My tire shop installed new front tires on my car: MS 225 60 R 16 98H. Pressure 35.
A note on the door frame of my car recommends:
P215 60 R16 with a pressure of 30.
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Are the new tires alright for my car?
Should I change the (cold) pressure to 30 as recommended?
I appreciate your comments.
Henry
http://www.miata.net/garage/tirecalc.html
This calc shows new vs old tire size.
It throws your speedometer off by 6.7% According to this site calculator, when speedo says 60mph you are only really doing 56mph. I would make them put on the correct size.
The first mistake that this tire shop made was to place the new tires on the front wheels. All of the major tire companies have a policy that the “best” tires (obviously, the new tires) should be mounted on the REAR wheels.
As to the tire size, as long as the load rating (98) is adequate, and as long as the tires do not rub against the fenders when making a sharp turn, then they should be okay. Just be aware that a wider tire will have less traction on snow than a narrower tire. (yes, that may be counterintuitive, but it is true) However, if you move these tires to the rear wheels of your FWD car, snow traction should not be a real issue.
As to tire pressure, I am an advocate of using somewhat higher tire pressures than the car manufacturer recommends. This is for several reasons. First of all, you will get slightly better handling, slightly better tread wear, and slightly better gas mileage if your tires are inflated about 3 lbs over the car manufacturer’s recommendations. The ride quality may deteriorate very slightly, but I believe that the other positive factors outweigh this one slightly negative factor.
Another reason to use slightly higher tire pressure than the car mfr recommends is because low winter temperatures will reduce your tire pressure, to the tune of 1 lb for every 10 degree drop in temperature. If you begin with 30 lbs of inflation at…let’s say…60 degrees…when the ambient temperature drops to 20 degrees, you have seriously under-inflated tires, and that is a safety hazard. A “cushion” of a few lbs extra inflation helps you to avoid underinflated tires.
Is 5 lbs over the recommended pressure too much?
I can’t answer that definitely, except to say that as long as you don’t exceed the maximum pressure listed on the tire sidewall, and as long as you don’t object to the ride quality with that higher pressure, it is probably okay. However, your tire pressure should be the same in all 4 tires, unless Ford specified a pressure differential between the front and rear tires.
Go back to that tire shop, and tell them that you want the tires moved to the rear position, as is the policy of the company that made the tires. Then, buy your own good-quality dial-type tire pressure gauge and make sure that all 4 tires are inflated correctly.
You got that backwards and its 1.8%. On top of that, there is about a 3% difference just from going from worn out tires to brand new identical tires.
What size are the rear tires? If the tire sizes do not match, the tire shop should replace the tires with the same size as the rears. Even if the tire sizes match the new tires should be on the back of the car in any case.
Ed B.
All tires should be the same size. Maybe you had 225’s on the rear and that is what your shop assumed you wanted all the way around. 35 psi is a good starting cold pressure. Most people do not check their tire pressure frequently enough and factory air pressure should be considered minimum. Since most tires loose about 1 psi per month, you are good for about 5 months.
The tire pressure recommendations are at 72 degrees. The tires will lose about 1% for every 10 degrees or about 1 psi for every 24 degrees, but that does not mean that you should add more air as the weather gets colder. The lower pressure in colder weather allows the tires to warm up faster and increase traction.
Dear All:
Thank you so much for your comments. I learned a lot and I feel much, much better now.
Wish you all well.
Henry