KillerBeagle

I have a 2006 Trek Madone 5.9 with a Chris King headset and need to replace the Bontrager XXX fork. The top of the steerer tube is definitely 1 1/8", but the bottom inch or so at the fork crown is very slightly tapered - not nearly to 1.5", more like 1 3/16". Is this tiny amount of tapering the standard for a 1 1/8" fork, or is this something different?

On the Chris King website I see only crown races / baseplates in 1 1/8" and 1 1/4" so I'm not really sure what I've got. I need to figure out if the baseplate I already have will work if I buy a "standard" 1 1/8" steerer fork.

Jeff Wills

It's standard to have a small ledge for the fork's crown race. For a 1 1/8" headset, this dimension is 30.0mm (sorry about the confusion in units... but it's a bicycle). Some more recent forks/frames have a really tapered steerer tube (top is 1 1/8" diameter, bottom is 1 1/2" diameter) but I don't think you have this.

Buy a 1 1/8" headset- you'll be fine.

KillerBeagle

Ah, ok, I measured the existing crown race at roughly 1 3/16" which is just over 30mm, so your explanation makes perfect sense.

Thank you!

BCRider

If the base of the steerer tube wasn't flared out to the race shoulder you'd have to drive the headset lower race all the way down the tube. And no that would NOT be much fun. Hence why the flare at the base just at the crown.

Retro Grouch 

Actually, that makes sense here in the US because we're in denial over the fact that we're sloooowly converting to the metric system.

I find it less understandable that countries which have used the metric system of measures for decades still mix measurements.

jccaclimber

Just be thankful you haven't run in to 'kilogram*meters' lately on a spec sheet for torque. A shiver goes down my spine every time I see that.

Jeff Wills

Would you rather measure it in Newtons?

dabac

See below.

Yours, and a few others, are such big markets that any supplier reasonably eager to sell will make his product presentations in a way that will be readily recogizable/understandable to you.

Besides, a definition hasn't got to be logical to work. As long as it's unambiguous it can be dealt with.

HillRider

It's no a matter of denial, it's that most people can't immediately revise all of their lifetime of measurement concepts to a new-to-them system overnight. Yes, we are gradually converting but that's because it takes people a long time to make the adjustment and adopt the new way of thinking.

The UK, which is "Officially" metric and has been for decades, still posts its speed limits in Miles per Hour and it's distances between tows in miles and most petrol stations list the price both per liter and per (Imperial) gallon.