The owners manual for my '66 Toronado shows the tire pressures at 24-26 PSI. Is it just me or do these numbers seem low? Just wondering if the pressures were this low due to the tire construction at the time or something? Like, should I run higher px #'s with modern tires?

 

Back then these cars came with bias plies and the construction was different. Most tire pressures were 28-32#'s. No you should not run those pressures for modern tires.

 

Those numbers were for 'Bias Ply' tires that came equipped on the car when it was new. The recommended tire pressure is found on the sidewall of all tires. It can vary depending on the size, type and manufacturer and your own personal taste. Just don't inflate them beyond the recommended maximum pressure and always check the pressure and inflate them when they are cold (not driven on). But generally Radial tires air pressure is much higher. I wouldn't want to give you a set figure and it be higher or lower than what's on your vehicle and cause your tires to wear out prematurely or even worse explode.

 

Actually, what's listed on the side is the maximum, not the recommended, pressure. The recommended pressure varies from situation to situation.

Yes, the low to mid-20s PSI recommended back in the '60s was both for bias ply tires AND to make for a softer ride. Things are different with radials. I run 30 to 32 psi on all of my old car tires now. Gives just the right amount of radial tire bulge.

 

Why does the manual bother to make a distinction between A/C and non-A/C if the tire recommendation is the same for both?

 

Great advice here, thanks everyone. Confirmed kinda what I thought but it's nice to hear from others.

With regards to the AC/Non-AC.......great question. The '66 CSM is full of interesting things in the Toronado section that are inexplicable. I guess it's just the typical first year stuff. I should really grab a '67 CSM just for comparison sakes and to see if they updated the silly stuff like that.

 

I have a '67 chassis service manual, and here's what it has in the Toronado section on tires.

For recommended pressures, they're even lower. and no distinction is made between "average" and "full" load. For both situations, its front 24 psi, rear 22 psi.

The chart on tire size for A/C vs. non-A/C is identical to what you show. 8.85-15 T-FD for both situations. So, again, what's the point of the chart?

 

Keep in mind that in the 1960s, recommended tire pressures were intended to provide the best ride, not the best mileage or even tire mileage. And as noted, bias ply tires have stiffer sidewalls, so the recommended pressure will be different for radials. The same caution applies to engine tune up settings, which were developed for nearly new, totally stock engines running the gasoline available when the cars were built. Tire pressure and tune up specs today are more of a trial and error process.

 

Thanks Joe, great info. Just curious, in your experience, would you say that when it comes to tune-ups using modern fuels do you tend to need more ignition advance or less.......or is it just a crapshoot and you have to fiddle around to figure out what the engine needs?

 

Good grief! I have no idea then.....very strange. Thanks for the info though.

 

Could be either. And obviously any changes to the engine will change the optimum initial timing.

 

I think the difference between AC or no AC is weight.

 

Depends on the car. My 2017 Dodge Challenger GT AWD has a recommended 30 psi cold. Even the regular Challenger's are 32 psi. The last set of GT tires I ran another 4 to 6 psi, wore in the middle and were almost scary at the end, even with the correct pressure. I ran more since I was towing my boat and couldn't get XL tires. The ridiculously expensive Extreme Contact DWS06+, set them at 30 psi and are XL. Now not running a bias ply means the factory pressures are basically a useless number. I say run 32 psi and see how it handles and rides. I have my 70 Cutlass around that psi, rides like a old car with an overfilled trunk, perfect.