My 2002 S60 has the 235 45 R17 wheels and the recommended pressure located on the gas cap door does not show a pressure for the 235 45 R17.

The pressure on the gas flap is 39 front 39 rear -- doesn't show a tire size.

There is an optional pressure on the door flap -- 205 55 R16 tire pressure is 29 front 29 rear.

I have no idea what pressure to put in my bigger 17 inch tires? Any ideas are appreciated.

 

Doesn't really matter that much. 39 is fine. 36 is fine. Anywhere from 28 to 40 is fine.

 

Read the tire pressure label a little closer. Mine (16" wheels) says 38 with 29 being optional, but at 29 it is recommended no more than 3 total people in the car. The weight carrying capacity for tires when the pressure is dropped, which is why the tire sidewall will state what the capacity is at the max pressure, though they don't step it down and tell you what the capacity is at any other pressure. So at 29 you are ok if there tends to never be more than 3 people in the car, and certainly 29 would give you a softer ride. The trade off then is handling and fuel economy. Personally I desire as good of fuel economy as I can get without the ride getting too harsh, and 38 is too stiff, so I run 35 trying to get the best of both worlds.

 

Aside from really wanting to know the PSI, the reason I asked is because my wife complains about the feel at 70 MPH. To me it feels ok. Been here before with the caddie, spent a lot of money and balancing, new tires, new front motor mount but it never met her satisfaction.

She commutes 60 miles a day, has back problems and feels everything.

So I was thinking that maybe the PSI in the tires could change the ride.

 

Yes it does have the people matrix but it doesn't have the bigger size on the flap. That is my question, about the larger size tires.

If only it was easy to go by the max tire PSI on the tire wall which is 51 PSI.

 

Do not run the max. Tire pressure increases with temperature.

Your car probably didn't come with 17 inch wheels, otherwise it would be on the sticker.

 

Yes I know not to run at max PSI because of the rise of pressure. It is also why I never let those oil change places check my tire pressure on warm / hot tires. I normally check mine in the morning before they've rolled on inch.

The previous owner was an enthusiast, IPD stickers abound, the K&N filter and I believe that they added the bigger wheels. They do rub when the wheel is turned to the max. I've thought about getting bigger limiters but we don’t' go max on the wheel that often to worry.

I read that it also isn't a good measure to take pressures in the morning when it is very, very cold outside.

I used to get nitrogen in my Jag tires but finally decided that I could not see any value in it. The theory of nitro in tires seems to make sense but in everyday application I never found a reason to continue.

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The attachment is the Volvo S60 Specifications - Model Year 2002

The Amalthea" 14-Spoke Alloy Wheels w/ 235/45/HR17 Tire is a N/A on my model S60 AWD. I fairly certain the 14 spoke are on the car but I'm not going out in the rain to count.

 

You are correct about only checking/filling tires "cold". Unfortunately some people don't have an air compressor at home and their only option is to drive to a gas station or have it checked during a service, but if you are filling a truly cold tire you can fill the tire to the max pressure because that rating is established for a cold tire and the pressure increase that occurs when the tire warms up is built into the rating. But if you drive it even 1/2 a mile to a gas station then you are not checking a cold tire anymore. No reason you would want to run 51 PSI, but in the case of trailer tires they should always be run at max pressure, otherwise their load capacity is compromised and the tire can be in danger of overheating.

On a side note, on a trip from San Diego to the Grand Canyon the resulting 6700 ft elevation change resulted in my trailer tires being 65 lbs when we left San Diego and 69 lbs the next morning when they were checked at the Grand Canyon despite also having a 20 degree less ambient temperature, so there are other forces in play as well.

 

Volvo suggests two tire pressures. One is around 32/33psi, the other around 38psi.

Don't know the reason of having two settings. Generally, tires are inflated to 32psi on most cars. Main reason- uniform tire wear. Too inflated tire will wear faster on the center line.

Volvo has already a stiff suspension especially when it gets older. For a comfy ride, keep it around 28-30psi.

At 38 psi the tires get quite stiff, and it's terrible on poorly maintained roads, even more for a low profile tire.

If the roads in your area are smooth, try the 38psi. It gets a little more mileage, and better handling. As others said, if the tire is inflated at 38psi on a chill morning, on hot weather the pressure will increase by much, above 40psi and may get into issues with tire wear.

A tire with little remaining thread also significantly affects absorbing street imperfections.

Finally, if she has back issues, is driver seat cushion in good shape? Volvo seats are prone to significant cushion wear, which greatly reduces comfort.

 

Yes the Volvo has a stiff suspension and I like it.

The seat cushion is almost perfect. She is very particular about the back issue, she'll complain if I put my hand down on the kitchen chair too hard. I hate back problems, been there done that one!

I hate giving up any more MPG with a lower PSI. Her average is a bit under 22 on her commute. It is highway but there are the areas that the highway backs up and is stop and go.

Good roads? I live in PA --- we are consistently voted the worst roads in the USA. Our governor just added a 10 cent a gallon tax for road maintenance. So what did they do with the other gas road taxes? What makes me think this tax will get wasted?

She is going to take the caddie to work tomorrow, I'll have the Volvo so I can experiment with different PSI. In the morning I'll drop it down to 32 all around and take it for a spin. Then I'll let it sit, drive the Subbie for my day and try a higher PSI in late afternoon.

But really the person that needs to be in the car is my wife. I am fine with the way it feels now.

Probably a 16 inch stock wheel with a higher side wall would suit her better but I really like the way this wheel/tire corners and man does it stick to the road in the cornering.

 

Solved the problem...it was a question of balance. Yep -- removed the tires balanced all four, installed 38 PSI on each tire and at 75 MPH it is smooth. My wife is happy with it.

Yesterday I took my neighbour / mechanic / car sales guy to pick up a BMW to run through the auction. There was a car there, a dead car with a set of 95% perfect 225 45 17 tires. I was tempted to get them and use them on the Volvo. We aren't high performance drivers and the lower total height would help solve the turn the wheel far and it hits the inside of the wheel well.

The 225/45/17 tire equals
Width - 8.85825
Wall height - 3.986
Total height - 24.9724

The 235/45/17
Width - 9.25195
Wall height 4.1633775
Total height - 25.3267

There is minimal difference in the foot print between the two tires.

 

Have you tried all seat adjustments? This seat can be adjusted so it takes various 'shapes', it changes the geometry quite a lot and that can help. I too have lower back issues, and I set it to a position that might be awkward for others, but it helps my back As for the cushion, I mean the bottom one and the lower back one are prone to get 'crushed' that is not as firm as a new ones.. the front passenger seat on my car is like a new one while the drivers seat has been used by a heavy person for 100k miles and is quite weak by now.

 

I knew which cushions you were referring to and they are in very good shape. The drivers seat cushion is in such good shape that IMO someone replaced it with a lower mileage seat. There is no mushy feeling on the sides or the top.

My chirapractor always said to keep your seat as close to the wheel as possible. She used drives with it back fairly far from the wheel and I've tried to get her to change. I also have lower back problems and used to drive 10 hours a day, my chiro was correct, seat close and less strain on the back.

I sent an e-mail to ask her how the ride was today, after the balancing. She replied "Much, much better – thank you again! "

 

No recommendations made by me but I found info about tire PSI

"we received the following rule of thumb from Oscar Pereda, an engineer for BFGoodrich. He calls it a "realistic starting point," saying it has never been just right, but is a good place to start. The rule is:

(Vehicle Weight in lb/100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock.

Example: Stock 911, 3,000 lb.
(3000/100) = 30 psi
Add 2 psi all around = 32 psi
Add 2 psi to heavy end = 34 psi at rear
With modified suspension, the result is 30 psi front, 32 psi rear.

Read more: Tire Pressure Guide - Tech - Sport Compact Car Magazine

Not sure about the curb weight of my car with the 17 inch wheels but on a 15 inch wheel a 2002 Volvo S60 Curb Weight 3146 lbs. Tires / Wheel Size P195/65HR15

So if my four 17 inch wheels take that weight up to 3200 that would mean
3200/100 = 32
Add 2 PSI all around = 34
Add 2 PSI to heavy end = 36


But wait now --- what about adding passengers? If the normal daily drive contains two passengers it could add another 350 pounds to the curb weight. That would mean a curb weight of 3550

3550 / 100 = 35.5
Add 2 PSI all around = 37.5
Add 2 PSI to the heavy rear = 39.5

I also ran across articles expressing that even if your tires heat up to max pressure that is quoted on the side wall, experiencing a burst tire is very unlikely. One quote said that even though tire manufactures don't give out their burst strength he is confident that it is easily at double the side wall max pressure quote.

Hm? Thinking about my heavy Jaguar that comes in at @4400 pounds makes me wonder about the equation from GF Goodrich guy. It would mean that my PSI would be @ 44 PSI?