monique.hubrechtsgm Posted July 13, 2017 Share Posted July 13, 2017 Today i pumped up them to 4.5 bar front and 5bar rear. Which is my driviing situation loaded. I did this under my motorhome carport in the morning at 20 deg celcius. I did this whit three gauges having a spread of 0.4 bar mismatch between them. What is a realible pressure gauge? Your gas meter at home is +/- 2 percent. But checked against weight and measure.Hopefully they are in the minus. In industry they use ultrasonic metres which are in a band of .25 percent.If you tank diesel it is 0.1 persent. Gas or air is very difficult to measure. So what is a good tyre Gauge Or should we depend on the human eye. On the road stations it is even worse. The problem is that you need a air tight connection to read the figure. But their connnections are worned out. An alternative would be your driving height measured on a a flat surface front -rear fully loaded at the correct tyre pressure. Link to comment Share on other sites More sharing options...
Solomongrundy Posted July 13, 2017 Share Posted July 13, 2017 I bought one of these Draper gauges and took it to check it at a couple of Local Tyre depots and when tested it was no more than 0.5 lb psi out. If you need to be more accurate than that then you really are worrying too much about your tyre pressures. :-D :-D :-D :-D Link to comment Share on other sites More sharing options...
Robbo Posted July 13, 2017 Share Posted July 13, 2017 Monique, do you really need 4.5 bar front and 5.0 bar rear? I use 3.5 bar front and 5.0 bar rear on a 4250Kg chassis. Have you taken your 'van to a weighbridge and checked the appropriate pressures with the tyre manufacturer ? Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 14, 2017 Share Posted July 14, 2017 I have 4 tyre-pressure gauges (2 dial-type and 2 digital) that can cope with the high pressures that the tyres fitted to motorhomes are commonly inflated to. My ‘best’ gauge is an “ACCU-GAGE DF160X" as shown here https://www.ghmeiser.com/dial-gauges.htm but the other 3 gauges provide near as dammit the same readings, and the readings from the hand-held gauges also match the readings from the Tyrepal TPMS system fitted to my motorhome. The following links are to AutoExpress pressure-gauge reviews http://www.autoexpress.co.uk/accessories-tyres/85474/best-tyre-pressure-gauge-2016-group-test http://www.autoexpress.co.uk/accessories-tyres/36242/pressure-gauges-tested and it’s perhaps worth highlighting that a ‘survival’ test was carried out. If a gauge is mistreated it should be expected that it won’t appreciate it and this might explain why the readouts from Monique’s 3 gauges were significantly different. I would have thought that an accurracy of 1% should be sufficient and that a reasonable quality hand-held gauge should achieve this. Gauges fitted to electric tyre pumps (in my experience) can be hopelessly inaccurate. Monique’s “driving height” method essentially relies on very accurate measurement of the ground-to-wheel-rim distance when the vehicle is static. I just cannot see that distance alltering sufficiently to obtain reliable data when a pressure should be, say, 5.0bar, but is in fact 4.7bar. And then there’s the “fully loaded” requirement to consider. Much better and simpler to use a gauge that is known to be accurate, when flat ground and loading criteria become irrelevant. Regarding Moniques’s choice of 4.5bar (front tyres) and 5.0bar (rear tyres), I use the same pressures on my Rapido that has tyres with a similar specification (215/70 R15CP) to her Burstner's. I’m guessing that a 2010 Carthago Chic with a 4250kg chassis has 215/75 R16CP tyres and - if that’s correct - directly comparing Robbo’s and Monique’s choice of inflation-pressures is questionable. In any case, there’s a difference between ‘need' (ie. using the lowest pressure that is safe for the weight being placed on the tyre) and 'choose to use’ (ie. using a pressure that will be above the lowest safe figure and produce on-road behaviour that the driver favours). Link to comment Share on other sites More sharing options...
Robbo Posted July 14, 2017 Share Posted July 14, 2017 Derek - my tyres are 225/75R16C Continental Vanco 2, so not directly comparable with Monique's CP tyres or pressures. So, Monique, please ignore my comments about your tyre pressures. Like you, Derek, I've recently installed a Tyrepal solar. On a recent trip to mid-France I was surprised at the rise in pressure, something like an increase of 20%. Initially, I had to keep increasing the higher limit, to stop the buzzer repeatedly going off. In a way, this gave me added confidence to use the minimum recommended cold inflation pressure, as after only a few miles the pressure was increasing anyway. This of course was in summer conditions and winter conditions would undoubtedly be significantly different. Link to comment Share on other sites More sharing options...
747 Posted July 14, 2017 Share Posted July 14, 2017 Robbo - 2017-07-14 9:29 AM Derek - my tyres are 225/75R16C Continental Vanco 2, so not directly comparable with Monique's CP tyres or pressures. So, Monique, please ignore my comments about your tyre pressures. Like you, Derek, I've recently installed a Tyrepal solar. On a recent trip to mid-France I was surprised at the rise in pressure, something like an increase of 20%. Initially, I had to keep increasing the higher limit, to stop the buzzer repeatedly going off. In a way, this gave me added confidence to use the minimum recommended cold inflation pressure, as after only a few miles the pressure was increasing anyway. This of course was in summer conditions and winter conditions would undoubtedly be significantly different. I also think Monique is running at too high a pressure. If it is 5 Bar when checked, it will be much higher during a Motorway run for example. I have removed a spare tyre to inflate and check it. With the Sun shining on it the pressure rose a few pounds (and it was just propped up against a wall). I run a 4.5 ton Tag Axle van with 50 PSI on the 2 rear axles and 65 PSI on the front. If the pressures are a little bit low before we head off I know they will increase with travelling. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 14, 2017 Share Posted July 14, 2017 747 - 2017-07-14 10:04 AM I also think Monique is running at too high a pressure... I don’t.. A Ducato-based tandem-axle 4500kg-chassis motorhome will have had 215/75 R16 ‘camping-car’ tyres as original equipment and the recommended inflation pressures will have been 5.5bar/80psi for all six wheels. This would undoubtedly result in a VERY firm ride at the rear and I can understand someone deciding to use 3.5bar/50psi pressure for the rear tyres as (after all) there are four tyres to share the load and the maximum authorised loading for each individula rear axle will be relatively low. 65psi is roughly 4.5bar, which is what Monique and I use for our 215/70R15CP front tyres and 5.0bar (72psi approx.) seems OK as far as I’m concerned for a ’single wheel’ rear axle with 15”-diameter wheels and relatively small cross-section tyres. Tyre manufacturers quote ‘cold’ pressure-to-load data based on an ambient temperature of 20 degrees Centigrade. TyrePal suggests setting the high pressure alert at 20% above recommended pressure, and this should deal with the rise in pressure that occurs when a tyre warms up when a vehicle is being driven. All tyres heat up in use, but choosing to use low inflation pressures on the basis that the heating process will increase the pressure is asking for trouble if the pressure chosen is insufficient. Link to comment Share on other sites More sharing options...
747 Posted July 15, 2017 Share Posted July 15, 2017 Derek Uzzell - 2017-07-14 2:27 PM 747 - 2017-07-14 10:04 AM I also think Monique is running at too high a pressure... I don’t.. A Ducato-based tandem-axle 4500kg-chassis motorhome will have had 215/75 R16 ‘camping-car’ tyres as original equipment and the recommended inflation pressures will have been 5.5bar/80psi for all six wheels. This would undoubtedly result in a VERY firm ride at the rear and I can understand someone deciding to use 3.5bar/50psi pressure for the rear tyres as (after all) there are four tyres to share the load and the maximum authorised loading for each individula rear axle will be relatively low. 65psi is roughly 4.5bar, which is what Monique and I use for our 215/70R15CP front tyres and 5.0bar (72psi approx.) seems OK as far as I’m concerned for a ’single wheel’ rear axle with 15”-diameter wheels and relatively small cross-section tyres. Tyre manufacturers quote ‘cold’ pressure-to-load data based on an ambient temperature of 20 degrees Centigrade. TyrePal suggests setting the high pressure alert at 20% above recommended pressure, and this should deal with the rise in pressure that occurs when a tyre warms up when a vehicle is being driven. All tyres heat up in use, but choosing to use low inflation pressures on the basis that the heating process will increase the pressure is asking for trouble if the pressure chosen is insufficient. Derek, I have seen similar comments before about rear tyre pressures on a tag axle needing to be around 5 Bar. In fact they were at that pressure when I picked up my current van from the Dealer. I banged and crashed my way home, risking the loss of Fillings and hearing loss. 8-) Could you (or anyone else) please explain to me why the rear axles, rated at a max load of 1500 Kg, are required to have a pressure a mile over the recommendations for that weight? My tyres are 225/70 16 Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 15, 2017 Share Posted July 15, 2017 747 It’s a lost-in-the-mists-of-time recommendation (probably stemming from when Michelin introduced the “XC Camping” tyre) that all 16”-diameter ‘camping-car’ tyres, whether fitted to the front or rear axle of a motorhome and irrespective of how heavy, how big or how many axles the motorhome has, be inflated to 5.5bar/80psi. It’s like religion - don’t ask for a credible and/ot logical explanation... (Are you sure your tyres are 225/70 R16? I would have thought they’d be 75-profile.) Link to comment Share on other sites More sharing options...
747 Posted July 15, 2017 Share Posted July 15, 2017 Derek Uzzell - 2017-07-15 9:51 AM 747 It’s a lost-in-the-mists-of-time recommendation (probably stemming from when Michelin introduced the “XC Camping” tyre) that all 16”-diameter ‘camping-car’ tyres, whether fitted to the front or rear axle of a motorhome and irrespective of how heavy, how big or how many axles the motorhome has, be inflated to 5.5bar/80psi. It’s like religion - don’t ask for a credible and/ot logical explanation... (Are you sure your tyres are 225/70 R16? I would have thought they’d be 75-profile.) They will be 75 profile Derek but it was raining when I made the post and I would rather guess than get wet. :D Link to comment Share on other sites More sharing options...
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