12 replies to this topic

[Outnabout]

My 2017 Ram has 20” but the spare is 18”. Seems like matching the spare to the wheels that came with the rig would be a given, guess not. Better than the donut on my Subaru though.

[Jon R]

And when it comes time to replace the tires, you'll pay $200-$250 more for a set of 20's. 

 

I'm surprised Ford only supplies the 18" spare regardless.  Seems like too much of a mis-match in OD.

I am ordering a GMC, and the "LT275/70-18 spare regardless of wheels purchased" I described was for the 2021 GM HD trucks, not Ford.  I went through the Ford "build and price" web site process and Ford simply says a spare is included.  I couldn't find where the size was specified.  I don't know whether Ford matches the spare to the installed wheel and tire size. 

 

The OD difference between 275/70-18 and 275/65-20 is about 0.9 inches according to on-line tire comparison calculators, for about a 2.8% difference in non-compensated speedometer reading.  My GMC dealer didn't think they recalibrate the speedometer for the different tire options.  Not sure they really know, though. 

 

I've decided to get the 18s.  Thanks again for all the advice. 

[Advmoto18]

If budget is not a consideration...

 

Go with 17" Innov8 forged wheels!   These things are sweet and EXPENSIVE!  17" affords an even more compliant ride when aired down compared to 18".