My speedometer has been off about 4 mpH at 65. I had new tires installed and calculated the conversion factor. The original factor was 975. The new factor for the new tires is 983. I changed it and the speedometer is now 3 mph off.

So would I run into problems of I bump the factor up to 1007 (a change of 8 changed my mph by 1 mph) to get the speed closer to correct. By problems I mean shifting/abs/cruise control problems.