Another question for
@gaijin ,
@bloc,
@TeCKis300 ,
@KLF , and others--since you guys all know much more than me about these matters:
I'm learning here that increased tire flex and heat at higher speeds is what causes issues when you air down tires below the recommended pressure. However, I wonder if anyone has any insights on how time intervals come into play. There's clear consensus that you don't want to be driving around the highway on KO2s at 35PSI forever. But what about 30 minutes twice a day? Or 90 minutes every 2 days?
Is the safety factor here an incremental thing over time, like X-rays, where the more you get, the higher your risk as you age? Or is the safety factor here more of an each-time thing, like playing Russian Roulette? The camera I mentioned won't be in use all the time and doesn't even have to stay on its mount. So I wonder if, as part of the overall solution, I could air down for short periods of driving on paved roads.
This is gray area that doesn't have firm guidelines or objective data on how best to tailor tire pressures. There's some other strategies to cross check.
That said, tire pressures have lots of opportunity for tailoring and it's not the rigid interpretation some make it out to be. Within reason and understanding, tire pressures can be situationally lowered. Just as it's been done forever for off-roading.
As mentioned, not exceeding temperature which plies start delaminating and separating is the operating ceiling. Generally considered to be 200*F. RCTIP (use LX) pressures are established for max speed, max load, but there's some other major contributors.
1) Lower than max speed (112 mph) - largest opportunity to lower pressures
2) Lower than max stock loads - opportunity to lower pressure, but if you're heavier that should be considered
3) Low ambient temp - opportunity to lower
4) Stop and go, i.e. not continuous highway running - opportunity to lower as tires have more opportunity to dissipate heat
5) Performance driving - may need to increase pressures
I would have no hesitation situationally going to 35 PSI, or even far less. Assuming you're not operating anywhere near max speeds.
If you want a way to sanity check, get a non-contact thermometer, and check sidewall temps against that 200*F ceiling. That's generally considered a safe operating ceiling and there's margin above that before sidewalls begin failing.
In regards to the earlier 4WD discussion - absolutely one can use different pressures between axles, again, if done within reason and understanding. Axle loads are not always even anyways which causes rotational differences in tires that the driveline has to deal with. When towing, I know my rear axle may be upwards of 1200-1800 lbs over the fronts. I adjust my rears ~4PSI higher than fronts. I know you're talking about lowering pressures, which I would use the above paragraphs as basis to lower.
