Morning all;
First post. I did probably a dumb thing, but hopefully didn't do any damage. I have 2020 F150 XL 4wd with basic steel wheels, tires 245/70/17. I bought used a set of ford factory 18" wheels with 275/70/18 tires. I really wasn't ready to swap them out yet as the stock tires have plenty of tread left. But, I got antsy and wanted to see what they looked like on the truck. So I swapped out the rears only, looks great. I took it down the road slowly and everything sounded and felt fine until I hit the one mile mark and all broke loose on the dash. Advance trac fault, brake fault and the steering felt stiffer, sluggish. Brought it right home slowly and shut it off. Waited 5 minutes, started it up and all faults gone. Did another short drive and same thing.
Is it because I have 17 on front and the 18's on the back? Maybe a front/rear wheel syncro thing?
Thanks and Merry Christmas to all.
Also have this post in aftermarket section, but thought it would get more attention here.

 

you have a rolling diameter difference of 9% front to rear, this is going to be out of spec and do what you've described. If you put them on all 4 corners you shouldnt have that issue but your speedo will be way out of whack and odometer inaccurate

my ancient mustang doesnt have all that but when on the dyno or running the drag setup I'll get an ABS light because of the wheel speed difference

 

thank you.

 

Swap the other two, plug in Forscan and true up your speedo, then reset your codes. You should be good to go.

 

Front wheels swapped, everything is now fine.
thanks.

 

Just to add additional information.
It has noting to do with your 17" rims. The tires are different diameter.

I know you've already swapped to 4-equals now but it's important to understand the rims don't matter. A post about rim size affecting tires, etc posts about every 2 weeks. Always good to share the education.