Easy question for the wise - front axle
 

Hi. Quick question. I'm building a disc cross bike and have a 'standard' size fork. I am going to get a 29er disc wheelset. Do I have to use the 'standard' (and what is the original std?) size axle? I see all of these ones with 15mm axles, are these oversize and won't fit? Or am I good to go with any? Thanks.

These days, the "standards" are rapidly changing, but the 9mm q/r or 9mm bolt-on would still be the standard likely to fit your cross fork.

The 15mm thru axle will not fit your fork, but is currently the front-runner for what the next "standard" may become...

Standard in the sense of one size being standard is a meaningless concept as applies to bicycles. There are multiple standards which exist at the same time.

9mm is the standard for front QR axles and fork ends, 5/16 or 8mm is another standard used for lower end bolt on wheels, and there's the 15mm thru-axle standard which is growing, but likely will stay for heavy use or DH mtn bikes.

In any case, a 15mm system calls for an entirely different fork, and will not work on one built for "standard" QR wheels.

I may not like it, but I suspect that most complete bikes over a grand will have thru-axles front and rear before 2020. More to do with safety/liability than any of the stiffness claims being used in present day ad-copy.

Probably 15mm thru up front, and 142/12mm thru out back...even on roadies.

If you're willing to take it, I'll bet you 5 beers it doesn't happen. We'll settle in seven years if we're both still around.

You're on. I'd be glad to buy you those beers, b/c I dislike the new "standards".