Chris King Gripnut weirdness
 

This winter I decided to re-furbish my old steel framed 531c Mercian, vintage 1988. Originally built up with Shimano Sante which has a v.low headset stack height (32.5mm). Sante headset got replaced with 105SC in 90s, and I've just chucked the 105SC away 'cos it was notchy. To replace it this time only available headset that looks to fit is a 1" Chris King Gripnut. I got a NoThreadset and a Gripnut Conversion from separate sources. Bearing cups and crown race went in place easily (with correct tools), however there seems to be a defect with the (ebayed) Gripnut.

On the NoThreadset adjustable race the taper that locates in the bearing inner race is very flush to the underside face, but on the Gripnut the similar taper is produced on a boss that stands 1.5 - 2mm proud of the underside face. Consequently the Gripnut when assembled leaves a stoopid great gap between it and the top bearing cup. Clearly something is wrong, and assembling the NoThreadset parts shows this gap should be more like 0.2mm.

Before I rush out to order another Gripnut, which may possibly be exactly the same, please could one of you kind people confirm the taper on a Gripnut is usually in the same form as that on a NoThreadset? The alternatives for my build are pretty nuclear, new forks minimum.:(

I have emailed Chris King tech people but they's not answering!

I got a Grip nut Headset on my Bike Friday , just commuting across town
I had the headset coming loose , I'd tighten it up every couple weeks ..

then, I finally took the thing apart, had my tech chat with The CK people and BF service.

the stainless steel collet tab, in it's edge, it has to stay in the keyway
in the adjusting nut as you thread it down, on the fork,

then the taper in the locking nut forces down on the conic shape of the collet.
It is the Collet that is the grip, in grip nut.
the top ring threads into the adjusting ring ..

the frame cup, both, that holds their sealed bearings, is the same, I think,
on 2 nut, grip nut, and threadless.

it is the parts above the top race that differ..

Evan Gaspar answered the email sent to info@chrisking.com

I have had a 1" 2 nut on my touring bike for 20+ years.

I swapped the top nut on that one to a steel Tange, because
it also incorporated an O ring to not have rainwater
leaking around the stem .. as much.. as W/O.

anyhow, if you dont get the collet and the adjusting nut assembled properly
that may be some of the mm gap that you take issue with.

I'll field this tomorrow, I believe we have some 1" GripNuts to verify what's what. I understand your explanation... you need a comparison between a NoThread top and the bottom part of a GripNut.

@fietsbob, thanks I understand that some have had problems with the assembly of the three parts that make up the Gripnut, but that's not the issue I'm having.

@MechBgon, that's it exactly, thanks :O)

perhaps the bigger Grip nut is different. , I had to get 2 40mm headset wrenches ,
to properly service mine,

These are 1 1/8" versions and both of them have the bevel sitting proud like your GripNut does:

http://i240.photobucket.com/albums/f...s/IMG_0603.jpg

Both of them have an air gap when mated to the bearing cup, probably big enough to fit 2 or 3 sheets of paper into, but the profile as viewed from the side looks "right" so I think this is by design. It's possible that either CK made a running change in how deep the bearing sits in the cups, or that 1" is different, or some other explanation I'm not thinking of.

mechBgon, big thanks for the picture. I can see what the problem is now, here's a pic of the parts I have for comparison:
https://lh6.googleusercontent.com/-b...0/IMG_0038.JPG

Part on left is the NoThreadset top cap, see how shallow the boss is. Part on right is the Gripnut, the boss matches the two 1 1/8" parts in your picture. You can see how big the 'air gap' is, possibly the first time I've used an orange for a technical purpose :O) But seems I have two options now, a) new forks and use the NoThreadset, or b) new Chris King Headset :(

Here's the deal, I just received another new 1" Chris King NoThreadset in the post, and it is exactly the same as the other one. Should I be surprised? but the fact is the claims that a Gripnut conversion will work with any Chris King headset are plain wrong. [correction - read the rest of the thread] I'd like to get Chris King's opinion on this but still no response to either email I've sent. Anyone fancy a cheap 1" NoThreadset keep an eye on eBay, I am off to have a good swear.

Might be a bit OCD on needing that thin gap, perhaps.. think about a 2 nut instead?

Of course, the top cap is thicker ,
it has to be internally threaded, lock nut externally threaded and internally tapered,
to compress the collet, as it is tightened down..

http://chrisking.com/tech >> http://chrisking.com/files/pdfs/GripNut.pdf

Hmm, you could be missing the point here fietsbob. I'll admit to OCD of course! There should be a gap of a few thou to allow free movement but 1/8" is not right on a top dollar part. The claim is the Gripnut converts any CK headset but it isn't true and you can see the difference between what should be identical forms on each part. If there was enough steerer tube to use a 2Nut I wouldn't be messing with a Gripnut. Thanks for your thoughts though :0) Next step, I am going to get the steerer tube replaced.

Hehe... oranges, they're so versatile :D I do wonder what the explanation is. I had 1" NoThread and GripNuts for this bike, depending on whether it had its threaded original fork or the aftermarket one installed, and for the record, they both fit the same. I would definitely have noticed a big air gap, and so would the guy I eventually sold it to:

http://i240.photobucket.com/albums/f...paramount1.jpg

Update (for my own peace of mind). Frameset is now with Argos Cycles in Bristol for a re-finish to flamboyant red, and new steerer tube so I have more options. Lovely shiny Cane Creek Classic 100 Threaded Headset waiting to be fitted. Email traffic under way with Edward Rogers of Chris King (as of 18 Jan) so I live in hope of finally understanding the problem and whatever I find out will be posted here for others' delight/to avoid the mistakes I made.

Well I did indeed get an answer from Edward Rogers, it turns out the Grip Nut I have is intended for use with a BMX headset which runs different bearings.

Ahhh, so there's a method to the madness after all.

And to finish the story happily ever after, in today's post was the correct part courtesy of that nice Mr Edward Rogers :O)