Question...

I'm on 255/85/16 Cooper ST Maxx and used the Hypertech Speedo calibrator to correct my speedo an odometer. Everything was spot on, when I put in my old tire size (30.6") and new size (32.8").

Just got regeared yesterday, and adjusted the Hypertech... Old (3.91) New (5.29). Kept the tire size adjustment in there. Now my speedo is reading about 5 mph slow.

Read in a couple other threads that the speedo isn't affected in the Autos by a gear change... Is that correct?

 

Yes I am almost 100% certain this is the case as the speedometer gets its information from the abs sensors.

This is very interesting tho. I'm subbing for answers

 

If it can't or doesn't, they need to change their site:

 

I called Hypertech and told them the situation... They seriously told me to mess around with my tire sizes until it's right... That doesn't seem like a solid solution to me.

 

I was going to joke about doing that but that's a work around, not a fix!

 

These trucks get their speed reading from a point that is before the differentials so changing the gearing does not affect the speedo

 

Then why is my speedometer off by 4 mph.