If I have an electric speedometer, do I need the "sleeve" that people talk about buying along with the speedo gears?

From what I read on the SE Thirdgen speedo gear tutorial, it implies that you only need a sleeve if it's a cable driven speedo, which mine is not.

Also, I'm having trouble figuring out what tire size to use for my gear choice calculations. I have the stock 92 Z28 wheels that I would swear are 16's, but I took a tape measure to them and they were 17.5?? What's the deal? Am I only supposed to measure from the interior of the rim or the absolute outer diameter?

Thanks.

 

Not even a single view yet? Come on guys, pleeeeease?

 

They are 16's and go with 245/50/16 tires. If you are going with a 3.42 gear go with 15/41 speedo gears. Anybody know the part # for the 15 tooth drive gear and the 41 tooth driven gear for electric speedos. I am also not sure if you need a new VSS or not.

 

Hey--you measure from the inside of the tire bead--pretty car. I'm putting a '91 T5 into my '82--the T5 has the electronic speedo drive. Do know what I need to put in there to drive my mechanical speedo? Thanks.

 

I'm going to 3.73s. I ONLY need to know whether or not I have to buy a different "sleeve" or if that only applies to cable-driven applications.

 

I would really like to know as well.