1" crown race fitting prob

[KeepItSteel]

Trying to fit a 1" Chris King crown race to my 1" steel road fork.

Am even using a Park race setting tool. Trouble is the race seems just a bit too tight to seat on the fork, its sticking on the lip that its supposed to be pressed against.
Despite a hefty whack, the crown race just sits there, loosly fitted.

Do I need to have the base/lip of the steering tube reamed to remove a tiny amount of material, or do I need to get more hefty with the mallet?
Have never had to have a fork reamed, should any good LBS be able to do this? as I dont trust many in my local area.

I dont want to whack much harder for fear of bending the fork drop outs on the work surface.
Never had this problem with 1.1/8th, is it a 1" thing?

 

[one-eyed_jim]

It's quite likely to be a JIS/ISO problem. An ISO crown race is 26.4mm, while JIS is 27.0:

http://sheldonbrown.com/cribsheet-headsets.html

(and see here for a detailed table of dimensions:

http://www.sutherlandsbicycle.com/Chapter12.pdf )

If in doubt, measure. Every cyclist should own a Vernier caliper.

If it's not going on, don't just whack it harder: you risk cracking the race. You need to get the crown race seat milled by a competent bike shop. It's not expensive.

 

[KeepItSteel]

thanks, what would your thoughts be on splitting the curent race (baseplate)?

Ive discovered that King can supply an alternate baseplate, probably in the large dimension (27mm).
I'll measure mine and if its less than 27mm ill try and get my hands on one.

 

[one-eyed_jim]

thanks, what would your thoughts be on splitting the curent race (baseplate)?

You mean deliberately splitting it? Not a good idea. If you're looking at a JIS fork, the split baseplate wouldn't seat the bearing correctly. You're talking about nearly 2mm difference in circumference (0.6mm x pi). The only reasonable course of action is to have the fork milled.

Ive discovered that King can supply an alternate baseplate, probably in the large dimension (27mm).

I can't see any mention of JIS baseplates on the King site, although they will supply a slightly oversized baseplate to compensate for an undersized bearing seat. In the long run it makes more sense to have the fork milled to ISO.

But as I said, the first step is to measure the fork and the parts you have to be certain where the problem lies.

 

[KeepItSteel]

ok, will be getting measures and milled.

I spotted this on the King website:

'''See chart below for correct crown race seat size.

Base Plate Seat O.D. 1" Standard 26.5mm
1" BMX 26.5mm
1-1/8" 30.1mm
1-1/4" 33.1mm''

Which makes me think they may supply a 26.5 as standard with their 1" headsets?
If so, and thats what I do have, then no wonder it wont fit if my fork is ISO.

A bit nervous handing the fork over as its the original supplied one with the frame, here's to competent LBS'..

 

[one-eyed_jim]

I spotted this on the King website:

'''See chart below for correct crown race seat size.''

Which makes me think they may supply a 26.5 as standard with their 1" headsets?

26.5mm is the ideal diameter of the (ISO) bearing seat on the fork. The ISO baseplate should be 26.4mm for a 0.1mm interference fit. The fork may not be JIS - it may just have been milled oversized.

It can be helpful to provide clues to the provenance of the frame - brand, age, country of manufacture and so on, and whether or not it's been fitted with a headset before. It's hard to read between the lines with so little to go on.

 

[KeepItSteel]

The fork is from a '98 Kona Kapu and is the original MudShark 1" steel.

It's a used frame/fork and came fitted with a campag headset. It wasnt tricky getting the campag race off, a few mild taps.

 

[one-eyed_jim]

Hmmm, if the race that came off was a Campag, it's very unlikely that the fork is JIS.

In any case, the action you need to take is the same. Measure first. Mill if necessary.

 

[chipper]

Just to say,I've fitted a number of Chris King headsets,there precision made and have very tight tolerances . As a result you almost always need to mill the fork shoulder to get the crown race to fit correctly.

 

[KeepItSteel]

Hthanks guys, ill go get measured up and mill if neccessary