HI all.. We just purchased a 2005 F 150 truck and the front tires are 245 70 r 17. The rear tires are 245 75 r 17. Now, the front end shakes bad so we were told the front tires should be replaced. The recommended munfacture recommends 235 70 r 17. My question is, if we replace the front with the manufactures suggestion, would that be a problem keeping the 245 75's on the rear or should we change them all out? We will be towing a 18' boat. Thanks in advance!

 

You should have the same size front and rear...

 

X2

 

And if it's a 4x4 that's a must.

 

Unless you use it like we did back in the '60's, you really should have all 4 tires the same size. Look on the door jamb at drivers door, there should be a sticker denoting what size tire the truck originally had, along with proper pressure.
For some of you guys that say it's a mortal sin to have two different size tires, there's a few of us that remember these,
https://www.hagerty.com/articles-vid...nd-still-cheap

 

Was a common sight to see a 70's muscle car with taller wider rear tires as well. None of those older vehicles had the sophisticated electronically controlled systems found on today's vehicles though.
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Same size and ideally same tread tires at all 4 corners.
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Thanks for the information! I found out I am able to go from the manufacturers suggestion of 235's and go to 245 and even as wide as 255. I chose 245's on all 4 tires. Thanks again!