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PostPosted: Mon Feb 02, 2015 12:40 pm 
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Dear weenies,

I have a Specialized Allez (2014 Smartweld) frameset and I'm wondering whether I can install an aftermarket fork. I've asked my Specialized dealer, but they didn't know. Anyway, let's please not discuss whether or not it's a good idea to swap forks on the Allez, I just want to know if it's somehow possible.

The problem seems to be the lower head tube dimensions. The lower headset is an integrated bearing that is classified by the Specialized compatibility matrix as "ACB 49*7*37*45D Eco", and it is raised into the frame by about 7 to 10 mm (which requires a special crown race that is also raised). However, although this is an integrated bearing, it is not placed directly into the head tube, but rather seated in a cup, like a semi-integrated headset. If I were to remove that cup, could I press in a semi-integrated headset which could take a 1.5" tapered fork? I guess it all depends on the inner diameter of the head tube. The outer diameter seems to be something like 58 mm, so assuming normal wall thickness, the inner diameter should be about 52 mm. There seems to be no semi-integrated headset for 52 mm inner diameter head tubes.

Has anyone looked into this? Is there anything that could be done?


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PostPosted: Mon Feb 02, 2015 5:11 pm 
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Location: Europe
This very same question crossed my mind as well, as I looked at the S-Works Allez with interest. AFAIK there are no aftermarket forks made for a 1-3/8" lower headset bearings. There are a number of forks made for 1-1/4" lower bearings, like the 3T Rigida, THM Carbones Scapula CT (w/integrated crown race) and the Enve Tapered.

What would be great solution is if someone could turn a baseplate/crown race for a lower bearing to fit aforementioned forks and a 1-3/8" lower bearing. Chris King has stocked conversion baseplates for many years, except they don't make them in 1-1/4" for 1-3/8" bearings. If you want, I can help to draw one up. PM me and we can discuss details.

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Posted: Mon Feb 02, 2015 5:11 pm 


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PostPosted: Mon Feb 02, 2015 11:29 pm 
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In my opinion, most forks can't take a conversion crown race that would fit the lower bearing on the Allez. The race would have to be raised by about 20 mm. Most tapered forks have a short straight segment where the crown race goes, but it's almost never 20 mm tall. I suppose it would be pretty bad, stability-wise, if the fork were to taper to a smaller diameter within the crown race.

It might be smarter to think about a custom-made lower bearing cup that fits a ZS49/40 bearing. ZS49/40 bearings are unusual, but they are sold by FSA in their Gravity headsets. Such a cup/bearing would fit 1 1/8" -> 1.5" tapered forks, which would be the optimal solution, since those forks usually have 55-58 mm outer crown diameters (ENVE 2.0 55 mm, 3T rigida 58 mm) to fit the 58 mm head tube on the Allez. The original fork is only 50 mm wide and creates a very visible, unsmooth transition between frame and fork.

On the other hand, if the head tube is indeed 52 mm wide on the inside, it could directly fit 52 mm integrated bearings (cane creek IS52) without a cup. All that's needed is a retaining structure. Maybe such a retaining mechanism could be welded into the head tube from above without compromising its mechanical integrity.

@mythical, I take it you don't actually own the Allez? I'll take some pictures of my fork, headset and head tube tomorrow, maybe we can think of a smart solution.

Personally, I'm pretty annoyed by Specialized's decision to sell a frame that's incompatible with industry standard forks and lower headsets. It's a completely unnecessary annoyance to their customers.

Btw, while discussing technical details I'm reminded that English is my third language, so please forgive me if I sound a little off.


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PostPosted: Tue Feb 03, 2015 2:36 am 
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Sometimes you can find S-Works SL4 forks on eBay. That should shave a few grams.


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PostPosted: Tue Feb 03, 2015 3:45 am 
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Location: Pa USA
Your English is better than many native speakers...


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PostPosted: Wed Feb 04, 2015 12:54 am 
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cmus wrote:
In my opinion, most forks can't take a conversion crown race that would fit the lower bearing on the Allez. The race would have to be raised by about 20 mm.
Actually, it doesn't. With my solution, stack height will remain the same. For strength and stability it's best to use the biggest possible bearing that fits the frame anyway.

cmus wrote:
@mythical, I take it you don't actually own the Allez?
I'm looking at an S-Works Allez frameset, and I really like what I've seen but I find the fork ugly and heavy, even though it is the same fork that the Tarmac uses. Actually, I only like the frame and nothing else that comes with the frameset. If I decide to go for this frameset, I will only use the frame and choose another headset, fork, seatpost, seat collar and bottom bracket, and design and make my own fork crown race.

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PostPosted: Sun Feb 08, 2015 3:16 pm 
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By "raised crown race" I don't mean the stack height. Here are some snaphots to illustrate:

This is the fork with its integrated (laminated) crown race:
Image

The lower bearing goes here:
Image

This is the head tube with its pressed-in bearing cup. There's a little ridge about 10 mm inside, which marks the actual bearing retainer.
Image

As you can see, the bearing is raised by about 10mm into the head tube. Any fork that is supposed to fit the original headset would have to have a straight segment of about 20mm where the crown race would go. This is the problem, as I see it. I've looked at some tapered forks and I've noticed that they all have a rather short straight segment, intended for ordinary (=not raised) crown races, then they begin tapering to a lower diameter.

Of course, this might be a moot point if you're able to manufacture a race that precisely fits the angle of the fork's tapered steerer tube. But I suspect this is much more difficult than making a crown race that has a constant internal diameter. I'm curious, how would you go about making a custom crown race? Do you make a mold of the crown/steerer tube, like a dentist would? Or do you just take precise measurements? Would you press the race onto the steerer tube or would it have to be retained by something like epoxy glue?

Quote:
Actually, I only like the frame and nothing else that comes with the frameset. If I decide to go for this frameset, I will only use the frame and choose another headset, fork, seatpost, seat collar and bottom bracket, and design and make my own fork crown race.


I totally agree. I don't find the fork itself ugly, it's just visibly smaller than the head tube (fork 50mm, head tube 58mm outer diameter), which I think makes the combination ugly. On the other hand, most or all 1 1/4" forks are also smaller than the head tube, so there isn't much to be gained in this respect. 1 1/2" forks would fit nicely, as the have about the same outer diameter as the head tube.

Do you maybe have a specific fork in mind, that would fit well with the Allez?

Quote:
Your English is better than many native speakers...

Thanks a lot! :) I haven't actively used my English in 10 years, but I read or watch movies daily, so I didn't forget anything.

P.S.: I apologize for the large pictures, I didn't know how to make thumbnails.


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PostPosted: Tue Mar 24, 2015 2:27 pm 
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Joined: Mon Mar 23, 2015 12:53 am
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I may have found a for that works. Will post pics soon


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PostPosted: Tue Apr 28, 2015 11:19 pm 
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Any updates, Viniebaby?


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Posted: Tue Apr 28, 2015 11:19 pm 


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