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davidbrady · (This post was last modified: 09-07-2016 10:46 by travelite.)

(09-06-2016 13:12)al perna Wrote: so we set them at 115 cold , is 140 acceptable when hot ? I have seen 143 driving from Indio Ca to Yuma Az.
I then put them at 110 and they get up to 125 or so . I will pull over for a while when they are approaching 140 . Your thoughts ?

Hi Al,

Those temperatures sound fine to me. I've seen 140 deg F on a summer day. The temps vary from axle to axle with the inside duals running hotter than the outside, but the range is usually within 125 to 140 deg F. What we need to look out for is an anomaly. If all your tires are within this range but one stands out at 160 then somethings up. As long as they're all around the same temp and they're consistent then things are fine. If one stands out then it could be a dragging brake or a leaking seal or a failing hub bearing or a failing tire. I always measure my temps right at the shoulder where the tread bends into the sidewall. This is the area of maximum stress and maximum work.

Getting back to inflation pressures, there is a 10 to 15% reserve built into the tire load inflation tables. The manufacturers want a constant sidewall deflection and they set the load table pressures accordingly. The reserve is there to handle rough roads, high speeds, fast corners, hard braking, and wide temperature swings. Remember, if we lower our pressures in search of a softer ride we're eating into that reserve. Also, once we eat into the reserve we need to be more vigilant in maintaining pressures so that we don't cross over the zero reserve boundary.