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Fork Length Question

5K views 7 replies 5 participants last post by  I like bicycles. 
#1 ·
So I'm trying to build on a Kona Big Unit frame. Spec says fork length (axle to crown?) is 506 m.m.

KONA BIKES | 2014 BIKES | TRAIL 29" HT | BIG UNIT (FRAME ONLY) Click on geometry

When I look for carbon forks on sites like Jenson they are more like 470 m.m. I see no 505 m.m. carbon forks anywhere.

So does this mean if I put in a 470 mm fork I alter the head tube angle and totally change handling of bike?

Not sure what the 506 refers to on the Kona site linked above but again I cannot find a 506 mm rigid carbon fork in a search.

Any help is appreciated
 
#2 ·
Yes, dropping 35 mm of length will mess with the bike's handling.

Don't be overly specific in your search. Try looking for a carbon 29er fork. I bet it has about the right axle-crown length. 505 or 507 would be fine. :) Really, +/- 10 should be okay. But not -35.

You could just buy the matching Kona fork. I bet Niner's carbon fork is about right. If you don't mind steel, there are a ton of nice options. Are you more driven by price or by getting to put some carbon on your bike?
 
#3 ·
Want a light build so I'm looking at carbon.

Niner and others all seem to be at 470 mm

Components > Forks > Rigid Forks | Jenson USA Online Bike Shop

Im good with brakes, BB, crankset etc but the front end is a bit confusing.

integrated, internal,threadless headset etc. Read up on it and Cane Creek has some good info but looks like Ill need help from LBS as far as headset as I suppose without proper press I'll mess things up.

I could just ask LBS to get me a good fork but I want tolearn on my own if possible.

Just cannot find a 505 fork. I may contact Kona about this.

Lots to learn but I'm getting there.

Any suggestions are appreciated. Just when I get ISIS, GigaX, square taper and JIS figured out I get the front fork curve ball thrown at me !
 
#5 ·
505 to 510mm axle to crown = a 100mm suspension fork
Around 490mm axle to crown = a 80mm suspension fork

I've seen 80mm suspension corrected rigid forks with listed axle to crown of 465 to 470mm
I've seen rigid forks listed as 100mm suspension corrected with a axle to crown of 470mm
Whisky Parts have a rigid carbon fork with 480mm axle to crown.
White Brothers have a rigid carbon fork with 490mm axle to crown.

If you're riding a 100mm suspension fork with the sag set at 20% it'll have a axle to crown length of 485 to 490mm, you won't be riding it with the fully extended length of 505 to 510mm

http://www.universalcycles.com/shopping/index.php?category=703
 
#8 ·
If you think about the bike's geometry, when you increase the length of the fork, the head tube angle is going to be increased. Say it's at 67º now, a lengthier fork could quickly turn that to 64º. Doesn't seem like much, but your turning will feel less responsive and the balance is going to be a little awkward, especially at higher speeds.
 
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