Headset bearing cartridge/crown race compatibilities
 

Okay, so after becoming intimately acquainted with first bottom bracket standards, and then bits and pieces from the drivetrain, it's now time for some headsetting. I'm new to this part of the bike, so forgive any gross blunders.

I picked up an aluminium Cube Agree frame to build up a singlespeed/fixed machine, and have been enjoying it for the past few weeks. I was just a couple of days ago presented with an offer I couldn't refuse on a Trek Madone 9-series fork, which aside from being lighter than the Easton EC70SL in the Cube, also has a lower rake, which I suspect will improve the frame's (already delightful) handling. It has the same 1 1/8th steerer tapering to 1 1/2 inch, and has just the right amount of steerer for my slammed stem. So far, so good, but as with all suspiciously smooth operations, it threw up a surprise in the form of the respective headset bearing standards in the two forks.

The Cube has an integrated headset, and the inferior bearing cartridge reads '1.5 inch ACB 36° x 45° 0751 (there may be a decimal point somewhere in that last sequence of numbers, and the last digit may not be a '1'—I can't make it out for a patch of corrosion). The Easton fork comes with a split race installed, on which the bearings cartridge sits not-very-snugly (to my eyes, although that's obviously how it is because the frame/fork came like that and works well thus). The Trek fork seems to have an integrated race, and the Easton-specific bearing cartridge doesn't sit low enough on the tapered part of the steerer so as to stop it from moving side to side—it's clear that the chamfered edge on the inside of the cartridge isn't long enough to span the filled-in angle that forms the integrated crown race of the Trek fork.

I assume that I will be needing a new inferior bearing cartridge to fit the Trek fork. I've found a couple of sources for 'Madone' bearings, but they differ in the technical specs they list. Bikecomponents.de gives 'Outer Diameter: 52 mm' (which matches the OD of the Easton cartridge), 'Compatibility: 40 Series headsets, 1" , 1 1/8" or 1.5", Angle: 36° x 45°, ZN40 standard'; whereas en eBay page selling inferior bearings for the Madone gives 'OD:51 x ID:40 x H:6.5 x A:36/36'. Alltricks.es gives the reference as 'Cane Creek BB ACB SS 6808', which matches the reference on the eBay page, but then says '51 x 40 x 7 mm', which matces the OD and ID but is a different height. It also gives the IS code as 'IS51/40', a standard for which r2-bike.com gives the following details: 'Insertion dimension Ø: 51 mm - 52 mm, Bearing seat: 45° / 45°'. So here the outr/inner angles (I assume they are listed in this order) too are different from both previous sources that quoted them. Oh dear. What a mess.

So now I don't know who to listen to, or which cartridge to buy, if any. Do any of you knowledgable folks have any insight to give?

For some context, here are a couple of pictures. You can see the long, sloping crown race on the Trek fork, and how the Easton bearings don't have the right length angles to fit it. One thing that is baffling me (aside from the four shops listing the specs differently) is how a cartridge with less vertical height than this one (either 6.5 or 7 mm depending who one trusts, for the Trek one) versus 8 mm for the Easton, is going to sit well on that long chamfered edge on the Trek crown.

https://cimg0.ibsrv.net/gimg/bikefor...4d7285faf1.jpg
https://cimg1.ibsrv.net/gimg/bikefor...35cf6739f3.jpg

Try fsaeasyheadset.com

Hmm. Once I've entered in 30 mm as the ID of the upper cartridge, the widget baulks at the 40 mm ID of the lower cartridge (it only wants 30 mm as the lower cartridge ID). Not sure why, but that's definitely how they are, measured in front of me. Perhaps it's just for FSA headsets.

To add some information re the angles, the Cane Creek website (https://www.canecreek.com/product/forty/) states that 'All complete Cane Creek headset assemblies (top or bottom) will use a 36x45 degree contact angle bearing, with the exception of our IS47/33 and EC44/33 headset assemblies. IS47/33 and EC44/33 will use a 45x45 degree contact angle bearing.'. The bearing diameters for the frame (and forks, seeing as they have the same 1.5 inch steerers) are 51 mm OD and 40 mm ID, so IS51/40. So this lends support to the 36/45 degree angle theory (looking good for bikecomponents.de).

The 36/45 lower bearing that you have should be correct for that fork.. Have you tried actually installing it in the frame. The lower bearing is not intended to sit flush with the crown and it will rock back and forth on the integrated crown race until it is installed in the frame.

I gave it another go, and without the Easton fork race (first photo) the fork crown rubs against the bottom of the headtube. With the race installed (which sits as shown in the second photo here, with whopping great gaps below it and around the steerer), the fork sits tightly in the frame (when preloaded), although there is then a sizeable gap between it and the headtube (third photo). Is that as good as it's going to get?

https://cimg9.ibsrv.net/gimg/bikefor...dfe48b0685.jpg
https://cimg0.ibsrv.net/gimg/bikefor...cc70433161.jpg
https://cimg1.ibsrv.net/gimg/bikefor...70e98e0972.jpg

Looking at the clearance from the crown for the Easton fork with its race installed (first photo) and Trek fork (second photo), it seems that the mm or two difference would be eliminated with a thicker cartridge, buttThe Easton cartridge is 8 mm high, and the Trek one is listed variously as 6.5 or 7 mm, which would give a result in the other direction. It's also true that the Trek cartridge has a smaller bevel at the top (see pics here: https://www.bike-components.de/en/Ca...-mm-o79206613/), which would make it sit lower, and give more clearance. But then again, the inner bevel is wider, which will make it sit lower on the fork, potentially offsetting the effect of the top bevel.

Could I avoid buying new bearings (if that would even help) with some kind of angled spacer that sits on top of the cartridge (between it and the headtube bevel) or below it, but with a wider bevel than the Easton race, and therefore a snugger fit?

https://cimg5.ibsrv.net/gimg/bikefor...ad19489c49.jpg
https://cimg6.ibsrv.net/gimg/bikefor...e40354be74.jpg

I found this guy with almost the exact same problem: https://bicycles.stackexchange.com/q...up-and-bearing. He ended up making a shim, which apparently worked well. Is that what it'll take then?

Otherwise, I'll see what this chart throws up: http://www.canecreek.com/wp-content/...his-poster.pdf.

1) Measure the headtube ID
2) Measure the fork OD
3) Buy the bearings to match
4) test fit with preload.

Thats about as simple as it gets

1) Done
2) Done
3) Apparently I already have them
4) Doesn't fit

You bought the wrong bearings then. Re measure and see if that highlights anything.

As a matter of course, I triple-measured before I came here to bother you guys. And I didn't buy the bearings separately; they came with the frame and old fork.

Everything checks out. 40 mm OD on tapered fork steerer at crown, 36 degree chamfer on integrated crown race - the bearings I have fit that spec, and were in the frame with the old fork, so they fit the frame's specs too.

Great. Did you dry fit with preload?

I did, and that's when the Trek fork crown rubbed on the frame.

Cool. So.

1. No fork installed. Bearing fit dry and snug by hand. On the lower bearing is the face of the bearing flush with or proud of the headtube face?

It is slighty recessed, by perhaps 2 mm.

Ok there is the issue. You have the wrong lower bearing. You can measure the seat Hight in the HT or contact the frame manufacturer for the proper bearing. The bearing you have now is what is limiting you. Don’t make a shim, it will F things up.

Well, if that's the case it's definitely good to know. What doesn't square in my mind is that the bearing gives a perfect fit with the original fork.

In any case, this would imply that I need a bearing with a higher profile, of say 10 mm if the current bearing is 8 mm high and the new fork needs another 2 mm or so to clear the frame. And yet all the bearings I can find related to the new fork are only 6.5 or 7 mm high. I've never seen a 9 or 10 mm one referred to. Do they exist?

What’s the difference between the two forks? In terms of steerer tube / crown area?

The steerer tubes are the same: 1 1/8 inch to 1 1/2 inch tapers. The Easton (old) fork has a flat crown with a separate race, whereas the Trek fork has an integrated race. The most recent two photos above show the respective crowns on the white Easton and orange Trek.

Assuming you got the tapers correct on the bearings for the orange fork. Then the orange fork is not compatible with your frame. The engineering is physically different. I don’t know of a solution in that case. I’d find a fork that uses a regular crown race and go with that.

For better or worse, I'm afraid it's not in my nature not to find a fix for this. As it stands, I accept that the fork is not 'compatible', but that doesn't mean that it never will be. 'The engineering is physically different' is too vague to preclude potential solutions, such as a taller bearing, or a well-made shim. It's just engineering, after all. :)

A taller bearing will work, I’m not sure they make such a thing though in that size. Have you tried calling cane creek ? Would be an easy one to see if they do.
you're welcome
James

I haven't, but I've been in touch with the guy who made the shim, and he said that he was (and that they don't make a taller bearing).

Thanks :). Although we don't have a solution yet, your walkthrough definitely helped me to realise that the various widths and angles constitute the complete set of parameters, and therefore that nothing is being missed and that's what we're working with.

I can see a 3mm shim theoretically working. One that sits inside the frame behind the bearing.
- Although in my style of riding I know its a less expensive and painful endeavour to buy a correct fork rather than run risk of smash my face off on a fast descent due to some mis calculation.

Yeah, I think it could too. I redid the calculations and 1.5 to 2 mm should be enough. Really, as long as the fork steerer is well secured, at worst the shim could result in uneven wear of the bearings and their stiffening up over time. I would expect that to occur gradually though, such that the face-plant could be avoided. The guy from stackexchange is sending one 1.5 mm one and one 2.7 mm one over. I'll see how the machining looks and give it a go if it looks OK, but they do look rather well done.