best alternative is a bicycle track pump.


Seriously. Cheap, bomb-proof, fast, much easier work than you'd expect - even taking van tyres to 3bar+.

[FiF]

Dogwatch said:

I bought one of the cheap ones - lasted for one tyre then went out in a cloud of smoke! I only wanted 31 psi.

I use a halfords one powered off the 12v socket on my jump-starter pack. A pre-set function is essential but calibrate it with a proper pressure gauge.

Now that's an excellent idea, I've just bought one of those in order to provide backup power to a dashcam when parked. Excellent extra use for it, saves having the engine running, and faffing about arranging the lead from side to side. Do multiple cars too, thanks for giving me the tip.

[GreenV8S]

TR4man said:

I've alsways understood that tyre pressures should be checked when the tyres are cold, so have always checked and adjusted them at home.

I'd be interested to know whether there is that much difference between hot and cold tyre pressures though - does anyone know whether it really matters?

It does make a difference. For example, raising the temperature by 30C (quite a big change for a road car) would raise a 30psi tyre by about 4 psi. How big a temperature difference you actually get, and how much the pressure difference matters, obviously depends on the circumstances. If you're tweaking the pressure for optimum performance, I'd say it should be done under the actual driving conditions. If you're just making sure the pressure is to spec, you need to measure it under the conditions that are specced.

[FiF]

GreenV8S said:

TR4man said:

I've alsways understood that tyre pressures should be checked when the tyres are cold, so have always checked and adjusted them at home.

I'd be interested to know whether there is that much difference between hot and cold tyre pressures though - does anyone know whether it really matters?

It does make a difference. For example, raising the temperature by 30C (quite a big change for a road car) would raise a 30psi tyre by about 4 psi. How big a temperature difference you actually get, and how much the pressure difference matters, obviously depends on the circumstances. If you're tweaking the pressure for optimum performance, I'd say it should be done under the actual driving conditions. If you're just making sure the pressure is to spec, you need to measure it under the conditions that are specced.

Agreed, and observed experience tells me that there are differences if the cold tyre pressure is checked and set when ambient temperature is 20°C, or 10°C or 0°C.

[robwilk]

I can recommend this one Ive had one for years, I always use a better gauge to check the pressure but inflator works fine.
https://www.amazon.co.uk/RAC750-Powered-Inflator-S...

[Jakg]

I've got one of these - https://www.amazon.co.uk/Michelin-Rapid-12262-Tyre... - had it five years and never had any problems.


I've got a slow puncture so I've been pumping up the tyres once or twice a week and it takes a bit of time which is getting a bit annoying so half heartedly after one of these - http://www.ebay.co.uk/itm/160PSI-Pro-Air-Compresso... - quotes over 4x more air per minute.

[TR4man]

GreenV8S said:

TR4man said:

I've alsways understood that tyre pressures should be checked when the tyres are cold, so have always checked and adjusted them at home.

I'd be interested to know whether there is that much difference between hot and cold tyre pressures though - does anyone know whether it really matters?

It does make a difference. For example, raising the temperature by 30C (quite a big change for a road car) would raise a 30psi tyre by about 4 psi. How big a temperature difference you actually get, and how much the pressure difference matters, obviously depends on the circumstances. If you're tweaking the pressure for optimum performance, I'd say it should be done under the actual driving conditions. If you're just making sure the pressure is to spec, you need to measure it under the conditions that are specced.

That's interesting. So does that mean when using a garage pressure tester, it will be inaccurate anyway because your tyres will be warm and you could be making adjustments based upon inaccurate pressure readings?

[Rick101]

I doubt temprature is an issue unless it's a particulally warm day and you've been caning for a good few miles.

Driving round to the local garage at legal speeds and temperature fluctuation would be negligible. I imagine it would be far less impact than how far the garage gauge is probably out!


On another note, just done my tyres. Have 2 electric pumps but left the key in the house so tried using the cycle pump as advised on here. Quite surprised how easy and quick it is to top up. Ideal for 5-10psi. More than 15psi and I'd have gone back for the key I think.

[the_stoat]

TooMany2cvs said:

Nobody's linked to this thread yet?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

If you're stopping short of a full-fat compressor (and the <£100 ones the Aldidl twins punt out periodically are excellent for the money), then the best alternative is a bicycle track pump.


Seriously. Cheap, bomb-proof, fast, much easier work than you'd expect - even taking van tyres to 3bar+.

That is what I use, nice and light to carry to track days.

[GreenV8S]

TR4man said:

That's interesting. So does that mean when using a garage pressure tester, it will be inaccurate anyway because your tyres will be warm and you could be making adjustments based upon inaccurate pressure readings?

Unless you know the tester is calibrated, you'd have to assume it is randomly inaccurate. If you care about getting the pressure accurate, take your own gauge along.

[phillpot]

GreenV8S said:

Unless you know the tester is calibrated, you'd have to assume it is randomly inaccurate. If you care about getting the pressure accurate, take your own gauge along.

That could also be randomly inaccurate



Joking aside, we have tested and calibrated tyre pressure gauges at work and I was quite impressed how accurate my cheap Ebay digital gauge is

Edited by phillpot on Monday 27th February 23:53

[chrispj]

TR4man said:

I'd be interested to know whether there is that much difference between hot and cold tyre pressures though - does anyone know whether it really matters?

The rear tyres on my Evora go from 33 at cold to settle out at 38 over the first 10 - 15 miles of driving according to the dash pressure read-out.

[phillpot]

chrispj said:

The rear tyres on my Evora go from 33 at cold to settle out at 38 over the first 10 - 15 miles of driving

That near enough agrees with this I found on internet...........

As the tyres deform on the road as they turn, it creates resistance and some of this is turned into heat. This causes the air in the tyres to expand and it increases the pressure by about 1 PSI for every five minutes up to a maximum of between 4-5 PSI. It’s best to check and adjust your tyre pressures after the vehicle has been sitting a couple of hours. Wet weather can mitigate this somewhat as driving through water dissipates the heat.


Another article suggests approx 1 psi rise for every 5 degrees ambient temperature rise.


Some Tyre places are now offering Nitrogen filling which I understand is less affected by temperature change?

[croyde]

I use my cycle stand pump and double check the pressure via the indicator in my newer car. I use a pressure checker on my older one.

The new one shows the tyres at 32 psi at cold. Can get up to 35 psi after a few miles.

[E-bmw]

phillpot said:

Some Tyre places are now offering Nitrogen filling which I understand is less affected by temperature change?

All smoke & mirrors if you ask me!

Yes, I understand the physics but...... All racing teams do this anyway, why are they always "tyre warming"/"keeping tyre temperature up"/etc?

On top of that, are you going to take it back to where you got the Nitrogen put in for a top up, or use air & negate the effect anyway?

[Rick101]

Nitrogen inflation. One load of snake oil if I've ever heard it!

Air is near 80% nitrogen anyway.

People are quite happy to run around on mismatched tyres from wan-ki and cra-pi but them get sold on nitrogen inflation. Not that they then check pressures for the next 20K miles long life service!

[Krikkit]

E-bmw said:

phillpot said:

Some Tyre places are now offering Nitrogen filling which I understand is less affected by temperature change?

All smoke & mirrors if you ask me!

Yes, I understand the physics but...... All racing teams do this anyway, why are they always "tyre warming"/"keeping tyre temperature up"/etc?

On top of that, are you going to take it back to where you got the Nitrogen put in for a top up, or use air & negate the effect anyway?

You might "understand" physics... But you don't understand chemistry, or the basic principles of racing.

Not to defend the Nitrogen filling thing of course, it's pointless for anything but the most highly honed racing environments imo.

Edited by Krikkit on Tuesday 28th February 14:08

[croyde]

phillpot said:

That could also be randomly inaccurate



Joking aside, we have tested and calibrated tyre pressure gauges at work and I was quite impressed how accurate my cheap Ebay digital gauge is

Edited by phillpot on Monday 27th February 23:53

On the strength of that, I bought the last one

[GreenV8S]

E-bmw said:

All smoke & mirrors if you ask me!

I believe the point is to persuade owners to go back to them for routine tyre pressure checks and so they can be sold to on a regular basis. The benefits of nitrogen over fresh air are negligible in normal road use and massively outweighed by the fact that it discourages owners from checking their own tyre pressures.

[amancalledrob]

On the bike I have to check pressures cold because even 2-3psi causes noticeable differences in handling, and to that end I've got a cheap Ring compressor and a reliable analogue gauge to verify with afterwards. Front tyre for example should be 36psi so if I inflate to 38.5 according to the digital gauge on the compressor I usually find myself letting up to 1psi out again with the button on the analogue gauge.

Having it has made doing the car tyres much easier, although if I'm going shopping anyway I just chuck the gauge in the car and use the free compressor at the supermarket