Speedo reading slow

[TACHY]

At highway cruising speeds (70-90) speedo reading 5 mph below gps. Is there enough difference in circumference of Bridgestone tires to account for this?

 

[Nafod]

Bridgestone rear- 28.6"
Goodyear rear 28.92"

2000 RPM in 6th gear would be a 3.43 mph diff

 

[TACHY]

If Bridgestone smaller, wouldn't that translate to high rather than low speedo readings?

 

[Joe Dozzo]

Factory speedo or Speedhut? With the Speedhut (and Bridgestones), the speedo was 10% slow (when it sorta worked). Went back to factory and now seems spot on...

 

[TACHY]

Factory

 

[Art138]

I don‘t think factory speedo was ever that accurate; at 60mphs gps recorded 57 mph on Goodyear’s. Pretty much the same variance with Bridgestones.