Hi. I couldn't find an answer by searching because it all seemed to be about tug tyre pressure.My question is about motorhome pressures. On bitumen my tyres run at 80 psi and work really well but on badly corrugated roads I am wondering what others run their tyres at. Up till now I've kept them the same but gone very very slowly which is not ideal as the ride is terrible. What do others do on really bad roads with the same set up. I've got a good compressor so that isn't a problem but I would like to know if others drop the pressure and if you do how low do you go without destroying your tyres. Would really appreciate any advise. Dave
nswoutback said
04:11 PM Jun 11, 2018
The steps for highway travel;-
1) Establish tyre load
2) Establish tyre size / full specification (read all the critical numbers and words stamped on the tyre).
3) Establish optimum tyre inflation pressure from the best reference, the load inflation charts.
If you propose to reduce tyre inflation pressure for slower travel speeds, the steps are;-
4) Determine the proposed maximum speed and adhere to this maximum speed.
5) Apply the tyre inflation pressure factor based on the chosen speed multiplied by the optimum tyre inflation pressure.
Peter_n_Margaret said
04:57 PM Jun 11, 2018
Keep a close watch on tyre temperatures.
I do this by measuring the temperature with an infra red thermometer every 15 minutes or so and ensuring that it does not exceed 65C. If it starts to get close, SLOW DOWN.
It is excessive temperature that will destroy the tyres.
Cheers,
Peter
dave48 said
07:49 PM Jun 11, 2018
Thanks guys. Thanks Peter I'm always wary of the temperature. Andrew I'm not quite sure what you mean by 5) Apply the tyre inflation pressure factor based on the chosen speed multiplied by the optimum tyre inflation pressure. Would you be kind enough to explain. Dave
nswoutback said
10:45 PM Jun 11, 2018
If you do not exceed say 70km/hr, you might drop the pressure to say 80% of highway pressure.
If you do not exceed say 50km/hr, you might drop the pressure to say 67% of highway pressure.
Aus-Kiwi said
11:12 PM Jun 11, 2018
Explorer pressures 90lb is recommended . Up north I dropped pressures to 70lb . It took a lot of harshness, body harmonics out . Tyre was warm to touch with bare hands . Was tempted to try lower pressures ? But thought leave it ! 19.5 /70 series 225 Michelinās . Theory is I am WELL under max weight . 70 Lb on duel tyres did not effect driving !
dave48 said
06:31 AM Jun 12, 2018
Thanks guys I really appreciate it. Will now do some testing but Know roughly what pressures are involved. Great help. Cheers Dave
oldred83 said
01:16 AM Jun 23, 2018
Hello Andrew..
I have read with interest your thread on Tyre Pressure.
Cooper tyres recommend the following...
"There is no universal right pressure for all tyres. The proper inflation level is dependant on many factors such as what tyres you have, type of vehicle, amount of load, how the vehicle is being driven and the condition of the road to name a few. The important thing to remember is, as load increases, you will need to increase pressure but never exceed the maximum pressure stamped on the sidewall of the tyre. For harsher road surfaces, a lower pressure with lower speed may be needed to avoid tyre damage".
"As a general rule, the following can be used - for road use only: For passenger tyres, inflate your cold tyres to the recommended tyre pressure on your vehicles tyre placard*. Then to determine if you have the correct pressure for a given load, note the cold pressure reading. Drive for at least 20-30 minutes to ensure they have reached operating temperature and then check again. Ideally, they should be about 4psi above the cold pressure. If the pressure is more than 4psi above the cold pressure, you should add more air. That is because there is too much friction, which builds up more heat than desirable. Conversely, if they are less than 4psi above cold pressure, the cold pressure is too high. Adjust your pressures accordingly.
For Light Truck and 4x4 tyres, use 6psi as a guide, but rough and corrugated roads cause more flexing and your tyres may rise more than 4 or 6psi. In which case applying this rule is not recommended".
However, the principle can still be used. The lower the tyre pressure, the slower one should drive. Pick a speed which suits you, your rig and your other half. Lower the tyre pressures gradually. Say 5 psi at a time. Monitor your tyre pressures, record the readings. This process will take a while, but you will eventually determine the optimum pressure for the different grades of corrugated road for the speed you are comfortable at. Remember, you will not find the exact pressure, as ther are too many variants in road surfaces, temperature
oldred83 said
01:28 AM Jun 23, 2018
Hello Andrew..
I have read with interest your thread on Tyre Pressure.
Cooper tyres recommend the following...
"There is no universal right pressure for all tyres. The proper inflation level is dependant on many factors such as what tyres you have, type of vehicle, amount of load, how the vehicle is being driven and the condition of the road to name a few. The important thing to remember is, as load increases, you will need to increase pressure but never exceed the maximum pressure stamped on the sidewall of the tyre. For harsher road surfaces, a lower pressure with lower speed may be needed to avoid tyre damage".
"As a general rule, the following can be used - for road use only: For passenger tyres, inflate your cold tyres to the recommended tyre pressure on your vehicles tyre placard*. Then to determine if you have the correct pressure for a given load, note the cold pressure reading. Drive for at least 20-30 minutes to ensure they have reached operating temperature and then check again. Ideally, they should be about 4psi above the cold pressure. If the pressure is more than 4psi above the cold pressure, you should add more air. That is because there is too much friction, which builds up more heat than desirable. Conversely, if they are less than 4psi above cold pressure, the cold pressure is too high. Adjust your pressures accordingly.
For Light Truck and 4x4 tyres, use 6psi as a guide, but rough and corrugated roads cause more flexing and your tyres may rise more than 4 or 6psi. In which case applying this rule is not recommended".
However, the principle can still be used. The lower the tyre pressure, the slower one should drive. Pick a speed which suits you, your rig and your other half. Lower the tyre pressures gradually. Say 5 psi at a time. Monitor your tyre pressures, record the readings. This process will take a while, but you will eventually determine the optimum pressure for the different grades of corrugated road for the speed you are comfortable at. Remember, you will not find the exact pressure, as there are too many variants in road surfaces, road temperatures, loads, driving conditions etc etc, but a bit of time experimenting with pressures and feeling the temperatures of the tyres will eventually pay off.
On another note, it is my experience the notion of rising above the corrugations by driving fast over them, especially severe corrugations is a sure fired way to damage your rig, damage contents, increase the risk of losing control and frustrating tempers. I know it can be very frustrating, but the bigger the corrugations the slower you need to travel.
Kind Regards
Oldred83
StewG said
02:07 PM Jun 23, 2018
I also was unsure about tyre pressures for my new rig. After extensive Googling and use of other forums I selected nominal pressures for the six tyres involved and bought a Tyre Pressure Monitoring System to be able to monitor pressure and temperature constantly while on the move. After some teething problems with the TPMS; the caravan tyres would not report back to the display until a transponder was installed at the back of the car - now installed permanently on the caravan. Pressures, of course are highly dependent on temperature and ambient temperatures vary widely throughout Oz. So it is hard to give an exact pressure, but if you have a good compressor and accurate gauge, it is easy enough to experiment until you're happy with the results that give you economy, comfort, grip, sidewall protection and even wear of tyres (not necessarily all at the same time).
Hi. I couldn't find an answer by searching because it all seemed to be about tug tyre pressure.My question is about motorhome pressures. On bitumen my tyres run at 80 psi and work really well but on badly corrugated roads I am wondering what others run their tyres at. Up till now I've kept them the same but gone very very slowly which is not ideal as the ride is terrible. What do others do on really bad roads with the same set up. I've got a good compressor so that isn't a problem but I would like to know if others drop the pressure and if you do how low do you go without destroying your tyres. Would really appreciate any advise. Dave
1) Establish tyre load
2) Establish tyre size / full specification (read all the critical numbers and words stamped on the tyre).
3) Establish optimum tyre inflation pressure from the best reference, the load inflation charts.
If you propose to reduce tyre inflation pressure for slower travel speeds, the steps are;-
4) Determine the proposed maximum speed and adhere to this maximum speed.
5) Apply the tyre inflation pressure factor based on the chosen speed multiplied by the optimum tyre inflation pressure.
I do this by measuring the temperature with an infra red thermometer every 15 minutes or so and ensuring that it does not exceed 65C. If it starts to get close, SLOW DOWN.
It is excessive temperature that will destroy the tyres.
Cheers,
Peter
If you do not exceed say 50km/hr, you might drop the pressure to say 67% of highway pressure.
I have read with interest your thread on Tyre Pressure.
Cooper tyres recommend the following...
"There is no universal right pressure for all tyres. The proper inflation level is dependant on many factors such as what tyres you have, type of vehicle, amount of load, how the vehicle is being driven and the condition of the road to name a few. The important thing to remember is, as load increases, you will need to increase pressure but never exceed the maximum pressure stamped on the sidewall of the tyre. For harsher road surfaces, a lower pressure with lower speed may be needed to avoid tyre damage".
"As a general rule, the following can be used - for road use only: For passenger tyres, inflate your cold tyres to the recommended tyre pressure on your vehicles tyre placard*. Then to determine if you have the correct pressure for a given load, note the cold pressure reading. Drive for at least 20-30 minutes to ensure they have reached operating temperature and then check again. Ideally, they should be about 4psi above the cold pressure. If the pressure is more than 4psi above the cold pressure, you should add more air. That is because there is too much friction, which builds up more heat than desirable. Conversely, if they are less than 4psi above cold pressure, the cold pressure is too high. Adjust your pressures accordingly.
For Light Truck and 4x4 tyres, use 6psi as a guide, but rough and corrugated roads cause more flexing and your tyres may rise more than 4 or 6psi. In which case applying this rule is not recommended".
However, the principle can still be used. The lower the tyre pressure, the slower one should drive. Pick a speed which suits you, your rig and your other half. Lower the tyre pressures gradually. Say 5 psi at a time. Monitor your tyre pressures, record the readings. This process will take a while, but you will eventually determine the optimum pressure for the different grades of corrugated road for the speed you are comfortable at. Remember, you will not find the exact pressure, as ther are too many variants in road surfaces, temperature
I have read with interest your thread on Tyre Pressure.
Cooper tyres recommend the following...
"There is no universal right pressure for all tyres. The proper inflation level is dependant on many factors such as what tyres you have, type of vehicle, amount of load, how the vehicle is being driven and the condition of the road to name a few. The important thing to remember is, as load increases, you will need to increase pressure but never exceed the maximum pressure stamped on the sidewall of the tyre. For harsher road surfaces, a lower pressure with lower speed may be needed to avoid tyre damage".
"As a general rule, the following can be used - for road use only: For passenger tyres, inflate your cold tyres to the recommended tyre pressure on your vehicles tyre placard*. Then to determine if you have the correct pressure for a given load, note the cold pressure reading. Drive for at least 20-30 minutes to ensure they have reached operating temperature and then check again. Ideally, they should be about 4psi above the cold pressure. If the pressure is more than 4psi above the cold pressure, you should add more air. That is because there is too much friction, which builds up more heat than desirable. Conversely, if they are less than 4psi above cold pressure, the cold pressure is too high. Adjust your pressures accordingly.
For Light Truck and 4x4 tyres, use 6psi as a guide, but rough and corrugated roads cause more flexing and your tyres may rise more than 4 or 6psi. In which case applying this rule is not recommended".
However, the principle can still be used. The lower the tyre pressure, the slower one should drive. Pick a speed which suits you, your rig and your other half. Lower the tyre pressures gradually. Say 5 psi at a time. Monitor your tyre pressures, record the readings. This process will take a while, but you will eventually determine the optimum pressure for the different grades of corrugated road for the speed you are comfortable at. Remember, you will not find the exact pressure, as there are too many variants in road surfaces, road temperatures, loads, driving conditions etc etc, but a bit of time experimenting with pressures and feeling the temperatures of the tyres will eventually pay off.
On another note, it is my experience the notion of rising above the corrugations by driving fast over them, especially severe corrugations is a sure fired way to damage your rig, damage contents, increase the risk of losing control and frustrating tempers. I know it can be very frustrating, but the bigger the corrugations the slower you need to travel.
Kind Regards
Oldred83
I also was unsure about tyre pressures for my new rig. After extensive Googling and use of other forums I selected nominal pressures for the six tyres involved and bought a Tyre Pressure Monitoring System to be able to monitor pressure and temperature constantly while on the move. After some teething problems with the TPMS; the caravan tyres would not report back to the display until a transponder was installed at the back of the car - now installed permanently on the caravan. Pressures, of course are highly dependent on temperature and ambient temperatures vary widely throughout Oz. So it is hard to give an exact pressure, but if you have a good compressor and accurate gauge, it is easy enough to experiment until you're happy with the results that give you economy, comfort, grip, sidewall protection and even wear of tyres (not necessarily all at the same time).