I'm thinking about replacing my Rubicon rims and tires with 18" Sahara rims and tires for a 5000 mile road trip this summer. Do the bigger Sahara 18" rims (with smaller stock tires) measure to be about the same height as the smaller Rubicon 17" rims (with larger BFG stock tires)?
I'm wondering if switching to the Sahara rims and tires will change my spedo or rpm's much. What do you think?

 

Stock Rubi 255/75-17 tires are almost identical to the stock Sahara 255/70-18 so your speedo should be fine.

 

x2...very near identical height and width...should have no issues.

 

Thanks guys!

 

It's exactly the same:

Stock Rubi 255 75 17 = 43.18 cm + 19.13 cm + 19.13 cm = 81.44 cm (32.06")

Stock Sahara 255 70 18 = 45.72 cm + 17.85 cm + 17.85 cm = 81.42 cm (32.06")

 

With 18" factory wheels, you can go up to 275/70-18s (33.2") and they should not rub, even with factory backspacing (only .5" wider than stock tires). There's very little selection in the standard 255/70-18 size.

The difference will effect speedo reading (3.4%), but only about 2.1 mph of error at 60 mph (62.1 actual speed). No real need to reprogram for that.

There's a handy tire diameter/speedo error calculator on the web here: Tire diameter vs speedometer error




My regards,

Widewing