- Joined
- Jan 22, 2019
- Posts
- 4,290
- Reaction score
- 18,521
- Location
- Cheyenne, WY
- Ram Year
- 2018 2500
- Engine
- 6.7 CTD
OK so not sure how this is possible but it's true. I changed tire size yesterday from my Pirelli All-terrain Plus 275/60R20 (33") to BFG KO2 275/65R20 (34") due to needing higher load capacity for towing. I read the instructions on changing tire size in Alfa and it's pretty straight forward so i got my tape measure, level, MX and Alfa ready and went to it.
Now before the tires were installed they rolled one next to the Pirelli's and yes they were visibly about an inch taller. I placed the level on top dead center tire and measured the tire height at about 33.2" with 45 PSI inflation. What? Not even close to 34"! Yet they are visibly taller than were the other tires. Double checked the specs and they are 34" Now i knew this going in but wth? So with the wife in tow we got on the freeway and i had her fire up phone GPS and we checked speeds. At 65 on the speedo her GPS said 65! WTH! I don't get it. Because i'm **** i'm checking again today smh.
In a previous life I was a Jeeper and did tire size changes through about 5 times (on 2 Jeeps). The difference in "size" and what it really is would not even win a horseshoe match.
The best way I found to get the right size was to get a speed reading from a GPS (stand-a-lone or phone) and keep changing the settings until the trucks speedo and the GPS indicated speed is the same.