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Fork length?(3 posts)

Fork length?HerrLURP
Mar 29, 2001 6:29 PM
I am considering purchasing a Carbon fork for my bike....however I am not sure of what length I'll need. My bike has a 1" threaded headset, so I know I'll need a 1" threaded fork for 700c wheels....now my bike is a 53cm C-C Lemond....about how much threads and length will I need on the fork? THanks!
re: Fork length?Akirasho
Mar 29, 2001 7:47 PM
...err on the side of excess...

You'll need a steerer that takes into account your bike's headtube length and the stack height...

(From Sheldon't site: Stack Height

The stack height is the vertical space taken up by the headset. With a conventional threaded fork, the steerer tube is longer than the head tube by some amount. If a headset is chosen with a stack height greater than this difference, there may not be enough of the steerer free above the upper bearing race for the keyed washer and lock nut to be installed. In the case of threadless headsets, the stack height also includes the height of the part of the handlebar stem that clamps to the steerer)...

of your headset. Add these two dimensions and get a steerer that's a bit longer. The amount of threads will be dependent on the headset you use. Chris King recommends that 11-14mm of threaded steerer protrude above the upper bearing cup.

In the case of a particularily long steerer, additional threads may be cut by a skilled shop (most home wrenches don't own the dies).

Buying the fork is fairly straightforward... but if you're not sure of the above, you might cough up a few bucks and let the shop install it for you.

Be the bike.
measure, maybe go threadless...dave
Mar 31, 2001 6:25 AM
Measure from the bottom of the headset, where it rests on the fork, to the top of the headset locknut. Convert from inches to millimeters by multiplying by 25.4. Get a fork that is at least 5mm longer than this length, but not more than 30mm longer. Most steering tubes have 50mm or 2 inches of threading. You will have to cut the steering tube to the exact length yourself.

A typical 53cm frame would have a head tube length around 110mm. Add 35-40mm for headset stack height and you get 150mm. A 160mm length would be OK in this example.

You should consider going to a threadless system. It's the perfect time to get a new headset and stem.