Quote:
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Originally Posted by Texas_Camper
Tire pressure is critical. Goodyear Marathons need 50 psi, measured while the tires are cold. The tire pressure should be checked before every trip, and every three days on long tows.
T_C
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Leon,
For those of us who live in the frozen TUNDRA regions of the Upper U S, it is necessary to define what the measure of "cold" is.
I'm going with 70 deg F. When I travel in the winter, OAT can be around freezing, either direction. I've found the 42-44 psi is approx. equivalent to 50 psi at 70 F. Probably should calculate the tire volume and use gas tables to devise an equation of "cold" pressure as a function of OAT. But, hey, I'm retired
. I'm happy using TLAR*.
Update: Using p1/p2 = t1/t2 I get 46.4 psi as the correct pressure equivalent at 32 deg F. Press in lb/in'sq and temp in Rankin [deg F + 460 ]. Assuming constant volume.
So, rule of thumb{?}: 1 psi less than 50 for each 10 deg decrease from 70 F OAT.
Further Update 10-4-04: 40 F today. Pressure came in at 45 psi; s/b 47 psi. Will be down to 25 F tonight and up to 70 F on Weds. Futher tests to be conducted!
Also saw a comment about driving speed. Just as a reminder, the GY Marathons on most TM's are rated for
65 MPH max. I NEVER, ever exceed 65 MPH (14" tire, 2720) except to pass on a two lane road - but, maybe that's just me. Same as I never exceeded Vne* in an airplane. Limitations are there to protect the manufacturer
(...ermmm..operator?).
Denny_A
*: That Looks About Right / Velocity never exceed.