I have a 1937 Packard with new bias ply tires from Coker. The sidewall says max. 36psi. Coker says to inflate them to 35psi. But the original owners manual says 23psi. What should I do?
35psi
I doubt anyone here would know anything that specific (though I may be wrong).
I’d contact Coker directly and get their recommendation : http://www.cokertire.com/
Coker’s staff are listed on this page : http://www.cokertire.com/page/staff/ along with their tel extension numbers.
If you were driving on original 1937 tires (or modern facsimiles made from 1937 materials) you should inflate to 23 psi. But tires made from today’s materials and today’s specs are much improved. Follow Coker’s recommendation of 35 psi.
If you explained the issue to Coker and they still recommend 35 PSI, then use 35 PSI. If the recommendation was on the printed material that cam with the tire, you might want to call them.
Tire Guides lists 5 different Packard models for 1937. There are different tire sizes for each model … and different inflation pressures. Since you didn’t tell us what the tire size was - nor the model, your best bet is to follow Coker Tire’s advice.
Besides, I’ll bet that their recommendation includes the fact that in 1937 they didn’t have interstate highways with the sustained 70 mph speeds, and the tire pressures were designed with 1937 highways in mind.