But I think a 2 1/4" length kingpin is best for the RTX. This little bit of extra length is especially helpful when using Tracker Stimulator Bushings that are usually around 9/16" to 5/8" in height. I prefer using the full height for both the top and the bottom bushings. Also, If you are planning on using the new Radikal Bushings in your RTX (and using the full height of 9/16" for both bushings top and bottom) the 2 1/4" kingpin would again be the better alternative over the stock 2" kingpin.
Here is a technical drawing of a Grade-8 3/8" Hex Head Cap Screw with 24-thread in 2 1/4" length:
![Image](http://www.slalomskateboarder.com/Trucks/RTxKingpinSwap.gif)
Of interest for some of you out there (especially after reading the paragraph below this), a quick upgrade for a deck with both an RTX front and RTS rear, I have found that of the three RTS's that I bought all of them had 2 1/4" kingpins. So you could just put the stock 2 1/4" RTS kingpin into your RTX and then put a new longer 2 1/2" kingpin back in your RTS. Since the RTS is usually a back truck which is ran flat to de-wedge the kingpin will not be sticking out as much. And if you wanted to use full 5/8" height of Stimulator bushings, and even 9/16" height of the new Radikal bushings, for both the top and bottom bushing in the RTS a 2 1/2" kingpin would be better.
If you go to the local hardware stores you will generally not find a 2 1/4" length in 3/8" Grade-8 cap screws. Most general hardware stores and automotive supply stores only carry 2" length then make the jump to 2 1/2" length skipping the 2 1/4" length altogether.
Sure, you can just use a 2 1/2" length for your RTX's (that is easy to purchase from any local hardware store) but the 2 1/4" length is an exact fit for the RTX when using 5/8" Stimulator bushings. Also, a 2 1/2" kingpin in a front RTX with a good amount of wedge would stick down very close to the ground if you ever decided you wanted to use a 62mm wheel like the cambria.
You can purchase 2 1/4" length cap screws from http://www.mcmaster.com , just put in the part number 91286A254. However, you have to purchase a box of 25 cap screws. But this is only $7.50 or so for 25 plus the ground shipping. And you could sell or give the extras to your friends to fix up their trucks. Single 2 1/2" cap screws at your local general hardware stores can cost 70 to 95 cents each, so this is not a bad deal.
I was emailed and told that Indy 101's are also 2" kingpin stock and could benefit from a 1/4" longer kingpin too if using taller bushings.