8mm, 5/16 in. I am utterly confused!

[vasocreta]

Ok, I am one of those poor, sorry-ass, newbie, dweebish skaters who got into this game way late and just look like a dumb fool anytime I step on a skateboard. With that said, I also slalom. Yes, slalom is cool to do, but it is still seemingly dweebish to some if that is all you do. And that is all I have done. So, I guess I'm dweebish.

Anyway...I need more traction on my back truck. Maybe I also need to learn to keep my weight better distributed over the rear truck, but we can get to that later. So, I have heard that 8mm axles are more precise than the stock axles that come on most trucks. I ride Tracker RTS's in the rear and will continue to ride that until appropriate funds come my way to buy a Splitfire or some other expensive gizmo that will help stick my wheels to the ground. Until then, I was considering the less expensive road of grabbing one of those modified RTS's from Sk8kings: http://sk8kings.com/Merchant2/mercha...ategory_Code=T

They say that the axle is 5/16in. Yet all the hype I have heard is about 8mm axles because they allow for less slop between bearing and axle. And, though I am no math major, I know that 8mm = .315 inches and 5/16in, converted to decimal form is .3125. I also took machine drafting in high school and know that the difference between those numbers is not alot, but tolerances depend on application.

Wow, I take the long road to a point. So, does anyone care to educate my dumb self on this topic? If I buy a $45 modified RTS, am I gaining anything more than riding an $18-20 stock RTS? And when folks talk about 8mm axles, do they mean that the axle started at 8mm and was then machined down to 5/16", and because it was machined down it is more precise that a stock axle simple fabricated at 5/16"?

Thanks for your patience and feedback.

[Civ]

the stock axels are undersized, an 8mm axel in just slightly larger in diameter than 5/16ths, this means less play between your bearings and the axels, less play means your wheels are more inline and will offer more grip.

There are more riders here with better and more detailed info than I have.

But thats the jist of it.

[Mile_High_Mark]

For a rear truck, I highly recommend the Airflow. The split axle is in line with the kingpin, which gives you great traction. Plus it has 8mm axles, so there's no slop between the axle and bearings. Use Biltins and the interface is rock solid. While not cheap ($110), it's certainly something you won't "outgrow" as your skills progress.

A mod'd RT-X like the one you mentioned would make for a very good front truck.

[EBasil]

You've got the measurements right, in terms of the decimals. Here are some nuggets without the glue to put them in a paragraph:

--"8mm axles" is a term bandied about quite a bit that, like "10mm spacers" is a form of slang. Since the intended inner diameter of our bearings is exactly 8mm (+/- whatever the tolerances are for that factory), a truly 8mm axle wouldn't fit without using a lot of force. "Size doesn't fit Size" is an old maxim that you can use to remember this, but 8mm axles in an 8mm bore would be a slight interference fit and we'd have to press them on. "8mm axles" are usually either on of two things: an 8mm "nominal" (ie labeled) rod-stock that might measure from .312 to .314 or so, or a larger piece of rod stock that's been lathed down to .312 to .314 or so.

--OEM axles in many trucks are usually made with "nominal 5/16" stock", and can wildy vary from .302" to .310" or so. So, they're pretty much undersized.

--True 5/16" axles would be way better than a stock axle, but not necessarily as good as one machined to "8mm". They could be exactly the same as some "8mm axles", too.

--Those stainless-steel oversized axles in the Trackers are bigger than OEM, but I don't know how they actually measure out. I ordered one, though, and will measure it when in comes in.

[vasocreta]

Thanks for the replies, dudes.

time to save up some dough.