I was doing a deep dive into the tire pressure tables because I got bored at work.
Anyone know how T&RA and ETRTO derive the data for the inflation/load tables? Is it real world testing at different speed/load and checking tire temperatures? It's also strange to me that these tables aren't tire model specific in any way. It's all calculated just from size and load ratings. And really the load ratings don't affect the tables, other than the max load. A load C and load E LT tire will have same RCTIP assuming the load is within range of both tires.
The guide that gets posted here regularly, doesn't really speak to where the data comes from. Also it says to calculate load between data points in the table you can do a linear approximation. But strangely, the data is not linear across all it's data points per tire size. I was going to make a quick cheat sheet to calculate RCTIP based on min and max load and min and max PSI, but I noticed pretty quickly the calculated data didn't fit the tables.
Either way, for everyone's RCTIP pleasures, I'm attaching the spreadsheet I made to calculate RCTIP. Looks like you can't add a .xlsx file to mud. Here's a link to it on Google Docs. I don't think Google Sheets will run it very well as I'm sure I'm using some Excel only features to make everything work.
It has a lot of tire data also that you can use to compare sidewall and sizes. There is no "real" tire data in here, only calculated from the tire size and matched to the inflation tables.
Based solely on the data I have gone through, I'd say RCTIP is probably just a good starting place, but certainly experimentation with different pressures around RCTIP are more than safe enough and in some cases may be more ideal than the standard RCTIP calculation. It seems the recommendations are far too broad (as far as the application) to be a concrete answer to safe/ideal inflation. It all seems very specific with the PSI to load equations and what not, but when 5 different manufacturers can make the same size tire, in AT/RT/MT configurations, and the same tables apply to all 15 of those tires, the specificity loses some of it's shine.
Anyone know how T&RA and ETRTO derive the data for the inflation/load tables? Is it real world testing at different speed/load and checking tire temperatures? It's also strange to me that these tables aren't tire model specific in any way. It's all calculated just from size and load ratings. And really the load ratings don't affect the tables, other than the max load. A load C and load E LT tire will have same RCTIP assuming the load is within range of both tires.
The guide that gets posted here regularly, doesn't really speak to where the data comes from. Also it says to calculate load between data points in the table you can do a linear approximation. But strangely, the data is not linear across all it's data points per tire size. I was going to make a quick cheat sheet to calculate RCTIP based on min and max load and min and max PSI, but I noticed pretty quickly the calculated data didn't fit the tables.
It has a lot of tire data also that you can use to compare sidewall and sizes. There is no "real" tire data in here, only calculated from the tire size and matched to the inflation tables.
Based solely on the data I have gone through, I'd say RCTIP is probably just a good starting place, but certainly experimentation with different pressures around RCTIP are more than safe enough and in some cases may be more ideal than the standard RCTIP calculation. It seems the recommendations are far too broad (as far as the application) to be a concrete answer to safe/ideal inflation. It all seems very specific with the PSI to load equations and what not, but when 5 different manufacturers can make the same size tire, in AT/RT/MT configurations, and the same tables apply to all 15 of those tires, the specificity loses some of it's shine.