Can i change the tire of my 1990 model to 245x70x16?if not what is the biggest tire size that i can use?tnx

if these rims are 13" 5.5jj rims then the biggest tire that you can fit safely is about 195 85 r13
if you go too wide on the tire then the tire beads will not sit properly on the rim and will roll on turns causing a blow out at the worst possible time
talk with a tire shop and get the details on the biggest tire that you can fit legally and safely on the car
after all when it comes to safety , looks can be deadly

All tires on a 4x4 must be the same size or there will be a transmission wind up , you could damage the transmission and jam the gear change.

in the manual or a tag on door or doorpost driverside

Here's what you need to do. You need to get the tire size off of the tire on your vehicle. Lets say its P205/75R14 or something like that. Go to this link, type that size into the tire on the left, then you can change the tire on the right to whatever size you. You will be amazed what will fit on that vehicle. I wouldnt go over 20" rims if i were you. 22's will leave you very little tire and a very bad ride.

Here's some info on your bolt pattern and wheel offset.

1990 Buick LeSabre 5 lug 4.53 inch or 115 mm High Positive Offset

Heres the tire size calculator
http://www.miata.net/garage/tirecalcold.html

Any question, comment back. If you are looking for 20" rims, 255/30/20 is a common tire that you can find reasonably cheap and lines up perfectly with most vehicles.

that depends on if your doing a stock upgrade or if your have ing a lift kit also installed, depending on the kit itself, would open or limit the tire and or rim size

open your driver side or passenger side door and either on the strike jam or on the door your gonna find a sticker that will list the factory tire size thats best suited for your car.

The correct tire size is a 235/75R15 XL

I believe it will fit. If you go to DiscountTires.com you can use their site for alternate tire sizes. Especially handy is the feature which shows you the Speedometer error for different size tires. The site will also show you recommended and popular substitute tire and wheel sizes.

The 1999 model had a 265/65/17 as an alternative. You may want to ask the Tire store you intend to use if they can reconfigure your Speedo to be accurate. Some of the Fords can be done electrically without changing Speedo gears.

I did something similar by going from a "60" series to a "65" series in the same width. On my Grand Marquis, I gained 5% mileage improvement, but have to watch Speedo until I get it reconfigured. I hope this helps to answer your questions.

205 75 14. There should be a sticker on your door jam.

most ford pickup rims are 15*7 its kind of a narrow tire therefore the biggest tires are 285/75. those will fit fine too big will rub, crack the sidewall, even cause a blow-out. you can go to your local goodyear and they will lookup your vehicle find the biggest-best tire fore your application, then give you a quote to take with you.