Tyre pressures.

[singlespeed]

RS133

 

[poweller23]

Looks like my photo there

 

[benmc]

gees ive only been going at 31 psi all round i put up to 34 before and felt sketchy as! 37 will be crazy!

 

[LC]

32 on 17s and 29 on 15's for me :-/

 

[singlespeed]

With ROV work, there's several times when we are standing by, ready for the next work task, but waiting for other departments to finish their bits first. So, there's usually a fair bit of browsing time and this trip has been exceptionally slow.

Anyway, I stumbled upon an article about tyres and their temperatures, pressures and how that relates to them working correctly. We've probably all seen tyre warmers on race cars and chances are that most of us will have had a cheeky feel of our tyres after a good run and noted how warm they feel. It's something which I certainly knew about but never bothered putting it into practice as the tyre wear pattern on my tyres has always been fairly even, so I assumed the pressures were somewhere close to what was required.

Ideally the temperature will be the same across the width of the tyre, which would mean that all the rubber is doing its fair share of the work. However factors like suspension toe and camber will alter the loadings whilst travelling in a straight line and the steering input and roll will affect it whilst cornering. This generally results in there being a temperature gradient across the tyre rather than it being a consistent temperature.

My pressure gauge had recently broken, so I had already decided to buy a new one and now a tyre temperature probe setup was on the cards. Although, I only needed a temperature probe because my multimeter has a setting to take a thermocouple and measure temperature.

A quick test this morning to confirm the tyre probe was reasonably accurate with my multimeter found it was slightly out. Ice in the freezer gave a reading of 4deg and freshly boiled water gave 106deg, so there's a bias to the readings but I'm not too bothered about a precise reading, just consistent readings.

Firstly, I haven't checked the tyre pressures since preparing to go down to FCS, when I set the pressures to 32psi front and 28psi rear using my old pressure gauge. So, armed with a pump and temp probe, I headed out for a bit of testing, consisting of a 20 mile warm up, then a run up the back road towards Lossie which has a few straight sections and a nice series of bends, followed by a quick turn round and reverse run before stopping in the church car park for some readings.

Left front tyre temps:-
outside shoulder - 51
outside centre - 44
inside centre - 47
inside shoulder - 58

Right front tyre temps:-
Outside shoulder - 51
outside centre - 45
inside centre - 48
inside shoulder - 58

So it was safe to say the fronts needed some air adding as the shoulders were doing more work than the centre section

Shame I forgot a pen and paper to write down all the readings, so I made do with the phone which was a bit too slow going so I concentrated on the fronts. The rears were fairly close, across the width just needing a slight increase in pressure, so I didn't bother noting them down. Curious to see what difference there would be after adjusting the pressures, I decided to just do the right hand side so I could compare consistency, with the thinking of waiting for all the tyres to fully cool and get final working cold pressures later. After adding 15 pumps of air to both of the right hand tyres, I repeated the run upto Lossie and back before taking more readings as above. The right rear was now spot on and the right front was better but still running hotter on the shoulders. After repeating the run a few more times and adding 15 pumps to the right front each time, the left front readings were within a degree of the original readings and the right front was looking much better

Right front tyre temps (after increasing pressure):-
Outside shoulder - 49
outside centre - 51
inside centre - 53
inside shoulder - 55

With that, you can see there's a nice gradient across the width of the tyre and the shoulders are running cooler than before whilst the centre section is hotter. This should mean the centre section will now be doing more work, generating more grip, whilst the inside shoulder evening out the work load across the tyre

Getting home, just out of curiosity, I tried the new pressure gauge to get some hot pressure readings
Left front - 33psi
Right front - 51psi :shock:
left rear - 30psi
Right rear - 33psi

Now to wait and see what they cool down to before setting the left side pressures to the same as the right.

Now then, who's bored of that lot :lol:

 

[Brad133]

With ROV work, there's several times when we are standing by, ready for the next work task, but waiting for other departments to finish their bits first. So, there's usually a fair bit of browsing time and this trip has been exceptionally slow.

Anyway, I stumbled upon an article about tyres and their temperatures, pressures and how that relates to them working correctly. We've probably all seen tyre warmers on race cars and chances are that most of us will have had a cheeky feel of our tyres after a good run and noted how warm they feel. It's something which I certainly knew about but never bothered putting it into practice as the tyre wear pattern on my tyres has always been fairly even, so I assumed the pressures were somewhere close to what was required.

Ideally the temperature will be the same across the width of the tyre, which would mean that all the rubber is doing its fair share of the work. However factors like suspension toe and camber will alter the loadings whilst travelling in a straight line and the steering input and roll will affect it whilst cornering. This generally results in there being a temperature gradient across the tyre rather than it being a consistent temperature.

My pressure gauge had recently broken, so I had already decided to buy a new one and now a tyre temperature probe setup was on the cards. Although, I only needed a temperature probe because my multimeter has a setting to take a thermocouple and measure temperature.

A quick test this morning to confirm the tyre probe was reasonably accurate with my multimeter found it was slightly out. Ice in the freezer gave a reading of 4deg and freshly boiled water gave 106deg, so there's a bias to the readings but I'm not too bothered about a precise reading, just consistent readings.

Firstly, I haven't checked the tyre pressures since preparing to go down to FCS, when I set the pressures to 32psi front and 28psi rear using my old pressure gauge. So, armed with a pump and temp probe, I headed out for a bit of testing, consisting of a 20 mile warm up, then a run up the back road towards Lossie which has a few straight sections and a nice series of bends, followed by a quick turn round and reverse run before stopping in the church car park for some readings.

Left front tyre temps:-
outside shoulder - 51
outside centre - 44
inside centre - 47
inside shoulder - 58

Right front tyre temps:-
Outside shoulder - 51
outside centre - 45
inside centre - 48
inside shoulder - 58

So it was safe to say the fronts needed some air adding as the shoulders were doing more work than the centre section

Shame I forgot a pen and paper to write down all the readings, so I made do with the phone which was a bit too slow going so I concentrated on the fronts. The rears were fairly close, across the width just needing a slight increase in pressure, so I didn't bother noting them down. Curious to see what difference there would be after adjusting the pressures, I decided to just do the right hand side so I could compare consistency, with the thinking of waiting for all the tyres to fully cool and get final working cold pressures later. After adding 15 pumps of air to both of the right hand tyres, I repeated the run upto Lossie and back before taking more readings as above. The right rear was now spot on and the right front was better but still running hotter on the shoulders. After repeating the run a few more times and adding 15 pumps to the right front each time, the left front readings were within a degree of the original readings and the right front was looking much better

Right front tyre temps (after increasing pressure):-
Outside shoulder - 49
outside centre - 51
inside centre - 53
inside shoulder - 55

With that, you can see there's a nice gradient across the width of the tyre and the shoulders are running cooler than before whilst the centre section is hotter. This should mean the centre section will now be doing more work, generating more grip, whilst the inside shoulder evening out the work load across the tyre

Getting home, just out of curiosity, I tried the new pressure gauge to get some hot pressure readings
Left front - 33psi
Right front - 51psi :shock:
left rear - 30psi
Right rear - 33psi

Now to wait and see what they cool down to before setting the left side pressures to the same as the right.

Now then, who's bored of that lot :lol:

Hats of to you Neil! I just read all that and it took me a while, 51 psi?? isn't that a bit high?

 

[oscar]

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yep you're right, taking geometry into account the idea is on a straight the harder you accelerate ... your preset toe in / toe out should neutralise to 0 +/- but in the real world this will never happen, it will always vary depending upon load as neil says. this will vary over different types of roads lol

if i read that correctly, i think the just of it was hot air expands ... thus a pressure increase occurs!? but this varies with differing toe in / toe out settings, as well as camber settings. couple that with ambient road temperatures, your tyre pressures will be all over the place so that you can never truly rely on your usual tyre pressure guage reading methods to adjust the pre-set pressures for differing road or track conditions??????

did i just type two paragraphs of the same thing?

 

[singlespeed]

Yes Oscar theres loads of variables that come into play. Road/track temps, the speed your driving at as well as the suspension geometry and tyre construction and size etc.

Now they have cooled down, the pressures that I ended up with are
Front 46psi
Rear 31psi
So thats now the left side set the same as the right.

If it was on track, I could probably drop the pressure as the tyres will be working harder, get hotter and the air will expand more. However, for a quick blast at a decent pace without being a complete tool, the above may work... more testing to come

 

[LC]

Tyre pressure OCD it's like being in f1

 

[LC]

Always good to check the book though??

this is from autodata

 

[CleggmeisterRS]

My favourite is 38 front and 36 rear, 205 40 r17, feels more responsive if a bit firm on the lousy roads we have.