The owner's manual for out '66 122 says tire pressure should be 20 psi front and 23 psi rear for normal driving (one person light load). I suspect that this pressure was for bias ply tires. Should the pressure be different for radial tires? The car still has original springs and sway bar but Bilstein shocks.

Thank you,

Joe M

Thanks all for the great information. I decided to stop driving the car until new lower control arm bushings are installed (see previous thread). Even if the car can handle metal on metal with derubberized bushings, I'd hate to torture the poor thing after it survived so well for so long.

The bushings are supposed to show up on Thursday. I can't wait to get her back on the road again. This is the first time in four years not having a roundfender at my disposal.

Joe M

20/23 will be terribly low for modern radial-ply tires.
In addition to all the nice info try this:
Start at your max reccomended side-wall pressure (typically 32-40 psi depending on brand, size, etc...).
Drive.
Now, lower them 5# (cold) and drive again.
Continue the experiment until you find a nice balance of comfort and driving precision (turn-in, wander, steering effort at low speed, etc.).

Not a good idea to go lower than factory and (in the case of radials) I'd stay 5# over factory.

The front to rear bias is to help with corner steering transitions and is a nice thing to preserve.

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Mike!

I guess it all depends on what tires you have, how fast you go around corners, etc. I currenty have 40 psi on the front tires and 35 on the rears. They are different brand tires though. I once swapped them over (back to front) I found that with that setup I still liked the 40 / 35 psi combination, but then 35 on the front and 40 at the back, so I could just leave the presure on each tire as they were.
I think most people use lower presures tho, but I would not go below 30 psi, but that might just be me...

cheers, ben
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

I always go a bit harder since I do quite a lot of motorway driving - about 28 front and rear or 30 rear when I'm loaded in the back.

I find that the steering in town gets annoyingly heavy when the tire pressure is set at the original specs.

Tom

I don't normally read this forum (hit the wrong key) - however I recently asked a similar question re a 240 and got quite a bit of tire info:

http://www.brickboard.com/RWD/index.htm?id=963796

Hi. Please, use the manufacturer tyre suggested pressure range.

Tyre pressure is function of the design of the tyre, not the car model (by a example, I use local 4 ply nylon tires designed for 400 kg e/o, and set it 24 psi front and 28 psi rear).

Of course, tires are designed for take a predetermined weight, and it is important (Amazon weight near 1000kg, plus people plus travel bags, it is near 1500 kg, on my case my tires support 1600kg max (4 x 400 kg). If you dont know that data, usually you can check it on any web tires store or on the web site of the manufacturer.

You can add a additional 3 psi pressure if you run like Tas (looney tunes, no pun intented if you are a concious driver), but is a good idea to don't pass the max pressure stated by the manufacturer (or the max safe speed for that tyre).

Happy volving.
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Joaquin / Rojo 121 / Lima, Peru

Joaquin:

Excellent information. Thanks for elucidating.

Best regards,

Joe M

What tires(brand and size) are you using? And how spirited do you do your driving? Do you like driving aggressively? If you do, more pressure would do you better, but don't go over your tire's ratings...
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Kyle - '68 142? - Oregon Volvo Tuners?

Kyle:

The tires were put on by the PO just before we bought it -- "Centered" (don't ask) 165 R15 on stock rims. I commute from the country to the city so driving runs from twisty mountain roads to open highway to miles of stop and go. The car is used for errands too, so it can be loaded down on occaision.

For now I am going to try Phil's suggestion of 27 psi all around. That's what was in the back already with 25 psi in the front.

Regards,

Joe M

Er, that's 28 psi front and rear. I'm so confused . . .

They stagger the pressure front to rear to make the rears slightly stiffer (assuming you have the same tires on both ends). That helps insure that in a quick transition to cornering that the rear end won't wag slightly more than the front, which can lead to an actual oversteer in the right conditions.
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I'm JohnMc, and I approved this message.

I like 28 front and rear.