Superformance Speedo Issues

[Hydramada]

Originally Posted by Bannon

Thanks folks. Took the car out today for the first real drive. Passed inspection which was the last hurdle. Speedo just seems to be way off. Doing 70mph it hit 50 mph. I'll try to check the cable like was suggested soon.

The car originally had 15in rims and tires from the factory. With my prior experience with 4wd drive vehicles, you need to change a tranny gear when you swap tire sizes and rear end ratios. I have seen in previous posts that there is no "calibration" of these speedo's since they are magnetic. If that is true, can someone explain that to me?
Additionally, if this was due to a tire swap, the 285/45/17's on these would be physically shorter than the 15in tire package so I would expect the speedo to be off the other way.

Thanks again for the replies and the questions from an only dangerously knowledgeable shade tree mechanic...
JB

Yup, you need a new gear for the transmission end of the cable. When I went to 17" from 15" I got a new gear from Dennis at Olthoff Racing. Give them a call when he gets back from Road Atlanta and they can help you determine what you need.